Messages in this thread | | | Subject | Re: [PATCH 1/2 v2] tracing/arm64: Have max stack tracer handle the case of return address after data | From | Jiping Ma <> | Date | Fri, 9 Aug 2019 10:17:19 +0800 |
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On 2019年08月09日 01:24, Steven Rostedt wrote: > On Thu, 8 Aug 2019 18:11:53 +0100 > Will Deacon <will@kernel.org> wrote: > >>> We could make it more descriptive of what it will do and not the reason >>> for why it is done... >>> >>> >>> ARCH_FTRACE_SHIFT_STACK_TRACER >> Acked-by: Will Deacon <will@kernel.org> > Thanks Will! > > Here's the official patch. > > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org> > > 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_RET_ADDR_AFTER_LOCAL_VARS that an architecture may set
ARCH_FTRACE_SHIFT_STACK_TRACER is used in the code.
Jiping
> 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.ma2@windriver.com > > Reported-by: Jiping Ma <jiping.ma2@windriver.com> > Acked-by: Will Deacon <will@kernel.org> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > arch/arm64/include/asm/ftrace.h | 13 +++++++++++++ > kernel/trace/trace_stack.c | 14 ++++++++++++++ > 2 files changed, 27 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 5ab5200b2bdc..d48667b04c41 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -14,6 +14,19 @@ > #define MCOUNT_ADDR ((unsigned long)_mcount) > #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE > > +/* > + * 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__ > #include <linux/compat.h> > > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index 5d16f73898db..642a850af81a 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -158,6 +158,20 @@ static void check_stack(unsigned long ip, unsigned long *stack) > i++; > } > > +#ifdef ARCH_FTRACE_SHIFT_STACK_TRACER > + /* > + * Some archs will store the link register before calling > + * nested functions. This means the saved return address > + * comes after the local storage, and we need to shift > + * for that. > + */ > + if (x > 1) { > + memmove(&stack_trace_index[0], &stack_trace_index[1], > + sizeof(stack_trace_index[0]) * (x - 1)); > + x--; > + } > +#endif > + > stack_trace_nr_entries = x; > > if (task_stack_end_corrupted(current)) {
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