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Message-Id: <1465414726-197858-11-git-send-email-hpa@linux.intel.com>
Date: Wed, 8 Jun 2016 12:38:46 -0700
From: "H. Peter Anvin" <hpa@...ux.intel.com>
To: Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Andy Lutomirski <luto@...capital.net>,
Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: [PATCH v2 10/10] 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@...ux.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.
---
arch/x86/include/asm/archrandom.h | 128 ++++++++++++++++++--------------------
arch/x86/kernel/cpu/rdrand.c | 4 +-
2 files changed, 62 insertions(+), 70 deletions(-)
diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
index ab6f599..5b0579a 100644
--- a/arch/x86/include/asm/archrandom.h
+++ b/arch/x86/include/asm/archrandom.h
@@ -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 */
diff --git a/arch/x86/kernel/cpu/rdrand.c b/arch/x86/kernel/cpu/rdrand.c
index f6f50c4..cfa97ff 100644
--- a/arch/x86/kernel/cpu/rdrand.c
+++ b/arch/x86/kernel/cpu/rdrand.c
@@ -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
--
2.7.3.0.11.gd79db92
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