x86/kprobes: Cleanup kprobes on ftrace code

Cleanup kprobes on ftrace code for x86.
 - Set instruction pointer (ip + MCOUNT_INSN_SIZE) after pre_handler only
   when p->post_handler exists.
 - Use INT3_INSN_SIZE instead of 1.
 - Use instruction_pointer/instruction_pointer_set() functions instead of
   accessing regs->ip directly.

Link: https://lore.kernel.org/all/172951436219.167263.18330240454389154327.stgit@devnote2/
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 15af7e98e161a406f7f48229de59f62a2f9a9538..2be55ec3f392c10b335167a90053b67029121cb4 100644 (file)
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -9,6 +9,7 @@
 #include <linux/hardirq.h>
 #include <linux/preempt.h>
 #include <linux/ftrace.h>
+#include <asm/text-patching.h>
 
 #include "common.h"
 
@@ -36,23 +37,25 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
        if (kprobe_running()) {
                kprobes_inc_nmissed_count(p);
        } else {
-               unsigned long orig_ip = regs->ip;
+               unsigned long orig_ip = instruction_pointer(regs);
+
                /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
-               regs->ip = ip + sizeof(kprobe_opcode_t);
+               instruction_pointer_set(regs, ip + INT3_INSN_SIZE);
 
                __this_cpu_write(current_kprobe, p);
                kcb->kprobe_status = KPROBE_HIT_ACTIVE;
                if (!p->pre_handler || !p->pre_handler(p, regs)) {
-                       /*
-                        * Emulate singlestep (and also recover regs->ip)
-                        * as if there is a 5byte nop
-                        */
-                       regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
                        if (unlikely(p->post_handler)) {
+                               /*
+                                * Emulate singlestep (and also recover regs->ip)
+                                * as if there is a 5byte nop
+                                */
+                               instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
                                kcb->kprobe_status = KPROBE_HIT_SSDONE;
                                p->post_handler(p, regs, 0);
                        }
-                       regs->ip = orig_ip;
+                       /* Recover IP address */
+                       instruction_pointer_set(regs, orig_ip);
                }
                /*
                 * If pre_handler returns !0, it changes regs->ip. We have to