From: Steven Rostedt <rostedt@goodmis.org>
To: Borislav Petkov <bp@suse.de>
Cc: tip-bot2 for Jiri Slaby <tip-bot2@linutronix.de>,
linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
Jiri Slaby <jslaby@suse.cz>, "H. Peter Anvin" <hpa@zytor.com>,
Ingo Molnar <mingo@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
linux-arch@vger.kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>, x86-ml <x86@kernel.org>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>
Subject: Re: [tip: x86/asm] x86/asm/ftrace: Mark function_hook as function
Date: Fri, 18 Oct 2019 13:37:35 -0400 [thread overview]
Message-ID: <20191018133735.77e90e36@gandalf.local.home> (raw)
In-Reply-To: <20191018171354.GB20368@zn.tnic>
On Fri, 18 Oct 2019 19:13:54 +0200
Borislav Petkov <bp@suse.de> wrote:
> On Fri, Oct 18, 2019 at 12:49:56PM -0400, Steven Rostedt wrote:
> > On Fri, 18 Oct 2019 12:48:00 -0400
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > > > Relabel function_hook to be marked really as a function. It is called
> > > > from C and has the same expectations towards the stack etc.
> > >
> >
> > And to go even further, it *does not* have the same expectations
> > towards the stack.
> >
> > I think this patch should not be applied.
>
> There are a couple more markings like that now:
>
> $ git grep function_hook
> Documentation/asm-annotations.rst:120: SYM_FUNC_START(function_hook)
> Documentation/asm-annotations.rst:122: SYM_FUNC_END(function_hook)
> arch/x86/kernel/ftrace_32.S:15:# define function_hook __fentry__
> arch/x86/kernel/ftrace_32.S:24:SYM_FUNC_START(function_hook)
> arch/x86/kernel/ftrace_32.S:26:SYM_FUNC_END(function_hook)
> arch/x86/kernel/ftrace_64.S:17:# define function_hook __fentry__
> arch/x86/kernel/ftrace_64.S:135:SYM_FUNC_START(function_hook)
> arch/x86/kernel/ftrace_64.S:137:SYM_FUNC_END(function_hook)
> arch/x86/kernel/ftrace_64.S:251:SYM_FUNC_START(function_hook)
> arch/x86/kernel/ftrace_64.S:282:SYM_FUNC_END(function_hook)
>
> Frankly, I wouldn't mark this function at all as it is special and I see
> a little sense to have it in stack traces but maybe Jiri has another
> angle here. I'll let him comment.
It just needs to be visible by modules and what not, otherwise linking
will fail.
>
> I guess with the new nomenclature that can be SYM_CODE_* now...
>
> Then, this magic "function" or a global symbol with an address or
> whatever that is (oh, there's #define trickery too) definitely deserves
> a comment above it to explain what it is. I even have to build the .s
> file to see what it turns into:
The #define was because we use to support mcount or __fentry__, now we
just support __fentry__, and function_hook describes it better ;-)
>
> .globl __fentry__ ; .p2align 4, 0x90 ; __fentry__:
> retq
> .type __fentry__, @function ; .size __fentry__, .-__fentry__
>
> Yeah, it is called on every function entry:
>
> callq ffffffff81a01760 <__fentry__>
>
> but can we please explain with a comment above it what it is?
Heh, I guess we could, which would probably be quite a long comment as
it's the key behind ftrace itself.
-- Steve
next prev parent reply other threads:[~2019-10-18 17:37 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-11 11:50 [PATCH v9 00/28] New macros for assembler symbols Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 01/28] linkage: Introduce new " Jiri Slaby
2019-10-14 9:31 ` Rafael J. Wysocki
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 02/28] x86/asm/suspend: Use SYM_DATA for data Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 03/28] x86/asm: Annotate relocate_kernel_{32,64}.c Jiri Slaby
2019-10-14 13:15 ` Borislav Petkov
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 04/28] x86/asm/entry: Annotate THUNKs Jiri Slaby
2019-10-14 13:38 ` Borislav Petkov
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 05/28] x86/asm: Annotate local pseudo-functions Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 06/28] x86/asm/crypto: Annotate local functions Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 07/28] x86/boot: " Jiri Slaby
2019-10-14 14:27 ` Borislav Petkov
2019-10-15 5:43 ` Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 08/28] x86/uaccess: Annotate local function Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 09/28] x86/asm: Annotate aliases Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 10/28] x86/asm/entry: Annotate interrupt symbols properly Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 11/28] x86/asm/head: Annotate data appropriately Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 12/28] x86/boot: " Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 13/28] um: " Jiri Slaby
2019-10-15 15:37 ` Richard Weinberger
2019-10-18 16:30 ` [tip: x86/asm] x86/um: " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 14/28] xen/pvh: " Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 15/28] x86/asm/purgatory: Start using annotations Jiri Slaby
2019-10-15 17:03 ` Borislav Petkov
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 16/28] x86/asm: Do not annotate functions by GLOBAL Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm: Do not annotate functions with GLOBAL tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 17/28] x86/asm: Use SYM_INNER_LABEL instead of GLOBAL Jiri Slaby
2019-10-15 17:31 ` Borislav Petkov
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 18/28] x86/asm/realmode: Use SYM_DATA_* " Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:50 ` [PATCH v9 19/28] x86/asm: Kill the last GLOBAL user and remove the macro Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm: Remove " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 20/28] x86/asm: Make some functions local Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 21/28] x86/asm/ftrace: Mark function_hook as function Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
2019-10-18 16:48 ` Steven Rostedt
2019-10-18 16:49 ` Steven Rostedt
2019-10-18 17:13 ` Borislav Petkov
2019-10-18 17:37 ` Steven Rostedt [this message]
2019-10-18 19:48 ` Borislav Petkov
2019-10-18 20:31 ` Steven Rostedt
2019-10-19 7:34 ` Borislav Petkov
2019-10-21 14:10 ` [PATCH] x86/ftrace: Get rid of function_hook Borislav Petkov
2019-10-21 14:33 ` Steven Rostedt
2019-10-22 11:38 ` Jiri Slaby
2019-10-22 12:56 ` Borislav Petkov
2019-10-22 12:57 ` [PATCH -v2] " Borislav Petkov
2019-10-25 9:00 ` [tip: x86/asm] " tip-bot2 for Borislav Petkov
2019-10-11 11:51 ` [PATCH v9 22/28] x86_64/asm: Add ENDs to some functions and relabel with SYM_CODE_* Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm/64: " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 23/28] x86_64/asm: Change all ENTRY+END to SYM_CODE_* Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm/64: " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 24/28] x86_64/asm: Change all ENTRY+ENDPROC to SYM_FUNC_* Jiri Slaby
2019-10-16 7:12 ` Borislav Petkov
2019-10-18 6:56 ` Herbert Xu
2019-10-11 11:51 ` [PATCH v9 25/28] x86_32/asm: Add ENDs to some functions and relabel with SYM_CODE_* Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm/32: " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 26/28] x86_32/asm: Change all ENTRY+END to SYM_CODE_* Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm/32: " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 27/28] x86_32/asm: Change all ENTRY+ENDPROC to SYM_FUNC_* Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] x86/asm/32: " tip-bot2 for Jiri Slaby
2019-10-11 11:51 ` [PATCH v9 28/28] x86/asm: Replace WEAK uses by SYM_INNER_LABEL_ALIGN Jiri Slaby
2019-10-18 16:30 ` [tip: x86/asm] " tip-bot2 for Jiri Slaby
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