dmidecode: Add reading of SMBIOS tables from sysfs

Add preferential reading of the SMBIOS tables from
/sys/firmware/dmi/tables.  If these files are not present or
not valid, the previously supported methods of locating SMBIOS
tables are attempted.

Messages indicating which source is used for the tables
have been added.  These are printed before the tables have
been validated so they can go at the top of the output.  This
also shows what methods have been tried and failed due to invalid
tables.

The address of the entry point is not known when read from sysfs,
so it is not printed in that case.

A placeholder print is added where 64-bit entry point processing
will be added.

Contributed by Roy Franz.

Author: jdelvare

CHANGELOG

@@ -3,6 +3,7 @@
 	* util.c, util.h: Add utility function read_file, which reads an
 	  entire binary file into a buffer.
 	* dmidecode.c: Add passing of flags parameter to dmi_table.
+	* dmidecode.c: Add reading of SMBIOS tables from sysfs.
 
 2015-04-20  Jean Delvare  <[email protected]>
 

dmidecode.c

@@ -73,6 +73,9 @@ static const char *bad_index = "<BAD INDEX>";
 
 #define FLAG_NO_FILE_OFFSET     (1 << 0)
 
+#define SYS_ENTRY_FILE "/sys/firmware/dmi/tables/smbios_entry_point"
+#define SYS_TABLE_FILE "/sys/firmware/dmi/tables/DMI"
+
 /*
  * Type-independant Stuff
  */
@@ -4669,7 +4672,38 @@ int main(int argc, char * const argv[])
 		goto done;
 	}
 
-	/* First try EFI (ia64, Intel-based Mac) */
+	/*
+	 * First try reading from sysfs tables.  The entry point file could
+	 * contain one of several types of entry points, so read enough for
+	 * the largest one, then determine what type it contains.
+	 */
+	if ((buf = read_file(0x20, SYS_ENTRY_FILE)) != NULL)
+	{
+		if (!(opt.flags & FLAG_QUIET))
+			printf("Getting SMBIOS data from sysfs.\n");
+		if (memcmp(buf, "_SM3_", 5) == 0)
+		{
+			if (!(opt.flags & FLAG_QUIET))
+				printf("SMBIOS v3 64-bit entry point found, but not supported.\n");
+		}
+		else if (memcmp(buf, "_SM_", 4) == 0)
+		{
+			if (smbios_decode(buf, SYS_TABLE_FILE, FLAG_NO_FILE_OFFSET))
+				found++;
+		}
+		else if (memcmp(buf, "_DMI_", 5) == 0)
+		{
+			if (legacy_decode(buf, SYS_TABLE_FILE, FLAG_NO_FILE_OFFSET))
+				found++;
+		}
+
+		if (found)
+			goto done;
+		if (!(opt.flags & FLAG_QUIET))
+			printf("Failed to get SMBIOS data from sysfs.\n");
+	}
+
+	/* Next try EFI (ia64, Intel-based Mac) */
 	efi = address_from_efi(&fp);
 	switch (efi)
 	{
@@ -4680,6 +4714,9 @@ int main(int argc, char * const argv[])
 			goto exit_free;
 	}
 
+	if (!(opt.flags & FLAG_QUIET))
+		printf("Found SMBIOS entry point in EFI, reading table from %s.\n",
+		       opt.devmem);
 	if ((buf = mem_chunk(fp, 0x20, opt.devmem)) == NULL)
 	{
 		ret = 1;
@@ -4691,6 +4728,8 @@ int main(int argc, char * const argv[])
 	goto done;
 
 memory_scan:
+	if (!(opt.flags & FLAG_QUIET))
+		printf("Scanning %s for entry point.\n", opt.devmem);
 	/* Fallback to memory scan (x86, x86_64) */
 	if ((buf = mem_chunk(0xF0000, 0x10000, opt.devmem)) == NULL)
 	{

man/dmidecode.8

@@ -25,8 +25,12 @@ and developed by the \s-1DMTF\s0 (Desktop Management Task Force).
 
 As you run it,
 .B dmidecode
-will try to locate the \s-1DMI\s0 table. If it succeeds, it will then parse
-this table and display a list of records like this one:
+will try to locate the \s-1DMI\s0 table. It will first try to read the DMI table
+from sysfs, and next try reading directly from memory if sysfs access failed.
+If
+.B dmidecode
+succeeds in locating a valid DMI table, it will then parse this table
+and display a list of records like this one:
 
 Handle 0x0002, DMI type 2, 8 bytes.
 Base Board Information
@@ -241,6 +245,8 @@ The DMI table is located at offset 0x20.
 
 .SH FILES
 .I /dev/mem
+.I /sys/firmware/dmi/tables/smbios_entry_point (Linux only)
+.I /sys/firmware/dmi/tables/DMI (Linux only)
 .SH BUGS
 More often than not, information contained in the \s-1DMI\s0 tables is inaccurate,
 incomplete or simply wrong.