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x86/unwind: Fix guess-unwinder regression 

My attempt at fixing some KASAN false positive warnings was rather brain
dead, and it broke the guess unwinder.  With frame pointers disabled,
/proc/<pid>/stack is broken:

  # cat /proc/1/stack
  [<ffffffffffffffff>] 0xffffffffffffffff

Restore the code flow to more closely resemble its previous state, while
still using READ_ONCE_NOCHECK() macros to silence KASAN false positives.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: c2d75e03d6 ("x86/unwind: Prevent KASAN false positive warnings in guess unwinder")
Link: http://lkml.kernel.org/r/b824f92c2c22eca5ec95ac56bd2a7c84cf0b9df9.1480309971.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2016-11-27 23:13:07 -06:00 committed by Ingo Molnar
parent adee8705d2
commit 55f856e640
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kernel/unwind_guess.c
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@ -7,11 +7,13 @@
unsigned long unwind_get_return_address(struct unwind_state *state)
{
unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
unsigned long addr;
if (unwind_done(state))
return 0;
addr = READ_ONCE_NOCHECK(*state->sp);
return ftrace_graph_ret_addr(state->task, &state->graph_idx,
addr, state->sp);
}
@ -25,11 +27,12 @@ bool unwind_next_frame(struct unwind_state *state)
return false;
do {
unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
for (state->sp++; state->sp < info->end; state->sp++) {
unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
for (state->sp++; state->sp < info->end; state->sp++)
if (__kernel_text_address(addr))
return true;
}
state->sp = info->next_sp;