bzip2/lzma: remove nasty uncompressed size hack in pre-boot environment

decompress_bunzip2 and decompress_unlzma have a nasty hack that subtracts
4 from the input length if being called in the pre-boot environment.

This is a nasty hack because it relies on the fact that flush = NULL only
when called from the pre-boot environment (i.e.
arch/x86/boot/compressed/misc.c).  initramfs.c/do_mounts_rd.c pass in a
flush buffer (flush != NULL).

This hack prevents the decompressors from being used with flush = NULL by
other callers unless knowledge of the hack is propagated to them.

This patch removes the hack by making decompress (called only from the
pre-boot environment) a wrapper function that subtracts 4 from the input
length before calling the decompressor.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 5 deletions

diff --git a/lib/decompress_unlzma.c b/lib/decompress_unlzma.c
index 32123a1340e..d3f9468e49d 100644
--- a/lib/decompress_unlzma.c
+++ b/lib/decompress_unlzma.c
@@ -29,7 +29,9 @@
  *Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
-#ifndef STATIC
+#ifdef STATIC
+#define PREBOOT
+#else
 #include <linux/decompress/unlzma.h>
 #endif /* STATIC */
 
@@ -543,9 +545,7 @@ STATIC inline int INIT unlzma(unsigned char *buf, int in_len,
         int ret = -1;
 
         set_error_fn(error_fn);
-        if (!flush)
-                in_len -= 4; /* Uncompressed size hack active in pre-boot
-                                environment */
+
         if (buf)
                 inbuf = buf;
         else
@@ -645,4 +645,15 @@ exit_0:
         return ret;
 }
 
-#define decompress unlzma
+#ifdef PREBOOT
+STATIC int INIT decompress(unsigned char *buf, int in_len,
+                              int(*fill)(void*, unsigned int),
+                              int(*flush)(void*, unsigned int),
+                              unsigned char *output,
+                              int *posp,
+                              void(*error_fn)(char *x)
+        )
+{
+        return unlzma(buf, in_len - 4, fill, flush, output, posp, error_fn);
+}
+#endif