Commit d15cb3da authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/livepatch: Validate __fentry__ location 



Currently livepatch assumes __fentry__ lives at func+0, which is most
likely untrue with IBT on. Instead make it use ftrace_location() by
default which both validates and finds the actual ip if there is any
in the same symbol.

Suggested-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154318.285971256@infradead.org
parent aebfd125

arch/powerpc/include/asm/livepatch.h

+0 −10
Original line number Diff line number Diff line
@@ -19,16 +19,6 @@ static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip) 
	regs_set_return_ip(regs, ip);

}



#define klp_get_ftrace_location klp_get_ftrace_location

static inline unsigned long klp_get_ftrace_location(unsigned long faddr)

{

	/*

	 * Live patch works only with -mprofile-kernel on PPC. In this case,

	 * the ftrace location is always within the first 16 bytes.

	 */

	return ftrace_location_range(faddr, faddr + 16);

}



static inline void klp_init_thread_info(struct task_struct *p)

{

	/* + 1 to account for STACK_END_MAGIC */

kernel/livepatch/patch.c

+2 −17
Original line number Diff line number Diff line
@@ -124,19 +124,6 @@ static void notrace klp_ftrace_handler(unsigned long ip, 
	ftrace_test_recursion_unlock(bit);

}



/*

 * Convert a function address into the appropriate ftrace location.

 *

 * Usually this is just the address of the function, but on some architectures

 * it's more complicated so allow them to provide a custom behaviour.

 */

#ifndef klp_get_ftrace_location

static unsigned long klp_get_ftrace_location(unsigned long faddr)

{

	return faddr;

}

#endif



static void klp_unpatch_func(struct klp_func *func)

{

	struct klp_ops *ops;
@@ -153,8 +140,7 @@ static void klp_unpatch_func(struct klp_func *func) 
	if (list_is_singular(&ops->func_stack)) {

		unsigned long ftrace_loc;



		ftrace_loc =

			klp_get_ftrace_location((unsigned long)func->old_func);

		ftrace_loc = ftrace_location((unsigned long)func->old_func);

		if (WARN_ON(!ftrace_loc))

			return;
@@ -186,8 +172,7 @@ static int klp_patch_func(struct klp_func *func) 
	if (!ops) {

		unsigned long ftrace_loc;



		ftrace_loc =

			klp_get_ftrace_location((unsigned long)func->old_func);

		ftrace_loc = ftrace_location((unsigned long)func->old_func);

		if (!ftrace_loc) {

			pr_err("failed to find location for function '%s'\n",

				func->old_name);