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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: 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,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	linux-ia64@vger.kernel.org
Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code
Date: Sat, 20 Mar 2021 22:05:43 +0900	[thread overview]
Message-ID: <20210320220543.e1558ce3a351554c6be3ea26@kernel.org> (raw)
In-Reply-To: <20210320211616.a976fc66d0c51e13d3121e2f@kernel.org>

On Sat, 20 Mar 2021 21:16:16 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Fri, 19 Mar 2021 21:22:39 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > 
> > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC
> > information is generated on the kretprobe_trampoline correctly.
> > 
> 
> Test bot also found a new warning for this.
> 
> > >> arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x25: call without frame pointer save/setup
> 
> With CONFIG_FRAME_POINTER=y.
> 
> Of course this can be fixed with additional "push %bp; mov %sp, %bp" before calling
> trampoline_handler. But actually we know that this function has a bit special
> stack frame too. 
> 
> Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when CONFIG_FRAME_POINTER=y ?

So something like this. Does it work?

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b31058a152b6..651f337dc880 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -760,6 +760,10 @@ int kprobe_int3_handler(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(kprobe_int3_handler);
 
+#ifdef CONFIG_FRAME_POINTER
+#undef UNWIND_HINT_FUNC
+#define UNWIND_HINT_FUNC
+#endif
 /*
  * When a retprobed function returns, this code saves registers and
  * calls trampoline_handler() runs, which calls the kretprobe's handler.
@@ -797,7 +801,14 @@ asm(
 	".size kretprobe_trampoline, .-kretprobe_trampoline\n"
 );
 NOKPROBE_SYMBOL(kretprobe_trampoline);
-
+#ifdef CONFIG_FRAME_POINTER
+/*
+ * kretprobe_trampoline skips updating frame pointer. The frame pointer
+ * saved in trampoline_handler points to the real caller function's
+ * frame pointer.
+ */
+STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
+#endif
 
 /*
  * Called from kretprobe_trampoline

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2021-03-20 13:06 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19 12:21 [PATCH -tip v3 00/11] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-03-19 12:21 ` [PATCH -tip v3 01/11] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-03-19 12:22 ` [PATCH -tip v3 02/11] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu
2021-03-19 12:22 ` [PATCH -tip v3 03/11] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-03-19 12:22 ` [PATCH -tip v3 04/11] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-03-19 12:22 ` [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu
2021-03-20 12:16   ` Masami Hiramatsu
2021-03-20 13:05     ` Masami Hiramatsu [this message]
2021-03-21 17:52       ` Josh Poimboeuf
2021-03-22  0:08         ` Masami Hiramatsu
2021-03-21 17:50     ` Josh Poimboeuf
2021-03-19 12:22 ` [PATCH -tip v3 06/11] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-03-19 12:23 ` [PATCH -tip v3 07/11] ia64: " Masami Hiramatsu
2021-03-20  1:04   ` Masami Hiramatsu
2021-03-19 12:23 ` [PATCH -tip v3 08/11] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Masami Hiramatsu
2021-03-21 12:54   ` Masami Hiramatsu
2021-03-19 12:23 ` [PATCH -tip v3 09/11] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu
2021-03-19 12:23 ` [PATCH -tip v3 10/11] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-03-19 12:23 ` [PATCH -tip v3 11/11] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu

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