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* stackdepot: use gfp_nested_mask() instead of open coded maskingDave Chinner2024-05-191-9/+2
| | | | | | | | | | | | | | | | | | | | | | | | | The stackdepot code is used by KASAN and lockdep for recoding stack traces. Both of these track allocation context information, and so their internal allocations must obey the caller allocation contexts to avoid generating their own false positive warnings that have nothing to do with the code they are instrumenting/tracking. We also don't want recording stack traces to deplete emergency memory reserves - debug code is useless if it creates new issues that can't be replicated when the debug code is disabled. Switch the stackdepot allocation masking to use gfp_nested_mask() to address these issues. gfp_nested_mask() also strips GFP_ZONEMASK naturally, so that greatly simplifies this code. Link: https://lkml.kernel.org/r/20240430054604.4169568-3-david@fromorbit.com Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Marco Elver <elver@google.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Andrey Konovalov <andreyknvl@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: respect __GFP_NOLOCKDEP allocation flagAndrey Ryabinin2024-04-241-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If stack_depot_save_flags() allocates memory it always drops __GFP_NOLOCKDEP flag. So when KASAN tries to track __GFP_NOLOCKDEP allocation we may end up with lockdep splat like bellow: ====================================================== WARNING: possible circular locking dependency detected 6.9.0-rc3+ #49 Not tainted ------------------------------------------------------ kswapd0/149 is trying to acquire lock: ffff88811346a920 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_reclaim_inode+0x3ac/0x590 [xfs] but task is already holding lock: ffffffff8bb33100 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x5d9/0xad0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: __lock_acquire+0x7da/0x1030 lock_acquire+0x15d/0x400 fs_reclaim_acquire+0xb5/0x100 prepare_alloc_pages.constprop.0+0xc5/0x230 __alloc_pages+0x12a/0x3f0 alloc_pages_mpol+0x175/0x340 stack_depot_save_flags+0x4c5/0x510 kasan_save_stack+0x30/0x40 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x83/0x90 kmem_cache_alloc+0x15e/0x4a0 __alloc_object+0x35/0x370 __create_object+0x22/0x90 __kmalloc_node_track_caller+0x477/0x5b0 krealloc+0x5f/0x110 xfs_iext_insert_raw+0x4b2/0x6e0 [xfs] xfs_iext_insert+0x2e/0x130 [xfs] xfs_iread_bmbt_block+0x1a9/0x4d0 [xfs] xfs_btree_visit_block+0xfb/0x290 [xfs] xfs_btree_visit_blocks+0x215/0x2c0 [xfs] xfs_iread_extents+0x1a2/0x2e0 [xfs] xfs_buffered_write_iomap_begin+0x376/0x10a0 [xfs] iomap_iter+0x1d1/0x2d0 iomap_file_buffered_write+0x120/0x1a0 xfs_file_buffered_write+0x128/0x4b0 [xfs] vfs_write+0x675/0x890 ksys_write+0xc3/0x160 do_syscall_64+0x94/0x170 entry_SYSCALL_64_after_hwframe+0x71/0x79 Always preserve __GFP_NOLOCKDEP to fix this. Link: https://lkml.kernel.org/r/20240418141133.22950-1-ryabinin.a.a@gmail.com Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB") Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com> Reported-by: Xiubo Li <xiubli@redhat.com> Closes: https://lore.kernel.org/all/a0caa289-ca02-48eb-9bf2-d86fd47b71f4@redhat.com/ Reported-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Closes: https://lore.kernel.org/all/f9ff999a-e170-b66b-7caf-293f2b147ac2@opensource.wdc.com/ Suggested-by: Dave Chinner <david@fromorbit.com> Tested-by: Xiubo Li <xiubli@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Alexander Potapenko <glider@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: rename pool_index to pool_index_plus_1Peter Collingbourne2024-04-051-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 3ee34eabac2a ("lib/stackdepot: fix first entry having a 0-handle") changed the meaning of the pool_index field to mean "the pool index plus 1". This made the code accessing this field less self-documenting, as well as causing debuggers such as drgn to not be able to easily remain compatible with both old and new kernels, because they typically do that by testing for presence of the new field. Because stackdepot is a debugging tool, we should make sure that it is debugger friendly. Therefore, give the field a different name to improve readability as well as enabling debugger backwards compatibility. This is needed in 6.9, which would otherwise become an odd release with the new semantics and old name so debuggers wouldn't recognize the new semantics there. Fixes: 3ee34eabac2a ("lib/stackdepot: fix first entry having a 0-handle") Link: https://lkml.kernel.org/r/20240402001500.53533-1-pcc@google.com Link: https://linux-review.googlesource.com/id/Ib3e70c36c1d230dd0a118dc22649b33e768b9f88 Signed-off-by: Peter Collingbourne <pcc@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Alexander Potapenko <glider@google.com> Acked-by: Marco Elver <elver@google.com> Acked-by: Oscar Salvador <osalvador@suse.de> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Omar Sandoval <osandov@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: off by one in depot_fetch_stack()Dan Carpenter2024-03-041-1/+1
| | | | | | | | | | | | | | | | | | The stack_pools[] array has DEPOT_MAX_POOLS. The "pools_num" tracks the number of pools which are initialized. See depot_init_pool() for more details. If pool_index == pools_num_cached, this will read one element beyond what we want. If not all the pools are initialized, then the pool will be NULL, triggering a WARN(), and if they are all initialized it will read one element beyond the end of the array. Link: https://lkml.kernel.org/r/361ac881-60b7-471f-91e5-5bf8fe8042b2@moroto.mountain Fixes: b29d31885814 ("lib/stackdepot: store free stack records in a freelist") Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* mm,page_owner: maintain own list of stack_records structsOscar Salvador2024-02-231-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | page_owner needs to increment a stack_record refcount when a new allocation occurs, and decrement it on a free operation. In order to do that, we need to have a way to get a stack_record from a handle. Implement __stack_depot_get_stack_record() which just does that, and make it public so page_owner can use it. Also, traversing all stackdepot buckets comes with its own complexity, plus we would have to implement a way to mark only those stack_records that were originated from page_owner, as those are the ones we are interested in. For that reason, page_owner maintains its own list of stack_records, because traversing that list is faster than traversing all buckets while keeping at the same time a low complexity. For now, add to stack_list only the stack_records of dummy_handle and failure_handle, and set their refcount of 1. Further patches will add code to increment or decrement stack_records count on allocation and free operation. Link: https://lkml.kernel.org/r/20240215215907.20121-4-osalvador@suse.de Signed-off-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Marco Elver <elver@google.com> Acked-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: move stack_record struct definition into the headerOscar Salvador2024-02-231-43/+0
| | | | | | | | | | | | | | | | In order to move the heavy lifting into page_owner code, this one needs to have access to the stack_record structure, which right now sits in lib/stackdepot.c. Move it to the stackdepot.h header so page_owner can access stack_record's struct fields. Link: https://lkml.kernel.org/r/20240215215907.20121-3-osalvador@suse.de Signed-off-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Marco Elver <elver@google.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: fix first entry having a 0-handleOscar Salvador2024-02-231-7/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "page_owner: print stacks and their outstanding allocations", v10. page_owner is a great debug functionality tool that lets us know about all pages that have been allocated/freed and their specific stacktrace. This comes very handy when debugging memory leaks, since with some scripting we can see the outstanding allocations, which might point to a memory leak. In my experience, that is one of the most useful cases, but it can get really tedious to screen through all pages and try to reconstruct the stack <-> allocated/freed relationship, becoming most of the time a daunting and slow process when we have tons of allocation/free operations. This patchset aims to ease that by adding a new functionality into page_owner. This functionality creates a new directory called 'page_owner_stacks' under 'sys/kernel//debug' with a read-only file called 'show_stacks', which prints out all the stacks followed by their outstanding number of allocations (being that the times the stacktrace has allocated but not freed yet). This gives us a clear and a quick overview of stacks <-> allocated/free. We take advantage of the new refcount_f field that stack_record struct gained, and increment/decrement the stack refcount on every __set_page_owner() (alloc operation) and __reset_page_owner (free operation) call. Unfortunately, we cannot use the new stackdepot api STACK_DEPOT_FLAG_GET because it does not fulfill page_owner needs, meaning we would have to special case things, at which point makes more sense for page_owner to do its own {dec,inc}rementing of the stacks. E.g: Using STACK_DEPOT_FLAG_PUT, once the refcount reaches 0, such stack gets evicted, so page_owner would lose information. This patchset also creates a new file called 'set_threshold' within 'page_owner_stacks' directory, and by writing a value to it, the stacks which refcount is below such value will be filtered out. A PoC can be found below: # cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks.txt # head -40 page_owner_full_stacks.txt prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 alloc_pages_mpol+0x91/0x1f0 folio_alloc+0x14/0x50 filemap_alloc_folio+0xb2/0x100 page_cache_ra_unbounded+0x96/0x180 filemap_get_pages+0xfd/0x590 filemap_read+0xcc/0x330 blkdev_read_iter+0xb8/0x150 vfs_read+0x285/0x320 ksys_read+0xa5/0xe0 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 521 prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 alloc_pages_mpol+0x91/0x1f0 folio_alloc+0x14/0x50 filemap_alloc_folio+0xb2/0x100 __filemap_get_folio+0x14a/0x490 ext4_write_begin+0xbd/0x4b0 [ext4] generic_perform_write+0xc1/0x1e0 ext4_buffered_write_iter+0x68/0xe0 [ext4] ext4_file_write_iter+0x70/0x740 [ext4] vfs_write+0x33d/0x420 ksys_write+0xa5/0xe0 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 4609 ... ... # echo 5000 > /sys/kernel/debug/page_owner_stacks/set_threshold # cat /sys/kernel/debug/page_owner_stacks/show_stacks > page_owner_full_stacks_5000.txt # head -40 page_owner_full_stacks_5000.txt prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 alloc_pages_mpol+0x91/0x1f0 folio_alloc+0x14/0x50 filemap_alloc_folio+0xb2/0x100 __filemap_get_folio+0x14a/0x490 ext4_write_begin+0xbd/0x4b0 [ext4] generic_perform_write+0xc1/0x1e0 ext4_buffered_write_iter+0x68/0xe0 [ext4] ext4_file_write_iter+0x70/0x740 [ext4] vfs_write+0x33d/0x420 ksys_pwrite64+0x75/0x90 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 6781 prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 pcpu_populate_chunk+0xec/0x350 pcpu_balance_workfn+0x2d1/0x4a0 process_scheduled_works+0x84/0x380 worker_thread+0x12a/0x2a0 kthread+0xe3/0x110 ret_from_fork+0x30/0x50 ret_from_fork_asm+0x1b/0x30 stack_count: 8641 This patch (of 7): The very first entry of stack_record gets a handle of 0, but this is wrong because stackdepot treats a 0-handle as a non-valid one. E.g: See the check in stack_depot_fetch() Fix this by adding and offset of 1. This bug has been lurking since the very beginning of stackdepot, but no one really cared as it seems. Because of that I am not adding a Fixes tag. Link: https://lkml.kernel.org/r/20240215215907.20121-1-osalvador@suse.de Link: https://lkml.kernel.org/r/20240215215907.20121-2-osalvador@suse.de Co-developed-by: Marco Elver <elver@google.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Oscar Salvador <osalvador@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: use variable size records for non-evictable entriesMarco Elver2024-02-231-123/+127
