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function_graph: Handle tail calls for stack unwinding

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For the tail-call, there would be 2 or more ftrace_ret_stacks on the
ret_stack, which records "return_to_handler" as the return address except
for the last one.  But on the real stack, there should be 1 entry because
tail-call reuses the return address on the stack and jump to the next
function.

In ftrace_graph_ret_addr() that is used for stack unwinding, skip tail
calls as a real stack unwinder would do.

Link: https://lore.kernel.org/linux-trace-kernel/171509096221.162236.8806372072523195752.stgit@devnote2
Link: https://lore.kernel.org/linux-trace-kernel/20240603190821.717065217@goodmis.org

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guo Ren <guoren@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu (Google) 2024-06-03 15:07:09 -04:00 committed by Steven Rostedt (Google)
parent 7aa1eaef9f
commit 375bb57292
1 changed files with 16 additions and 3 deletions
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19
kernel/trace/fgraph.c
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@ -594,16 +594,26 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
unsigned long ret, unsigned long *retp)
{
struct ftrace_ret_stack *ret_stack;
unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler);
int i = task->curr_ret_stack;
if (ret != (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
if (ret != return_handler)
return ret;
while (i > 0) {
ret_stack = get_ret_stack(current, i, &i);
if (!ret_stack)
break;
if (ret_stack->retp == retp)
/*
* For the tail-call, there would be 2 or more ftrace_ret_stacks on
* the ret_stack, which records "return_to_handler" as the return
* address except for the last one.
* But on the real stack, there should be 1 entry because tail-call
* reuses the return address on the stack and jump to the next function.
* Thus we will continue to find real return address.
*/
if (ret_stack->retp == retp &&
ret_stack->ret != return_handler)
return ret_stack->ret;
}
@ -614,10 +624,11 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
unsigned long ret, unsigned long *retp)
{
struct ftrace_ret_stack *ret_stack;
unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler);
int offset = task->curr_ret_stack;
int i;
if (ret != (unsigned long)dereference_kernel_function_descriptor(return_to_handler))
if (ret != return_handler)
return ret;
if (!idx)
@ -626,6 +637,8 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
i = *idx;
do {
ret_stack = get_ret_stack(task, offset, &offset);
if (ret_stack && ret_stack->ret == return_handler)
continue;
i--;
} while (i >= 0 && ret_stack);