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authorJosh Poimboeuf <jpoimboe@redhat.com>2020-05-22 08:54:35 -0500
committerPeter Zijlstra <peterz@infradead.org>2020-05-22 19:55:17 +0200
commit187b96db5ca79423618dfa29a05c438c34f9e1f0 (patch)
treef5eea6c1e32249cfab3bc512fbe136e85d691bcc /arch
parentd7110a26e5905ec2fe3fc88bc6a538901accb72b (diff)
downloadlinux-sh-187b96db5ca79423618dfa29a05c438c34f9e1f0.tar.gz
x86/unwind/orc: Fix unwind_get_return_address_ptr() for inactive tasks
Normally, show_trace_log_lvl() scans the stack, looking for text addresses to print. In parallel, it unwinds the stack with unwind_next_frame(). If the stack address matches the pointer returned by unwind_get_return_address_ptr() for the current frame, the text address is printed normally without a question mark. Otherwise it's considered a breadcrumb (potentially from a previous call path) and it's printed with a question mark to indicate that the address is unreliable and typically can be ignored. Since the following commit: f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks") ... for inactive tasks, show_trace_log_lvl() prints *only* unreliable addresses (prepended with '?'). That happens because, for the first frame of an inactive task, unwind_get_return_address_ptr() returns the wrong return address pointer: one word *below* the task stack pointer. show_trace_log_lvl() starts scanning at the stack pointer itself, so it never finds the first 'reliable' address, causing only guesses to being printed. The first frame of an inactive task isn't a normal stack frame. It's actually just an instance of 'struct inactive_task_frame' which is left behind by __switch_to_asm(). Now that this inactive frame is actually exposed to callers, fix unwind_get_return_address_ptr() to interpret it properly. Fixes: f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks") Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200522135435.vbxs7umku5pyrdbk@treble
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/unwind_orc.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index fa79e4227d3d..7f969b2d240f 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -320,12 +320,19 @@ EXPORT_SYMBOL_GPL(unwind_get_return_address);
unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
{
+ struct task_struct *task = state->task;
+
if (unwind_done(state))
return NULL;
if (state->regs)
return &state->regs->ip;
+ if (task != current && state->sp == task->thread.sp) {
+ struct inactive_task_frame *frame = (void *)task->thread.sp;
+ return &frame->ret_addr;
+ }
+
if (state->sp)
return (unsigned long *)state->sp - 1;