linux-kernel - [PATCH] init/Kconfig: lower to GCC version 9 check for -Warray-bounds

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Date: Sat,  8 Jun 2024 01:40:27 +0000
From: Zhouyi Zhou <zhouzhouyi@...il.com>
To: akpm@...ux-foundation.org,
	pmladek@...e.com,
	masahiroy@...nel.org,
	yoann.congal@...le.fr,
	rdunlap@...radead.org,
	gustavoars@...nel.org,
	nphamcs@...il.com,
	vincent.guittot@...aro.org,
	linux-kernel@...r.kernel.org,
	rcu@...r.kernel.org
Cc: Zhouyi Zhou <zhouzhouyi@...il.com>
Subject: [PATCH] init/Kconfig: lower to GCC version 9 check for -Warray-bounds

commit 3e00f5802fab ("init/Kconfig: lower GCC version check for -Warray-bounds")
lowers GCC version check for -Warray-bounds, but I continue to see false positives
from -Warray-bounds in GCC 9.4.

This happens after
commit b44759705f7d ("bitmap: make bitmap_{get,set}_value8() use bitmap_{read,write}()")

During the rcuturture test in Ubuntu 20.04 GCC 9.4.0 x86_64, the compiling of
drivers/gpio/gpio-pca953x.c issues following warning:

```
  CC      drivers/gpio/gpio-pca953x.o
In file included from drivers/gpio/gpio-pca953x.c:12:
drivers/gpio/gpio-pca953x.c: In function ‘pca953x_probe’:
./include/linux/bitmap.h:799:17: error: array subscript [1, 1024] is outside array bounds of ‘long unsigned int[1]’ [-Werror=array-bounds]
  799 |  map[index + 1] &= BITMAP_FIRST_WORD_MASK(start + nbits);
      |                 ^~
In file included from ./include/linux/atomic.h:5,
                 from drivers/gpio/gpio-pca953x.c:11:
drivers/gpio/gpio-pca953x.c:1015:17: note: while referencing ‘val’
 1015 |  DECLARE_BITMAP(val, MAX_LINE);
      |                 ^~~
./include/linux/types.h:11:16: note: in definition of macro ‘DECLARE_BITMAP’
   11 |  unsigned long name[BITS_TO_LONGS(bits)]
      |                ^~~~
In file included from drivers/gpio/gpio-pca953x.c:12:
./include/linux/bitmap.h:800:17: error: array subscript [1, 1024] is outside array bounds of ‘long unsigned int[1]’ [-Werror=array-bounds]
  800 |  map[index + 1] |= (value >> space);
      |  ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
In file included from ./include/linux/atomic.h:5,
                 from drivers/gpio/gpio-pca953x.c:11:
drivers/gpio/gpio-pca953x.c:1015:17: note: while referencing ‘val’
 1015 |  DECLARE_BITMAP(val, MAX_LINE);
      |                 ^~~
./include/linux/types.h:11:16: note: in definition of macro ‘DECLARE_BITMAP’
   11 |  unsigned long name[BITS_TO_LONGS(bits)]
```   

Disable gcc-9+ array-bounds avoid above warning.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
---
 init/Kconfig | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 72404c1f2157..27ce2ded95b6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -876,14 +876,14 @@ config CC_IMPLICIT_FALLTHROUGH
 	default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
 	default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
 
-# Currently, disable gcc-10+ array-bounds globally.
+# Currently, disable gcc-9+ array-bounds globally.
 # It's still broken in gcc-13, so no upper bound yet.
-config GCC10_NO_ARRAY_BOUNDS
+config GCC9_NO_ARRAY_BOUNDS
 	def_bool y
 
 config CC_NO_ARRAY_BOUNDS
 	bool
-	default y if CC_IS_GCC && GCC_VERSION >= 100000 && GCC10_NO_ARRAY_BOUNDS
+	default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC9_NO_ARRAY_BOUNDS
 
 # Currently, disable -Wstringop-overflow for GCC globally.
 config GCC_NO_STRINGOP_OVERFLOW
-- 
2.25.1