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x86/kprobes: Cleanup kprobes on ftrace code

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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) <mhiramat@kernel.org>
This commit is contained in:
Masami Hiramatsu (Google) 2024-10-21 21:39:22 +09:00
parent 3fbff98889
commit 4638d7ebef
1 changed files with 11 additions and 8 deletions
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19
arch/x86/kernel/kprobes/ftrace.c
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@ -9,6 +9,7 @@
#include <linux/hardirq.h> #include <linux/hardirq.h>
#include <linux/preempt.h> #include <linux/preempt.h>
#include <linux/ftrace.h> #include <linux/ftrace.h>
#include <asm/text-patching.h>
#include "common.h" #include "common.h"
@ -36,23 +37,25 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
if (kprobe_running()) { if (kprobe_running()) {
kprobes_inc_nmissed_count(p); kprobes_inc_nmissed_count(p);
} else { } else {
unsigned long orig_ip = regs->ip; unsigned long orig_ip = instruction_pointer(regs);
/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ /* 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); __this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE; kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (!p->pre_handler || !p->pre_handler(p, regs)) { 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)) { 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; kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0); 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 * If pre_handler returns !0, it changes regs->ip. We have to