linux-kernel - [PATCH] drm/radeon: reduce stack frame size for radeon_cs

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Message-Id: <20250610093125.2645138-1-arnd@kernel.org>
Date: Tue, 10 Jun 2025 11:31:20 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Nathan Chancellor <nathan@...nel.org>,
	Marek Olšák <marek.olsak@....com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Sunil Khatri <sunil.khatri@....com>,
	Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] drm/radeon: reduce stack frame size for radeon_cs_ioctl

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

Clang inlines radeon_cs_parser_relocs() into radeon_cs_ioctl(), and
since both of these use a lot of stack space, the sum of them can
make it exceed a limit of 1280 bytes:

drivers/gpu/drm/radeon/radeon_cs.c:669:5: error: stack frame size (1328) exceeds limit (1280) in 'radeon_cs_ioctl' [-Werror,-Wframe-larger-than]
  669 | int radeon_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
      |     ^

Mark radeon_cs_parser_relocs as noinline_for_stack, so clang and gcc
both behave in a consistent way. Calling into radeon_cs_parser_relocs()
still uses a lot of stack space here, but this is not any worse than it
already was, and the other code paths are better now.

Fixes: c9b76548899c ("drm/radeon: validate relocations in the order determined by userspace v3")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/radeon/radeon_cs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/radeon_cs.c b/drivers/gpu/drm/radeon/radeon_cs.c
index b8e6202f1d5b..220a9b107b15 100644
--- a/drivers/gpu/drm/radeon/radeon_cs.c
+++ b/drivers/gpu/drm/radeon/radeon_cs.c
@@ -78,7 +78,7 @@ static void radeon_cs_buckets_get_list(struct radeon_cs_buckets *b,
 	}
 }
 
-static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
+static noinline_for_stack int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 {
 	struct radeon_cs_chunk *chunk;
 	struct radeon_cs_buckets buckets;
-- 
2.39.5