[dmidecode] [PATCH 3/4] Add reading of SMBIOS tables from sysfs

[Roy Franz]

This patch adds 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.
This patch does change the output of dmidecode slightly:
- 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 invalid
  tables.
- the address of the entrypoint 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.

Signed-off-by: Roy Franz <address@hidden>
---
 dmidecode.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/dmidecode.c b/dmidecode.c
index 1d19a1b..ef4259d 100644
--- a/dmidecode.c
+++ b/dmidecode.c
@@ -70,6 +70,8 @@
 static const char *bad_index = "<BAD INDEX>";
 
 #define SUPPORTED_SMBIOS_VER 0x0208
+#define SYS_ENTRY_FILE "/sys/firmware/dmi/tables/smbios_entry_point"
+#define SYS_TABLE_FILE "/sys/firmware/dmi/tables/DMI"
 
 /*
  * Type-independant Stuff
@@ -4674,6 +4676,35 @@ int main(int argc, char * const argv[])
                goto done;
        }
 
+       /*
+        * 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)
+       {
+               printf("Getting SMBIOS data from sysfs\n");
+               if (memcmp(buf, "_DMI_", 5) == 0)
+               {
+                       if (legacy_decode(buf, SYS_TABLE_FILE, 0))
+                               found++;
+               }
+               else if (memcmp(buf, "_SM_", 4) == 0)
+               {
+                       if (smbios_decode(buf, SYS_TABLE_FILE, 0))
+                               found++;
+               }
+               else if (memcmp(buf, "_SM3_", 5) == 0)
+               {
+                       printf("SMBIOS v3 64 bit entry point found, but not 
supported\n");
+               }
+
+               if (found)
+                       goto done;
+               else
+                       printf("Failed to get SMBIOS data from sysfs, trying 
/dev/mem\n");
+       }
+
        /* Next try EFI (ia64, Intel-based Mac) */
        efi = address_from_efi(&fp);
        switch (efi)
@@ -4685,6 +4716,7 @@ int main(int argc, char * const argv[])
                        goto exit_free;
        }
 
+       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;
@@ -4696,6 +4728,7 @@ int main(int argc, char * const argv[])
        goto done;
 
 memory_scan:
+       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)
        {
-- 
1.9.1