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x86, asm: Use CC_SET()/CC_OUT() and static_cpu_has() in archrandom.h 

Use CC_SET()/CC_OUT() and static_cpu_has().  This produces code good
enough to eliminate ad hoc use of alternatives in <asm/archrandom.h>,
greatly simplifying the code.

While we are at it, make x86_init_rdrand() compile out completely if
we don't need it.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1465414726-197858-11-git-send-email-hpa@linux.intel.com

v2: fix a conflict between <linux/random.h> and <asm/archrandom.h>
    discovered by Ingo Molnar.  There are a few places in x86-specific
    code where we need all of <arch/archrandom.h> even when
    CONFIG_ARCH_RANDOM is disabled, so <linux/random.h> does not
    suffice.
This commit is contained in:
H. Peter Anvin 2016-06-08 12:38:46 -07:00
parent 66928b4eb9
commit 3b29039863
2 changed files with 62 additions and 70 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

128
arch/x86/include/asm/archrandom.h
View File

@ -25,8 +25,6 @@
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/alternative.h>
#include <asm/nops.h>
#define RDRAND_RETRY_LOOPS 10
@ -40,97 +38,91 @@
# define RDSEED_LONG RDSEED_INT
#endif
#ifdef CONFIG_ARCH_RANDOM
/* Unconditional execution of RDRAND and RDSEED */
/* Instead of arch_get_random_long() when alternatives haven't run. */
static inline bool rdrand_long(unsigned long *v)
{
int ok;
asm volatile("1: " RDRAND_LONG "\n\t"
"jc 2f\n\t"
"decl %0\n\t"
"jnz 1b\n\t"
"2:"
: "=r" (ok), "=a" (*v)
: "0" (RDRAND_RETRY_LOOPS));
return !!ok;
bool ok;
unsigned int retry = RDRAND_RETRY_LOOPS;
do {
asm volatile(RDRAND_LONG "\n\t"
CC_SET(c)
: CC_OUT(c) (ok), "=a" (*v));
if (ok)
return true;
} while (--retry);
return false;
}
static inline bool rdrand_int(unsigned int *v)
{
bool ok;
unsigned int retry = RDRAND_RETRY_LOOPS;
do {
asm volatile(RDRAND_INT "\n\t"
CC_SET(c)
: CC_OUT(c) (ok), "=a" (*v));
if (ok)
return true;
} while (--retry);
return false;
}
/* A single attempt at RDSEED */
static inline bool rdseed_long(unsigned long *v)
{
bool ok;
asm volatile(RDSEED_LONG "\n\t"
"setc %0"
: "=qm" (ok), "=a" (*v));
CC_SET(c)
: CC_OUT(c) (ok), "=a" (*v));
return ok;
}
#define GET_RANDOM(name, type, rdrand, nop) \
static inline bool name(type *v) \
{ \
int ok; \
alternative_io("movl $0, %0\n\t" \
nop, \
"\n1: " rdrand "\n\t" \
"jc 2f\n\t" \
"decl %0\n\t" \
"jnz 1b\n\t" \
"2:", \
X86_FEATURE_RDRAND, \
ASM_OUTPUT2("=r" (ok), "=a" (*v)), \
"0" (RDRAND_RETRY_LOOPS)); \
return !!ok; \
static inline bool rdseed_int(unsigned int *v)
{
bool ok;
asm volatile(RDSEED_INT "\n\t"
CC_SET(c)
: CC_OUT(c) (ok), "=a" (*v));
return ok;
}
#define GET_SEED(name, type, rdseed, nop) \
static inline bool name(type *v) \
{ \
bool ok; \
alternative_io("movb $0, %0\n\t" \
nop, \
rdseed "\n\t" \
"setc %0", \
X86_FEATURE_RDSEED, \
ASM_OUTPUT2("=q" (ok), "=a" (*v))); \
return ok; \
}
#ifdef CONFIG_X86_64
GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP5);
GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
#else
GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP4);
GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
#endif /* CONFIG_X86_64 */
/* Conditional execution based on CPU type */
#define arch_has_random() static_cpu_has(X86_FEATURE_RDRAND)
#define arch_has_random_seed() static_cpu_has(X86_FEATURE_RDSEED)
#else
/*
* These are the generic interfaces; they must not be declared if the
* stubs in <linux/random.h> are to be invoked,
* i.e. CONFIG_ARCH_RANDOM is not defined.
*/
#ifdef CONFIG_ARCH_RANDOM
static inline bool rdrand_long(unsigned long *v)
static inline bool arch_get_random_long(unsigned long *v)
{
return 0;
return arch_has_random() ? rdrand_long(v) : false;
}
static inline bool rdseed_long(unsigned long *v)
static inline bool arch_get_random_int(unsigned int *v)
{
return 0;
return arch_has_random() ? rdrand_int(v) : false;
}
#endif /* CONFIG_ARCH_RANDOM */
static inline bool arch_get_random_seed_long(unsigned long *v)
{
return arch_has_random_seed() ? rdseed_long(v) : false;
}
static inline bool arch_get_random_seed_int(unsigned int *v)
{
return arch_has_random_seed() ? rdseed_int(v) : false;
}
extern void x86_init_rdrand(struct cpuinfo_x86 *c);
#else /* !CONFIG_ARCH_RANDOM */
static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { }
#endif /* !CONFIG_ARCH_RANDOM */
#endif /* ASM_X86_ARCHRANDOM_H */

4
arch/x86/kernel/cpu/rdrand.c
View File

@ -39,9 +39,9 @@ __setup("nordrand", x86_rdrand_setup);
*/
#define SANITY_CHECK_LOOPS 8
#ifdef CONFIG_ARCH_RANDOM
void x86_init_rdrand(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_ARCH_RANDOM
unsigned long tmp;
int i;
@ -55,5 +55,5 @@ void x86_init_rdrand(struct cpuinfo_x86 *c)
return;
}
}
#endif
}
#endif