diff mbox series

[v11,3/8] ARM: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

Message ID c61eb9290c3e817d4d70c429c0e987e3ec51a3c4.1680954589.git.pengdonglin@sangfor.com.cn (mailing list archive)
State Accepted
Headers show
Series function_graph: Support recording and printing the return value of function | expand

Commit Message

pengdonglin April 8, 2023, 12:42 p.m. UTC 
The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the ARM platform.

We introduce a new structure called fgraph_ret_regs for the ARM platform
to hold return registers and the frame pointer. We then fill its content
in the return_to_handler and pass its address to the function
ftrace_return_to_handler to record the return value.

Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
---
v10:
 - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition

v9:
 - Fix stack pointer align issues
 - Update the commit message

v8:
 - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
 arch/arm/Kconfig               |  1 +
 arch/arm/include/asm/ftrace.h  | 22 ++++++++++++++++++++++
 arch/arm/kernel/asm-offsets.c  |  8 +++++++-
 arch/arm/kernel/entry-ftrace.S | 10 ++++++----
 4 files changed, 36 insertions(+), 5 deletions(-)

Comments

Steven Rostedt June 9, 2023, 1:57 a.m. UTC | #1 
On Sat,  8 Apr 2023 05:42:17 -0700
Donglin Peng <pengdonglin@sangfor.com.cn> wrote:

> The previous patch ("function_graph: Support recording and printing
> the return value of function") has laid the groundwork for the for
> the funcgraph-retval, and this modification makes it available on
> the ARM platform.
> 
> We introduce a new structure called fgraph_ret_regs for the ARM platform
> to hold return registers and the frame pointer. We then fill its content
> in the return_to_handler and pass its address to the function
> ftrace_return_to_handler to record the return value.
> 
> Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>

I really don't want to add this without an ack from an arm maintainer.

I have the patches queued (for testing), but I may remove the ones that do
not have the appropriate acks.

-- Steve


> ---
> v10:
>  - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
> 
> v9:
>  - Fix stack pointer align issues
>  - Update the commit message
> 
> v8:
>  - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
>  arch/arm/Kconfig               |  1 +
>  arch/arm/include/asm/ftrace.h  | 22 ++++++++++++++++++++++
>  arch/arm/kernel/asm-offsets.c  |  8 +++++++-
>  arch/arm/kernel/entry-ftrace.S | 10 ++++++----
>  4 files changed, 36 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index e24a9820e12f..73061379855a 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -98,6 +98,7 @@ config ARM
>  	select HAVE_FAST_GUP if ARM_LPAE
>  	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>  	select HAVE_FUNCTION_ERROR_INJECTION
> +	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
>  	select HAVE_GCC_PLUGINS
> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
> index 7e9251ca29fe..3c457902b355 100644
> --- a/arch/arm/include/asm/ftrace.h
> +++ b/arch/arm/include/asm/ftrace.h
> @@ -77,4 +77,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
>  
>  #endif /* ifndef __ASSEMBLY__ */
>  
> +#ifndef __ASSEMBLY__
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +struct fgraph_ret_regs {
> +	/* r0 - r3 */
> +	unsigned long regs[4];
> +
> +	unsigned long fp;
> +	unsigned long __unused;
> +};
> +
> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->regs[0];
> +}
> +
> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->fp;
> +}
> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> +#endif
> +
>  #endif /* _ASM_ARM_FTRACE */
> diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
> index 38121c59cbc2..18bb85115b21 100644
> --- a/arch/arm/kernel/asm-offsets.c
> +++ b/arch/arm/kernel/asm-offsets.c
> @@ -23,6 +23,7 @@
>  #include <asm/suspend.h>
>  #include <asm/vdso_datapage.h>
>  #include <asm/hardware/cache-l2x0.h>
> +#include <asm/ftrace.h>
>  #include <linux/kbuild.h>
>  #include <linux/arm-smccc.h>
>  #include "signal.h"
> @@ -170,5 +171,10 @@ int main(void)
>    DEFINE(KEXEC_INDIR_PAGE,	offsetof(struct kexec_relocate_data, kexec_indirection_page));
>    DEFINE(KEXEC_MACH_TYPE,	offsetof(struct kexec_relocate_data, kexec_mach_type));
>    DEFINE(KEXEC_R2,		offsetof(struct kexec_relocate_data, kexec_r2));
> -  return 0; 
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +  BLANK();
> +  DEFINE(FGRET_REGS_SIZE,	sizeof(struct fgraph_ret_regs));
> +  BLANK();
> +#endif
> +  return 0;
>  }
> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
> index 3e7bcaca5e07..d41a1676608c 100644
> --- a/arch/arm/kernel/entry-ftrace.S
> +++ b/arch/arm/kernel/entry-ftrace.S
> @@ -257,11 +257,13 @@ ENDPROC(ftrace_graph_regs_caller)
>  
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  ENTRY(return_to_handler)
> -	stmdb	sp!, {r0-r3}
> -	add	r0, sp, #16		@ sp at exit of instrumented routine
> +	mov	ip, sp				@ sp at exit of instrumented routine
> +	stmdb	sp!, {r0-r3, ip, lr}		@ fill fgraph_ret_regs
> +	mov	r0, sp
>  	bl	ftrace_return_to_handler
> -	mov	lr, r0			@ r0 has real ret addr
> -	ldmia	sp!, {r0-r3}
> +	mov	lr, r0				@ r0 has real ret addr
> +	ldmia	sp, {r0-r3}
> +	add	sp, sp, #FGRET_REGS_SIZE	@ restore stack pointer
>  	ret	lr
>  ENDPROC(return_to_handler)
>  #endif
pengdonglin June 9, 2023, 3:22 a.m. UTC | #2 
On 2023/6/9 9:57, Steven Rostedt wrote:
> On Sat,  8 Apr 2023 05:42:17 -0700
> Donglin Peng <pengdonglin@sangfor.com.cn> wrote:
> 
>> The previous patch ("function_graph: Support recording and printing
>> the return value of function") has laid the groundwork for the for
>> the funcgraph-retval, and this modification makes it available on
>> the ARM platform.
>>
>> We introduce a new structure called fgraph_ret_regs for the ARM platform
>> to hold return registers and the frame pointer. We then fill its content
>> in the return_to_handler and pass its address to the function
>> ftrace_return_to_handler to record the return value.
>>
>> Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
> 
> I really don't want to add this without an ack from an arm maintainer.
> 
> I have the patches queued (for testing), but I may remove the ones that do
> not have the appropriate acks.
> 
> -- Steve
> 

