Messages in this thread Patch in this message | | | Date | Wed, 9 Oct 2019 15:28:44 +0200 | From | Peter Zijlstra <> | Subject | Re: x86/kprobes bug? (was: [PATCH 1/3] x86/alternatives: Teach text_poke_bp() to emulate instructions) |
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On Wed, Oct 09, 2019 at 03:26:39PM +0200, Peter Zijlstra wrote: > So I suppose I'm suggesting we do something like the below on top of > what I already have here: > > git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/ftrace > > All it needs are a few comments ;-) Also note how this nicely gets rid > of the one text_poke_bp(.emulate) user, so we can go and remove that as > well. > > --- > arch/x86/include/asm/text-patching.h | 1 + > arch/x86/kernel/alternative.c | 11 ++++++++--- > arch/x86/kernel/kprobes/core.c | 1 + > arch/x86/kernel/kprobes/opt.c | 12 ++++-------- > 4 files changed, 14 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h > index d553175212b3..d3269558e5b5 100644 > --- a/arch/x86/include/asm/text-patching.h > +++ b/arch/x86/include/asm/text-patching.h > @@ -42,6 +42,7 @@ extern void text_poke_early(void *addr, const void *opcode, size_t len); > * an inconsistent instruction while you patch. > */ > extern void *text_poke(void *addr, const void *opcode, size_t len); > +extern void text_poke_sync(void); > extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len); > extern int poke_int3_handler(struct pt_regs *regs); > extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate); > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c > index 34a08bc68e9a..9e81ab542190 100644 > --- a/arch/x86/kernel/alternative.c > +++ b/arch/x86/kernel/alternative.c > @@ -936,6 +936,11 @@ static void do_sync_core(void *info) > sync_core(); > } > > +void text_poke_sync(void) > +{ > + on_each_cpu(do_sync_core, NULL, 1); > +} > + > struct text_poke_loc { > s32 rel_addr; /* addr := _stext + rel_addr */ > s32 rel32; > @@ -1089,7 +1094,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries > for (i = 0; i < nr_entries; i++) > text_poke(text_poke_addr(&tp[i]), &int3, sizeof(int3)); > > - on_each_cpu(do_sync_core, NULL, 1); > + text_poke_sync(); > > /* > * Second step: update all but the first byte of the patched range. > @@ -1111,7 +1116,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries > * not necessary and we'd be safe even without it. But > * better safe than sorry (plus there's not only Intel). > */ > - on_each_cpu(do_sync_core, NULL, 1); > + text_poke_sync(); > } > > /* > @@ -1127,7 +1132,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries > } > > if (do_sync) > - on_each_cpu(do_sync_core, NULL, 1); > + text_poke_sync(); > > /* > * sync_core() implies an smp_mb() and orders this store against
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 7e4a8a1c9d9a..04858ea7cd76 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -498,11 +498,13 @@ int arch_prepare_kprobe(struct kprobe *p) void arch_arm_kprobe(struct kprobe *p) { text_poke(p->addr, ((unsigned char []){INT3_INSN_OPCODE}), 1); + text_poke_sync(); } void arch_disarm_kprobe(struct kprobe *p) { text_poke(p->addr, &p->opcode, 1); + text_poke_sync(); } void arch_remove_kprobe(struct kprobe *p) > void arch_remove_kprobe(struct kprobe *p) > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c > index 36d7249f2145..30a2646cfc8a 100644 > --- a/arch/x86/kernel/kprobes/opt.c > +++ b/arch/x86/kernel/kprobes/opt.c > @@ -446,14 +446,10 @@ void arch_optimize_kprobes(struct list_head *oplist) > /* Replace a relative jump with a breakpoint (int3). */ > void arch_unoptimize_kprobe(struct optimized_kprobe *op) > { > - u8 insn_buff[JMP32_INSN_SIZE]; > - > - /* Set int3 to first byte for kprobes */ > - insn_buff[0] = INT3_INSN_OPCODE; > - memcpy(insn_buff + 1, op->optinsn.copied_insn, DISP32_SIZE); > - > - text_poke_bp(op->kp.addr, insn_buff, JMP32_INSN_SIZE, > - text_gen_insn(JMP32_INSN_OPCODE, op->kp.addr, op->optinsn.insn)); > + arch_arm_kprobe(&op->kp); > + text_poke(op->kp.addr + INT3_INSN_SIZE, > + op->optinsn.copied_insn, DISP32_SIZE); > + text_poke_sync(); > } > > /*
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