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the introduction of stack depot evictions, each stack record is now fixed size, so that future reuse after an eviction can safely store differently sized stack traces. In all cases that do not make use of evictions, this wastes lots of space. Fix it by re-introducing variable size stack records (up to the max allowed size) for entries that will never be evicted. We know if an entry will never be evicted if the flag STACK_DEPOT_FLAG_GET is not provided, since a later stack_depot_put() attempt is undefined behavior. With my current kernel config that enables KASAN and also SLUB owner tracking, I observe (after a kernel boot) a whopping reduction of 296 stack depot pools, which translates into 4736 KiB saved. The savings here are from SLUB owner tracking only, because KASAN generic mode still uses refcounting. Before: pools: 893 allocations: 29841 frees: 6524 in_use: 23317 freelist_size: 3454 After: pools: 597 refcounted_allocations: 17547 refcounted_frees: 6477 refcounted_in_use: 11070 freelist_size: 3497 persistent_count: 12163 persistent_bytes: 1717008 [elver@google.com: fix -Wstringop-overflow warning] Link: https://lore.kernel.org/all/20240201135747.18eca98e@canb.auug.org.au/ Link: https://lkml.kernel.org/r/20240201090434.1762340-1-elver@google.com Link: https://lore.kernel.org/all/CABXGCsOzpRPZGg23QqJAzKnqkZPKzvieeg=W7sgjgi3q0pBo0g@mail.gmail.com/ Link: https://lkml.kernel.org/r/20240129100708.39460-1-elver@google.com Link: https://lore.kernel.org/all/CABXGCsOzpRPZGg23QqJAzKnqkZPKzvieeg=W7sgjgi3q0pBo0g@mail.gmail.com/ Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces") Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: make fast paths lock-less againMarco Elver2024-01-251-111/+211
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the introduction of the pool_rwlock (reader-writer lock), several fast paths end up taking the pool_rwlock as readers. Furthermore, stack_depot_put() unconditionally takes the pool_rwlock as a writer. Despite allowing readers to make forward-progress concurrently, reader-writer locks have inherent cache contention issues, which does not scale well on systems with large CPU counts. Rework the synchronization story of stack depot to again avoid taking any locks in the fast paths. This is done by relying on RCU-protected list traversal, and the NMI-safe subset of RCU to delay reuse of freed stack records. See code comments for more details. Along with the performance issues, this also fixes incorrect nesting of rwlock within a raw_spinlock, given that stack depot should still be usable from anywhere: | [ BUG: Invalid wait context ] | ----------------------------- | swapper/0/1 is trying to lock: | ffffffff89869be8 (pool_rwlock){..--}-{3:3}, at: stack_depot_save_flags | other info that might help us debug this: | context-{5:5} | 2 locks held by swapper/0/1: | #0: ffffffff89632440 (rcu_read_lock){....}-{1:3}, at: __queue_work | #1: ffff888100092018 (&pool->lock){-.-.}-{2:2}, at: __queue_work <-- raw_spin_lock Stack depot usage stats are similar to the previous version after a KASAN kernel boot: $ cat /sys/kernel/debug/stackdepot/stats pools: 838 allocations: 29865 frees: 6604 in_use: 23261 freelist_size: 1879 The number of pools is the same as previously. The freelist size is minimally larger, but this may also be due to variance across system boots. This shows that even though we do not eagerly wait for the next RCU grace period (such as with synchronize_rcu() or call_rcu()) after freeing a stack record - requiring depot_pop_free() to "poll" if an entry may be used - new allocations are very likely to happen in later RCU grace periods. Link: https://lkml.kernel.org/r/20240118110216.2539519-2-elver@google.com Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces") Reported-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: add stats counters exported via debugfsMarco Elver2024-01-251-0/+53
| | | | | | | | | | | | | | | | | | | | | | | | | Add a few basic stats counters for stack depot that can be used to derive if stack depot is working as intended. This is a snapshot of the new stats after booting a system with a KASAN-enabled kernel: $ cat /sys/kernel/debug/stackdepot/stats pools: 838 allocations: 29861 frees: 6561 in_use: 23300 freelist_size: 1840 Generally, "pools" should be well below the max; once the system is booted, "in_use" should remain relatively steady. Link: https://lkml.kernel.org/r/20240118110216.2539519-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: add printk_deferred_enter/exit guardsAndrey Konovalov2023-12-291-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "lib/stackdepot, kasan: fixes for stack eviction series", v3. A few fixes for the stack depot eviction series ("stackdepot: allow evicting stack traces"). This patch (of 5): Stack depot functions can be called from various contexts that do allocations, including with console locks taken. At the same time, stack depot functions might print WARNING's or refcount-related failures. This can cause a deadlock on console locks. Add printk_deferred_enter/exit guards to stack depot to avoid this. Link: https://lkml.kernel.org/r/cover.1703020707.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/82092f9040d075a161d1264377d51e0bac847e8a.1703020707.git.andreyknvl@google.com Fixes: 108be8def46e ("lib/stackdepot: allow users to evict stack traces") Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB") Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Closes: https://lore.kernel.org/all/000000000000f56750060b9ad216@google.com/ Reviewed-by: Marco Elver <elver@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: adjust DEPOT_POOLS_CAP for KMSANAndrey Konovalov2023-12-101-0/+10
