[ALPHA] Fixup fallout from force_successful_syscall_return change.

arch/alpha/kernel/asm-offsets.c

@@ -31,6 +31,7 @@ void foo(void)
         DEFINE(TASK_TGID, offsetof(struct task_struct, tgid));
         BLANK();
 
+	DEFINE(SIZEOF_PT_REGS, sizeof(struct pt_regs));
 	DEFINE(PT_PTRACED, PT_PTRACED);
 	DEFINE(CLONE_VM, CLONE_VM);
 	DEFINE(CLONE_UNTRACED, CLONE_UNTRACED);

arch/alpha/kernel/head.S

@@ -9,6 +9,7 @@
 
 #include <linux/config.h>
 #include <asm/system.h>
+#include <asm/asm_offsets.h>
 
 .globl swapper_pg_dir
 .globl _stext
@@ -25,7 +26,7 @@ __start:
 	/* We need to get current_task_info loaded up...  */
 	lda	$8,init_thread_union
 	/* ... and find our stack ... */
-	lda	$30,0x4000($8)
+	lda	$30,0x4000 - SIZEOF_PT_REGS($8)
 	/* ... and then we can start the kernel.  */
 	jsr	$26,start_kernel
 	call_pal PAL_halt

include/asm-alpha/ptrace.h

@@ -71,15 +71,8 @@ struct switch_stack {
 #define instruction_pointer(regs) ((regs)->pc)
 extern void show_regs(struct pt_regs *);
 
-/*
- * TODO: if kernel-only threads do not have a dummy pt_regs structure at the
- * top of the stack, this would cause kernel stack corruption.  Either check
- * first that we're not dealing with a kernel thread or change the kernel
- * stacks to allocate a dummy pt_regs structure.
- */
-
-#define alpha_task_regs(task)	((struct pt_regs *) \
-			((long) task->thread_info + PAGE_SIZE) - 1)
+#define alpha_task_regs(task) \
+  ((struct pt_regs *) ((long) (task)->thread_info + 2*PAGE_SIZE) - 1)
 
 #define force_successful_syscall_return() (alpha_task_regs(current)->r0 = 0)