[PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[behanw]

From: Behan Webster <behanw@converseincode.com>

This patch set moves from using locally defined named registers to access the
stack pointer to using a globally defined named register. This allows the code
to work both with gcc and clang.

The LLVMLinux project aims to fully build the Linux kernel using both gcc and
clang (the C front end for the LLVM compiler infrastructure project). 

Behan Webster (4):
  arm64: LLVMLinux: Add current_stack_pointer() for arm64
  arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
  arm64: LLVMLinux: Calculate current_thread_info from
    current_stack_pointer
  arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c

 arch/arm64/include/asm/thread_info.h | 9 +++++++--
 arch/arm64/kernel/stacktrace.c       | 3 +--
 arch/arm64/kernel/traps.c            | 3 +--
 3 files changed, 9 insertions(+), 6 deletions(-)

-- 
1.9.1

[PATCH 1/4] arm64: LLVMLinux: Add current_stack_pointer() for arm64

[behanw]

From: Behan Webster <behanw@converseincode.com>

Define a global named register for current_stack_pointer. The use of this new
variable guarantees that both gcc and clang can access this register in C code.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
---
 arch/arm64/include/asm/thread_info.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index e40b6d0..e6b6094 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -69,6 +69,11 @@ struct thread_info {
 #define init_stack		(init_thread_union.stack)
 
 /*
+ * how to get the current stack pointer from C
+ */
+register unsigned long current_stack_pointer asm ("sp");
+
+/*
  * how to get the thread information struct from C
  */
 static inline struct thread_info *current_thread_info(void) __attribute_const__;
-- 
1.9.1

[PATCH 2/4] arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Jan-Simon M??ller <dl9pf@gmx.de>
---
 arch/arm64/kernel/stacktrace.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 55437ba..407991b 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -111,10 +111,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 		frame.sp = thread_saved_sp(tsk);
 		frame.pc = thread_saved_pc(tsk);
 	} else {
-		register unsigned long current_sp asm("sp");
 		data.no_sched_functions = 0;
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.pc = (unsigned long)save_stack_trace_tsk;
 	}
 
-- 
1.9.1

[PATCH 3/4] arm64: LLVMLinux: Calculate current_thread_info from current_stack_pointer

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Jan-Simon M??ller <dl9pf@gmx.de>
---
 arch/arm64/include/asm/thread_info.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index e6b6094..c2432d2 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -80,8 +80,8 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__;
 
 static inline struct thread_info *current_thread_info(void)
 {
-	register unsigned long sp asm ("sp");
-	return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
+	return (struct thread_info *) \
+		(current_stack_pointer & ~(THREAD_SIZE - 1));
 }
 
 #define thread_saved_pc(tsk)	\
-- 
1.9.1

Re: [PATCH 3/4] arm64: LLVMLinux: Calculate current_thread_info from current_stack_pointer

[Andreas Färber]

Hi,

Am 31.07.2014 01:57, schrieb behanw@converseincode.com:
> From: Behan Webster <behanw@converseincode.com>
> 
> Use the global current_stack_pointer to get the value of the stack pointer.
> This change supports being able to compile the kernel with both gcc and clang.
> 
> Signed-off-by: Behan Webster <behanw@converseincode.com>
> Signed-off-by: Mark Charlebois <charlebm@gmail.com>
> Reviewed-by: Jan-Simon M??ller <dl9pf@gmx.de>

Something went wrong with ö encoding here and in 2/4.

> ---
>  arch/arm64/include/asm/thread_info.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index e6b6094..c2432d2 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -80,8 +80,8 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__;
>  
>  static inline struct thread_info *current_thread_info(void)
>  {
> -	register unsigned long sp asm ("sp");
> -	return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
> +	return (struct thread_info *) \

This is not a macro, so \ seems superfluous.

Looks okay otherwise.

