From: Christophe Leroy <christophe.leroy@xxxxxxxxxx> Subject: mm: uninline copy_overflow() While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE, I ended up with more than 50 times the following function in vmlinux because GCC doesn't honor the 'inline' keyword: c00243bc <copy_overflow>: c00243bc: 94 21 ff f0 stwu r1,-16(r1) c00243c0: 7c 85 23 78 mr r5,r4 c00243c4: 7c 64 1b 78 mr r4,r3 c00243c8: 3c 60 c0 62 lis r3,-16286 c00243cc: 7c 08 02 a6 mflr r0 c00243d0: 38 63 5e e5 addi r3,r3,24293 c00243d4: 90 01 00 14 stw r0,20(r1) c00243d8: 4b ff 82 45 bl c001c61c <__warn_printk> c00243dc: 0f e0 00 00 twui r0,0 c00243e0: 80 01 00 14 lwz r0,20(r1) c00243e4: 38 21 00 10 addi r1,r1,16 c00243e8: 7c 08 03 a6 mtlr r0 c00243ec: 4e 80 00 20 blr With -Winline, GCC tells: /include/linux/thread_info.h:212:20: warning: inlining failed in call to 'copy_overflow': call is unlikely and code size would grow [-Winline] copy_overflow() is a non conditional warning called by check_copy_size() on an error path. check_copy_size() have to remain inlined in order to benefit from constant folding, but copy_overflow() is not worth inlining. Uninline the warning when CONFIG_BUG is selected. When CONFIG_BUG is not selected, WARN() does nothing so skip it. This reduces the size of vmlinux by almost 4kbytes. Link: https://lkml.kernel.org/r/e1723b9cfa924bcefcd41f69d0025b38e4c9364e.1644819985.git.christophe.leroy@xxxxxxxxxx Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx> Cc: David Laight <David.Laight@xxxxxxxxxx> Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/thread_info.h | 5 ++++- mm/maccess.c | 6 ++++++ 2 files changed, 10 insertions(+), 1 deletion(-) --- a/include/linux/thread_info.h~mm-uninline-copy_overflow +++ a/include/linux/thread_info.h @@ -209,9 +209,12 @@ __bad_copy_from(void); extern void __compiletime_error("copy destination size is too small") __bad_copy_to(void); +void __copy_overflow(int size, unsigned long count); + static inline void copy_overflow(int size, unsigned long count) { - WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); + if (IS_ENABLED(CONFIG_BUG)) + __copy_overflow(size, count); } static __always_inline __must_check bool --- a/mm/maccess.c~mm-uninline-copy_overflow +++ a/mm/maccess.c @@ -335,3 +335,9 @@ long strnlen_user_nofault(const void __u return ret; } + +void __copy_overflow(int size, unsigned long count) +{ + WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); +} +EXPORT_SYMBOL(__copy_overflow); _
