spectre_memtools

String and memory handling functions based around the Spectre misfeature.

Functions:

static inline void spectre_init();

Calculates accurate timing values for the rest of the spectre_* functions. This function is automatically called at the start of your program when compiled with GCC/clang but it's fine to call more than once.

char read_memory_byte(const void * const address);

The core spectre function; reads the value stored at address speculatively.

void *spectre_memcpy(void * restrict dest, void const * restrict src, size_t n);
void *spectre_memmove(void *dest, void *src, size_t n);
int spectre_memcmp(const void *buf1, const void *buf2, size_t count);
void *spectre_memchr(const void *ptr, int ch, size_t count);
void *spectre_memmem(const void * restrict haystack, size_t haystacklen, const void * restrict needle, size_t needlelen);
char *spectre_memccpy(void * restrict dest, const void * restrict src, int c, size_t count);
size_t spectre_strlen(const char *str);
size_t spectre_strnlen(const char *str, size_t max_len);
char *spectre_strcpy(char * restrict dest, const char * restrict src);
char *spectre_strncpy(char * restrict dest, const char * restrict src, size_t count);

These functions are equivalent to their non spectre_* counterparts except that all const arguments are accessed speculatively.

Notes

These functions will not trigger hardware watchpoints on const arguments; software watchpoints will prevent speculation and cause an endless loop.

Functions that write data are unreliable when compiled at or above -O2 on clang, meaning spectre_memmove the spectre_*cpy family.