Commit 55f856e6 authored Nov 27, 2016 by Josh Poimboeuf Committed by Ingo Molnar Nov 28, 2016

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: c2d75e03 ("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>

parent adee8705

arch/x86/kernel/unwind_guess.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -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 {
		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;