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Date: Fri, 18 Feb 2022 17:49:06 +0100 From: Peter Zijlstra <peterz@...radead.org> To: x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com, jpoimboe@...hat.com, andrew.cooper3@...rix.com Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, ndesaulniers@...gle.com, keescook@...omium.org, samitolvanen@...gle.com, mark.rutland@....com, alyssa.milburn@...el.com, Miroslav Benes <mbenes@...e.cz> Subject: [PATCH 04/29] x86/livepatch: Validate __fentry__ location Currently livepatch assumes __fentry__ lives at func+0, which is most likely untrue with IBT on. Override the weak klp_get_ftrace_location() function with an arch specific version that's IBT aware. Also make the weak fallback verify the location is an actual ftrace location as a sanity check. Suggested-by: Miroslav Benes <mbenes@...e.cz> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> --- arch/x86/include/asm/livepatch.h | 9 +++++++++ kernel/livepatch/patch.c | 2 +- 2 files changed, 10 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -17,4 +17,13 @@ static inline void klp_arch_set_pc(struc ftrace_instruction_pointer_set(fregs, ip); } +#define klp_get_ftrace_location klp_get_ftrace_location +static inline unsigned long klp_get_ftrace_location(unsigned long faddr) +{ + unsigned long addr = ftrace_location(faddr); + if (!addr && IS_ENABLED(CONFIG_X86_IBT)) + addr = ftrace_location(faddr + 4); + return addr; +} + #endif /* _ASM_X86_LIVEPATCH_H */ --- a/kernel/livepatch/patch.c +++ b/kernel/livepatch/patch.c @@ -133,7 +133,7 @@ static void notrace klp_ftrace_handler(u #ifndef klp_get_ftrace_location static unsigned long klp_get_ftrace_location(unsigned long faddr) { - return faddr; + return ftrace_location(faddr); } #endif
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