Regards,
Andreas

> +		(current_stack_pointer & ~(THREAD_SIZE - 1));
>  }
>  
>  #define thread_saved_pc(tsk)	\

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

Re: [PATCH 3/4] arm64: LLVMLinux: Calculate current_thread_info from current_stack_pointer

[Behan Webster]

On 07/30/14 22:31, Andreas Färber wrote:
> Hi,
>
> Am 31.07.2014 01:57, schrieb behanw@converseincode.com:
>> From: Behan Webster <behanw@converseincode.com>
>>
>> Use the global current_stack_pointer to get the value of the stack pointer.
>> This change supports being able to compile the kernel with both gcc and clang.
>>
>> Signed-off-by: Behan Webster <behanw@converseincode.com>
>> Signed-off-by: Mark Charlebois <charlebm@gmail.com>
>> Reviewed-by: Jan-Simon M??ller <dl9pf@gmx.de>
> Something went wrong with ö encoding here and in 2/4.
Yeah. That keeps happening. :(

Thanks.

>> ---
>>   arch/arm64/include/asm/thread_info.h | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
>> index e6b6094..c2432d2 100644
>> --- a/arch/arm64/include/asm/thread_info.h
>> +++ b/arch/arm64/include/asm/thread_info.h
>> @@ -80,8 +80,8 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__;
>>   
>>   static inline struct thread_info *current_thread_info(void)
>>   {
>> -	register unsigned long sp asm ("sp");
>> -	return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
>> +	return (struct thread_info *) \
> This is not a macro, so \ seems superfluous.
Doh. Indeed. Will fix.

Behan

-- 
Behan Webster
behanw@converseincode.com

[PATCH 4/4] arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
---
 arch/arm64/kernel/traps.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index c43cfa9..0aeb316 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -132,7 +132,6 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
 	struct stackframe frame;
-	const register unsigned long current_sp asm ("sp");
 
 	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 
@@ -145,7 +144,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		frame.pc = regs->pc;
 	} else if (tsk == current) {
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.pc = (unsigned long)dump_backtrace;
 	} else {
 		/*
-- 
1.9.1

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Olof Johansson]

On Wed, Jul 30, 2014 at 4:57 PM,  <behanw@converseincode.com> wrote:
> From: Behan Webster <behanw@converseincode.com>
>
> This patch set moves from using locally defined named registers to access the
> stack pointer to using a globally defined named register. This allows the code
> to work both with gcc and clang.
>
> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
> clang (the C front end for the LLVM compiler infrastructure project).
>
> Behan Webster (4):
>   arm64: LLVMLinux: Add current_stack_pointer() for arm64
>   arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>   arm64: LLVMLinux: Calculate current_thread_info from
>     current_stack_pointer
>   arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c

Series:

Reviewed-by: Olof Johansson <olof@lixom.net>

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Will Deacon]

On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
> From: Behan Webster <behanw@converseincode.com>
> 
> This patch set moves from using locally defined named registers to access the
> stack pointer to using a globally defined named register. This allows the code
> to work both with gcc and clang.
> 
> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
> clang (the C front end for the LLVM compiler infrastructure project). 
> 
> Behan Webster (4):
>   arm64: LLVMLinux: Add current_stack_pointer() for arm64
>   arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>   arm64: LLVMLinux: Calculate current_thread_info from
>     current_stack_pointer
>   arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c

Once Andreas's comments have been addressed:

  Acked-by: Will Deacon <will.deacon@arm.com>

Please can you send a new series after the merge window?

Cheers,

Will

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Olof Johansson]

On Thu, Jul 31, 2014 at 3:33 AM, Will Deacon <will.deacon@arm.com> wrote:
> On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
>> From: Behan Webster <behanw@converseincode.com>
>>
>> This patch set moves from using locally defined named registers to access the
>> stack pointer to using a globally defined named register. This allows the code
>> to work both with gcc and clang.
>>
>> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
>> clang (the C front end for the LLVM compiler infrastructure project).
>>
>> Behan Webster (4):
>>   arm64: LLVMLinux: Add current_stack_pointer() for arm64
>>   arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>>   arm64: LLVMLinux: Calculate current_thread_info from
>>     current_stack_pointer
>>   arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
>
> Once Andreas's comments have been addressed:
>
>   Acked-by: Will Deacon <will.deacon@arm.com>
>
> Please can you send a new series after the merge window?

Given that the ARM64 KVM guys are still actively breaking -next, and
this is considerably smaller and lower risk than that, I think you can
take it for 3.17?


