firmware: dmi_scan: Look for SMBIOS 3 entry point first

Since version 3.0.0 of the SMBIOS specification, there can be
multiple entry points in memory, pointing to one or two DMI tables.
If both a 32-bit ("_SM_") entry point and a 64-bit ("_SM3_") entry
point are present, the specification requires that the latter points
to a table which is a super-set of the table pointed to by the
former. Therefore we should give preference to the 64-bit ("_SM3_")
entry point.

However, currently the code is picking the first valid entry point
it finds. Per specification, we should look for a 64-bit ("_SM3_")
entry point first, and if we can't find any, look for a 32-bit
("_SM_" or "_DMI_") entry point. Modify the code to do that.

Signed-off-by: Jean Delvare <jdelvare@suse.de>

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 93f7acdaac7ac19c057fc6b98a76c270a4646f24..82ee042f075cf90e5be7be6af1c1adf890e62078 100644 (file)
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -649,6 +649,21 @@ void __init dmi_scan_machine(void)
                if (p == NULL)
                        goto error;
 
+               /*
+                * Same logic as above, look for a 64-bit entry point
+                * first, and if not found, fall back to 32-bit entry point.
+                */
+               memcpy_fromio(buf, p, 16);
+               for (q = p + 16; q < p + 0x10000; q += 16) {
+                       memcpy_fromio(buf + 16, q, 16);
+                       if (!dmi_smbios3_present(buf)) {
+                               dmi_available = 1;
+                               dmi_early_unmap(p, 0x10000);
+                               goto out;
+                       }
+                       memcpy(buf, buf + 16, 16);
+               }
+
                /*
                 * Iterate over all possible DMI header addresses q.
                 * Maintain the 32 bytes around q in buf.  On the
@@ -659,7 +674,7 @@ void __init dmi_scan_machine(void)
                memset(buf, 0, 16);
                for (q = p; q < p + 0x10000; q += 16) {
                        memcpy_fromio(buf + 16, q, 16);
-                       if (!dmi_smbios3_present(buf) || !dmi_present(buf)) {
+                       if (!dmi_present(buf)) {
                                dmi_available = 1;
                                dmi_early_unmap(p, 0x10000);
                                goto out;