linux-kernel - Re: [PATCH] ftrace: x86: Fix a compile error about get_kernel

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Message-ID: <b4ef10d0-a1eb-4d9c-8ddc-d7815a2bb607@163.com>
Date: Thu, 6 Feb 2025 21:25:37 +0800
From: Haiyue Wang <haiyuewa@....com>
To: Peter Zijlstra <peterz@...radead.org>,
 Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
 Gabriel de Perthuis <g2p.code@...il.com>,
 Sami Tolvanen <samitolvanen@...gle.com>, Mark Rutland
 <mark.rutland@....com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, "H . Peter Anvin"
 <hpa@...or.com>, x86@...nel.org, linux-trace-kernel@...r.kernel.org,
 LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: x86: Fix a compile error about
 get_kernel_nofault()



On 2025/2/6 20:33, Peter Zijlstra wrote:
> On Thu, Feb 06, 2025 at 01:13:28PM +0100, Peter Zijlstra wrote:
> 
>> No, it just cleans up this utter trainwreck. I also noticed this is a
>> second (new) copy of this garbage. Clearly I didn't yell loud enough
>> last time and people didn't think to vomit when doing the copy/paste :/
>>
>> Function will look something like:
>>
>> unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
>> {
>> 	if (is_endbr(fentry_ip - ENDBR_INSN_SIZE))
>> 		fentry_op -= ENDBR_INSN_SIZE;
>> 	return fentry_ip;
>> }
>>
>> Let me finish local build test before I push out.
> 
> Bah, still waiting for a LLVM build, but patch should be here:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/ibt
> 
> I was supposed to merge this last cycle, but then akpm shat all over
> arch/x86/kernel/alternative.c and we had to clean that up :/
> 
> Notably, this patch, not sure it applies out of order.
> 
> ---
> 
> Subject: x86/ibt: Clean up is_endbr()
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Mon Nov 27 09:58:06 CET 2023
> 
> Pretty much every caller of is_endbr() actually wants to test something at an
> address and ends up doing get_kernel_nofault(). Fold the lot into a more
> convenient helper.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Acked-by: Alexei Starovoitov <ast@...nel.org>
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> ---
>   arch/x86/events/core.c         |    2 +-
>   arch/x86/include/asm/ftrace.h  |   17 +++--------------
>   arch/x86/include/asm/ibt.h     |    5 +++--
>   arch/x86/kernel/alternative.c  |   20 ++++++++++++++------
>   arch/x86/kernel/kprobes/core.c |   11 +----------
>   arch/x86/net/bpf_jit_comp.c    |    4 ++--
>   kernel/trace/bpf_trace.c       |   20 +++-----------------
>   7 files changed, 27 insertions(+), 52 deletions(-)
> 
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -2857,7 +2857,7 @@ static bool is_uprobe_at_func_entry(stru
>   		return true;
>   
>   	/* endbr64 (64-bit only) */
> -	if (user_64bit_mode(regs) && is_endbr(*(u32 *)auprobe->insn))
> +	if (user_64bit_mode(regs) && is_endbr((u32 *)auprobe->insn))
>   		return true;
>   
>   	return false;
> --- a/arch/x86/include/asm/ftrace.h
> +++ b/arch/x86/include/asm/ftrace.h
> @@ -2,6 +2,7 @@
>   #ifndef _ASM_X86_FTRACE_H
>   #define _ASM_X86_FTRACE_H
>   
> +#include "asm/ibt.h"

Then 
https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/tree/arch/x86/include/asm/ftrace.h?h=x86/ibt#n17

# include <asm/ibt.h> --> This line can be removed ?

>   #include <asm/ptrace.h>
>   
>   #ifdef CONFIG_FUNCTION_TRACER
> @@ -36,21 +37,9 @@ static inline unsigned long ftrace_call_
>   
>   static inline unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
>   {