From 55f856e640560494518eaf24fe9d2d2089fba71a Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Sun, 27 Nov 2016 23:13:07 -0600 Subject: [PATCH] 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//stack is broken: # cat /proc/1/stack [] 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 Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: c2d75e03d630 ("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 --- arch/x86/kernel/unwind_guess.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c index b80e8bf43cc6..22881ddcbb9f 100644 --- a/arch/x86/kernel/unwind_guess.c +++ b/arch/x86/kernel/unwind_guess.c @@ -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;