| | | | | | | | | | | | | | | | | | | | | | | | | KMSAN is frequently used in fuzzing scenarios and thus saves a lot of stack traces. As KMSAN does not support evicting stack traces from the stack depot, the stack depot capacity might be reached quickly with large stack records. Adjust the maximum number of stack depot pools for this case. The average size of a stack trace saved into the stack depot is ~16 frames. Thus, adjust the maximum pools number accordingly to keep the maximum number of stack traces that can be saved into the stack depot similar to the one that was allowed before the stack trace eviction changes. Link: https://lkml.kernel.org/r/301a115cf7ce8ddb42ef6de9151c2bb76ba728fc.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: allow users to evict stack tracesAndrey Konovalov2023-12-101-1/+36
| | | | | | | | | | | | | | | | | | | | | | | | | Add stack_depot_put, a function that decrements the reference counter on a stack record and removes it from the stack depot once the counter reaches 0. Internally, when removing a stack record, the function unlinks it from the hash table bucket and returns to the freelist. With this change, the users of stack depot can call stack_depot_put when keeping a stack trace in the stack depot is not needed anymore. This allows avoiding polluting the stack depot with irrelevant stack traces and thus have more space to store the relevant ones before the stack depot reaches its capacity. Link: https://lkml.kernel.org/r/1d1ad5692ee43d4fc2b3fd9d221331d30b36123f.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: add refcount for recordsAndrey Konovalov2023-12-101-2/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | Add a reference counter for how many times a stack records has been added to stack depot. Add a new STACK_DEPOT_FLAG_GET flag to stack_depot_save_flags that instructs the stack depot to increment the refcount. Do not yet decrement the refcount; this is implemented in one of the following patches. Do not yet enable any users to use the flag to avoid overflowing the refcount. This is preparatory patch for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/a3fc14a2359d019d2a008d4ff8b46a665371ffee.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot, kasan: add flags to __stack_depot_save and renameAndrey Konovalov2023-12-101-5/+11
| | | | | | | | | | | | | | | | | | | | | Change the bool can_alloc argument of __stack_depot_save to a u32 argument that accepts a set of flags. The following patch will add another flag to stack_depot_save_flags besides the existing STACK_DEPOT_FLAG_CAN_ALLOC. Also rename the function to stack_depot_save_flags, as __stack_depot_save is a cryptic name, Link: https://lkml.kernel.org/r/645fa15239621eebbd3a10331e5864b718839512.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: use list_head for stack record linksAndrey Konovalov2023-12-101-37/+50
| | | | | | | | | | | | | | | | | | | | Switch stack_record to use list_head for links in the hash table and in the freelist. This will allow removing entries from the hash table buckets. This is preparatory patch for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/4787d9a584cd33433d9ee1846b17fa3d3e1987ad.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: use read/write lockAndrey Konovalov2023-12-101-41/+46
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, stack depot uses the following locking scheme: 1. Lock-free accesses when looking up a stack record, which allows to have multiple users to look up records in parallel; 2. Spinlock for protecting the stack depot pools and the hash table when adding a new record. For implementing the eviction of stack traces from stack depot, the lock-free approach is not going to work anymore, as we will need to be able to also remove records from the hash table. Convert the spinlock into a read/write lock, and drop the atomic accesses, as they are no longer required. Looking up stack traces is now protected by the read lock and adding new records - by the write lock. One of the following patches will add a new function for evicting stack records, which will be protected by the write lock as well. With this change, multiple users can still look up records in parallel. This is preparatory patch for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/9f81ffcc4bb422ebb6326a65a770bf1918634cbb.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: store free stack records in a freelistAndrey Konovalov2023-12-101-49/+82
| | | | | | | | | | | | | | | | | | | | | | | | Instead of using the global pool_offset variable to find a free slot when storing a new stack record, mainlain a freelist of free slots within the allocated stack pools. A global next_stack variable is used as the head of the freelist, and the next field in the stack_record struct is reused as freelist link (when the record is not in the freelist, this field is used as a link in the hash table). This is preparatory patch for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/b9e4c79955c2121b69301778643b203d3fb09ccc.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: store next pool pointer in new_poolAndrey Konovalov2023-12-101-1/+5
| | | | | | | | | | | | | | | | | | | Instead of using the last pointer in stack_pools for storing the pointer to a new pool (which does not yet store any stack records), use a new new_pool variable. This a purely code readability change: it seems more logical to store the pointer to a pool with a special meaning in a dedicated variable. Link: https://lkml.kernel.org/r/448bc18296c16bef95cb3167697be6583dcc8ce3.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename next_pool_required to new_pool_requiredAndrey Konovalov2023-12-101-25/+24
| | | | | | | | | | | | | | | | | | Rename next_pool_required to new_pool_required. This a purely code readability change: the following patch will change stack depot to store the pointer to the new pool in a separate variable, and "new" seems like a more logical name. Link: https://lkml.kernel.org/r/fd7cd6c6eb250c13ec5d2009d75bb4ddd1470db9.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rework helpers for depot_alloc_stackAndrey Konovalov2023-12-101-37/+49
