[PATCH] Implement fmap support as used by coreboot

[PATCH] Implement fmap support as used by coreboot

[Vladimir Serbinenko]

This patch limits itself to fmap coming from booted coreboot,
not as used in images.

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
---
 grub-core/Makefile.core.def |   7 ++
 grub-core/partmap/fmap.c    | 172 ++++++++++++++++++++++++++++++++++++
 2 files changed, 179 insertions(+)
 create mode 100644 grub-core/partmap/fmap.c

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 8e1b1d9f3..28c5d9050 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -2016,6 +2016,13 @@ module = {
   common = partmap/apple.c;
 };
 
+module = {
+  name = part_fmap;
+  common = partmap/fmap.c;
+  enable = x86;
+  enable = coreboot;
+};
+
 module = {
   name = part_gpt;
   common = partmap/gpt.c;
diff --git a/grub-core/partmap/fmap.c b/grub-core/partmap/fmap.c
new file mode 100644
index 000000000..2625e4c75
--- /dev/null
+++ b/grub-core/partmap/fmap.c
@@ -0,0 +1,172 @@
+/* gpt.c - Read GUID Partition Tables (GPT).  */
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2023  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/disk.h>
+#include <grub/misc.h>
+#include <grub/mm.h>
+#include <grub/partition.h>
+#include <grub/dl.h>
+#include <grub/i18n.h>
+#include <grub/coreboot/lbio.h>
+
+GRUB_MOD_LICENSE ("GPLv3+");
+
+/* Definitions copied from fmap_serialized.h using BSDL.  */
+#define FMAP_SIGNATURE		"__FMAP__"
+#define FMAP_VER_MAJOR		1	/* this header's FMAP minor version */
+#define FMAP_VER_MINOR		1	/* this header's FMAP minor version */
+#define FMAP_STRLEN		32	/* maximum length for strings, */
+					/* including null-terminator */
+
+/* Mapping of volatile and static regions in firmware binary */
+struct grub_fmap_entry {
+  grub_uint32_t offset;                /* offset relative to base */
+  grub_uint32_t size;                  /* size in bytes */
+  grub_uint8_t  name[FMAP_STRLEN];     /* descriptive name */
+  grub_uint16_t flags;                 /* flags for this area */
+} GRUB_PACKED;
+
+struct grub_fmap_header {
+  grub_uint8_t  signature[8];		/* "__FMAP__" (0x5F5F464D41505F5F) */
+  grub_uint8_t  ver_major;		/* major version */
+  grub_uint8_t  ver_minor;		/* minor version */
+  grub_uint64_t base;			/* address of the firmware binary */
+  grub_uint32_t size;			/* size of firmware binary in bytes */
+  grub_uint8_t  name[FMAP_STRLEN];	/* name of this firmware binary */
+  grub_uint16_t nareas;		/* number of areas described by
+				   fmap_areas[] below */
+} GRUB_PACKED;
+
+static struct grub_partition_map grub_fmap_partition_map;
+
+\f
+
+static int
+validate_fmap_header(struct grub_fmap_header *header)
+{
+  if (grub_memcmp (header->signature, FMAP_SIGNATURE, sizeof (header->signature)) != 0)
+    return 0;
+  if (header->ver_major != FMAP_VER_MAJOR || header->ver_minor != FMAP_VER_MINOR)
+    return 0;
+  return 1;
+}
+
+static grub_uint64_t cbfsdisk_fmap_offset = 0xffffffff;
+
+static int cbtable_iter (grub_linuxbios_table_item_t item,
+			 void *ctxt_in __attribute__((unused)))
+{
+  if (item->tag == GRUB_LINUXBIOS_MEMBER_BOOT_MEDIA)
