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Message-ID: <Z_Ox7ibkULkJ_2Lx@krava>
Date: Mon, 7 Apr 2025 13:07:26 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
x86@...nel.org, Song Liu <songliubraving@...com>,
Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Alan Maguire <alan.maguire@...cle.com>,
David Laight <David.Laight@...lab.com>,
Thomas Weißschuh <thomas@...ch.de>
Subject: Re: [PATCH RFCv3 10/23] uprobes/x86: Add support to emulate nop5
instruction
On Fri, Apr 04, 2025 at 01:33:11PM -0700, Andrii Nakryiko wrote:
> On Thu, Mar 20, 2025 at 4:43 AM Jiri Olsa <jolsa@...nel.org> wrote:
> >
> > Adding support to emulate nop5 as the original uprobe instruction.
> >
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> > arch/x86/kernel/uprobes.c | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
>
> This optimization is independent from the sys_uprobe, right? Maybe
> send it as a stand-alone patch and let's land it sooner?
ok, will send it separately
> Also, how hard would it be to do the same for other nopX instructions?
will check, might be easy
thanks,
jirka
>
>
> > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> > index 5ee2cce4c63e..1661e0ab2a3d 100644
> > --- a/arch/x86/kernel/uprobes.c
> > +++ b/arch/x86/kernel/uprobes.c
> > @@ -308,6 +308,11 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool
> > return -ENOTSUPP;
> > }
> >
> > +static int is_nop5_insn(uprobe_opcode_t *insn)
> > +{
> > + return !memcmp(insn, x86_nops[5], 5);
> > +}
> > +
> > #ifdef CONFIG_X86_64
> >
> > asm (
> > @@ -865,6 +870,11 @@ void arch_uprobe_clear_state(struct mm_struct *mm)
> > hlist_for_each_entry_safe(tramp, n, &state->head_tramps, node)
> > destroy_uprobe_trampoline(tramp);
> > }
> > +
> > +static bool emulate_nop5_insn(struct arch_uprobe *auprobe)
> > +{
> > + return is_nop5_insn((uprobe_opcode_t *) &auprobe->insn);
> > +}
> > #else /* 32-bit: */
> > /*
> > * No RIP-relative addressing on 32-bit
> > @@ -878,6 +888,10 @@ static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> > static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> > {
> > }
> > +static bool emulate_nop5_insn(struct arch_uprobe *auprobe)
> > +{
> > + return false;
> > +}
> > #endif /* CONFIG_X86_64 */
> >
> > struct uprobe_xol_ops {
> > @@ -1109,6 +1123,8 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
> > break;
> >
> > case 0x0f:
> > + if (emulate_nop5_insn(auprobe))
> > + goto setup;
> > if (insn->opcode.nbytes != 2)
> > return -ENOSYS;
> > /*
> > --
> > 2.49.0
> >
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