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Split code in depot_alloc_stack and depot_init_pool into 3 functions: 1. depot_keep_next_pool that keeps preallocated memory for the next pool if required. 2. depot_update_pools that moves on to the next pool if there's no space left in the current pool, uses preallocated memory for the new current pool if required, and calls depot_keep_next_pool otherwise. 3. depot_alloc_stack that calls depot_update_pools and then allocates a stack record as before. This makes it somewhat easier to follow the logic of depot_alloc_stack and also serves as a preparation for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/71fb144d42b701fcb46708d7f4be6801a4a8270e.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: fix and clean-up atomic annotationsAndrey Konovalov2023-12-101-15/+14
| | | | | | | | | | | | | | | | | | | Drop smp_load_acquire from next_pool_required in depot_init_pool, as both depot_init_pool and the all smp_store_release's to this variable are executed under the stack depot lock. Also simplify and clean up comments accompanying the use of atomic accesses in the stack depot code. Link: https://lkml.kernel.org/r/c118ef044d8db80248d9e1f14592c72e8429e9d9.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: use fixed-sized slots for stack recordsAndrey Konovalov2023-12-101-4/+9
| | | | | | | | | | | | | | | | | | | | | | | | Instead of storing stack records in stack depot pools one right after another, use fixed-sized slots. Add a new Kconfig option STACKDEPOT_MAX_FRAMES that allows to select the size of the slot in frames. Use 64 as the default value, which is the maximum stack trace size both KASAN and KMSAN use right now. Also add descriptions for other stack depot Kconfig options. This is preparatory patch for implementing the eviction of stack records from the stack depot. Link: https://lkml.kernel.org/r/dce7d030a99ff61022509665187fac45b0827298.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: add depot_fetch_stack helperAndrey Konovalov2023-12-101-17/+28
| | | | | | | | | | | | | | | | | | Add a helper depot_fetch_stack function that fetches the pointer to a stack record. With this change, all static depot_* functions now operate on stack pools and the exported stack_depot_* functions operate on the hash table. Link: https://lkml.kernel.org/r/170d8c202f29dc8e3d5491ee074d1e9e029a46db.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: drop valid bit from handlesAndrey Konovalov2023-12-101-5/+2
| | | | | | | | | | | | | | Stack depot doesn't use the valid bit in handles in any way, so drop it. Link: https://lkml.kernel.org/r/34969bba2ca6e012c6ad071767197dee64dc5723.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: simplify __stack_depot_saveAndrey Konovalov2023-12-101-5/+4
| | | | | | | | | | | | | | | | | | The retval local variable in __stack_depot_save has the union type handle_parts, but the function never uses anything but the union's handle field. Define retval simply as depot_stack_handle_t to simplify the code. Link: https://lkml.kernel.org/r/3b0763c8057a1cf2f200ff250a5f9580ee36a28c.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: check disabled flag when fetchingAndrey Konovalov2023-12-101-1/+1
| | | | | | | | | | | | | | | Do not try fetching a stack trace from the stack depot if the stack_depot_disabled flag is enabled. Link: https://lkml.kernel.org/r/c3bfa3b7ab00b2e48ab75a3fbb9c67555777cb08.1700502145.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: print disabled message only if truly disabledAndrey Konovalov2023-12-101-9/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "stackdepot: allow evicting stack traces", v4. Currently, the stack depot grows indefinitely until it reaches its capacity. Once that happens, the stack depot stops saving new stack traces. This creates a problem for using the stack depot for in-field testing and in production. For such uses, an ideal stack trace storage should: 1. Allow saving fresh stack traces on systems with a large uptime while limiting the amount of memory used to store the traces; 2. Have a low performance impact. Implementing #1 in the stack depot is impossible with the current keep-forever approach. This series targets to address that. Issue #2 is left to be addressed in a future series. This series changes the stack depot implementation to allow evicting unneeded stack traces from the stack depot. The users of the stack depot can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and stack_depot_put APIs. Internal changes to the stack depot code include: 1. Storing stack traces in fixed-frame-sized slots (vs precisely-sized slots in the current implementation); the slot size is controlled via CONFIG_STACKDEPOT_MAX_FRAMES (default: 64 frames); 2. Keeping available slots in a freelist (vs keeping an offset to the next free slot); 3. Using a read/write lock for synchronization (vs a lock-free approach combined with a spinlock). This series also integrates the eviction functionality into KASAN: the tag-based modes evict stack traces when the corresponding entry leaves the stack ring, and Generic KASAN evicts stack traces for objects once those leave the quarantine. With KASAN, despite wasting some space on rounding up the size of each stack record, the total memory consumed by stack depot gets saturated due to the eviction of irrelevant stack traces from the stack depot. With the tag-based KASAN modes, the average total amount of memory used for stack traces becomes ~0.5 MB (with the current default stack ring size of 32k entries and the default CONFIG_STACKDEPOT_MAX_FRAMES of 64). With Generic KASAN, the stack traces take up ~1 MB per 1 GB of RAM (as the quarantine's size depends on the amount of RAM). However, with KMSAN, the stack depot ends up using ~4x more memory per a stack trace than before. Thus, for KMSAN, the stack depot capacity is increased accordingly. KMSAN uses a lot of RAM for shadow memory anyway, so the increased stack depot memory usage will not make a significant difference. Other users of the stack depot do not save stack traces as often as KASAN and KMSAN. Thus, the increased memory usage is taken as an acceptable trade-off. In the future, these other users can take advantage of the eviction API to limit the memory waste. There is no measurable boot time performance impact of these changes for