Hi Russell, can I get a ack for arm?

> 
>> ---
>> v10:
>>   - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
>>
>> v9:
>>   - Fix stack pointer align issues
>>   - Update the commit message
>>
>> v8:
>>   - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
>> ---
>>   arch/arm/Kconfig               |  1 +
>>   arch/arm/include/asm/ftrace.h  | 22 ++++++++++++++++++++++
>>   arch/arm/kernel/asm-offsets.c  |  8 +++++++-
>>   arch/arm/kernel/entry-ftrace.S | 10 ++++++----
>>   4 files changed, 36 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index e24a9820e12f..73061379855a 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -98,6 +98,7 @@ config ARM
>>   	select HAVE_FAST_GUP if ARM_LPAE
>>   	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>>   	select HAVE_FUNCTION_ERROR_INJECTION
>> +	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>>   	select HAVE_FUNCTION_GRAPH_TRACER
>>   	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
>>   	select HAVE_GCC_PLUGINS
>> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
>> index 7e9251ca29fe..3c457902b355 100644
>> --- a/arch/arm/include/asm/ftrace.h
>> +++ b/arch/arm/include/asm/ftrace.h
>> @@ -77,4 +77,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
>>   
>>   #endif /* ifndef __ASSEMBLY__ */
>>   
>> +#ifndef __ASSEMBLY__
>> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> +struct fgraph_ret_regs {
>> +	/* r0 - r3 */
>> +	unsigned long regs[4];
>> +
>> +	unsigned long fp;
>> +	unsigned long __unused;
>> +};
>> +
>> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
>> +{
>> +	return ret_regs->regs[0];
>> +}
>> +
>> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
>> +{
>> +	return ret_regs->fp;
>> +}
>> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
>> +#endif
>> +
>>   #endif /* _ASM_ARM_FTRACE */
>> diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
>> index 38121c59cbc2..18bb85115b21 100644
>> --- a/arch/arm/kernel/asm-offsets.c
>> +++ b/arch/arm/kernel/asm-offsets.c
>> @@ -23,6 +23,7 @@
>>   #include <asm/suspend.h>
>>   #include <asm/vdso_datapage.h>
>>   #include <asm/hardware/cache-l2x0.h>
>> +#include <asm/ftrace.h>
>>   #include <linux/kbuild.h>
>>   #include <linux/arm-smccc.h>
>>   #include "signal.h"
>> @@ -170,5 +171,10 @@ int main(void)
>>     DEFINE(KEXEC_INDIR_PAGE,	offsetof(struct kexec_relocate_data, kexec_indirection_page));
>>     DEFINE(KEXEC_MACH_TYPE,	offsetof(struct kexec_relocate_data, kexec_mach_type));
>>     DEFINE(KEXEC_R2,		offsetof(struct kexec_relocate_data, kexec_r2));
>> -  return 0;
>> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> +  BLANK();
>> +  DEFINE(FGRET_REGS_SIZE,	sizeof(struct fgraph_ret_regs));
>> +  BLANK();
>> +#endif
>> +  return 0;
>>   }
>> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
>> index 3e7bcaca5e07..d41a1676608c 100644
>> --- a/arch/arm/kernel/entry-ftrace.S
>> +++ b/arch/arm/kernel/entry-ftrace.S
>> @@ -257,11 +257,13 @@ ENDPROC(ftrace_graph_regs_caller)
>>   
>>   #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>>   ENTRY(return_to_handler)
>> -	stmdb	sp!, {r0-r3}
>> -	add	r0, sp, #16		@ sp at exit of instrumented routine
>> +	mov	ip, sp				@ sp at exit of instrumented routine
>> +	stmdb	sp!, {r0-r3, ip, lr}		@ fill fgraph_ret_regs
>> +	mov	r0, sp
>>   	bl	ftrace_return_to_handler
>> -	mov	lr, r0			@ r0 has real ret addr
>> -	ldmia	sp!, {r0-r3}
>> +	mov	lr, r0				@ r0 has real ret addr
>> +	ldmia	sp, {r0-r3}
>> +	add	sp, sp, #FGRET_REGS_SIZE	@ restore stack pointer
>>   	ret	lr
>>   ENDPROC(return_to_handler)
>>   #endif
>
Steven Rostedt June 9, 2023, 9:21 p.m. UTC | #3 
Hi Russell,

