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: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154318.285971256@infradead.org

diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
index 4fe018c..7b9dcd5 100644 (file)
--- a/arch/powerpc/include/asm/livepatch.h
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -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 */

diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index fe316c0..c172bf9 100644 (file)
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -124,19 +124,6 @@ unlock:
        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);