Commit 49791083 authored by Kurt Roeckx's avatar Kurt Roeckx
Browse files

Make the CRYPTO_memcmp() prototype match memcmp() 



Reviewed-by: default avatarAndy Polyakov <appro@openssl.org>
GH: #2633
parent 39176d44

crypto/cryptlib.c

+8 −19
Original line number Diff line number Diff line
@@ -313,26 +313,15 @@ void OPENSSL_die(const char *message, const char *file, int line) 
}



#if !defined(OPENSSL_CPUID_OBJ)

/* volatile unsigned char* pointers are there because

 * 1. Accessing a variable declared volatile via a pointer

 *    that lacks a volatile qualifier causes undefined behavior.

 * 2. When the variable itself is not volatile the compiler is

 *    not required to keep all those reads and can convert

 *    this into canonical memcmp() which doesn't read the whole block.

 * Pointers to volatile resolve the first problem fully. The second

 * problem cannot be resolved in any Standard-compliant way but this

 * works the problem around. Compilers typically react to

 * pointers to volatile by preserving the reads and writes through them.

 * The latter is not required by the Standard if the memory pointed to

 * is not volatile.

 * Pointers themselves are volatile in the function signature to work

 * around a subtle bug in gcc 4.6+ which causes writes through

 * pointers to volatile to not be emitted in some rare,

 * never needed in real life, pieces of code.

/*

 * The volatile is used to to ensure that the compiler generates code that reads

 * all values from the array and doesn't try to optimize this away. The standard

 * doesn't actually require this behavior if the original data pointed to is

 * not volatile, but compilers do this in practice anyway.

 *

 * There are also assembler versions of this function.

 */

int CRYPTO_memcmp(const volatile void * volatile in_a,

                  const volatile void * volatile in_b,

                  size_t len)

int CRYPTO_memcmp(const void * in_a, const void * in_b, size_t len)

{

    size_t i;

    const volatile unsigned char *a = in_a;

include/openssl/crypto.h

+1 −3
Original line number Diff line number Diff line
@@ -347,9 +347,7 @@ int OPENSSL_gmtime_diff(int *pday, int *psec, 
 * into a defined order as the return value when a != b is undefined, other

 * than to be non-zero.

 */

int CRYPTO_memcmp(const volatile void * volatile in_a,

                  const volatile void * volatile in_b,

                  size_t len);

int CRYPTO_memcmp(const void * in_a, const void * in_b, size_t len);



/* Standard initialisation options */

# define OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS 0x00000001L