From 8b5e99f02264130782a10ba5c0c759797fb064ee Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 16 Dec 2016 10:05:06 -0600 Subject: [PATCH] x86/unwind: Dump stack data on warnings The unwinder warnings are good at finding unexpected unwinder issues, but they often don't give enough data to be able to fully diagnose them. Print a one-time stack dump when a warning is detected. Signed-off-by: Josh Poimboeuf Cc: Borislav Petkov Cc: Andy Lutomirski Link: http://lkml.kernel.org/r/15607370e3ddb1732b6a73d5c65937864df16ac8.1481904011.git.jpoimboe@redhat.com Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/unwind.h | 2 +- arch/x86/kernel/unwind_frame.c | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h index c5a7f3a..6fa75b1 100644 --- a/arch/x86/include/asm/unwind.h +++ b/arch/x86/include/asm/unwind.h @@ -12,7 +12,7 @@ struct unwind_state { struct task_struct *task; int graph_idx; #ifdef CONFIG_FRAME_POINTER - unsigned long *bp; + unsigned long *bp, *orig_sp; struct pt_regs *regs; #else unsigned long *sp; diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index 33aeaae..20d4b4e 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -6,6 +6,37 @@ #define FRAME_HEADER_SIZE (sizeof(long) * 2) +static void unwind_dump(struct unwind_state *state, unsigned long *sp) +{ + static bool dumped_before = false; + bool prev_zero, zero = false; + unsigned long word; + + if (dumped_before) + return; + + dumped_before = true; + + printk_deferred("unwind stack type:%d next_sp:%p mask:%lx graph_idx:%d\n", + state->stack_info.type, state->stack_info.next_sp, + state->stack_mask, state->graph_idx); + + for (sp = state->orig_sp; sp < state->stack_info.end; sp++) { + word = READ_ONCE_NOCHECK(*sp); + + prev_zero = zero; + zero = word == 0; + + if (zero) { + if (!prev_zero) + printk_deferred("%p: %016x ...\n", sp, 0); + continue; + } + + printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word); + } +} + unsigned long unwind_get_return_address(struct unwind_state *state) { unsigned long addr; @@ -25,6 +56,7 @@ unsigned long unwind_get_return_address(struct unwind_state *state) "WARNING: unrecognized kernel stack return address %p at %p in %s:%d\n", (void *)addr, addr_p, state->task->comm, state->task->pid); + unwind_dump(state, addr_p); return 0; } @@ -74,6 +106,7 @@ static bool update_stack_state(struct unwind_state *state, void *addr, size_t len) { struct stack_info *info = &state->stack_info; + enum stack_type orig_type = info->type; /* * If addr isn't on the current stack, switch to the next one. @@ -87,6 +120,9 @@ static bool update_stack_state(struct unwind_state *state, void *addr, &state->stack_mask)) return false; + if (!state->orig_sp || info->type != orig_type) + state->orig_sp = addr; + return true; } @@ -185,11 +221,13 @@ bad_address: "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", state->regs, state->task->comm, state->task->pid, next_frame); + unwind_dump(state, (unsigned long *)state->regs); } else { printk_deferred_once(KERN_WARNING "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", state->bp, state->task->comm, state->task->pid, next_frame); + unwind_dump(state, state->bp); } the_end: state->stack_info.type = STACK_TYPE_UNKNOWN; -- 2.7.4