KASAN on x86-64. I haven't done any tests for arm64 modes (the stack depot without performance optimizations is not suitable for intended use of those anyway), but I expect a similar result. Obtaining and copying stack trace frames when saving them into stack depot is what takes the most time. This series does not yet provide a way to configure the maximum size of the stack depot externally (e.g. via a command-line parameter). This will be added in a separate series, possibly together with the performance improvement changes. This patch (of 22): Currently, if stack_depot_disable=off is passed to the kernel command-line after stack_depot_disable=on, stack depot prints a message that it is disabled, while it is actually enabled. Fix this by moving printing the disabled message to stack_depot_early_init. Place it before the __stack_depot_early_init_requested check, so that the message is printed even if early stack depot init has not been requested. Also drop the stack_table = NULL assignment from disable_stack_depot, as stack_table is NULL by default. Link: https://lkml.kernel.org/r/cover.1700502145.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/73a25c5fff29f3357cd7a9330e85e09bc8da2cbe.1700502145.git.andreyknvl@google.com Fixes: e1fdc403349c ("lib: stackdepot: add support to disable stack depot") Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Marco Elver <elver@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: kmsan: mark API outputs as initializedAlexander Potapenko2023-03-281-0/+12
| | | | | | | | | | | | | | | | | | KMSAN does not instrument stackdepot and may treat memory allocated by it as uninitialized. This is not a problem for KMSAN itself, because its functions calling stackdepot API are also not instrumented. But other kernel features (e.g. netdev tracker) may access stack depot from instrumented code, which will lead to false positives, unless we explicitly mark stackdepot outputs as initialized. Link: https://lkml.kernel.org/r/20230306111322.205724-1-glider@google.com Signed-off-by: Alexander Potapenko <glider@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Suggested-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Marco Elver <elver@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: move documentation comments to stackdepot.hAndrey Konovalov2023-02-161-87/+0
| | | | | | | | | | | | | | Move all interface- and usage-related documentation comments to include/linux/stackdepot.h. It makes sense to have them in the header where they are available to the interface users. [akpm@linux-foundation.org: grammar fix, per Alexander] Link: https://lkml.kernel.org/r/fbfee41495b306dd8881f9b1c1b80999c885e82f.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: various comments clean-upsAndrey Konovalov2023-02-161-61/+59
| | | | | | | | | | | | | | | | | Clean up comments in include/linux/stackdepot.h and lib/stackdepot.c: 1. Rework the initialization comment in stackdepot.h. 2. Rework the header comment in stackdepot.c. 3. Various clean-ups for other comments. Also adjust whitespaces for find_stack and depot_alloc_stack call sites. No functional changes. Link: https://lkml.kernel.org/r/5836231b7954355e2311fc9b5870f697ea8e1f7d.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: annotate racy pool_index accessesAndrey Konovalov2023-02-161-4/+13
| | | | | | | | | | | | | | | | | | | Accesses to pool_index are protected by pool_lock everywhere except in a sanity check in stack_depot_fetch. The read access there can race with the write access in depot_alloc_stack. Use WRITE/READ_ONCE() to annotate the racy accesses. As the sanity check is only used to print a warning in case of a violation of the stack depot interface usage, it does not make a lot of sense to use proper synchronization. [andreyknvl@google.com: s/pool_index/pool_index_cached/ in stack_depot_fetch()] Link: https://lkml.kernel.org/r/95cf53f0da2c112aa2cc54456cbcd6975c3ff343.1676129911.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/359ac9c13cd0869c56740fb2029f505e41593830.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stacktrace, kasan, kmsan: rework extra_bits interfaceAndrey Konovalov2023-02-161-9/+33
| | | | | | | | | | | | | | | | | | | | | | The current implementation of the extra_bits interface is confusing: passing extra_bits to __stack_depot_save makes it seem that the extra bits are somehow stored in stack depot. In reality, they are only embedded into a stack depot handle and are not used within stack depot. Drop the extra_bits argument from __stack_depot_save and instead provide a new stack_depot_set_extra_bits function (similar to the exsiting stack_depot_get_extra_bits) that saves extra bits into a stack depot handle. Update the callers of __stack_depot_save to use the new interace. This change also fixes a minor issue in the old code: __stack_depot_save does not return NULL if saving stack trace fails and extra_bits is used. Link: https://lkml.kernel.org/r/317123b5c05e2f82854fc55d8b285e0869d3cb77.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename next_pool_inited to next_pool_requiredAndrey Konovalov2023-02-161-9/+21
| | | | | | | | | | | | | | | | Stack depot uses next_pool_inited to mark that either the next pool is initialized or the limit on the number of pools is reached. However, the flag name only reflects the former part of its purpose, which is confusing. Rename next_pool_inited to next_pool_required and invert its value. Also annotate usages of next_pool_required with comments. Link: https://lkml.kernel.org/r/484fd2695dff7a9bdc437a32f8a6ee228535aa02.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: annotate depot_init_pool and depot_alloc_stackAndrey Konovalov2023-02-161-10/+24
| | | | | | | | | | | | | | Clean up the exisiting comments and add new ones to depot_init_pool and depot_alloc_stack. As a part of the clean-up, remove mentions of which variable is accessed by smp_store_release and smp_load_acquire: it is clear as is from the code. Link: https://lkml.kernel.org/r/f80b02951364e6b40deda965b4003de0cd1a532d.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stacktrace: drop impossible WARN_ON for depot_init_poolAndrey Konovalov2023-02-161-7/+5
