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kprobes/x86: Do not modify singlestep buffer while resuming

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Do not modify singlestep execution buffer (kprobe.ainsn.insn)
while resuming from single-stepping, instead, modifies
the buffer to add a jump back instruction at preparing
buffer.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ye Xiaolong <xiaolong.ye@intel.com>
Link: http://lkml.kernel.org/r/149076361560.22469.1610155860343077495.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Masami Hiramatsu 2017-03-29 14:00:25 +09:00 committed by Ingo Molnar
parent 17880e4d57
commit 804dec5bda
1 changed files with 20 additions and 22 deletions
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42
arch/x86/kernel/kprobes/core.c
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@ -399,23 +399,36 @@ int __copy_instruction(u8 *dest, u8 *src)
return length;
}
/* Prepare reljump right after instruction to boost */
static void prepare_boost(struct kprobe *p, int length)
{
if (can_boost(p->ainsn.insn, p->addr) &&
MAX_INSN_SIZE - length >= RELATIVEJUMP_SIZE) {
/*
* These instructions can be executed directly if it
* jumps back to correct address.
*/
synthesize_reljump(p->ainsn.insn + length, p->addr + length);
p->ainsn.boostable = 1;
} else {
p->ainsn.boostable = -1;
}
}
static int arch_copy_kprobe(struct kprobe *p)
{
int ret;
int len;
/* Copy an instruction with recovering if other optprobe modifies it.*/
ret = __copy_instruction(p->ainsn.insn, p->addr);
if (!ret)
len = __copy_instruction(p->ainsn.insn, p->addr);
if (!len)
return -EINVAL;
/*
* __copy_instruction can modify the displacement of the instruction,
* but it doesn't affect boostable check.
*/
if (can_boost(p->ainsn.insn, p->addr))
p->ainsn.boostable = 0;
else
p->ainsn.boostable = -1;
prepare_boost(p, len);
/* Check whether the instruction modifies Interrupt Flag or not */
p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
@ -878,21 +891,6 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs,
break;
}
if (p->ainsn.boostable == 0) {
if ((regs->ip > copy_ip) &&
(regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
/*
* These instructions can be executed directly if it
* jumps back to correct address.
*/
synthesize_reljump((void *)regs->ip,
(void *)orig_ip + (regs->ip - copy_ip));
p->ainsn.boostable = 1;
} else {
p->ainsn.boostable = -1;
}
}
regs->ip += orig_ip - copy_ip;
no_change: