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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 <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/15607370e3ddb1732b6a73d5c65937864df16ac8.1481904011.git.jpoimboe@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Josh Poimboeuf 2016-12-16 10:05:06 -06:00 committed by Thomas Gleixner
parent 8023e0e2a4
commit 8b5e99f022
2 changed files with 39 additions and 1 deletions
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2
arch/x86/include/asm/unwind.h
View File

@ -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;

38
arch/x86/kernel/unwind_frame.c
View File

@ -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;