From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Sometimes the one-line ORC unwinder warnings aren't very helpful. Add a
new 'unwind_debug' cmdline option which will dump the full stack
contents of the current task when an error condition is encountered.
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 6 +++
arch/x86/kernel/unwind_orc.c | 46 +++++++++++++++++++
2 files changed, 52 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index cc3ea8febc62..85d48f6052fd 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6317,6 +6317,12 @@
unknown_nmi_panic
[X86] Cause panic on unknown NMI.
+ unwind_debug [X86-64]
+ Enable unwinder debug output. This can be
+ useful for debugging certain unwinder error
+ conditions, including corrupt stacks and
+ bad/missing unwinder metadata.
+
usbcore.authorized_default=
[USB] Default USB device authorization:
(default -1 = authorized except for wireless USB,
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 38185aedf7d1..c539ca39e9f4 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -13,8 +13,13 @@
#define orc_warn_current(args...) \
({ \
+ static bool dumped_before;
if (state->task == current && !state->error) \
orc_warn(args); \
+ if (unwind_debug && !dumped_before) \
+ unwind_dump(state); \
+ dumped_before = true; \
+ } \
})
extern int __start_orc_unwind_ip[];
@@ -23,8 +28,49 @@ extern struct orc_entry __start_orc_unwind[];
extern struct orc_entry __stop_orc_unwind[];
static bool orc_init __ro_after_init;
+static bool unwind_debug __ro_after_init;
static unsigned int lookup_num_blocks __ro_after_init;
+static int __init unwind_debug_cmdline(char *str)
+{
+ unwind_debug = true;
+
+ return 0;
+}
+early_param("unwind_debug", unwind_debug_cmdline);
+
+static void unwind_dump(struct unwind_state *state)
+{
+ static bool dumped_before;
+ unsigned long word, *sp;
+ struct stack_info stack_info = {0};
+ unsigned long visit_mask = 0;
+
+ if (dumped_before)
+ return;
+
+ dumped_before = true;
+
+ printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
+ state->stack_info.type, state->stack_info.next_sp,
+ state->stack_mask, state->graph_idx);
+
+ for (sp = __builtin_frame_address(0); sp;
+ sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+ if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
+ break;
+
+ for (; sp < stack_info.end; sp++) {
+
+ word = READ_ONCE_NOCHECK(*sp);
+
+ printk_deferred("%0*lx: %0*lx (%pB)\n", BITS_PER_LONG/4,
+ (unsigned long)sp, BITS_PER_LONG/4,
+ word, (void *)word);
+ }
+ }
+}
+
static inline unsigned long orc_ip(const int *ip)
{
return (unsigned long)ip + *ip;
