From: Masami Hiramatsu <mhiramat@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
"Naveen N . Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@linux.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org, Sven Schnelle <svens@linux.ibm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/8] arm64: kprobes: Record frame pointer with kretprobe instance
Date: Thu, 14 Oct 2021 17:04:05 +0900 [thread overview]
Message-ID: <20211014170405.f59d287b30086efe7dd7f4d9@kernel.org> (raw)
In-Reply-To: <20211013100126.GA3187@C02TD0UTHF1T.local>
On Wed, 13 Oct 2021 11:01:39 +0100
Mark Rutland <mark.rutland@arm.com> wrote:
> On Fri, Oct 08, 2021 at 09:28:39PM +0900, Masami Hiramatsu wrote:
> > Record the frame pointer instead of stack address with kretprobe
> > instance as the identifier on the instance list.
> > Since arm64 always enable CONFIG_FRAME_POINTER, we can use the
> > actual frame pointer (x29).
>
> Just to check, why do we need to use the FP rather than SP? It wasn't
> clear to me if that's necessary later in the series, or if I'm missing
> something here.
Actually, this is for finding correct return address from the per-task
kretprobe instruction list (suppose it as a shadow stack) when it will
be searched in stack-backtracing. At that point, the framepointer will
be a reliable key.
>
> FWIW, I plan to rework arm64's ftrace bits to use FP for
> HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, so I'm happy to do likewise here.
Yes, I think you can use FP for that too.
>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Regardless of the above:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
Thank you!
>
> Mark.
>
> > ---
> > arch/arm64/kernel/probes/kprobes.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> > index e7ad6da980e8..d9dfa82c1f18 100644
> > --- a/arch/arm64/kernel/probes/kprobes.c
> > +++ b/arch/arm64/kernel/probes/kprobes.c
> > @@ -401,14 +401,14 @@ int __init arch_populate_kprobe_blacklist(void)
> >
> > void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
> > {
> > - return (void *)kretprobe_trampoline_handler(regs, (void *)kernel_stack_pointer(regs));
> > + return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
> > }
> >
> > void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
> > struct pt_regs *regs)
> > {
> > ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
> > - ri->fp = (void *)kernel_stack_pointer(regs);
> > + ri->fp = (void *)regs->regs[29];
> >
> > /* replace return addr (x30) with trampoline */
> > regs->regs[30] = (long)&__kretprobe_trampoline;
> >
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-10-14 8:04 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 12:28 [PATCH 0/8] kprobes: Make KUnit and add stacktrace on kretprobe tests Masami Hiramatsu
2021-10-08 12:28 ` [PATCH 1/8] kprobes: convert tests to kunit Masami Hiramatsu
2021-10-08 12:28 ` [PATCH 2/8] kprobes: Add a test case for stacktrace from kretprobe handler Masami Hiramatsu
2021-10-08 12:28 ` [PATCH 3/8] arm64: kprobes: Record frame pointer with kretprobe instance Masami Hiramatsu
2021-10-13 8:14 ` Will Deacon
2021-10-13 10:01 ` Mark Rutland
2021-10-14 8:04 ` Masami Hiramatsu [this message]
2021-10-14 9:13 ` Mark Rutland
2021-10-14 10:01 ` Masami Hiramatsu
2021-10-14 10:27 ` Mark Rutland
2021-10-14 13:50 ` Masami Hiramatsu
2021-10-08 12:28 ` [PATCH 4/8] arm64: kprobes: Make a frame pointer on __kretprobe_trampoline Masami Hiramatsu
2021-10-13 8:14 ` Will Deacon
2021-10-08 12:28 ` [PATCH 5/8] arm64: Recover kretprobe modified return address in stacktrace Masami Hiramatsu
2021-10-13 8:14 ` Will Deacon
2021-10-14 8:05 ` Masami Hiramatsu
2021-10-13 10:13 ` Mark Rutland
2021-10-14 9:57 ` Masami Hiramatsu
2021-10-08 12:29 ` [PATCH 6/8] ARM: clang: Do not relay on lr register for stacktrace Masami Hiramatsu
2021-10-11 18:45 ` Nick Desaulniers
2021-10-12 14:18 ` Masami Hiramatsu
2021-10-13 19:54 ` Nick Desaulniers
2021-10-14 16:53 ` Russell King (Oracle)
2021-10-15 0:18 ` Masami Hiramatsu
2021-10-08 12:29 ` [PATCH 7/8] ARM: kprobes: Make a frame pointer on __kretprobe_trampoline Masami Hiramatsu
2021-10-11 19:06 ` Nick Desaulniers
2021-10-08 12:29 ` [PATCH 8/8] ARM: Recover kretprobe modified return address in stacktrace Masami Hiramatsu
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