I noticed that this patch set only went to the linux-arm-kernel mailing
list but did not include you in the Cc.

Could you give an ack to this patch, and I can take it through my tree?

The full patch set went to linux-arm-kernel where I'm sure you have access
to.

Thanks!

-- Steve


On Sat,  8 Apr 2023 05:42:17 -0700
Donglin Peng <pengdonglin@sangfor.com.cn> wrote:

> The previous patch ("function_graph: Support recording and printing
> the return value of function") has laid the groundwork for the for
> the funcgraph-retval, and this modification makes it available on
> the ARM platform.
> 
> We introduce a new structure called fgraph_ret_regs for the ARM platform
> to hold return registers and the frame pointer. We then fill its content
> in the return_to_handler and pass its address to the function
> ftrace_return_to_handler to record the return value.
> 
> Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
> ---
> v10:
>  - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
> 
> v9:
>  - Fix stack pointer align issues
>  - Update the commit message
> 
> v8:
>  - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
>  arch/arm/Kconfig               |  1 +
>  arch/arm/include/asm/ftrace.h  | 22 ++++++++++++++++++++++
>  arch/arm/kernel/asm-offsets.c  |  8 +++++++-
>  arch/arm/kernel/entry-ftrace.S | 10 ++++++----
>  4 files changed, 36 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index e24a9820e12f..73061379855a 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -98,6 +98,7 @@ config ARM
>  	select HAVE_FAST_GUP if ARM_LPAE
>  	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>  	select HAVE_FUNCTION_ERROR_INJECTION
> +	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
>  	select HAVE_GCC_PLUGINS
> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
> index 7e9251ca29fe..3c457902b355 100644
> --- a/arch/arm/include/asm/ftrace.h
> +++ b/arch/arm/include/asm/ftrace.h
> @@ -77,4 +77,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
>  
>  #endif /* ifndef __ASSEMBLY__ */
>  
> +#ifndef __ASSEMBLY__
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +struct fgraph_ret_regs {
> +	/* r0 - r3 */
> +	unsigned long regs[4];
> +
> +	unsigned long fp;
> +	unsigned long __unused;
> +};
> +
> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->regs[0];
> +}
> +
> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->fp;
> +}
> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> +#endif
> +
>  #endif /* _ASM_ARM_FTRACE */
> diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
> index 38121c59cbc2..18bb85115b21 100644
> --- a/arch/arm/kernel/asm-offsets.c
> +++ b/arch/arm/kernel/asm-offsets.c
> @@ -23,6 +23,7 @@
>  #include <asm/suspend.h>
>  #include <asm/vdso_datapage.h>
>  #include <asm/hardware/cache-l2x0.h>
> +#include <asm/ftrace.h>
>  #include <linux/kbuild.h>
>  #include <linux/arm-smccc.h>
>  #include "signal.h"
> @@ -170,5 +171,10 @@ int main(void)
>    DEFINE(KEXEC_INDIR_PAGE,	offsetof(struct kexec_relocate_data, kexec_indirection_page));
>    DEFINE(KEXEC_MACH_TYPE,	offsetof(struct kexec_relocate_data, kexec_mach_type));
>    DEFINE(KEXEC_R2,		offsetof(struct kexec_relocate_data, kexec_r2));
> -  return 0; 
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +  BLANK();
> +  DEFINE(FGRET_REGS_SIZE,	sizeof(struct fgraph_ret_regs));
> +  BLANK();
> +#endif
> +  return 0;
>  }
> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
> index 3e7bcaca5e07..d41a1676608c 100644
> --- a/arch/arm/kernel/entry-ftrace.S
> +++ b/arch/arm/kernel/entry-ftrace.S
> @@ -257,11 +257,13 @@ ENDPROC(ftrace_graph_regs_caller)
>  
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  ENTRY(return_to_handler)
> -	stmdb	sp!, {r0-r3}
> -	add	r0, sp, #16		@ sp at exit of instrumented routine
> +	mov	ip, sp				@ sp at exit of instrumented routine
> +	stmdb	sp!, {r0-r3, ip, lr}		@ fill fgraph_ret_regs
> +	mov	r0, sp
>  	bl	ftrace_return_to_handler
> -	mov	lr, r0			@ r0 has real ret addr
> -	ldmia	sp!, {r0-r3}
> +	mov	lr, r0				@ r0 has real ret addr
> +	ldmia	sp, {r0-r3}
> +	add	sp, sp, #FGRET_REGS_SIZE	@ restore stack pointer
>  	ret	lr
>  ENDPROC(return_to_handler)
>  #endif
diff mbox series

