[PATCH 2/2] alpha: read $gp and $sp explicitly for clang

[Matt Turner <mattst88@gmail.com>]

clang honors a local `register unsigned long x __asm__("$N")` variable
only where it appears as an inline-asm operand; merely reading it does
not produce the contents of that register.  So trap_init() passed an
undefined global pointer to PAL_wrkgp, and load_PCB() stored an undefined
stack pointer into the PCB that swpctx then loaded.  Either one wedges an
early boot.

Read the registers explicitly instead: an inline mov for $gp in
trap_init(), and the file-scope current_stack_pointer for $sp in
load_PCB().  A file-scope register-asm variable is the form clang does
support.

Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/kernel/traps.c | 4 +++-
 arch/alpha/mm/init.c      | 3 +--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/alpha/kernel/traps.c b/arch/alpha/kernel/traps.c
index 7631129ac914..5b4f1ae2b74b 100644
--- a/arch/alpha/kernel/traps.c
+++ b/arch/alpha/kernel/traps.c
@@ -925,7 +925,9 @@ void
 trap_init(void)
 {
 	/* Tell PAL-code what global pointer we want in the kernel.  */
-	register unsigned long gptr __asm__("$29");
+	unsigned long gptr;
+
+	__asm__ volatile("mov $29, %0" : "=r"(gptr));
 	wrkgp(gptr);
 
 	wrent(entArith, 1);
diff --git a/arch/alpha/mm/init.c b/arch/alpha/mm/init.c
index 9531cbc761c0..f4d65a60c869 100644
--- a/arch/alpha/mm/init.c
+++ b/arch/alpha/mm/init.c
@@ -63,8 +63,7 @@ pgd_alloc(struct mm_struct *mm)
 static inline unsigned long
 load_PCB(struct pcb_struct *pcb)
 {
-	register unsigned long sp __asm__("$30");
-	pcb->ksp = sp;
+	pcb->ksp = (unsigned long)current_stack_pointer;
 	return __reload_thread(pcb);
 }
 

-- 
2.54.0