+    {
+      cbfsdisk_fmap_offset = ((struct grub_linuxbios_table_boot_media *) (item + 1))->fmap_offset;
+      return 1;
+    }
+
+  return 0;
+}
+
+static void
+discover_cbfsdisk_fmap_offset(void)
+{
+  static int discovery_done;
+  if (discovery_done)
+    return;
+   grub_linuxbios_table_iterate (cbtable_iter, NULL);
+}
+
+
+static grub_err_t
+grub_fmap_partition_map_iterate (grub_disk_t disk,
+				grub_partition_iterate_hook_t hook,
+				void *hook_data)
+{
+  struct grub_partition part;
+  struct grub_fmap_header header;
+  struct grub_fmap_entry entry;
+  unsigned int i;
+  grub_uint64_t header_offset = 0;
+  grub_uint64_t current_offset = 0;
+
+  if (disk->dev->id == GRUB_DISK_DEVICE_CBFSDISK_ID)
+    {
+      discover_cbfsdisk_fmap_offset();
+      header_offset = cbfsdisk_fmap_offset;
+      if (cbfsdisk_fmap_offset == 0xffffffff || cbfsdisk_fmap_offset == 0xffffffffffffffffULL)
+	return grub_error(GRUB_ERR_BAD_PART_TABLE, "fmap not declared");	
+    }
+  else
+    return grub_error(GRUB_ERR_BAD_PART_TABLE, "fmap in non-cbfs devices isn't implemented yet");
+
+  /* Read the FMAP header.  */
+  if (grub_disk_read (disk, header_offset >> GRUB_DISK_SECTOR_BITS, header_offset & (GRUB_DISK_SECTOR_SIZE - 1), sizeof (header), &header))
+	return grub_errno;
+
+  if (!validate_fmap_header(&header))
+    return grub_error (GRUB_ERR_BAD_PART_TABLE, "no valid FMAP header");
+
+  grub_dprintf ("fmap", "Read a valid FMAP header\n");
+
+  current_offset = header_offset + sizeof(header);
+
+  for (i = 0; i < grub_le_to_cpu16 (header.nareas); i++)
+    {
+      if (grub_disk_read (disk, current_offset >> GRUB_DISK_SECTOR_BITS, current_offset & (GRUB_DISK_SECTOR_SIZE - 1),
+			  sizeof (entry), &entry))
+	return grub_errno;
+
+      /* TODO: What to do if it's not 512-bytes aligned?  */
+      grub_uint64_t end = (grub_uint64_t) grub_le_to_cpu32 (entry.offset) + (grub_uint64_t) grub_le_to_cpu32 (entry.size);
+      part.start = grub_le_to_cpu32 (entry.offset) >> GRUB_DISK_SECTOR_BITS;
+      part.len = (end >> GRUB_DISK_SECTOR_BITS) - part.start;
+      part.offset = current_offset >> GRUB_DISK_SECTOR_BITS;
+      part.number = i;
+      part.index = current_offset & (GRUB_DISK_SECTOR_SIZE - 1);
+      part.partmap = &grub_fmap_partition_map;
+      part.parent = disk->partition;
+
+      grub_dprintf ("gpt", "FMAP entry %d: start=0x%llx, length=0x%llx\n", i,
+		    (unsigned long long) grub_le_to_cpu32 (entry.offset),
+		    (unsigned long long) grub_le_to_cpu32 (entry.size));
+
+      if (hook (disk, &part, hook_data))
+	return grub_errno;
+
+      current_offset += sizeof (entry);
+    }
+
+  return GRUB_ERR_NONE;
+}
+
+\f
+/* Partition map type.  */
+static struct grub_partition_map grub_fmap_partition_map =
+  {
+    .name = "fmap",
+    .iterate = grub_fmap_partition_map_iterate,
+  };
+
+GRUB_MOD_INIT(part_fmap)
+{
+  grub_partition_map_register (&grub_fmap_partition_map);
+}
+
+GRUB_MOD_FINI(part_fmap)
+{
+  grub_partition_map_unregister (&grub_fmap_partition_map);
+}
-- 
2.39.2


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