Bug#419994: More information about misdetection of e820 memory map

[Rafał Kupka]

Hello,

I make some more tests to find this bug.

--- grub-0.97/stage2/common.c	2004-03-27 17:25:44.000000000 +0100
+++ new/stage2/common.c	2007-04-19 16:00:00.000000000 +0200
@@ -181,6 +181,7 @@
   do
     {
       cont = get_mmap_entry ((void *) addr, cont);
+      printf("SMAP: addr:%x cont:%x\n", (unsigned long *) addr, cont);
 
       /* If the returned buffer's length is zero, quit. */
       if (! *((unsigned long *) addr))
@@ -190,6 +191,7 @@
       addr += *((unsigned long *) addr) + 4;
     }
   while (cont);
+  printf("mbi.mmap_length: %x\n", mbi.mmap_length);
 
   if (mbi.mmap_length)
     {

After applying above patch I've got this messages from grub:
SMAP: addr:54964 cont:1
SMAP: addr:5497c cont:2
SMAP: addr:54994 cont:3
SMAP: addr:549ac cont:4
SMAP: addr:549c4 cont:5
SMAP: addr:549dc cont:6
SMAP: addr:549f4 cont:7
SMAP: addr:54a0c cont:8
SMAP: addr:54a24 cont:9
SMAP: addr:54a3c cont:a
SMAP: addr:54a54 cont:0
mbi.mmap_length: 108

displaymem command works as expected, shows whole memory map.

But If I modify source to this version below, I just got:
mbi.mmap_length: 0
and there is no memory map in displaymem output.

--- grub-0.97/stage2/common.c	2004-03-27 17:25:44.000000000 +0100
+++ new/stage2/common.c	2007-04-19 16:00:00.000000000 +0200
@@ -181,6 +181,7 @@
   do
     {
       cont = get_mmap_entry ((void *) addr, cont);
+      /* printf("SMAP: addr:%x cont:%x\n", (unsigned long *) addr, cont); */
 
       /* If the returned buffer's length is zero, quit. */
       if (! *((unsigned long *) addr))
@@ -190,6 +191,7 @@
       addr += *((unsigned long *) addr) + 4;
     }
   while (cont);
+  printf("mbi.mmap_length: %x\n", mbi.mmap_length);
 
   if (mbi.mmap_length)
     {

I don't understand how mbi.mmap_length may have different value just by
commenting printf out. Something strange happens :(

Maybe this is some BIOS breakage, but Linux kernel always detect memory
correctly.

Motherboards affected:
 - MSI K9N SLI Platinum (with BIOS 1.5)
 - MSI K9N SLI-2F (BIOS version unknown)

Regards,
Kupson