[PATCH] Fix eisa_mmap evaluation, add memory existence check

[Christian Franke]

This patch fixes the broken evaluation of the E801 EISA memory map. The 
shift was too much, the high word is already shifted :-) The bug was 
hidden until the E820 memory map evaluation was broken due to the struct 
packing issue fixed in my last patch.

The extra handling of "0x3C00" case is IMO not necessary. Regions are 
merged a few lines later.

During testing, I added a primitive memory to detect such problems 
early. It was difficult to find why grub crashes during module load.

Christian

2007-10-23  Christian Franke  <address@hidden>

        * kern/i386/pc/init.c (addr_is_valid): New function.
        (add_mem_region): Add memory existence check.
        (grub_machine_init): Fix evaluation of eisa_mmap.



--- grub2.orig/kern/i386/pc/init.c      2007-10-22 22:22:51.359375000 +0200
+++ grub2/kern/i386/pc/init.c   2007-10-22 22:25:44.546875000 +0200
@@ -83,6 +83,19 @@ make_install_device (void)
   return grub_prefix;
 }
 
+/* Check memory address */
+static int
+addr_is_valid (grub_addr_t addr)
+{
+  volatile unsigned char * p = (volatile unsigned char *)addr;
+  unsigned char x, y;
+  x = *p;
+  *p = x ^ 0xcf;
+  y = *p;
+  *p = x;
+  return y == (x ^ 0xcf);
+}
+
 /* Add a memory region.  */
 static void
 add_mem_region (grub_addr_t addr, grub_size_t size)
@@ -91,6 +104,9 @@ add_mem_region (grub_addr_t addr, grub_s
     /* Ignore.  */
     return;
 
+  if (!(addr + size > addr && addr_is_valid (addr) && addr_is_valid 
(addr+size-1)))
+    grub_fatal ("invalid memory region %p - %p", (char*)addr, 
(char*)addr+size-1);
+
   mem_regions[num_regions].addr = addr;
   mem_regions[num_regions].size = size;
   num_regions++;
@@ -199,13 +215,8 @@ grub_machine_init (void)
 
       if (eisa_mmap)
        {
-         if ((eisa_mmap & 0xFFFF) == 0x3C00)
-           add_mem_region (0x100000, (eisa_mmap << 16) + 0x100000 * 15);
-         else
-           {
-             add_mem_region (0x100000, (eisa_mmap & 0xFFFF) << 10);
-             add_mem_region (0x1000000, eisa_mmap << 16);
-           }
+         add_mem_region (0x100000, (eisa_mmap & 0xFFFF) << 10);
+         add_mem_region (0x1000000, eisa_mmap & ~0xFFFF);
        }
       else
        add_mem_region (0x100000, grub_get_memsize (1) << 10);