[PATCH v2 0/7] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[PATCH v2 0/7] LLVMLinux: Patches to enable the kernel to be compiled with clang/LLVM

[behanw]

From: Behan Webster <behanw@converseincode.com>

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). 

Clang only supports global named registers for non-allocatable registers like
the stack pointer. By centralizing the definition of current_stack_pointer, the
use of named registers for ARM remains largely unchanged while working for both
gcc and clang.


Behan Webster (6):
  arm: LLVMLinux: Add global named register current_stack_pointer for
    ARM
  arm: LLVMLinux: Use current_stack_pointer to calculate pt_regs address
  arm: LLVMLinux: Use current_stack_pointer for return_address
  arm: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk
  arm: LLVMLinux: Calculate current_thread_info from
    current_stack_pointer
  arm: LLVMLinux: Use current_stack_pointer in unwind_backtrace

Mark Charlebois (1):
  arm: LLVMLinux: Use global stack register variable for percpu

 arch/arm/include/asm/percpu.h      | 4 ++--
 arch/arm/include/asm/ptrace.h      | 5 ++---
 arch/arm/include/asm/thread_info.h | 9 +++++++--
 arch/arm/kernel/return_address.c   | 3 +--
 arch/arm/kernel/stacktrace.c       | 4 +---
 arch/arm/kernel/unwind.c           | 3 +--
 6 files changed, 14 insertions(+), 14 deletions(-)

-- 
1.9.1

[PATCH v2 1/7] arm: LLVMLinux: Add global named register current_stack_pointer for ARM

[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/arm/include/asm/thread_info.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index fc44d37..bb43515 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -101,6 +101,11 @@ struct thread_info {
 #define init_stack		(init_thread_union.stack)
 
 /*
+ * how to get the current stack pointer in 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 2/7] arm: LLVMLinux: Use current_stack_pointer to calculate pt_regs address

[behanw]

From: Behan Webster <behanw@converseincode.com>

Use the global current_stack_pointer to calculate the end of the stack for
current_pt_regs()

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
---
 arch/arm/include/asm/ptrace.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 601264d..51622ba 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -154,9 +154,8 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs)
 	return regs->ARM_sp;
 }
 
-#define current_pt_regs(void) ({				\
-	register unsigned long sp asm ("sp");			\
-	(struct pt_regs *)((sp | (THREAD_SIZE - 1)) - 7) - 1;	\
+#define current_pt_regs(void) ({ (struct pt_regs *)			\
+		((current_stack_pointer | (THREAD_SIZE - 1)) - 7) - 1;	\
 })
 
 #endif /* __ASSEMBLY__ */
-- 
1.9.1

[PATCH v2 3/7] arm: LLVMLinux: Use current_stack_pointer for return_address

[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>
---
 arch/arm/kernel/return_address.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
index fafedd8..5bceaef 100644
--- a/arch/arm/kernel/return_address.c
+++ b/arch/arm/kernel/return_address.c
@@ -39,13 +39,12 @@ 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.lr = (unsigned long)__builtin_return_address(0);
 	frame.pc = (unsigned long)return_address;
 
-- 
1.9.1

[PATCH v2 4/7] arm: 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>
---
 arch/arm/kernel/stacktrace.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index f065eb0..92b7237 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -134,12 +134,10 @@ static noinline void __save_stack_trace(struct task_struct *tsk,
 		frame.pc = thread_saved_pc(tsk);
 #endif
 	} else {
-		register unsigned long current_sp asm ("sp");
-
 		/* We don't want this function nor the caller */
 		data.skip += 2;
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.lr = (unsigned long)__builtin_return_address(0);
 		frame.pc = (unsigned long)__save_stack_trace;
 	}
-- 
1.9.1

[PATCH v2 5/7] arm: 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>
---
 arch/arm/include/asm/thread_info.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index bb43515..b9dc3dc 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -112,8 +112,8 @@ 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 6/7] arm: LLVMLinux: Use current_stack_pointer in unwind_backtrace

[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>
---
 arch/arm/kernel/unwind.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index a61a1df..caea23b 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -471,7 +471,6 @@ int unwind_frame(struct stackframe *frame)
 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
 	struct stackframe frame;
-	register unsigned long current_sp asm ("sp");
 
 	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 
@@ -485,7 +484,7 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 			frame.pc = regs->ARM_lr;
 	} else if (tsk == current) {
 		frame.fp = (unsigned long)__builtin_frame_address(0);
-		frame.sp = current_sp;
+		frame.sp = current_stack_pointer;
 		frame.lr = (unsigned long)__builtin_return_address(0);
 		frame.pc = (unsigned long)unwind_backtrace;
 	} else {
-- 
1.9.1

[PATCH v2 7/7] arm: LLVMLinux: Use global stack register variable for percpu

[behanw]

From: Mark Charlebois <charlebm@gmail.com>

Using global current_stack_pointer works on both clang and gcc.
current_stack_pointer is an unsigned long and needs to be cast
as a pointer to dereference.

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

diff --git a/arch/arm/include/asm/percpu.h b/arch/arm/include/asm/percpu.h
index 209e650..a89b407 100644
--- a/arch/arm/include/asm/percpu.h
+++ b/arch/arm/include/asm/percpu.h
@@ -30,14 +30,14 @@ 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");
 
 	/*
 	 * Read TPIDRPRW.
 	 * We want to allow caching the value, so avoid using volatile and
 	 * instead use a fake stack read to hazard against barrier().
 	 */
-	asm("mrc p15, 0, %0, c13, c0, 4" : "=r" (off) : "Q" (*sp));
+	asm("mrc p15, 0, %0, c13, c0, 4" : "=r" (off)
+		: "Q" (*(const unsigned long *)current_stack_pointer));
 
 	return off;
 }
-- 
1.9.1