| | | | | | | | | | | | | | | | | | | | | | depot_init_pool has two call sites: 1. In depot_alloc_stack with a potentially NULL prealloc. 2. In __stack_depot_save with a non-NULL prealloc. At the same time depot_init_pool can only return false when prealloc is NULL. As the second call site makes sure that prealloc is not NULL, the WARN_ON there can never trigger. Thus, drop the WARN_ON and also move the prealloc check from depot_init_pool to its first call site. Also change the return type of depot_init_pool to void as it now always returns true. Link: https://lkml.kernel.org/r/ce149f9bdcbc80a92549b54da67eafb27f846b7b.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename init_stack_poolAndrey Konovalov2023-02-161-5/+5
| | | | | | | | | | | | Rename init_stack_pool to depot_init_pool to align the name with depot_alloc_stack. No functional changes. Link: https://lkml.kernel.org/r/23106a3e291d8df0aba33c0e2fe86dc596286479.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename handle and pool constantsAndrey Konovalov2023-02-161-29/+27
| | | | | | | | | | | | | | | | | | Change the "STACK_ALLOC_" prefix to "DEPOT_" for the constants that define the number of bits in stack depot handles and the maximum number of pools. The old prefix is unclear and makes wonder about how these constants are related to stack allocations. The new prefix is also shorter. Also simplify the comment for DEPOT_POOL_ORDER. No functional changes. Link: https://lkml.kernel.org/r/84fcceb0acc261a356a0ad4bdfab9ff04bea2445.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename slab to poolAndrey Konovalov2023-02-161-53/+53
| | | | | | | | | | | | | | | | | | | | | Use "pool" instead of "slab" for naming memory regions stack depot uses to store stack traces. Using "slab" is confusing, as stack depot pools have nothing to do with the slab allocator. Also give better names to pool-related global variables: change "depot_" prefix to "pool_" to point out that these variables are related to stack depot pools. Also rename the slabindex (poolindex) field in handle_parts to pool_index to align its name with the pool_index global variable. No functional changes. Link: https://lkml.kernel.org/r/923c507edb350c3b6ef85860f36be489dfc0ad21.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename hash table constants and variablesAndrey Konovalov2023-02-161-21/+21
| | | | | | | | | | | | | | | | | | | | Give more meaningful names to hash table-related constants and variables: 1. Rename STACK_HASH_SCALE to STACK_HASH_TABLE_SCALE to point out that it is related to scaling the hash table. 2. Rename STACK_HASH_ORDER_MIN/MAX to STACK_BUCKET_NUMBER_ORDER_MIN/MAX to point out that it is related to the number of hash table buckets. 3. Rename stack_hash_order to stack_bucket_number_order for the same reason as #2. No functional changes. Link: https://lkml.kernel.org/r/f166dd6f3cb2378aea78600714393dd568c33ee9.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: reorder and annotate global variablesAndrey Konovalov2023-02-161-10/+17
| | | | | | | | | | | | | | | | Group stack depot global variables by their purpose: 1. Hash table-related variables, 2. Slab-related variables, and add comments. Also clean up comments for hash table-related constants. Link: https://lkml.kernel.org/r/5606a6c70659065a25bee59cd10e57fc60bb4110.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: lower the indentation in stack_depot_initAndrey Konovalov2023-02-161-33/+37
| | | | | | | | | | | | stack_depot_init does most things inside an if check. Move them out and use a goto statement instead. No functional changes. Link: https://lkml.kernel.org/r/8e382f1f0c352e4b2ad47326fec7782af961fe8e.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: annotate init and early init functionsAndrey Konovalov2023-02-161-6/+21
| | | | | | | | | | | | | | | | Add comments to stack_depot_early_init and stack_depot_init to explain certain parts of their implementation. Also add a pr_info message to stack_depot_early_init similar to the one in stack_depot_init. Also move the scale variable in stack_depot_init to the scope where it is being used. Link: https://lkml.kernel.org/r/d17fbfbd4d73f38686c5e3d4824a6d62047213a1.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: rename stack_depot_disableAndrey Konovalov2023-02-161-10/+10
| | | | | | | | | | | | | | | | | Rename stack_depot_disable to stack_depot_disabled to make its name look similar to the names of other stack depot flags. Also put stack_depot_disabled's definition together with the other flags. Also rename is_stack_depot_disabled to disable_stack_depot: this name looks more conventional for a function that processes a boot parameter. No functional changes. Link: https://lkml.kernel.org/r/d78a07d222e689926e5ead229e4a2e3d87dc9aa7.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot, mm: rename stack_depot_want_early_initAndrey Konovalov2023-02-161-5/+5
| | | | | | | | | | | | | | | | | Rename stack_depot_want_early_init to stack_depot_request_early_init. The old name is confusing, as it hints at returning some kind of intention of stack depot. The new name reflects that this function requests an action from stack depot instead. No functional changes. [akpm@linux-foundation.org: update mm/kmemleak.c] Link: https://lkml.kernel.org/r/359f31bf67429a06e630b4395816a967214ef753.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: use pr_fmt to define message formatAndrey Konovalov2023-02-161-4/+6
| | | | | | | | | | Use pr_fmt to define the format for printing stack depot messages instead of duplicating the "Stack Depot" prefix in each message. Link: https://lkml.kernel.org/r/3d09db0171a0e92ff3eb0ee74de74558bc9b56c4.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: put functions in logical orderAndrey Konovalov2023-02-161-157/+157
