git.iko.soy/typeable/entropy
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typeable/entropy/cbits/rdrand.c
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1#ifdef HAVE_RDRAND
3#include <stdint.h>
4#include <stdlib.h>
6int cpu_has_rdrand()
7{
8 uint32_t ax,bx,cx,dx,func=1;
9 __asm__ volatile ("cpuid":\
10 "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));
11 return (cx & 0x40000000);
14#ifdef arch_x86_64
15// Returns 1 on success
16static inline int _rdrand64_step(uint64_t *therand)
18 unsigned char err;
19 asm volatile("rdrand %0 ; setc %1"
20 : "=r" (*therand), "=qm" (err));
21 return (int) err;
24// Returns 0 on success, non-zero on failure.
25int get_rand_bytes(uint8_t *therand, size_t len)
27 int cnt;
28 int fail=0;
29 uint8_t *p = therand;
30 uint8_t *end = therand + len;
31 if((uint64_t)p%8 != 0) {
32 uint64_t tmp;
33 fail |= !_rdrand64_step(&tmp);
34 while((uint64_t)p%8 != 0 && p != end) {
35 *p = (uint8_t)(tmp & 0xFF);
36 tmp = tmp >> 8;
37 p++;
38 }
39 }
40 for(; p <= end - sizeof(uint64_t); p+=sizeof(uint64_t)) {
41 fail |= !_rdrand64_step((uint64_t *)p);
42 }
43 if(p != end) {
44 uint64_t tmp;
45 int cnt;
46 fail |= !_rdrand64_step(&tmp);
47 while(p != end) {
48 *p = (uint8_t)(tmp & 0xFF);
49 tmp = tmp >> 8;
50 p++;
51 }
52 }
53 return fail;
55#endif /* x86-64 */
57#ifdef arch_i386
58// Returns 1 on success
59static inline int _rdrand32_step(uint32_t *therand)
61 unsigned char err;
62 asm volatile("rdrand %0 ; setc %1"
63 : "=r" (*therand), "=qm" (err));
64 return (int) err;
67int get_rand_bytes(uint8_t *therand, size_t len)
69 int cnt;
70 int fail=0;
71 uint8_t *p = therand;
72 uint8_t *end = therand + len;
73 if((uint32_t)p % sizeof(uint32_t) != 0) {
74 uint32_t tmp;
75 fail |= !_rdrand32_step(&tmp);
76 while((uint32_t)p % sizeof(uint32_t) != 0 && p != end) {
77 *p = (uint8_t)(tmp & 0xFF);
78 tmp = tmp >> 8;
79 p++;
80 }
81 }
82 for(; p <= end - sizeof(uint32_t); p+=sizeof(uint32_t)) {
83 fail |= !_rdrand32_step((uint32_t *)p);
84 }
85 if(p != end) {
86 uint32_t tmp;
87 int cnt;
88 fail |= !_rdrand32_step(&tmp);
89 while(p != end) {
90 *p = (uint8_t)(tmp & 0xFF);
91 tmp = tmp >> 8;
92 p++;
93 }
94 }
95 return fail;
97#endif /* i386 */
99#endif // RDRAND