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    Subject[PATCH 09/10] x86, asm: Use CC_SET()/CC_OUT() and static_cpu_has() in archrandom.h
    Date
    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.

    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    ---
    arch/x86/include/asm/archrandom.h | 113 ++++++++++++++++----------------------
    1 file changed, 47 insertions(+), 66 deletions(-)

    diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
    index ab6f599..654da36 100644
    --- a/arch/x86/include/asm/archrandom.h
    +++ b/arch/x86/include/asm/archrandom.h
    @@ -40,96 +40,77 @@
    # 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
    +static inline bool arch_get_random_long(unsigned long *v)
    +{
    + return arch_has_random() ? rdrand_long(v) : false;
    +}

    -static inline bool rdrand_long(unsigned long *v)
    +static inline bool arch_get_random_int(unsigned int *v)
    {
    - return 0;
    + return arch_has_random() ? rdrand_int(v) : false;
    }

    -static inline bool rdseed_long(unsigned long *v)
    +static inline bool arch_get_random_seed_long(unsigned long *v)
    {
    - return 0;
    + return arch_has_random_seed() ? rdseed_long(v) : false;
    }

    -#endif /* CONFIG_ARCH_RANDOM */
    +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);

    --
    2.7.3.0.11.gd79db92
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