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "lib/stackdepot: fixes and clean-ups", v2. A set of fixes, comments, and clean-ups I came up with while reading the stack depot code. This patch (of 18): Put stack depot functions' declarations and definitions in a more logical order: 1. Functions that save stack traces into stack depot. 2. Functions that fetch and print stack traces. 3. stack_depot_get_extra_bits that operates on stack depot handles and does not interact with the stack depot storage. No functional changes. Link: https://lkml.kernel.org/r/cover.1676063693.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/daca1319b665d826b94c596b992a8d8117846147.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Marco Elver <elver@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* stackdepot: reserve 5 extra bits in depot_stack_handle_tAlexander Potapenko2022-10-031-5/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some users (currently only KMSAN) may want to use spare bits in depot_stack_handle_t. Let them do so by adding @extra_bits to __stack_depot_save() to store arbitrary flags, and providing stack_depot_get_extra_bits() to retrieve those flags. Also adapt KASAN to the new prototype by passing extra_bits=0, as KASAN does not intend to store additional information in the stack handle. Link: https://lkml.kernel.org/r/20220915150417.722975-3-glider@google.com Signed-off-by: Alexander Potapenko <glider@google.com> Reviewed-by: Marco Elver <elver@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Eric Biggers <ebiggers@kernel.org> Cc: Eric Dumazet <edumazet@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Ilya Leoshkevich <iii@linux.ibm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Kees Cook <keescook@chromium.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vegard Nossum <vegard.nossum@oracle.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: replace CONFIG_STACK_HASH_ORDER with automatic sizingVlastimil Babka2022-07-171-10/+49
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As Linus explained [1], setting the stackdepot hash table size as a config option is suboptimal, especially as stackdepot becomes a dependency of less "expert" subsystems than initially (e.g. DRM, networking, SLUB_DEBUG): : (a) it introduces a new compile-time question that isn't sane to ask : a regular user, but is now exposed to regular users. : (b) this by default uses 1MB of memory for a feature that didn't in : the past, so now if you have small machines you need to make sure you : make a special kernel config for them. Ideally we would employ rhashtable for fully automatic resizing, which should be feasible for many of the new users, but problematic for the original users with restricted context that call __stack_depot_save() with can_alloc == false, i.e. KASAN. However we can easily remove the config option and scale the hash table automatically with system memory. The STACK_HASH_MASK constant becomes stack_hash_mask variable and is used only in one mask operation, so the overhead should be negligible to none. For early allocation we can employ the existing alloc_large_system_hash() function and perform similar scaling for the late allocation. The existing limits of the config option (between 4k and 1M buckets) are preserved, and scaling factor is set to one bucket per 16kB memory so on 64bit the max 1M buckets (8MB memory) is achieved with 16GB system, while a 1GB system will use 512kB. Because KASAN is reported to need the maximum number of buckets even with smaller amounts of memory [2], set it as such when kasan_enabled(). If needed, the automatic scaling could be complemented with a boot-time kernel parameter, but it feels pointless to add it without a specific use case. [1] https://lore.kernel.org/all/CAHk-=wjC5nS+fnf6EzRD9yQRJApAhxx7gRB87ZV+pAWo9oVrTg@mail.gmail.com/ [2] https://lore.kernel.org/all/CACT4Y+Y4GZfXOru2z5tFPzFdaSUd+GFc6KVL=bsa0+1m197cQQ@mail.gmail.com/ Link: https://lkml.kernel.org/r/20220620150249.16814-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Dmitry Vyukov <dvyukov@google.com> Cc: Marco Elver <elver@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* lib/stackdepot: allow requesting early initialization dynamicallyVlastimil Babka2022-04-061-22/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In a later patch we want to add stackdepot support for object owner tracking in slub caches, which is enabled by slub_debug boot parameter. This creates a bootstrap problem as some caches are created early in boot when slab_is_available() is false and thus stack_depot_init() tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are already beyond memblock_free_all(). Ideally memblock allocation should fail, yet it succeeds, but later the system crashes, which is a separately handled issue. To resolve this boostrap issue in a robust way, this patch adds another way to request stack_depot_early_init(), which happens at a well-defined point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT, code that's e.g. processing boot parameters (which happens early enough) can call a new function stack_depot_want_early_init(), which sets a flag that stack_depot_early_init() will check. In this patch we also convert page_owner to this approach. While it doesn't have the bootstrap issue as slub, it's also a functionality enabled by a boot param and can thus request stack_depot_early_init() with memblock allocation instead of later initialization with kvmalloc(). As suggested by Mike, make stack_depot_early_init() only attempt memblock allocation and stack_depot_init() only attempt kvmalloc(). Also change the latter to kvcalloc(). In both cases we can lose the explicit array zeroing, which the allocations do already. As suggested by Marco, provide empty implementations of the init functions for !CONFIG_STACKDEPOT builds to simplify the callers. [1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@ip-172-31-19-208.ap-northeast-1.compute.internal/ Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Suggested-by: Mike Rapoport <rppt@linux.ibm.com> Suggested-by: Marco Elver <elver@google.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Marco Elver <elver@google.com> Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Acked-by: David Rientjes <rientjes@google.com>
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