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From: Arnd Bergmann <arnd@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Kees Cook <kees@kernel.org>,
	linux-wireless@vger.kernel.org, b43-dev@lists.infradead.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] b43legacy: work around stack frame size warning
Date: Fri, 25 Sep 2026 15:07:36 +0200	[thread overview]
Message-ID: <20260925130749.4191347-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

I came across a rare warning in the b43legacy driver while building
randconfig kernels using clang-21.1.8, with KASAN enabled:

drivers/net/wireless/broadcom/b43legacy/main.c:3250:12: error: stack frame size (1392) exceeds limit (1280) in 'b43legacy_wireless_core_init' [-Werror,-Wframe-larger-than]
 3250 | static int b43legacy_wireless_core_init(struct b43legacy_wldev *dev)
      |            ^

There are no actual large variables on the stack here, just excessive
spills, and the code looks fine otherwise, so this is really an
optimization quirk in the compiler. Marking the prepare_phy_data_for_init()
function as noinline completely avoids the issue, with no function in
this file using more than 200 bytes of stack space, same as without KASAN.

Link: https://pastebin.com/raw/KpV124Ep # .config
Link: https://pastebin.com/CxWfsBN0 # assembler output, truncated
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/broadcom/b43legacy/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/net/wireless/broadcom/b43legacy/main.c
index 6b3e0b2bbca7..dfff3710dea3 100644
--- a/drivers/net/wireless/broadcom/b43legacy/main.c
+++ b/drivers/net/wireless/broadcom/b43legacy/main.c
@@ -3207,7 +3207,8 @@ static void b43legacy_wireless_core_exit(struct b43legacy_wldev *dev)
 	ssb_bus_may_powerdown(dev->dev->bus);
 }
 
-static void prepare_phy_data_for_init(struct b43legacy_wldev *dev)
+static noinline_for_stack void
+prepare_phy_data_for_init(struct b43legacy_wldev *dev)
 {
 	struct b43legacy_phy *phy = &dev->phy;
 	int i;
-- 
2.53.0


WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Kees Cook <kees@kernel.org>,
	linux-wireless@vger.kernel.org, b43-dev@lists.infradead.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] b43legacy: work around stack frame size warning
Date: Fri, 25 Sep 2026 15:07:36 +0200	[thread overview]
Message-ID: <20260925130749.4191347-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

I came across a rare warning in the b43legacy driver while building
randconfig kernels using clang-21.1.8, with KASAN enabled:

drivers/net/wireless/broadcom/b43legacy/main.c:3250:12: error: stack frame size (1392) exceeds limit (1280) in 'b43legacy_wireless_core_init' [-Werror,-Wframe-larger-than]
 3250 | static int b43legacy_wireless_core_init(struct b43legacy_wldev *dev)
      |            ^

There are no actual large variables on the stack here, just excessive
spills, and the code looks fine otherwise, so this is really an
optimization quirk in the compiler. Marking the prepare_phy_data_for_init()
function as noinline completely avoids the issue, with no function in
this file using more than 200 bytes of stack space, same as without KASAN.

Link: https://pastebin.com/raw/KpV124Ep # .config
Link: https://pastebin.com/CxWfsBN0 # assembler output, truncated
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/broadcom/b43legacy/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/net/wireless/broadcom/b43legacy/main.c
index 6b3e0b2bbca7..dfff3710dea3 100644
--- a/drivers/net/wireless/broadcom/b43legacy/main.c
+++ b/drivers/net/wireless/broadcom/b43legacy/main.c
@@ -3207,7 +3207,8 @@ static void b43legacy_wireless_core_exit(struct b43legacy_wldev *dev)
 	ssb_bus_may_powerdown(dev->dev->bus);
 }
 
-static void prepare_phy_data_for_init(struct b43legacy_wldev *dev)
+static noinline_for_stack void
+prepare_phy_data_for_init(struct b43legacy_wldev *dev)
 {
 	struct b43legacy_phy *phy = &dev->phy;
 	int i;
-- 
2.53.0


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             reply	other threads:[~2026-09-25 13:07 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-25 13:07 Arnd Bergmann [this message]
2026-09-25 13:07 ` [PATCH] b43legacy: work around stack frame size warning Arnd Bergmann

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