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Message-ID: <20230428093719.037081e3@gandalf.local.home>
Date: Fri, 28 Apr 2023 09:37:19 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Hou Wenlong" <houwenlong.hwl@...group.com>
Cc: linux-kernel@...r.kernel.org,
"Thomas Garnier" <thgarnie@...omium.org>,
"Lai Jiangshan" <jiangshan.ljs@...group.com>,
"Kees Cook" <keescook@...omium.org>,
"Masami Hiramatsu" <mhiramat@...nel.org>,
"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>, <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
<linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 21/43] x86/ftrace: Adapt assembly for PIE support
On Fri, 28 Apr 2023 17:51:01 +0800
"Hou Wenlong" <houwenlong.hwl@...group.com> wrote:
> Change the assembly code to use only relative references of symbols for
> the kernel to be PIE compatible.
>
> Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
> Cc: Thomas Garnier <thgarnie@...omium.org>
> Cc: Lai Jiangshan <jiangshan.ljs@...group.com>
> Cc: Kees Cook <keescook@...omium.org>
> ---
> arch/x86/kernel/ftrace_64.S | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> index eddb4fabc16f..411fa4148e18 100644
> --- a/arch/x86/kernel/ftrace_64.S
> +++ b/arch/x86/kernel/ftrace_64.S
> @@ -315,7 +315,14 @@ STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller)
> SYM_FUNC_START(__fentry__)
> CALL_DEPTH_ACCOUNT
>
> +#ifdef CONFIG_X86_PIE
> + pushq %r8
> + leaq ftrace_stub(%rip), %r8
> + cmpq %r8, ftrace_trace_function(%rip)
> + popq %r8
> +#else
> cmpq $ftrace_stub, ftrace_trace_function
> +#endif
> jnz trace
> RET
>
> @@ -329,7 +336,7 @@ trace:
> * ip and parent ip are used and the list function is called when
> * function tracing is enabled.
> */
> - movq ftrace_trace_function, %r8
> + movq ftrace_trace_function(%rip), %r8
> CALL_NOSPEC r8
> restore_mcount_regs
>
I really don't want to add more updates to !DYNAMIC_FTRACE. This code only
exists to make sure I don't break it for other architectures.
How about
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 442eccc00960..ee4d0713139d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -37,7 +37,7 @@ config X86_64
config FORCE_DYNAMIC_FTRACE
def_bool y
- depends on X86_32
+ depends on X86_32 || X86_PIE
depends on FUNCTION_TRACER
select DYNAMIC_FTRACE
help
?
-- Steve
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