diff options
Diffstat (limited to 'missing')
| -rw-r--r-- | missing/explicit_bzero.c | 80 |
1 files changed, 52 insertions, 28 deletions
diff --git a/missing/explicit_bzero.c b/missing/explicit_bzero.c index 99b2e2758c..061e72f800 100644 --- a/missing/explicit_bzero.c +++ b/missing/explicit_bzero.c @@ -5,11 +5,14 @@ #include <windows.h> #endif -/* - *BSD have explicit_bzero(). - Windows, OS-X have memset_s(). - Linux has none. *Sigh* -*/ +/* Similar to bzero(), but have a guarantee not to be eliminated from compiler + optimization. */ + +/* OS support note: + * BSD have explicit_bzero(). + * Windows, OS-X have memset_s(). + * Linux has none. *Sigh* + */ /* * Following URL explain why memset_s is added to the standard. @@ -21,35 +24,56 @@ #endif #ifndef HAVE_EXPLICIT_BZERO -/* Similar to bzero(), but have a guarantee not to be eliminated from compiler - optimization. */ + #ifdef HAVE_MEMSET_S +void +explicit_bzero(void *b, size_t len) +{ + memset_s(b, len, 0, len); +} + #elif defined SecureZeroMemory +void +explicit_bzero(void *b, size_t len) +{ + SecureZeroMemory(b, len); +} + + #elif defined HAVE_FUNC_WEAK + +/* A weak function never be optimization away. Even if nobody use it. */ +WEAK(void ruby_explicit_bzero_hook_unused(void *buf, size_t len)); +void +ruby_explicit_bzero_hook_unused(void *buf, size_t len) +{ +} + +void +explicit_bzero(void *b, size_t len) +{ + memset(b, len); + ruby_explicit_bzero_hook_unused(b, len); +} + + #else /* Your OS have no capability. Sigh. */ -#ifndef HAVE_MEMSET_S FUNC_UNOPTIMIZED(void explicit_bzero(void *b, size_t len)); -#endif #undef explicit_bzero void explicit_bzero(void *b, size_t len) { -#ifdef HAVE_MEMSET_S - memset_s(b, len, 0, len); -#elif defined SecureZeroMemory - SecureZeroMemory(b, len); -#else - { - /* - * TODO: volatile is not enough if compiler have a LTO (link time - * optimization) - */ - volatile char* p = (volatile char*)b; - - while(len) { - *p = 0; - p++; - len--; - } + /* + * volatile is not enough if compiler have a LTO (link time + * optimization). At least, the standard provide no guarantee. + * However, gcc and major other compiler never optimization a volatile + * variable away. So, using volatile is practically ok. + */ + volatile char* p = (volatile char*)b; + + while(len) { + *p = 0; + p++; + len--; } -#endif } -#endif + #endif +#endif /* HAVE_EXPLICIT_BZERO */ |