From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [tip: x86/asm] x86/asm/ftrace: Mark function_hook as function Date: Fri, 18 Oct 2019 12:48:00 -0400 Message-ID: <20191018124800.0a7006bb@gandalf.local.home> References: <20191011115108.12392-22-jslaby@suse.cz> <157141622788.29376.4016565749507481510.tip-bot2@tip-bot2> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <157141622788.29376.4016565749507481510.tip-bot2@tip-bot2> Sender: linux-kernel-owner@vger.kernel.org To: tip-bot2 for Jiri Slaby Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, Jiri Slaby , Borislav Petkov , "H. Peter Anvin" , Ingo Molnar , Josh Poimboeuf , linux-arch@vger.kernel.org, Masami Hiramatsu , Peter Zijlstra , Thomas Gleixner , x86-ml , Ingo Molnar , Borislav Petkov List-Id: linux-arch.vger.kernel.org On Fri, 18 Oct 2019 16:30:27 -0000 "tip-bot2 for Jiri Slaby" wrote: > The following commit has been merged into the x86/asm branch of tip: > > Commit-ID: f13ad88a984e8090226a8f62d75e87b770eefdf4 > Gitweb: https://git.kernel.org/tip/f13ad88a984e8090226a8f62d75e87b770eefdf4 > Author: Jiri Slaby > AuthorDate: Fri, 11 Oct 2019 13:51:01 +02:00 > Committer: Borislav Petkov > CommitterDate: Fri, 18 Oct 2019 11:35:41 +02:00 I just noticed this (sorry missed the original patch). > > x86/asm/ftrace: Mark function_hook as function > > Relabel function_hook to be marked really as a function. It is called > from C and has the same expectations towards the stack etc. This is wrong, function_hook is never called from C. It's called via fentry (use to be mcount), and does not have the same semantics as a C function. In fact, that's why it exists in assembly. Because it has to save and restore registers to make it possible to call a C function! -- Steve > > Signed-off-by: Jiri Slaby > Signed-off-by: Borislav Petkov > Cc: "H. Peter Anvin" > Cc: Ingo Molnar > Cc: Josh Poimboeuf > Cc: linux-arch@vger.kernel.org > Cc: Masami Hiramatsu > Cc: Peter Zijlstra > Cc: "Steven Rostedt (VMware)" > Cc: Thomas Gleixner > Cc: x86-ml > Link: https://lkml.kernel.org/r/20191011115108.12392-22-jslaby@suse.cz > --- > arch/x86/kernel/ftrace_32.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S > index e0061dc..219be13 100644 > --- a/arch/x86/kernel/ftrace_32.S > +++ b/arch/x86/kernel/ftrace_32.S > @@ -21,9 +21,9 @@ EXPORT_SYMBOL(__fentry__) > # define MCOUNT_FRAME 0 /* using frame = false */ > #endif > > -ENTRY(function_hook) > +SYM_FUNC_START(function_hook) > ret > -END(function_hook) > +SYM_FUNC_END(function_hook) > > ENTRY(ftrace_caller) > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:46084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728368AbfJRQsE (ORCPT ); Fri, 18 Oct 2019 12:48:04 -0400 Date: Fri, 18 Oct 2019 12:48:00 -0400 From: Steven Rostedt Subject: Re: [tip: x86/asm] x86/asm/ftrace: Mark function_hook as function Message-ID: <20191018124800.0a7006bb@gandalf.local.home> In-Reply-To: <157141622788.29376.4016565749507481510.tip-bot2@tip-bot2> References: <20191011115108.12392-22-jslaby@suse.cz> <157141622788.29376.4016565749507481510.tip-bot2@tip-bot2> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: tip-bot2 for Jiri Slaby Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, Jiri Slaby , Borislav Petkov , "H. Peter Anvin" , Ingo Molnar , Josh Poimboeuf , linux-arch@vger.kernel.org, Masami Hiramatsu , Peter Zijlstra , Thomas Gleixner , x86-ml , Ingo Molnar , Borislav Petkov Message-ID: <20191018164800.c-WuJ1X7r1HShqX_xwBPqq3-XNsJVAVzpwnMhKCpLR4@z> On Fri, 18 Oct 2019 16:30:27 -0000 "tip-bot2 for Jiri Slaby" wrote: > The following commit has been merged into the x86/asm branch of tip: > > Commit-ID: f13ad88a984e8090226a8f62d75e87b770eefdf4 > Gitweb: https://git.kernel.org/tip/f13ad88a984e8090226a8f62d75e87b770eefdf4 > Author: Jiri Slaby > AuthorDate: Fri, 11 Oct 2019 13:51:01 +02:00 > Committer: Borislav Petkov > CommitterDate: Fri, 18 Oct 2019 11:35:41 +02:00 I just noticed this (sorry missed the original patch). > > x86/asm/ftrace: Mark function_hook as function > > Relabel function_hook to be marked really as a function. It is called > from C and has the same expectations towards the stack etc. This is wrong, function_hook is never called from C. It's called via fentry (use to be mcount), and does not have the same semantics as a C function. In fact, that's why it exists in assembly. Because it has to save and restore registers to make it possible to call a C function! -- Steve > > Signed-off-by: Jiri Slaby > Signed-off-by: Borislav Petkov > Cc: "H. Peter Anvin" > Cc: Ingo Molnar > Cc: Josh Poimboeuf > Cc: linux-arch@vger.kernel.org > Cc: Masami Hiramatsu > Cc: Peter Zijlstra > Cc: "Steven Rostedt (VMware)" > Cc: Thomas Gleixner > Cc: x86-ml > Link: https://lkml.kernel.org/r/20191011115108.12392-22-jslaby@suse.cz > --- > arch/x86/kernel/ftrace_32.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S > index e0061dc..219be13 100644 > --- a/arch/x86/kernel/ftrace_32.S > +++ b/arch/x86/kernel/ftrace_32.S > @@ -21,9 +21,9 @@ EXPORT_SYMBOL(__fentry__) > # define MCOUNT_FRAME 0 /* using frame = false */ > #endif > > -ENTRY(function_hook) > +SYM_FUNC_START(function_hook) > ret > -END(function_hook) > +SYM_FUNC_END(function_hook) > > ENTRY(ftrace_caller) >