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* static_call: Don't make __static_call_return0 staticChristophe Leroy2022-04-051-541/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | System.map shows that vmlinux contains several instances of __static_call_return0(): c0004fc0 t __static_call_return0 c0011518 t __static_call_return0 c00d8160 t __static_call_return0 arch_static_call_transform() uses the middle one to check whether we are setting a call to __static_call_return0 or not: c0011520 <arch_static_call_transform>: c0011520: 3d 20 c0 01 lis r9,-16383 <== r9 = 0xc001 << 16 c0011524: 39 29 15 18 addi r9,r9,5400 <== r9 += 0x1518 c0011528: 7c 05 48 00 cmpw r5,r9 <== r9 has value 0xc0011518 here So if static_call_update() is called with one of the other instances of __static_call_return0(), arch_static_call_transform() won't recognise it. In order to work properly, global single instance of __static_call_return0() is required. Fixes: 3f2a8fc4b15d ("static_call/x86: Add __static_call_return0()") Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/30821468a0e7d28251954b578e5051dc09300d04.1647258493.git.christophe.leroy@csgroup.eu
* KVM: x86: allow defining return-0 static callsPaolo Bonzini2022-02-181-0/+1
| | | | | | | | | | A few vendor callbacks are only used by VMX, but they return an integer or bool value. Introduce KVM_X86_OP_OPTIONAL_RET0 for them: if a func is NULL in struct kvm_x86_ops, it will be changed to __static_call_return0 when updating static calls. Reviewed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* static_call: Fix static_call_text_reserved() vs __initPeter Zijlstra2021-07-051-5/+8
| | | | | | | | | | | | | | It turns out that static_call_text_reserved() was reporting __init text as being reserved past the time when the __init text was freed and re-used. This is mostly harmless and will at worst result in refusing a kprobe. Fixes: 6333e8f73b83 ("static_call: Avoid kprobes on inline static_call()s") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Link: https://lore.kernel.org/r/20210628113045.106211657@infradead.org
* static_call: Fix unused variable warn w/o MODULEMatthieu Baerts2021-04-091-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | Here is the warning converted as error and reported by GCC: kernel/static_call.c: In function ‘__static_call_update’: kernel/static_call.c:153:18: error: unused variable ‘mod’ [-Werror=unused-variable] 153 | struct module *mod = site_mod->mod; | ^~~ cc1: all warnings being treated as errors make[1]: *** [scripts/Makefile.build:271: kernel/static_call.o] Error 1 This is simply because since recently, we no longer use 'mod' variable elsewhere if MODULE is unset. When using 'make tinyconfig' to generate the default kconfig, MODULE is unset. There are different ways to fix this warning. Here I tried to minimised the number of modified lines and not add more #ifdef. We could also move the declaration of the 'mod' variable inside the if-statement or directly use site_mod->mod. Fixes: 698bacefe993 ("static_call: Align static_call_is_init() patching condition") Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210326105023.2058860-1-matthieu.baerts@tessares.net
* static_call: Fix static_call_update() sanity checkPeter Zijlstra2021-03-191-1/+10
| | | | | | | | | | | | | | | | | | Sites that match init_section_contains() get marked as INIT. For built-in code init_sections contains both __init and __exit text. OTOH kernel_text_address() only explicitly includes __init text (and there are no __exit text markers). Match what jump_label already does and ignore the warning for INIT sites. Also see the excellent changelog for commit: 8f35eaa5f2de ("jump_label: Don't warn on __exit jump entries") Fixes: 9183c3f9ed710 ("static_call: Add inline static call infrastructure") Reported-by: Sumit Garg <sumit.garg@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Sumit Garg <sumit.garg@linaro.org> Link: https://lkml.kernel.org/r/20210318113610.739542434@infradead.org
* static_call: Align static_call_is_init() patching conditionPeter Zijlstra2021-03-191-10/+4
| | | | | | | | | | | | | | | | The intent is to avoid writing init code after init (because the text might have been freed). The code is needlessly different between jump_label and static_call and not obviously correct. The existing code relies on the fact that the module loader clears the init layout, such that within_module_init() always fails, while jump_label relies on the module state which is more obvious and matches the kernel logic. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Sumit Garg <sumit.garg@linaro.org> Link: https://lkml.kernel.org/r/20210318113610.636651340@infradead.org
* static_call: Fix static_call_set_init()Peter Zijlstra2021-03-191-7/+10
| | | | | | | | | | | | It turns out that static_call_set_init() does not preserve the other flags; IOW. it clears TAIL if it was set. Fixes: 9183c3f9ed710 ("static_call: Add inline static call infrastructure") Reported-by: Sumit Garg <sumit.garg@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Sumit Garg <sumit.garg@linaro.org> Link: https://lkml.kernel.org/r/20210318113610.519406371@infradead.org
