x86: Mark archrandom.h functions __must_check

We must not use the pointer output without validating the
success of the random read.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200110145422.49141-8-broonie@kernel.orgSigned-off-by: Theodore Ts'o <tytso@mit.edu>

arch/x86/include/asm/archrandom.h

@@ -27,7 +27,7 @@
 
 /* Unconditional execution of RDRAND and RDSEED */
 
-static inline bool rdrand_long(unsigned long *v)
+static inline bool __must_check rdrand_long(unsigned long *v)
 {
 	bool ok;
 	unsigned int retry = RDRAND_RETRY_LOOPS;
@@ -41,7 +41,7 @@ static inline bool rdrand_long(unsigned long *v)
 	return false;
 }
 
-static inline bool rdrand_int(unsigned int *v)
+static inline bool __must_check rdrand_int(unsigned int *v)
 {
 	bool ok;
 	unsigned int retry = RDRAND_RETRY_LOOPS;
@@ -55,7 +55,7 @@ static inline bool rdrand_int(unsigned int *v)
 	return false;
 }
 
-static inline bool rdseed_long(unsigned long *v)
+static inline bool __must_check rdseed_long(unsigned long *v)
 {
 	bool ok;
 	asm volatile(RDSEED_LONG
@@ -64,7 +64,7 @@ static inline bool rdseed_long(unsigned long *v)
 	return ok;
 }
 
-static inline bool rdseed_int(unsigned int *v)
+static inline bool __must_check rdseed_int(unsigned int *v)
 {
 	bool ok;
 	asm volatile(RDSEED_INT
@@ -80,22 +80,22 @@ static inline bool rdseed_int(unsigned int *v)
  */
 #ifdef CONFIG_ARCH_RANDOM
 
-static inline bool arch_get_random_long(unsigned long *v)
+static inline bool __must_check arch_get_random_long(unsigned long *v)
 {
 	return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
 }
 
-static inline bool arch_get_random_int(unsigned int *v)
+static inline bool __must_check arch_get_random_int(unsigned int *v)
 {
 	return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
 }
 
-static inline bool arch_get_random_seed_long(unsigned long *v)
+static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
 {
 	return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
 }
 
-static inline bool arch_get_random_seed_int(unsigned int *v)
+static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
 {
 	return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
 }