On Wed, Aug 07, 2019 at 01:28:27PM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" <rost...@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 > 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> > Signed-off-by: Steven Rostedt (VMware) <rost...@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..961e98618db4 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_RET_ADDR_AFTER_LOCAL_VARS, 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_RET_ADDR_AFTER_LOCAL_VARS 1
FWIW (with whatever this got renamed to): Acked-by: Mark Rutland <mark.rutl...@arm.com> Thanks, Mark.