Patch

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e24a9820e12f..73061379855a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -98,6 +98,7 @@  config ARM
 	select HAVE_FAST_GUP if ARM_LPAE
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_ERROR_INJECTION
+	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
 	select HAVE_GCC_PLUGINS
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 7e9251ca29fe..3c457902b355 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -77,4 +77,26 @@  static inline bool arch_syscall_match_sym_name(const char *sym,
 
 #endif /* ifndef __ASSEMBLY__ */
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+struct fgraph_ret_regs {
+	/* r0 - r3 */
+	unsigned long regs[4];
+
+	unsigned long fp;
+	unsigned long __unused;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->fp;
+}
+#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
+#endif
+
 #endif /* _ASM_ARM_FTRACE */
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 38121c59cbc2..18bb85115b21 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -23,6 +23,7 @@ 
 #include <asm/suspend.h>
 #include <asm/vdso_datapage.h>
 #include <asm/hardware/cache-l2x0.h>
+#include <asm/ftrace.h>
 #include <linux/kbuild.h>
 #include <linux/arm-smccc.h>
 #include "signal.h"
@@ -170,5 +171,10 @@  int main(void)
   DEFINE(KEXEC_INDIR_PAGE,	offsetof(struct kexec_relocate_data, kexec_indirection_page));
   DEFINE(KEXEC_MACH_TYPE,	offsetof(struct kexec_relocate_data, kexec_mach_type));
   DEFINE(KEXEC_R2,		offsetof(struct kexec_relocate_data, kexec_r2));
-  return 0; 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+  BLANK();
+  DEFINE(FGRET_REGS_SIZE,	sizeof(struct fgraph_ret_regs));
+  BLANK();
+#endif
+  return 0;
 }
diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
index 3e7bcaca5e07..d41a1676608c 100644
--- a/arch/arm/kernel/entry-ftrace.S
+++ b/arch/arm/kernel/entry-ftrace.S
@@ -257,11 +257,13 @@  ENDPROC(ftrace_graph_regs_caller)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 ENTRY(return_to_handler)
-	stmdb	sp!, {r0-r3}
-	add	r0, sp, #16		@ sp at exit of instrumented routine
+	mov	ip, sp				@ sp at exit of instrumented routine
+	stmdb	sp!, {r0-r3, ip, lr}		@ fill fgraph_ret_regs
+	mov	r0, sp
 	bl	ftrace_return_to_handler
-	mov	lr, r0			@ r0 has real ret addr
-	ldmia	sp!, {r0-r3}
+	mov	lr, r0				@ r0 has real ret addr
+	ldmia	sp, {r0-r3}
+	add	sp, sp, #FGRET_REGS_SIZE	@ restore stack pointer
 	ret	lr
 ENDPROC(return_to_handler)
 #endif