-Olof

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Will Deacon]

On Thu, Jul 31, 2014 at 04:39:55PM +0100, Olof Johansson wrote:
> On Thu, Jul 31, 2014 at 3:33 AM, Will Deacon <will.deacon@arm.com> wrote:
> > On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
> >> From: Behan Webster <behanw@converseincode.com>
> >>
> >> This patch set moves from using locally defined named registers to access the
> >> stack pointer to using a globally defined named register. This allows the code
> >> to work both with gcc and clang.
> >>
> >> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
> >> clang (the C front end for the LLVM compiler infrastructure project).
> >>
> >> Behan Webster (4):
> >>   arm64: LLVMLinux: Add current_stack_pointer() for arm64
> >>   arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
> >>   arm64: LLVMLinux: Calculate current_thread_info from
> >>     current_stack_pointer
> >>   arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
> >
> > Once Andreas's comments have been addressed:
> >
> >   Acked-by: Will Deacon <will.deacon@arm.com>
> >
> > Please can you send a new series after the merge window?
> 
> Given that the ARM64 KVM guys are still actively breaking -next, and
> this is considerably smaller and lower risk than that, I think you can
> take it for 3.17?

Hey, those breakages are in the kvm tree not the arm64 tree! I'd really
rather wait on these as I don't see the rush to get them in for 3.17 and
it's not beyond the realms of possibility that they could cause problems
for a particular version of GCC (at the very least, I'd need to re-run
all the testing I've been doing).

Will

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Olof Johansson]

On Thu, Jul 31, 2014 at 8:48 AM, Will Deacon <will.deacon@arm.com> wrote:
> On Thu, Jul 31, 2014 at 04:39:55PM +0100, Olof Johansson wrote:
>> On Thu, Jul 31, 2014 at 3:33 AM, Will Deacon <will.deacon@arm.com> wrote:
>> > On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
>> >> From: Behan Webster <behanw@converseincode.com>
>> >>
>> >> This patch set moves from using locally defined named registers to access the
>> >> stack pointer to using a globally defined named register. This allows the code
>> >> to work both with gcc and clang.
>> >>
>> >> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
>> >> clang (the C front end for the LLVM compiler infrastructure project).
>> >>
>> >> Behan Webster (4):
>> >>   arm64: LLVMLinux: Add current_stack_pointer() for arm64
>> >>   arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>> >>   arm64: LLVMLinux: Calculate current_thread_info from
>> >>     current_stack_pointer
>> >>   arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
>> >
>> > Once Andreas's comments have been addressed:
>> >
>> >   Acked-by: Will Deacon <will.deacon@arm.com>
>> >
>> > Please can you send a new series after the merge window?
>>
>> Given that the ARM64 KVM guys are still actively breaking -next, and
>> this is considerably smaller and lower risk than that, I think you can
>> take it for 3.17?
>
> Hey, those breakages are in the kvm tree not the arm64 tree! I'd really
> rather wait on these as I don't see the rush to get them in for 3.17 and
> it's not beyond the realms of possibility that they could cause problems
> for a particular version of GCC (at the very least, I'd need to re-run
> all the testing I've been doing).


Yeah, it was somewhat tongue in cheek that made not have made it
across the wire.

3.18 is fine with me too even though I find the concerns to be quite unlikely.


-Olof

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Behan Webster]

On 07/31/14 03:33, Will Deacon wrote:
> On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
>> From: Behan Webster <behanw@converseincode.com>
>>
>> This patch set moves from using locally defined named registers to access the
>> stack pointer to using a globally defined named register. This allows the code
>> to work both with gcc and clang.
>>
>> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
>> clang (the C front end for the LLVM compiler infrastructure project).
>>
>> Behan Webster (4):
>>    arm64: LLVMLinux: Add current_stack_pointer() for arm64
>>    arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>>    arm64: LLVMLinux: Calculate current_thread_info from
>>      current_stack_pointer
>>    arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
> Once Andreas's comments have been addressed:
>
>    Acked-by: Will Deacon <will.deacon@arm.com>
>
> Please can you send a new series after the merge window?
Pity. I was hoping to get it in this merge window.

However, will resubmit for 3.18.

