From: Zqiang <qiang.zh...@windriver.com> This change is similar to the following patch, it also suitable for arm.
[ Author: Steven Rostedt (VMware) Email: rost...@goodmis.org Subject: tracing/arm64: Have max stack tracer handle the case of return address after data Date: Fri, 9 Aug 2019 02:15:05 +0000 Most archs (well at least x86) store the function call return address on the stack before storing the local variables for the function. The max stack tracer depends on this in its algorithm to display the stack size of each function it finds in the back trace. Some archs (arm64), may store the return address (from its link register) just before calling a nested function. There's no reason to save the link register on leaf functions, as it wont be updated. This breaks the algorithm of the max stack tracer. Add a new define ARCH_FTRACE_SHIFT_STACK_TRACER that an architecture may set if it stores the return address (link register) after it stores the function's local variables, and have the stack trace shift the values of the mapped stack size to the appropriate functions. Link: 20190802094103.163576-1-jiping....@windriver.com Reported-by: Jiping Ma <jiping....@windriver.com> Acked-by: Will Deacon <w...@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> Signed-off-by: Jiping Ma <jiping....@windriver.com> ] Signed-off-by: Zqiang <qiang.zh...@windriver.com> --- arch/arm/include/asm/ftrace.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index 48ec1d0337da..c70f8fb13ae3 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -10,6 +10,19 @@ #define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc)) #define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ +/* + * Currently, gcc tends to save the link register after the local variables + * on the stack. This causes the max stack tracer to report the function + * frame sizes for the wrong functions. By defining + * ARCH_FTRACE_SHIFT_STACK_TRACER, it will tell the stack tracer to expect + * to find the return address on the stack after the local variables have + * been set up. + * + * Note, this may change in the future, and we will need to deal with that + * if it were to happen. + */ +#define ARCH_FTRACE_SHIFT_STACK_TRACER 1 + #ifndef __ASSEMBLY__ extern void __gnu_mcount_nc(void); -- 2.29.2
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