linux-kernel - [PATCH] wifi: iwlegacy: work around excessive stack usage on clang/kasan

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Message-Id: <20250620113946.3987160-1-arnd@kernel.org>
Date: Fri, 20 Jun 2025 13:39:42 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Stanislaw Gruszka <stf_xl@...pl>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Johannes Berg <johannes.berg@...el.com>,
	linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] wifi: iwlegacy: work around excessive stack usage on clang/kasan

From: Arnd Bergmann <arnd@...db.de>

In some rare randconfig builds, I seem to trigger a bug in clang where
it unrolls a loop but then runs out of registers, which then get
spilled to the stack:

net/wireless/intel/iwlegacy/4965-rs.c:2262:1: error: stack frame size (1696) exceeds limit (1280) in 'il4965_rs_rate_init' [-Werror,-Wframe-larger-than]

This seems to be the same one I saw in the omapdrm driver, and there is
an easy workaround by not inlining the il4965_rs_rate_scale_clear_win
function.

Link: https://github.com/llvm/llvm-project/issues/143908
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/wireless/intel/iwlegacy/4965-rs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlegacy/4965-rs.c b/drivers/net/wireless/intel/iwlegacy/4965-rs.c
index 0e5130d1fccd..031d88bf6393 100644
--- a/drivers/net/wireless/intel/iwlegacy/4965-rs.c
+++ b/drivers/net/wireless/intel/iwlegacy/4965-rs.c
@@ -203,7 +203,8 @@ il4965_rs_extract_rate(u32 rate_n_flags)
 	return (u8) (rate_n_flags & 0xFF);
 }
 
-static void
+/* noinline works around https://github.com/llvm/llvm-project/issues/143908 */
+static noinline_for_stack void
 il4965_rs_rate_scale_clear_win(struct il_rate_scale_data *win)
 {
 	win->data = 0;
-- 
2.39.5