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| author | Andy Lutomirski <luto@kernel.org> | 2017-11-02 00:59:13 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-11-02 11:04:46 +0100 |
| commit | 20bb83443ea79087b5e5f8dab4e9d80bb9bf7acb (patch) | |
| tree | 0f12b47f202f739b1e22ee6e6734273a8071ef9b /arch/x86/kernel/process.c | |
| parent | f16b3da1dc936c0f8121741d0a1731bf242f2f56 (diff) | |
| download | linux-stable-20bb83443ea79087b5e5f8dab4e9d80bb9bf7acb.tar.gz linux-stable-20bb83443ea79087b5e5f8dab4e9d80bb9bf7acb.tar.bz2 linux-stable-20bb83443ea79087b5e5f8dab4e9d80bb9bf7acb.zip | |
x86/entry/64: Stop initializing TSS.sp0 at boot
In my quest to get rid of thread_struct::sp0, I want to clean up or
remove all of its readers. Two of them are in cpu_init() (32-bit and
64-bit), and they aren't needed. This is because we never enter
userspace at all on the threads that CPUs are initialized in.
Poison the initial TSS.sp0 and stop initializing it on CPU init.
The comment text mostly comes from Dave Hansen. Thanks!
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ee4a00540ad28c6cff475fbcc7769a4460acc861.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index bd6b85fac666..ff8a9acbcf8b 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -48,7 +48,13 @@ */ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = { .x86_tss = { - .sp0 = TOP_OF_INIT_STACK, + /* + * .sp0 is only used when entering ring 0 from a lower + * privilege level. Since the init task never runs anything + * but ring 0 code, there is no need for a valid value here. + * Poison it. + */ + .sp0 = (1UL << (BITS_PER_LONG-1)) + 1, #ifdef CONFIG_X86_32 .ss0 = __KERNEL_DS, .ss1 = __KERNEL_CS, |