tls: fix CONFIG_FEATURE_TLS_SHA1=y + CONFIG_SHA1_HWACCEL=y

The check for result hash size was buggy for CONFIG_SHA1_HWACCEL=y.

While at it, document CPUID use a bit better.

function                                             old     new   delta
get_shaNI                                              -      28     +28
sha1_end                                              66      79     +13
sha256_begin                                          83      60     -23
sha1_begin                                           111      88     -23
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/2 up/down: 41/-46)             Total: -5 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 23 insertions, 6 deletions

diff --git a/libbb/hash_md5_sha.c b/libbb/hash_md5_sha.c
index 88baf51dc..57a801459 100644
--- a/libbb/hash_md5_sha.c
+++ b/libbb/hash_md5_sha.c
@@ -15,18 +15,28 @@
 
 #if ENABLE_SHA1_HWACCEL || ENABLE_SHA256_HWACCEL
 # if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
-static void cpuid(unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx)
+static void cpuid_eax_ebx_ecx(unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx)
 {
         asm ("cpuid"
                 : "=a"(*eax), "=b"(*ebx), "=c"(*ecx), "=d"(*edx)
-                : "0"(*eax),  "1"(*ebx),  "2"(*ecx),  "3"(*edx)
+                : "0" (*eax), "1" (*ebx), "2" (*ecx)
         );
 }
 static smallint shaNI;
-static int get_shaNI(void)
+static NOINLINE int get_shaNI(void)
 {
-        unsigned eax = 7, ebx = ebx, ecx = 0, edx = edx;
-        cpuid(&eax, &ebx, &ecx, &edx);
+        /* Get leaf 7 subleaf 0. Exists on all CPUs since Merom (2006).
+         * "If a value entered for CPUID.EAX is higher than the maximum
+         * input value for basic or extended function for that processor
+         * then the data for the highest basic information leaf is returned".
+         * This means that Pentiums 4 would return leaf 5 or 6 instead of 7,
+         * which happen to have zero in EBX bit 29. Thus they should work too.
+         */
+        unsigned eax = 7;
+        unsigned ecx = 0;
+        unsigned ebx = 0; /* should not be needed, paranoia */
+        unsigned edx;
+        cpuid_eax_ebx_ecx(&eax, &ebx, &ecx, &edx);
         ebx = ((ebx >> 28) & 2) - 1; /* bit 29 -> 1 or -1 */
         shaNI = (int)ebx;
         return (int)ebx;
@@ -1300,7 +1310,14 @@ unsigned FAST_FUNC sha1_end(sha1_ctx_t *ctx, void *resbuf)
         /* SHA stores total in BE, need to swap on LE arches: */
         common64_end(ctx, /*swap_needed:*/ BB_LITTLE_ENDIAN);
 
-        hash_size = (ctx->process_block == sha1_process_block64) ? 5 : 8;
+        hash_size = 8;
+        if (ctx->process_block == sha1_process_block64
+#if ENABLE_SHA1_HWACCEL
+         || ctx->process_block == sha1_process_block64_shaNI
+#endif
+        ) {
+                hash_size = 5;
+        }
         /* This way we do not impose alignment constraints on resbuf: */
         if (BB_LITTLE_ENDIAN) {
                 unsigned i;