* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
+static inline void __noreturn BUG(void)This kind of sucks, doesn't it? It adds instructions into the kernel text, very frequently on fast paths. Those instructions are never executed, and we're blowing away i-cache just to quash compiler warnings.
+{
+ __asm__ __volatile__("break %0" : : "i" (BRK_BUG));
+ /* Fool GCC into thinking the function doesn't return. */
+ while (1)
+ ;
+}
For example, this:
--- a/arch/x86/include/asm/bug.h~a
+++ a/arch/x86/include/asm/bug.h
@@ -22,14 +22,12 @@ do { \
".popsection" \
: : "i" (__FILE__), "i" (__LINE__), \
"i" (sizeof(struct bug_entry))); \
- for (;;) ; \
} while (0)
#else
#define BUG() \
do { \
asm volatile("ud2"); \
- for (;;) ; \
} while (0)
#endif
_
reduces the size of i386 mm/vmalloc.o text by 56 bytes.
yes - the total image effect is significantly - recently looked at how much larger !CONFIG_BUG builds would get if we inserted an infinite loop into them - it was in the 50K text range (!).
but in the x86 ud2 case we could guarantee that we wont ever return from that exception. Mind sending a patch with a signoff, a description and an infinite loop in the u2d handler?