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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
	Daniel Xu <dxu@dxuuu.xyz>,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	kuba@kernel.org, mingo@redhat.com, ast@kernel.org,
	tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com,
	linux-ia64@vger.kernel.org,
	Abhishek Sagar <sagar.abhishek@gmail.com>
Subject: Re: [PATCH -tip v4 10/12] x86/kprobes: Push a fake return address at kretprobe_trampoline
Date: Thu, 25 Mar 2021 08:47:41 +0900	[thread overview]
Message-ID: <20210325084741.74bdb2b1d2ed00fe68840cea@kernel.org> (raw)
In-Reply-To: <20210324160143.wd43zribpeop2czn@treble>

On Wed, 24 Mar 2021 11:01:43 -0500
Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Wed, Mar 24, 2021 at 10:40:58AM +0900, Masami Hiramatsu wrote:
> > On Tue, 23 Mar 2021 23:30:07 +0100
> > Peter Zijlstra <peterz@infradead.org> wrote:
> > 
> > > On Mon, Mar 22, 2021 at 03:41:40PM +0900, Masami Hiramatsu wrote:
> > > >  	".global kretprobe_trampoline\n"
> > > >  	".type kretprobe_trampoline, @function\n"
> > > >  	"kretprobe_trampoline:\n"
> > > >  #ifdef CONFIG_X86_64
> > > 
> > > So what happens if we get an NMI here? That is, after the RET but before
> > > the push? Then our IP points into the trampoline but we've not done that
> > > push yet.
> > 
> > Not only NMI, but also interrupts can happen. There is no cli/sti here.
> > 
> > Anyway, thanks for pointing!
> > I think in UNWIND_HINT_TYPE_REGS and UNWIND_HINT_TYPE_REGS_PARTIAL cases
> > ORC unwinder also has to check the state->ip and if it is kretprobe_trampoline,
> > it should be recovered.
> > What about this?
> 
> I think the REGS and REGS_PARTIAL cases can also be affected by function
> graph tracing.  So should they use the generic unwind_recover_ret_addr()
> instead of unwind_recover_kretprobe()?

Yes, but I'm not sure this parameter can be applied.
For example, it passed "state->sp - sizeof(unsigned long)" as where the
return address stored address. Is that same on ftrace graph too?

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2021-03-24 23:48 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22  6:39 [PATCH -tip v4 00/12] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-03-22  6:39 ` [PATCH -tip v4 01/12] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-03-22  6:40 ` [PATCH -tip v4 02/12] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu
2021-03-22  6:40 ` [PATCH -tip v4 03/12] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-03-22  6:40 ` [PATCH -tip v4 04/12] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-03-22  6:40 ` [PATCH -tip v4 05/12] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu
2021-03-22  6:40 ` [PATCH -tip v4 06/12] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-03-22  6:41 ` [PATCH -tip v4 07/12] ia64: " Masami Hiramatsu
2021-03-22  6:41 ` [PATCH -tip v4 08/12] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Masami Hiramatsu
2021-03-23  0:04   ` Masami Hiramatsu
2021-03-22  6:41 ` [PATCH -tip v4 09/12] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Masami Hiramatsu
2021-03-22  6:41 ` [PATCH -tip v4 10/12] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu
2021-03-23 22:30   ` Peter Zijlstra
2021-03-24  1:40     ` Masami Hiramatsu
2021-03-24 16:01       ` Josh Poimboeuf
2021-03-24 23:47         ` Masami Hiramatsu [this message]
2021-03-25  0:26           ` Steven Rostedt
2021-03-25  3:25             ` Masami Hiramatsu
2021-03-25 18:05       ` Masami Hiramatsu
2021-03-26 12:03         ` Masami Hiramatsu
2021-03-26 14:20           ` Steven Rostedt
2021-03-30  4:58             ` Josh Poimboeuf
2021-03-22  6:41 ` [PATCH -tip v4 11/12] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-03-22  6:42 ` [PATCH -tip v4 12/12] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-03-22 15:11   ` Steven Rostedt
2021-03-22 23:56     ` Masami Hiramatsu

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