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Subject[tip: x86/urgent] x86/unwind/orc: Don't skip the first frame for inactive tasks
The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: f1d9a2abff66aa8156fbc1493abed468db63ea48
Gitweb: https://git.kernel.org/tip/f1d9a2abff66aa8156fbc1493abed468db63ea48
Author: Miroslav Benes <mbenes@suse.cz>
AuthorDate: Sat, 25 Apr 2020 05:03:07 -05:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 25 Apr 2020 12:22:29 +02:00

x86/unwind/orc: Don't skip the first frame for inactive tasks

When unwinding an inactive task, the ORC unwinder skips the first frame
by default. If both the 'regs' and 'first_frame' parameters of
unwind_start() are NULL, 'state->sp' and 'first_frame' are later
initialized to the same value for an inactive task. Given there is a
"less than or equal to" comparison used at the end of __unwind_start()
for skipping stack frames, the first frame is skipped.

Drop the equal part of the comparison and make the behavior equivalent
to the frame pointer unwinder.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Jones <dsj@fb.com>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lore.kernel.org/r/7f08db872ab59e807016910acdbe82f744de7065.1587808742.git.jpoimboe@redhat.com
---
arch/x86/kernel/unwind_orc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 45166fd..e9f5a20 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -657,7 +657,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
/* Otherwise, skip ahead to the user-specified starting frame: */
while (!unwind_done(state) &&
(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
- state->sp <= (unsigned long)first_frame))
+ state->sp < (unsigned long)first_frame))
unwind_next_frame(state);

return;
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