Thanks,

Behan

-- 
Behan Webster
behanw@converseincode.com

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Will Deacon]

Hi Behan,

On Fri, Aug 01, 2014 at 05:11:59AM +0100, Behan Webster wrote:
> On 07/31/14 03:33, Will Deacon wrote:
> > On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
> >> From: Behan Webster <behanw@converseincode.com>
> >>
> >> This patch set moves from using locally defined named registers to access the
> >> stack pointer to using a globally defined named register. This allows the code
> >> to work both with gcc and clang.
> >>
> >> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
> >> clang (the C front end for the LLVM compiler infrastructure project).
> >>
> >> Behan Webster (4):
> >>    arm64: LLVMLinux: Add current_stack_pointer() for arm64
> >>    arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
> >>    arm64: LLVMLinux: Calculate current_thread_info from
> >>      current_stack_pointer
> >>    arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
> > Once Andreas's comments have been addressed:
> >
> >    Acked-by: Will Deacon <will.deacon@arm.com>
> >
> > Please can you send a new series after the merge window?
> Pity. I was hoping to get it in this merge window.
> 
> However, will resubmit for 3.18.

Any chance of a v2 for this series, please? If you address the comments
pending for v1, I think it's good to merge.

Will

Re: [PATCH 0/4] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[Behan Webster]

On 08/26/14 07:16, Will Deacon wrote:
> Hi Behan,
>
> On Fri, Aug 01, 2014 at 05:11:59AM +0100, Behan Webster wrote:
>> On 07/31/14 03:33, Will Deacon wrote:
>>> On Thu, Jul 31, 2014 at 12:57:25AM +0100, behanw@converseincode.com wrote:
>>>> From: Behan Webster <behanw@converseincode.com>
>>>>
>>>> This patch set moves from using locally defined named registers to access the
>>>> stack pointer to using a globally defined named register. This allows the code
>>>> to work both with gcc and clang.
>>>>
>>>> The LLVMLinux project aims to fully build the Linux kernel using both gcc and
>>>> clang (the C front end for the LLVM compiler infrastructure project).
>>>>
>>>> Behan Webster (4):
>>>>     arm64: LLVMLinux: Add current_stack_pointer() for arm64
>>>>     arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
>>>>     arm64: LLVMLinux: Calculate current_thread_info from
>>>>       current_stack_pointer
>>>>     arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
>>> Once Andreas's comments have been addressed:
>>>
>>>     Acked-by: Will Deacon <will.deacon@arm.com>
>>>
>>> Please can you send a new series after the merge window?
>> Pity. I was hoping to get it in this merge window.
>>
>> However, will resubmit for 3.18.
> Any chance of a v2 for this series, please? If you address the comments
> pending for v1, I think it's good to merge.
Sure thing. 2 more named register patches added. Look for them at the 
end of the new patch series.

I kept missing you in Chicago. I was hoping to say "hi".

Behan

-- 
Behan Webster
behanw@converseincode.com

[PATCH V2 0/6] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[behanw]

From: Behan Webster <behanw@converseincode.com>

This patch set moves from using locally defined named registers to access the
stack pointer to using a globally defined named register. This allows the code
to work both with gcc and clang.

The LLVMLinux project aims to fully build the Linux kernel using both gcc and
clang (the C front end for the LLVM compiler infrastructure project). 


Behan Webster (5):
  arm64: LLVMLinux: Add current_stack_pointer() for arm64
  arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
  arm64: LLVMLinux: Calculate current_thread_info from
    current_stack_pointer
  arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c
  arm64: LLVMLinux: Use global stack pointer in return_address()

Mark Charlebois (1):
  arm64: LLVMLinux: Use global stack register variable for aarch64

 arch/arm64/include/asm/percpu.h      | 4 ++--
 arch/arm64/include/asm/thread_info.h | 9 +++++++--
 arch/arm64/kernel/return_address.c   | 3 +--
 arch/arm64/kernel/stacktrace.c       | 3 +--
 arch/arm64/kernel/traps.c            | 3 +--
 5 files changed, 12 insertions(+), 10 deletions(-)

-- 
1.9.1

[PATCH V2 1/6] arm64: LLVMLinux: Add current_stack_pointer() for arm64

[behanw]

