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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	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,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org,
	Abhishek Sagar <sagar.abhishek@gmail.com>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	wuqiang.matt@bytedance.com
Subject: Re: [PATCH -tip v8 11/13] x86/unwind: Recover kretprobe trampoline entry
Date: Wed, 7 Jul 2021 19:15:10 +0900	[thread overview]
Message-ID: <20210707191510.cb48ca4a20f0502ce6c46508@kernel.org> (raw)
In-Reply-To: <YOVj2VoyrcOvJfEB@hirez.programming.kicks-ass.net>

On Wed, 7 Jul 2021 10:20:41 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> > > Steve, can you clarify the ftrace side here? Afaict return_to_handler()
> > > is similarly affected.
> > 
> > I'm not exactly sure what the issue is. As Masami stated, kretprobe
> > uses a ret to return to the calling function, but ftrace uses a jmp.
> 
> I'll have to re-read the ftrace bits, but from the top of my head you
> cannot do an indirect jump and preserve all registers at the same time,
> so a return stub must use jump from stack aka. ret.
> 
> > kretprobe return tracing is more complex than the function graph return
> > tracing is (which is one of the issues I need to overcome to unify
> > them),
> 
> I'm not sure it is. IIRC the biggest pain point with kretprobe is that
> 'silly' property that the kretprobe_instance are not the same between
> kretprobes. Luckily, that's not actually used anywhere, so we can simply
> rip that out.

I actually don't want to keep this feature because no one use it.
(only systemtap needs it?)

Anyway, if we keep the idea-level compatibility (not code level),
what we need is 'void *data' in the struct kretprobe_instance.
User who needs it can allocate their own instance data for their
kretprobes when initialising it and sets in their entry handler.

Then we can have a simple kretprobe_instance.

Thank you,



-- 
Masami Hiramatsu <mhiramat@kernel.org>

  parent reply	other threads:[~2021-07-07 10:15 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-18  7:05 [PATCH -tip v8 00/13] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-06-18  7:05 ` [PATCH -tip v8 01/13] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-07-05  7:46   ` Ingo Molnar
2021-07-05 10:05     ` Masami Hiramatsu
2021-06-18  7:05 ` [PATCH -tip v8 02/13] kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor() Masami Hiramatsu
2021-07-05  7:48   ` Ingo Molnar
2021-07-05 12:03     ` Masami Hiramatsu
2021-07-07 18:28   ` Andrii Nakryiko
2021-07-08  4:08     ` Masami Hiramatsu
2021-06-18  7:05 ` [PATCH -tip v8 03/13] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-07-05  7:03   ` Ingo Molnar
2021-07-05 10:03     ` Masami Hiramatsu
2021-07-05  7:49   ` Ingo Molnar
2021-06-18  7:05 ` [PATCH -tip v8 04/13] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-07-05  7:42   ` Ingo Molnar
2021-07-05 14:11     ` Masami Hiramatsu
2021-06-18  7:06 ` [PATCH -tip v8 05/13] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu
2021-07-05  8:02   ` Ingo Molnar
2021-07-09 15:31     ` Masami Hiramatsu
2021-07-10  1:41       ` Masami Hiramatsu
2021-07-10 19:01         ` Josh Poimboeuf
2021-07-10 19:24           ` [PATCH 1/2] objtool: Add frame-pointer-specific function ignore Josh Poimboeuf
2021-07-11  1:16             ` Masami Hiramatsu
2021-07-29  2:31             ` Masami Hiramatsu
2021-07-10 19:25           ` [PATCH 2/2] objtool: Ignore unwind hints for ignored functions Josh Poimboeuf
2021-07-11  2:07             ` Masami Hiramatsu
2021-06-18  7:06 ` [PATCH -tip v8 06/13] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-06-18  7:06 ` [PATCH -tip v8 07/13] ia64: " Masami Hiramatsu
2021-06-18  7:06 ` [PATCH -tip v8 08/13] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Masami Hiramatsu
2021-07-05  8:04   ` Ingo Molnar
2021-07-05 14:40     ` Masami Hiramatsu
2021-06-18  7:06 ` [PATCH -tip v8 09/13] kprobes: Enable stacktrace from pt_regs in kretprobe handler Masami Hiramatsu
2021-06-18 14:04   ` Josh Poimboeuf
2021-06-18  7:06 ` [PATCH -tip v8 10/13] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu
2021-07-05  8:17   ` Ingo Molnar
2021-07-09 14:55     ` Masami Hiramatsu
2021-06-18  7:07 ` [PATCH -tip v8 11/13] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-07-05 11:36   ` Peter Zijlstra
2021-07-05 15:42     ` Masami Hiramatsu
2021-07-06  7:55       ` Peter Zijlstra
2021-07-06 15:11         ` Steven Rostedt
2021-07-07  8:20           ` Peter Zijlstra
2021-07-07  8:36             ` Peter Zijlstra
2021-07-07 10:15             ` Masami Hiramatsu [this message]
2021-07-07 10:20               ` Peter Zijlstra
2021-07-07 10:45                 ` Masami Hiramatsu
2021-07-07 13:29                   ` Masami Hiramatsu
2021-07-07 14:42                     ` Matt Wu
2021-07-11 14:09                       ` Masami Hiramatsu
2021-07-11 15:28                         ` Matt Wu
2021-07-12  4:57                           ` Masami Hiramatsu
2021-06-18  7:07 ` [PATCH -tip v8 12/13] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-06-18  7:07 ` [PATCH -tip v8 13/13] x86/kprobes: Fixup return address in generic trampoline handler Masami Hiramatsu
2021-07-05  8:34   ` Ingo Molnar
2021-07-06 12:57     ` Masami Hiramatsu
2021-06-18 17:44 ` [PATCH -tip v8 00/13] kprobes: Fix stacktrace with kretprobes on x86 Andrii Nakryiko
2021-06-28 13:50 ` Masami Hiramatsu

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