Author: cem Date: Wed May 8 00:45:16 2019 New Revision: 347239 URL: https://svnweb.freebsd.org/changeset/base/347239
Log: random: x86 driver: Prefer RDSEED over RDRAND when available Per https://software.intel.com/en-us/blogs/2012/11/17/the-difference-between-rdrand-and-rdseed , RDRAND is a PRNG seeded from the same source as RDSEED. The source is more suitable as PRNG seed material, so prefer it when the RDSEED intrinsic is available (indicated in CPU feature bits). Reviewed by: delphij, jhb, imp (earlier version) Approved by: secteam(delphij) Security: yes Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D20192 Modified: head/sys/dev/random/ivy.c Modified: head/sys/dev/random/ivy.c ============================================================================== --- head/sys/dev/random/ivy.c Wed May 8 00:40:08 2019 (r347238) +++ head/sys/dev/random/ivy.c Wed May 8 00:45:16 2019 (r347239) @@ -44,11 +44,13 @@ __FBSDID("$FreeBSD$"); #include <machine/md_var.h> #include <machine/specialreg.h> +#include <x86/ifunc.h> #include <dev/random/randomdev.h> #define RETRY_COUNT 10 +static bool has_rdrand, has_rdseed; static u_int random_ivy_read(void *, u_int); static struct random_source random_ivy = { @@ -57,10 +59,9 @@ static struct random_source random_ivy = { .rs_read = random_ivy_read }; -static inline int -ivy_rng_store(u_long *buf) +static int +x86_rdrand_store(u_long *buf) { -#ifdef __GNUCLIKE_ASM u_long rndval; int retry; @@ -75,11 +76,40 @@ ivy_rng_store(u_long *buf) : "+r" (retry), "=r" (rndval) : : "cc"); *buf = rndval; return (retry); -#else /* __GNUCLIKE_ASM */ - return (0); -#endif } +static int +x86_rdseed_store(u_long *buf) +{ + u_long rndval; + int retry; + + retry = RETRY_COUNT; + __asm __volatile( + "1:\n\t" + "rdseed %1\n\t" /* read randomness into rndval */ + "jc 2f\n\t" /* CF is set on success, exit retry loop */ + "dec %0\n\t" /* otherwise, retry-- */ + "jne 1b\n\t" /* and loop if retries are not exhausted */ + "2:" + : "+r" (retry), "=r" (rndval) : : "cc"); + *buf = rndval; + return (retry); +} + +DEFINE_IFUNC(static, int, x86_rng_store, (u_long *buf), static) +{ + has_rdrand = (cpu_feature2 & CPUID2_RDRAND); + has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED); + + if (has_rdseed) + return (x86_rdseed_store); + else if (has_rdrand) + return (x86_rdrand_store); + else + return (NULL); +} + /* It is required that buf length is a multiple of sizeof(u_long). */ static u_int random_ivy_read(void *buf, u_int c) @@ -90,7 +120,7 @@ random_ivy_read(void *buf, u_int c) KASSERT(c % sizeof(*b) == 0, ("partial read %d", c)); b = buf; for (count = c; count > 0; count -= sizeof(*b)) { - if (ivy_rng_store(&rndval) == 0) + if (x86_rng_store(&rndval) == 0) break; *b++ = rndval; } @@ -104,14 +134,14 @@ rdrand_modevent(module_t mod, int type, void *unused) switch (type) { case MOD_LOAD: - if (cpu_feature2 & CPUID2_RDRAND) { + if (has_rdrand || has_rdseed) { random_source_register(&random_ivy); printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident); } break; case MOD_UNLOAD: - if (cpu_feature2 & CPUID2_RDRAND) + if (has_rdrand || has_rdseed) random_source_deregister(&random_ivy); break; _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
