tracing/arm64: Have max stack tracer handle the case of return address after data (f7edb451) · Commits · 戴 / test

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.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 −0

Original line number	Diff line number	Diff line
		@@ -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>

kernel/trace/trace_stack.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -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)) {

Admin message