* static_call: Fix the module key fixupPeter Zijlstra2021-03-061-3/+4
| | | | | | | | | | | | | | | | Provided the target address of a R_X86_64_PC32 relocation is aligned, the low two bits should be invariant between the relative and absolute value. Turns out the address is not aligned and things go sideways, ensure we transfer the bits in the absolute form when fixing up the key address. Fixes: 73f44fe19d35 ("static_call: Allow module use without exposing static_call_key") Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lkml.kernel.org/r/20210225220351.GE4746@worktop.programming.kicks-ass.net
* static_call: Allow module use without exposing static_call_keyJosh Poimboeuf2021-02-171-2/+53
| | | | | | | | | | | | | | | | | | | | | | | | When exporting static_call_key; with EXPORT_STATIC_CALL*(), the module can use static_call_update() to change the function called. This is not desirable in general. Not exporting static_call_key however also disallows usage of static_call(), since objtool needs the key to construct the static_call_site. Solve this by allowing objtool to create the static_call_site using the trampoline address when it builds a module and cannot find the static_call_key symbol. The module loader will then try and map the trampole back to a key before it constructs the normal sites list. Doing this requires a trampoline -> key associsation, so add another magic section that keeps those. Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20210127231837.ifddpn7rhwdaepiu@treble
* static_call/x86: Add __static_call_return0()Peter Zijlstra2021-02-171-0/+5
| | | | | | | | | | | | | | | | | | Provide a stub function that return 0 and wire up the static call site patching to replace the CALL with a single 5 byte instruction that clears %RAX, the return value register. The function can be cast to any function pointer type that has a single %RAX return (including pointers). Also provide a version that returns an int for convenience. We are clearing the entire %RAX register in any case, whether the return value is 32 or 64 bits, since %RAX is always a scratch register anyway. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.org
* static_call: Fix return type of static_call_initNathan Chancellor2020-10-021-2/+3
| | | | | | | | | | | | | Functions that are passed to early_initcall should be of type initcall_t, which expects a return type of int. This is not currently an error but a patch in the Clang LTO series could change that in the future. Fixes: 9183c3f9ed71 ("static_call: Add inline static call infrastructure") Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Link: https://lore.kernel.org/lkml/20200903203053.3411268-17-samitolvanen@google.com/
* static_call: Allow early initPeter Zijlstra2020-09-011-4/+66
| | | | | | | | | | | | | | | In order to use static_call() to wire up x86_pmu, we need to initialize earlier, specifically before memory allocation works; copy some of the tricks from jump_label to enable this. Primarily we overload key->next to store a sites pointer when there are no modules, this avoids having to use kmalloc() to initialize the sites and allows us to run much earlier. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20200818135805.220737930@infradead.org
* static_call: Handle tail-callsPeter Zijlstra2020-09-011-8/+13
| | | | | | | | | | | | | | GCC can turn our static_call(name)(args...) into a tail call, in which case we get a JMP.d32 into the trampoline (which then does a further tail-call). Teach objtool to recognise and mark these in .static_call_sites and adjust the code patching to deal with this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20200818135805.101186767@infradead.org
* static_call: Add simple self-test for static callsPeter Zijlstra2020-09-011-0/+43
| | | | | | Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200818135804.922581202@infradead.org
* static_call: Avoid kprobes on inline static_call()sPeter Zijlstra2020-09-011-0/+68
| | | | | | | | | Similar to how we disallow kprobes on any other dynamic text (ftrace/jump_label) also disallow kprobes on inline static_call()s. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200818135804.744920586@infradead.org
* static_call: Add inline static call infrastructureJosh Poimboeuf2020-09-011-0/+303
Add infrastructure for an arch-specific CONFIG_HAVE_STATIC_CALL_INLINE option, which is a faster version of CONFIG_HAVE_STATIC_CALL. At runtime, the static call sites are patched directly, rather than using the out-of-line trampolines. Compared to out-of-line static calls, the performance benefits are more modest, but still measurable. Steven Rostedt did some tracepoint measurements: https://lkml.kernel.org/r/20181126155405.72b4f718@gandalf.local.home This code is heavily inspired by the jump label code (aka "static jumps"), as some of the concepts are very similar. For more details, see the comments in include/linux/static_call.h. [peterz: simplified interface; merged trampolines] Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20200818135804.684334440@infradead.org
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