diff options
| -rw-r--r-- | include/linux/compiler-gcc.h | 16 | ||||
| -rw-r--r-- | include/linux/compiler-intel.h | 3 | ||||
| -rw-r--r-- | include/linux/compiler.h | 4 | ||||
| -rw-r--r-- | lib/string.c | 2 |
4 files changed, 23 insertions, 2 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index cdf13ca7cac3..371e560d13cf 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -9,10 +9,24 @@ + __GNUC_MINOR__ * 100 \ + __GNUC_PATCHLEVEL__) - /* Optimization barrier */ + /* The "volatile" is due to gcc bugs */ #define barrier() __asm__ __volatile__("": : :"memory") +/* + * This version is i.e. to prevent dead stores elimination on @ptr + * where gcc and llvm may behave differently when otherwise using + * normal barrier(): while gcc behavior gets along with a normal + * barrier(), llvm needs an explicit input variable to be assumed + * clobbered. The issue is as follows: while the inline asm might + * access any memory it wants, the compiler could have fit all of + * @ptr into memory registers instead, and since @ptr never escaped + * from that, it proofed that the inline asm wasn't touching any of + * it. This version works well with both compilers, i.e. we're telling + * the compiler that the inline asm absolutely may see the contents + * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 + */ +#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") /* * This macro obfuscates arithmetic on a variable address so that gcc diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h index ba147a1727e6..0c9a2f2c2802 100644 --- a/include/linux/compiler-intel.h +++ b/include/linux/compiler-intel.h @@ -13,9 +13,12 @@ /* Intel ECC compiler doesn't support gcc specific asm stmts. * It uses intrinsics to do the equivalent things. */ +#undef barrier_data #undef RELOC_HIDE #undef OPTIMIZER_HIDE_VAR +#define barrier_data(ptr) barrier() + #define RELOC_HIDE(ptr, off) \ ({ unsigned long __ptr; \ __ptr = (unsigned long) (ptr); \ diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 0e41ca0e5927..867722591be2 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -169,6 +169,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); # define barrier() __memory_barrier() #endif +#ifndef barrier_data +# define barrier_data(ptr) barrier() +#endif + /* Unreachable code */ #ifndef unreachable # define unreachable() do { } while (1) diff --git a/lib/string.c b/lib/string.c index a5792019193c..bb3d4b6993c4 100644 --- a/lib/string.c +++ b/lib/string.c @@ -607,7 +607,7 @@ EXPORT_SYMBOL(memset); void memzero_explicit(void *s, size_t count) { memset(s, 0, count); - barrier(); + barrier_data(s); } EXPORT_SYMBOL(memzero_explicit); |