diff options
author | Josh Poimboeuf <jpoimboe@redhat.com> | 2020-05-22 08:54:35 -0500 |
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committer | Peter Zijlstra <peterz@infradead.org> | 2020-05-22 19:55:17 +0200 |
commit | 187b96db5ca79423618dfa29a05c438c34f9e1f0 (patch) | |
tree | f5eea6c1e32249cfab3bc512fbe136e85d691bcc /arch | |
parent | d7110a26e5905ec2fe3fc88bc6a538901accb72b (diff) |
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.c | 7 |
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; |