acpi: make bios_linker_loader_add_pointer() API offset based

cleanup bios_linker_loader_add_pointer() API by switching
arguments to taking offsets relative to corresponding files
instead of doing pointer arithmetic on behalf of user which
were confusing.

Also make offset inside of source file explicit in API
so that user won't have to manually set it in
destination file blob and while at it add additional
boundary checks.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 29 insertions, 24 deletions

diff --git a/hw/acpi/bios-linker-loader.c b/hw/acpi/bios-linker-loader.c
index b67da68e5f..3fb54dcf03 100644
--- a/hw/acpi/bios-linker-loader.c
+++ b/hw/acpi/bios-linker-loader.c
@@ -238,37 +238,38 @@ void bios_linker_loader_add_checksum(BIOSLinker *linker, const char *file_name,
 }
 
 /*
- * bios_linker_loader_add_pointer: ask guest to add address of source file
- * into destination file at the specified pointer.
+ * bios_linker_loader_add_pointer: ask guest to patch address in
+ * destination file with a pointer to source file
  *
  * @linker: linker object instance
  * @dest_file: destination file that must be changed
+ * @dst_patched_offset: location within destination file blob to be patched
+ *                      with the pointer to @src_file+@src_offset (i.e. source
+ *                      blob allocated in guest memory + @src_offset), in bytes
+ * @dst_patched_offset_size: size of the pointer to be patched
+ *                      at @dst_patched_offset in @dest_file blob, in bytes
  * @src_file: source file who's address must be taken
- * @pointer: location of the pointer to be patched within destination file blob
- * @pointer_size: size of pointer to be patched, in bytes
- *
- * Notes:
- * - @pointer_size bytes must have been pushed into blob associated with
- *   @dest_file and reside at address @pointer.
- * - Guest address is added to initial value at @pointer
- *   into copy of @dest_file in Guest memory.
- *   e.g. to get start of src_file in guest memory, put 0x0 there
- *   to get address of a field at offset 0x10 in src_file, put 0x10 there
- * - Both @dest_file and @src_file must be
- *   loaded into Guest memory using bios_linker_loader_alloc
+ * @src_offset: location within source file blob to which
+ *              @dest_file+@dst_patched_offset will point to after
+ *              firmware's executed ADD_POINTER command
  */
 void bios_linker_loader_add_pointer(BIOSLinker *linker,
                                     const char *dest_file,
+                                    uint32_t dst_patched_offset,
+                                    uint8_t dst_patched_size,
                                     const char *src_file,
-                                    void *pointer,
-                                    uint8_t pointer_size)
+                                    uint32_t src_offset)
 {
+    uint64_t le_src_offset;
     BiosLinkerLoaderEntry entry;
-    const BiosLinkerFileEntry *file = bios_linker_find_file(linker, dest_file);
-    ptrdiff_t offset = (gchar *)pointer - file->blob->data;
+    const BiosLinkerFileEntry *dst_file =
+        bios_linker_find_file(linker, dest_file);
+    const BiosLinkerFileEntry *source_file =
+        bios_linker_find_file(linker, src_file);
 
-    assert(offset >= 0);
-    assert(offset + pointer_size <= file->blob->len);
+    assert(dst_patched_offset < dst_file->blob->len);
+    assert(dst_patched_offset + dst_patched_size <= dst_file->blob->len);
+    assert(src_offset < source_file->blob->len);
 
     memset(&entry, 0, sizeof entry);
     strncpy(entry.pointer.dest_file, dest_file,
@@ -276,10 +277,14 @@ void bios_linker_loader_add_pointer(BIOSLinker *linker,
     strncpy(entry.pointer.src_file, src_file,
             sizeof entry.pointer.src_file - 1);
     entry.command = cpu_to_le32(BIOS_LINKER_LOADER_COMMAND_ADD_POINTER);
-    entry.pointer.offset = cpu_to_le32(offset);
-    entry.pointer.size = pointer_size;
-    assert(pointer_size == 1 || pointer_size == 2 ||
-           pointer_size == 4 || pointer_size == 8);
+    entry.pointer.offset = cpu_to_le32(dst_patched_offset);
+    entry.pointer.size = dst_patched_size;
+    assert(dst_patched_size == 1 || dst_patched_size == 2 ||
+           dst_patched_size == 4 || dst_patched_size == 8);
+
+    le_src_offset = cpu_to_le64(src_offset);
+    memcpy(dst_file->blob->data + dst_patched_offset,
+           &le_src_offset, dst_patched_size);
 
     g_array_append_vals(linker->cmd_blob, &entry, sizeof entry);
 }