[PATCH v3 2/5] alpha: stop storing the user stack pointer in pt_regs

[Matt Turner]

Nothing reads pt_regs->usp now that user_stack_pointer() uses the PCB.
Drop the stores, which saves a PAL_rdusp call on every syscall, and
give the field back its old name.

Assisted-by: Claude:claude-opus-5-5
Reviewed-by: Magnus Lindholm <linmag7@xxxxxxxxx>
Tested-by: Magnus Lindholm <linmag7@xxxxxxxxx>
Acked-by: Ian Rogers <irogers@xxxxxxxxxx>
Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>
---
 arch/alpha/include/uapi/asm/ptrace.h | 2 +-
 arch/alpha/kernel/asm-offsets.c      | 1 -
 arch/alpha/kernel/entry.S            | 5 -----
 arch/alpha/kernel/traps.c            | 8 --------
 4 files changed, 1 insertion(+), 15 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/ptrace.h b/arch/alpha/include/uapi/asm/ptrace.h
index 9d86b2a1526e..72ed913a910f 100644
--- a/arch/alpha/include/uapi/asm/ptrace.h
+++ b/arch/alpha/include/uapi/asm/ptrace.h
@@ -43,7 +43,7 @@ struct pt_regs {
 	unsigned long trap_a1;
 	unsigned long trap_a2;
 /* This makes the stack 16-byte aligned as GCC expects */
-	unsigned long usp;
+	unsigned long __pad0;
 /* These are saved by PAL-code: */
 	unsigned long ps;
 	unsigned long pc;
diff --git a/arch/alpha/kernel/asm-offsets.c b/arch/alpha/kernel/asm-offsets.c
index c89792c86044..22ed3c975b1c 100644
--- a/arch/alpha/kernel/asm-offsets.c
+++ b/arch/alpha/kernel/asm-offsets.c
@@ -30,7 +30,6 @@ static void __used foo(void)
 
 	DEFINE(HAE_CACHE, offsetof(struct alpha_machine_vector, hae_cache));
 	DEFINE(HAE_REG, offsetof(struct alpha_machine_vector, hae_register));
-	DEFINE(PT_REGS_USP, offsetof(struct pt_regs, usp));
 
 	DEFINE(TI_FLAGS,        offsetof(struct thread_info, flags));
 	DEFINE(TI_SYSCALL_WORK, offsetof(struct thread_info, syscall_work));
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index bfa116d455fb..790389a15c3c 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -476,11 +476,6 @@ entSys:
 	ldq	$1, 0($sp)	/* syscall nr from saved r0 */
 	stq	$1, 8($sp)	/* regs->r1 = shadow syscall nr */
 
-	mov	$0, $8
-	call_pal PAL_rdusp
-	stq	$0, PT_REGS_USP($sp)
-	mov	$8, $0
-
 	lda	$8, 0x3fff
 	bic	$sp, $8, $8
 
diff --git a/arch/alpha/kernel/traps.c b/arch/alpha/kernel/traps.c
index cfaef96c4ce8..5882c65b7ef1 100644
--- a/arch/alpha/kernel/traps.c
+++ b/arch/alpha/kernel/traps.c
@@ -30,12 +30,6 @@
 
 #include "proto.h"
 
-static __always_inline void alpha_snapshot_usp(struct pt_regs *regs)
-{
-	if (user_mode(regs))
-		regs->usp = rdusp();
-}
-
 void
 dik_show_regs(struct pt_regs *regs, unsigned long *r9_15)
 {
@@ -186,7 +180,6 @@ do_entArith(unsigned long summary, unsigned long write_mask,
 {
 	long si_code = FPE_FLTINV;
 
-	alpha_snapshot_usp(regs);
 	if (summary & 1) {
 		/* Software-completion summary bit is set, so try to
 		   emulate the instruction.  If the processor supports
@@ -208,7 +201,6 @@ do_entIF(unsigned long type, struct pt_regs *regs)
 {
 	int signo, code;
 
-	alpha_snapshot_usp(regs);
 	if (type == 3) { /* FEN fault */
 		/* Irritating users can call PAL_clrfen to disable the
 		   FPU for the process.  The kernel will then trap in

-- 
2.55.0