Re: [Qemu-devel] [PATCH v19 3/9] pc: add a Virtual Machine Generation ID device

[Michael S. Tsirkin]

On Wed, Feb 10, 2016 at 10:51:47AM +0200, Michael S. Tsirkin wrote:
> So maybe we should
> leave this alone, wait until we see an actual user - this way we can
> figure out the implementation constraints better.

What I'm definitely interested in seeing is improving the
bios_linker_loader API within QEMU.

Is the below going in the right direction, in your opinion?


diff --git a/include/hw/acpi/bios-linker-loader.h 
b/include/hw/acpi/bios-linker-loader.h
index 498c0af..78d9a16 100644
--- a/include/hw/acpi/bios-linker-loader.h
+++ b/include/hw/acpi/bios-linker-loader.h
@@ -17,6 +17,17 @@ void bios_linker_loader_add_checksum(GArray *linker, const 
char *file,
                                      void *start, unsigned size,
                                      uint8_t *checksum);
 
+/*
+ * bios_linker_loader_add_pointer: ask guest to append address of source file
+ * into destination file at the specified pointer.
+ *
+ * @linker: linker file array
+ * @dest_file: destination file that must be changed
+ * @src_file: source file whos address must be taken
+ * @table: destination file array
+ * @pointer: location of the pointer to be patched within destination file
+ * @pointer_size: size of pointer to be patched, in bytes
+ */
 void bios_linker_loader_add_pointer(GArray *linker,
                                     const char *dest_file,
                                     const char *src_file,
diff --git a/hw/acpi/bios-linker-loader.c b/hw/acpi/bios-linker-loader.c
index e04d60a..84be25a 100644
--- a/hw/acpi/bios-linker-loader.c
+++ b/hw/acpi/bios-linker-loader.c
@@ -142,7 +142,13 @@ void bios_linker_loader_add_pointer(GArray *linker,
                                     uint8_t pointer_size)
 {
     BiosLinkerLoaderEntry entry;
-    size_t offset = (gchar *)pointer - table->data;
+    size_t offset;
+
+    assert((gchar *)pointer >= table->data);
+
+    offset = (gchar *)pointer - table->data;
+
+    assert(offset + pointer_size < table->len);
 
     memset(&entry, 0, sizeof entry);
     strncpy(entry.pointer.dest_file, dest_file,

-- 
MST