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Commit 3b290398 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

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: default avatarH. 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.
parent 66928b4e

arch/x86/include/asm/archrandom.h

+60 −68
Original line number Diff line number Diff line
@@ -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;						\

}



#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;						\

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;

}



#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 */

arch/x86/kernel/cpu/rdrand.c

+2 −2
Original line number Diff line number Diff line
@@ -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