From: Masami Hiramatsu <mhiramat@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Daniel Xu <dxu@dxuuu.xyz>, Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
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,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes
Date: Mon, 8 Mar 2021 22:05:59 +0900 [thread overview]
Message-ID: <20210308220559.ed5c7a074d7146f004388195@kernel.org> (raw)
In-Reply-To: <20210308115210.732f2c42bf347c15fbb2a828@kernel.org>
On Mon, 8 Mar 2021 11:52:10 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> So, here is my idea;
>
> 1) Change the trampline code to prepare stack frame at first and save
> registers on it, instead of "push". This will makes ORC easy to setup
> stackframe information for this code.
> 2) change the return addres fixup timing. Instead of using return value
> of trampoline handler, before removing the real return address from
> current->kretprobe_instances.
> 3) Then, if orc_find() finds the ip is in the kretprobe_trampoline, it
> checks the contents of the end of stackframe (at the place of regs->sp)
> is same as the address of it. If it is, it can find the correct address
> from current->kretprobe_instances. If not, there is a correct address.
Another trickly idea is put a call on top of kretprobe_trampoline like this.
"__kretprobe_trampoline:\n"
" call kretprobe_trampoline\n"
"kretprobe_trampoline:\n"
" pushq %rsp\n"
" pushfq\n"
SAVE_REGS_STRING
" movq %rsp, %rdi\n"
" call trampoline_handler\n"
/* Replace __kretprobe_trampoline with true return address. */
" movq %rax, 20*8(%rsp)\n"
RESTORE_REGS_STRING
" popfq\n"
" popq %rsp\n"
" ret\n"
This will leave a marker (kretprobe_trampoline or __kretprobe_trampoline+5) on
the top of stack, and the stack frame seems like a normal function. If objtool
can make an ORC info by disassembling kretprobe_trampoline, I guess it is
easy to make a stack frame information.
But anyway, from the inside of target function, it still see "__kretprobe_trampoline"
on the stack instead of caller_func, so orc_kretprobe_find() is still needed.
I'm not familier with the UNWIND_HINT macro, so if it is easy to handle the original
case, I think my first idea will be better.
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-03-08 13:06 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 15:38 [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 1/5] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 2/5] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 3/5] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-03-10 14:21 ` Miroslav Benes
2021-03-10 15:42 ` Masami Hiramatsu
2021-03-11 13:37 ` Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 4/5] kprobes: stacktrace: Recover the address changed by kretprobe Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 5/5] tracing: Remove kretprobe unknown indicator from stacktrace Masami Hiramatsu
2021-03-05 15:44 ` Steven Rostedt
2021-03-05 19:16 ` [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes Daniel Xu
2021-03-06 1:13 ` Masami Hiramatsu
2021-03-07 21:23 ` Daniel Xu
2021-03-08 2:52 ` Masami Hiramatsu
2021-03-08 13:05 ` Masami Hiramatsu [this message]
2021-03-09 1:19 ` Josh Poimboeuf
2021-03-10 9:57 ` Masami Hiramatsu
2021-03-10 15:08 ` Josh Poimboeuf
2021-03-10 15:55 ` Masami Hiramatsu
2021-03-10 18:31 ` Josh Poimboeuf
2021-03-11 0:20 ` Masami Hiramatsu
2021-03-11 1:06 ` Josh Poimboeuf
2021-03-11 1:54 ` Masami Hiramatsu
2021-03-11 16:51 ` Josh Poimboeuf
2021-03-12 3:22 ` Masami Hiramatsu
2021-03-10 22:46 ` Daniel Xu
2021-03-09 21:34 ` Daniel Xu
2021-03-10 10:50 ` Masami Hiramatsu
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