Commit 89da5a69 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Josh Poimboeuf
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x86/unwind/orc: Add 'unwind_debug' cmdline option 



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.

Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/6afb9e48a05fd2046bfad47e69b061b43dfd0e0e.1681331449.git.jpoimboe@kernel.org


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent dc1d0553

Documentation/admin-guide/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -6563,6 +6563,12 @@ 
	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,

arch/x86/kernel/unwind_orc.c

+48 −1
Original line number Diff line number Diff line
@@ -13,8 +13,14 @@ 


#define orc_warn_current(args...)					\

({									\

	if (state->task == current && !state->error)			\

	static bool dumped_before;					\

	if (state->task == current && !state->error) {			\

		orc_warn(args);						\

		if (unwind_debug && !dumped_before) {			\

			dumped_before = true;				\

			unwind_dump(state);				\

		}							\

	}								\

})



extern int __start_orc_unwind_ip[];
@@ -23,8 +29,49 @@ 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;