diff mbox series

[RFC,21/43] x86/ftrace: Adapt assembly for PIE support

Message ID 0092ce94b325ad8eb47ff4f95e012f9af1a127de.1682673543.git.houwenlong.hwl@antgroup.com
State New
Headers
Series x86/pie: Make kernel image's virtual address flexible |

Commit Message

Hou Wenlong April 28, 2023, 9:51 a.m. UTC 
  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@antgroup.com>
Cc: Thomas Garnier <thgarnie@chromium.org>
Cc: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Cc: Kees Cook <keescook@chromium.org>
---
 arch/x86/kernel/ftrace_64.S | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Comments

Steven Rostedt April 28, 2023, 1:37 p.m. UTC | #1 
On Fri, 28 Apr 2023 17:51:01 +0800
"Hou Wenlong" <houwenlong.hwl@antgroup.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@antgroup.com>
> Cc: Thomas Garnier <thgarnie@chromium.org>
> Cc: Lai Jiangshan <jiangshan.ljs@antgroup.com>
> Cc: Kees Cook <keescook@chromium.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
Hou Wenlong April 29, 2023, 3:43 a.m. UTC | #2 
On Fri, Apr 28, 2023 at 09:37:19PM +0800, Steven Rostedt wrote:
> On Fri, 28 Apr 2023 17:51:01 +0800
> "Hou Wenlong" <houwenlong.hwl@antgroup.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@antgroup.com>
> > Cc: Thomas Garnier <thgarnie@chromium.org>
> > Cc: Lai Jiangshan <jiangshan.ljs@antgroup.com>
> > Cc: Kees Cook <keescook@chromium.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
> 
> 
> ?
>
OK, I'll drop it. Actually, I select DYNAMIC_FTRACE when
CONFIG_RETPOLINE is enabled for PIE due to the indirect call for
__fentry__() in patch 34.

Thanks.
> -- Steve
diff mbox series

Patch

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