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Date: Fri, 2 Dec 2022 07:30:02 +0900 From: Masami Hiramatsu (Google) <mhiramat@...nel.org> To: Oleg Nesterov <oleg@...hat.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Denys Vlasenko <dvlasenk@...hat.com>, Seiji Nishikawa <snishika@...hat.com>, x86@...nel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] uprobes/x86: allow to probe a "nop" insn with 0x66 prefix On Thu, 1 Dec 2022 15:26:44 +0100 Oleg Nesterov <oleg@...hat.com> wrote: > From: Denys Vlasenko <dvlasenk@...hat.com> > > Intel icc -hotpatch inserts 2-byte "0x66 0x90" NOP at the start of each > function to reserve extra space for hot-patching, and currently it is not > possible to probe these functions because branch_setup_xol_ops() wrongly > nacks NOP with REP prefix. Looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org> Thank you! > > Fixes: 250bbd12c2fe ("uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns") > Reported-by: Seiji Nishikawa <snishika@...hat.com> > Signed-off-by: Oleg Nesterov <oleg@...hat.com> > --- > arch/x86/kernel/uprobes.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > index b63cf8f7745e..6c07f6daaa22 100644 > --- a/arch/x86/kernel/uprobes.c > +++ b/arch/x86/kernel/uprobes.c > @@ -722,8 +722,9 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) > switch (opc1) { > case 0xeb: /* jmp 8 */ > case 0xe9: /* jmp 32 */ > - case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */ > break; > + case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */ > + goto setup; > > case 0xe8: /* call relative */ > branch_clear_offset(auprobe, insn); > @@ -753,6 +754,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) > return -ENOTSUPP; > } > > +setup: > auprobe->branch.opc1 = opc1; > auprobe->branch.ilen = insn->length; > auprobe->branch.offs = insn->immediate.value; > -- > 2.25.1.362.g51ebf55 > > -- Masami Hiramatsu (Google) <mhiramat@...nel.org>
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