[PATCH 6.18 094/314] unwind: Simplify unwind_user_next_fp() alignment check

Sasha Levin
2026-03-10T11:26:10Z

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 5578534e4b92350995a20068f2e6ea3186c62d7f ]

2^log_2(n) == n

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://patch.msgid.link/20250924080119.497867836@infradead.org
Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/unwind/user.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 97a8415e3216f..9dcde797b5d93 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -19,7 +19,6 @@ static int unwind_user_next_fp(struct unwind_user_state *state)
{
const struct unwind_user_frame *frame = &fp_frame;
unsigned long cfa, fp, ra;
- unsigned int shift;

if (frame->use_fp) {
if (state->fp < state->sp)
@@ -37,8 +36,7 @@ static int unwind_user_next_fp(struct unwind_user_state *state)
return -EINVAL;

/* Make sure that the address is word aligned */
- shift = sizeof(long) == 4 ? 2 : 3;
- if (cfa & ((1 << shift) - 1))
+ if (cfa & (sizeof(long) - 1))
return -EINVAL;

/* Find the Return Address (RA) */
--
2.51.0