firmware: dmi_scan: Look for SMBIOS 3 entry point first (c9aba143) · Commits · 戴 / test

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>

drivers/firmware/dmi_scan.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -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;

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