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 <jdelv...@suse.de>
---
* Note 1: I can't test the 64-bit ("_SM3_") entry point case. I
would appreciate if someone with access to a machine supporting
legacy (non-UEFI) mode and implementing a 64-bit table could test
and report.
* Note 2: I'm not particularly happy with this change as it will
make the entry point scan 3 times slower on average for legacy
machines, but I couldn't come up with anything smarter. If anyone
can think of a better implementation, please let me know.
drivers/firmware/dmi_scan.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
--- linux-4.10-rc4.orig/drivers/firmware/dmi_scan.c 2017-01-04
14:05:09.392301072 +0100
+++ linux-4.10-rc4/drivers/firmware/dmi_scan.c 2017-01-16 11:55:24.500984728
+0100
@@ -649,6 +649,21 @@ void __init dmi_scan_machine(void)
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
* first iteration, substitute zero for the
@@ -658,7 +673,7 @@ 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;
--
Jean Delvare
SUSE L3 Support
