From: Chenggang Qin <[email protected]> For x86_64, the exact value of user stack's esp should be got by KSTK_ESP(current). current->thread.usersp is copied from PDA while enter ring0. Now, we output the value of sp from pt_regs. But pt_regs->sp has changed before it was pushed into kernel stack.
So, we cannot get the correct callchain while unwind some user stacks. For example, if the stack contains __lll_unlock_wake()/__lll_lock_wait(), the callchain will break some times with the latest version of libunwind. The root cause is the sp that is used by libunwind may be wrong. If we use KSTK_ESP(current), the correct callchain can be got everytime. Other architectures also have KSTK_ESP() macro. Signed-off-by: Chenggang Qin <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: David Ahern <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Wu Fengguang <[email protected]> Cc: Yanmin Zhang <[email protected]> --- arch/x86/kernel/perf_regs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c index e309cc5..5da8df8 100644 --- a/arch/x86/kernel/perf_regs.c +++ b/arch/x86/kernel/perf_regs.c @@ -60,6 +60,9 @@ u64 perf_reg_value(struct pt_regs *regs, int idx) if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset))) return 0; + if (idx == PERF_REG_X86_SP) + return KSTK_ESP(current); + return regs_get_register(regs, pt_regs_offset[idx]); } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
