From: Andrei Borzenkov <arvidjaar@gmail.com>
Date: Fri, 8 May 2015 03:15:16 +0000 (+0300)
Subject: acpi: do not skip BIOS scan if EBDA length is zero
X-Git-Tag: 2.02-beta3~312
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=07258815e96aab2c72593d0129d17051cbf68d27;p=thirdparty%2Fgrub.git

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 05a6dcad4..c3861f594 100644
--- 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 d415d2305..297f5d05f 100644
--- 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)