acpi: do not skip BIOS scan if EBDA length is zero

EBDA layout is not standardized so we cannot assume first two bytes
are length. Neither is it required by ACPI standard. HP 8710W is known
to contain zeroes here.

Closes: 45002

diff --git a/grub-core/commands/acpi.c b/grub-core/commands/acpi.c
index 05a6dcad45e4c788c20d8fc352803434bba1a7c4..c3861f594615f582f76bb22c8bdc55b441e85f10 100644 (file)
--- a/grub-core/commands/acpi.c
+++ b/grub-core/commands/acpi.c
@@ -180,8 +180,10 @@ grub_acpi_create_ebda (void)
   struct grub_acpi_rsdp_v20 *v2;
 
   ebda = (grub_uint8_t *) (grub_addr_t) ((*((grub_uint16_t *)0x40e)) << 4);
+  grub_dprintf ("acpi", "EBDA @%p\n", ebda);
   if (ebda)
     ebda_kb_len = *(grub_uint16_t *) ebda;
+  grub_dprintf ("acpi", "EBDA length 0x%x\n", ebda_kb_len);
   if (ebda_kb_len > 16)
     ebda_kb_len = 0;
   ctx.ebda_len = (ebda_kb_len + 1) << 10;
@@ -495,6 +497,8 @@ grub_cmd_acpi (struct grub_extcmd_context *ctxt, int argc, char **args)
   if (! rsdp)
     rsdp = grub_machine_acpi_get_rsdpv1 ();
 
+  grub_dprintf ("acpi", "RSDP @%p\n", rsdp);
+
   if (rsdp)
     {
       grub_uint32_t *entry_ptr;

diff --git a/grub-core/commands/i386/pc/acpi.c b/grub-core/commands/i386/pc/acpi.c
index d415d2305a84890a21c83b62b6165b2fb6946946..297f5d05f3b04d2a15184b44af53ba5369242ba7 100644 (file)
--- a/grub-core/commands/i386/pc/acpi.c
+++ b/grub-core/commands/i386/pc/acpi.c
@@ -29,14 +29,15 @@ grub_machine_acpi_get_rsdpv1 (void)
   grub_dprintf ("acpi", "Looking for RSDP. Scanning EBDA\n");
   ebda = (grub_uint8_t *) ((* ((grub_uint16_t *) 0x40e)) << 4);
   ebda_len = * (grub_uint16_t *) ebda;
-  if (! ebda_len)
-    return 0;
+  if (! ebda_len) /* FIXME do we really need this check? */
+    goto scan_bios;
   for (ptr = ebda; ptr < ebda + 0x400; ptr += 16)
     if (grub_memcmp (ptr, GRUB_RSDP_SIGNATURE, GRUB_RSDP_SIGNATURE_SIZE) == 0
        && grub_byte_checksum (ptr, sizeof (struct grub_acpi_rsdp_v10)) == 0
        && ((struct grub_acpi_rsdp_v10 *) ptr)->revision == 0)
       return (struct grub_acpi_rsdp_v10 *) ptr;
 
+scan_bios:
   grub_dprintf ("acpi", "Looking for RSDP. Scanning BIOS\n");
   for (ptr = (grub_uint8_t *) 0xe0000; ptr < (grub_uint8_t *) 0x100000;
        ptr += 16)
@@ -56,8 +57,8 @@ grub_machine_acpi_get_rsdpv2 (void)
   grub_dprintf ("acpi", "Looking for RSDP. Scanning EBDA\n");
   ebda = (grub_uint8_t *) ((* ((grub_uint16_t *) 0x40e)) << 4);
   ebda_len = * (grub_uint16_t *) ebda;
-  if (! ebda_len)
-    return 0;
+  if (! ebda_len) /* FIXME do we really need this check? */
+    goto scan_bios;
   for (ptr = ebda; ptr < ebda + 0x400; ptr += 16)
     if (grub_memcmp (ptr, GRUB_RSDP_SIGNATURE, GRUB_RSDP_SIGNATURE_SIZE) == 0
        && grub_byte_checksum (ptr, sizeof (struct grub_acpi_rsdp_v10)) == 0
@@ -67,6 +68,7 @@ grub_machine_acpi_get_rsdpv2 (void)
        == 0)
       return (struct grub_acpi_rsdp_v20 *) ptr;
 
+scan_bios:
   grub_dprintf ("acpi", "Looking for RSDP. Scanning BIOS\n");
   for (ptr = (grub_uint8_t *) 0xe0000; ptr < (grub_uint8_t *) 0x100000;
        ptr += 16)