libsa: smbios: Favor the v3 (64-bit) entry point on non-EFI boot

When both the 32-bit and 64-bit entry points are present, the SMBIOS
specification says that the 64-bit entry point always has at least all
the structures the 32-bit entry point refers.  In other words, the
32-bit entry point is provided for compatibility, so we assume the
64-bit one has more chances to be filled with adequate values.

Doing this also increases consistency with the kernel's smbios(4)
driver.

Reviewed by:    imp, markj
MFC after:      2 weeks
Relnotes:       yes
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D49287

1 files changed, 18 insertions, 8 deletions

diff --git a/stand/libsa/smbios.c b/stand/libsa/smbios.c
index 4deea4f31b11..2477c0ccf2d3 100644
--- a/stand/libsa/smbios.c
+++ b/stand/libsa/smbios.c
@@ -180,16 +180,10 @@ static caddr_t
 smbios_sigsearch(const caddr_t addr, const uint32_t len)
 {
 	caddr_t		cp;
+	caddr_t		v2_p = NULL;
 
 	/* Search on 16-byte boundaries. */
 	for (cp = addr; cp < addr + len; cp += SMBIOS_STEP) {
-		/* v2.1, 32-bit Entry point */
-		if (strncmp(cp, SMBIOS_SIG, sizeof(SMBIOS_SIG) - 1) == 0 &&
-		    smbios_checksum(cp, SMBIOS_GET8(cp, 0x05)) == 0 &&
-		    strncmp(cp + 0x10, SMBIOS_DMI_SIG, 5) == 0 &&
-		    smbios_checksum(cp + 0x10, 0x0f) == 0)
-			return (cp);
-
 #ifdef SMBIOS_64BIT_EP
 		/* v3.0, 64-bit Entry point */
 		if (strncmp(cp, SMBIOS3_SIG, sizeof(SMBIOS3_SIG) - 1) == 0 &&
@@ -205,8 +199,24 @@ smbios_sigsearch(const caddr_t addr, const uint32_t len)
 			return (cp);
 		}
 #endif
+
+		/* v2.1, 32-bit Entry point */
+		if (strncmp(cp, SMBIOS_SIG, sizeof(SMBIOS_SIG) - 1) == 0 &&
+		    smbios_checksum(cp, SMBIOS_GET8(cp, 0x05)) == 0 &&
+		    strncmp(cp + 0x10, SMBIOS_DMI_SIG, 5) == 0 &&
+		    smbios_checksum(cp + 0x10, 0x0f) == 0) {
+			/*
+			 * Note that we saw this entry point, but don't return
+			 * it right now on SMBIOS_64BIT_EP as we favor the 64-bit
+			 * one if present.
+			 */
+			v2_p = cp;
+#ifndef SMBIOS_64BIT_EP
+			break;
+#endif
+		}
 	}
-	return (NULL);
+	return (v2_p);
 }
 
 static const char*