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Commit fb40d7a8 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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x86/jump-label: Show where and what was wrong on errors 



When modifying text sections for jump labels, a paranoid check is
performed. If the check fails, the system "bugs". But why it failed
is not shown.

The BUG_ON()s in the jump label update code is replaced with bug_at(ip).
This is a function that will show what pointer failed, and what was
at the location of the failure that made jump label panic.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 9c85f3bd

arch/x86/kernel/jump_label.c

+18 −3
Original line number Diff line number Diff line
@@ -24,6 +24,18 @@ union jump_code_union { 
	} __attribute__((packed));

};



static void bug_at(unsigned char *ip, int line)

{

	/*

	 * The location is not an op that we were expecting.

	 * Something went wrong. Crash the box, as something could be

	 * corrupting the kernel.

	 */

	pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",

	       ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);

	BUG();

}



static void __jump_label_transform(struct jump_entry *entry,

				   enum jump_label_type type,

				   void *(*poker)(void *, const void *, size_t),
@@ -37,7 +49,8 @@ static void __jump_label_transform(struct jump_entry *entry, 
		 * We are enabling this jump label. If it is not a nop

		 * then something must have gone wrong.

		 */

		BUG_ON(memcmp((void *)entry->code, ideal_nop, 5) != 0);

		if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))

			bug_at((void *)entry->code, __LINE__);



		code.jump = 0xe9;

		code.offset = entry->target -
@@ -51,12 +64,14 @@ static void __jump_label_transform(struct jump_entry *entry, 
		 */

		if (init) {

			const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };

			BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0);

			if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))

				bug_at((void *)entry->code, __LINE__);

		} else {

			code.jump = 0xe9;

			code.offset = entry->target -

				(entry->code + JUMP_LABEL_NOP_SIZE);

			BUG_ON(memcmp((void *)entry->code, &code, 5) != 0);

			if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))

				bug_at((void *)entry->code, __LINE__);

		}

		memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);

	}