From: Behan Webster <behanw@converseincode.com>

Define a global named register for current_stack_pointer. The use of this new
variable guarantees that both gcc and clang can access this register in C code.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Olof Johansson <olof@lixom.net>
Acked-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/thread_info.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 45108d8..356e037 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -69,6 +69,11 @@ struct thread_info {
 #define init_stack		(init_thread_union.stack)
 
 /*
+ * how to get the current stack pointer from C
+ */
+register unsigned long current_stack_pointer asm ("sp");
+
+/*
  * how to get the thread information struct from C
  */
 static inline struct thread_info *current_thread_info(void) __attribute_const__;
-- 
1.9.1

[PATCH V2 2/6] arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Olof Johansson <olof@lixom.net>
Acked-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/stacktrace.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 55437ba..407991b 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -111,10 +111,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 		frame.sp = thread_saved_sp(tsk);
 		frame.pc = thread_saved_pc(tsk);
 	} else {
-		register unsigned long current_sp asm("sp");
 		data.no_sched_functions = 0;
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.pc = (unsigned long)save_stack_trace_tsk;
 	}
 
-- 
1.9.1

[PATCH V2 3/6] arm64: LLVMLinux: Calculate current_thread_info from current_stack_pointer

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Olof Johansson <olof@lixom.net>
Acked-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/thread_info.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 356e037..459bf8e 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -80,8 +80,8 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__;
 
 static inline struct thread_info *current_thread_info(void)
 {
-	register unsigned long sp asm ("sp");
-	return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
+	return (struct thread_info *)
+		(current_stack_pointer & ~(THREAD_SIZE - 1));
 }
 
 #define thread_saved_pc(tsk)	\
-- 
1.9.1

[PATCH V2 4/6] arm64: LLVMLinux: Use current_stack_pointer in kernel/traps.c

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to get the value of the stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Olof Johansson <olof@lixom.net>
Acked-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/traps.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 02cd3f0..de1b085 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -132,7 +132,6 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
 	struct stackframe frame;
-	const register unsigned long current_sp asm ("sp");
 
 	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 
@@ -145,7 +144,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		frame.pc = regs->pc;
 	} else if (tsk == current) {
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.pc = (unsigned long)dump_backtrace;
 	} else {
 		/*
-- 
1.9.1

[PATCH V2 5/6] arm64: LLVMLinux: Use global stack register variable for aarch64

[behanw]

From: Mark Charlebois <charlebm@gmail.com>

To support both Clang and GCC, use the global stack register variable vs
a local register variable.

Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
---
 arch/arm64/include/asm/percpu.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 453a179..5279e57 100644
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -26,13 +26,13 @@ static inline void set_my_cpu_offset(unsigned long off)
 static inline unsigned long __my_cpu_offset(void)
 {
 	unsigned long off;
-	register unsigned long *sp asm ("sp");
 
 	/*
 	 * We want to allow caching the value, so avoid using volatile and
 	 * instead use a fake stack read to hazard against barrier().
 	 */
-	asm("mrs %0, tpidr_el1" : "=r" (off) : "Q" (*sp));
+	asm("mrs %0, tpidr_el1" : "=r" (off) :
+		"Q" (*(const unsigned long *)current_stack_pointer));
 
 	return off;
 }
-- 
1.9.1

[PATCH V2 6/6] arm64: LLVMLinux: Use global stack pointer in return_address()

[behanw]

From: Behan Webster <behanw@converseincode.com>

The global register current_stack_pointer holds the current stack pointer.
This change supports being able to compile the kernel with both gcc and clang.

Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
---
 arch/arm64/kernel/return_address.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c
index 89102a6..6c4fd28 100644
--- a/arch/arm64/kernel/return_address.c
+++ b/arch/arm64/kernel/return_address.c
@@ -36,13 +36,12 @@ void *return_address(unsigned int level)
 {
 	struct return_address_data data;
 	struct stackframe frame;
-	register unsigned long current_sp asm ("sp");
 
 	data.level = level + 2;
 	data.addr = NULL;
 
 	frame.fp = (unsigned long)__builtin_frame_address(0);
-	frame.sp = current_sp;
+	frame.sp = current_stack_pointer;
 	frame.pc = (unsigned long)return_address; /* dummy */
 
 	walk_stackframe(&frame, save_return_addr, &data);
-- 
1.9.1