bzip2/lzma: use a table to search for initramfs compression formats

Impact: Code simplification

Instead of open-coding testing for initramfs compression formats, use
a table.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 35 insertions, 47 deletions

diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index dcaeb1f90b32..9c9d7dbcf9ca 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -43,13 +43,31 @@ static int __init crd_load(int in_fd, int out_fd, decompress_fn deco);
  * numbers could not be found.
  *
  * We currently check for the following magic numbers:
- *      minix
- *      ext2
+ *      minix
+ *      ext2
  *      romfs
  *      cramfs
- *      gzip
+ *      gzip
  */
-static int __init 
+static const struct compress_format {
+        unsigned char magic[2];
+        const char *name;
+        decompress_fn decompressor;
+} compressed_formats[] = {
+#ifdef CONFIG_RD_GZIP
+        { {037, 0213}, "gzip", gunzip },
+        { {037, 0236}, "gzip", gunzip },
+#endif
+#ifdef CONFIG_RD_BZIP2
+        { {0x42, 0x5a}, "bzip2", bunzip2 },
+#endif
+#ifdef CONFIG_RD_LZMA
+        { {0x5d, 0x00}, "lzma", unlzma },
+#endif
+        { {0, 0}, NULL, NULL }
+};
+
+static int __init
 identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor)
 {
         const int size = 512;
@@ -59,6 +77,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor)
         struct cramfs_super *cramfsb;
         int nblocks = -1;
         unsigned char *buf;
+        const struct compress_format *cf;
 
         buf = kmalloc(size, GFP_KERNEL);
         if (!buf)
@@ -71,52 +90,21 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor)
         memset(buf, 0xe5, size);
 
         /*
-         * Read block 0 to test for gzipped kernel
+         * Read block 0 to test for compressed kernel
          */
         sys_lseek(fd, start_block * BLOCK_SIZE, 0);
         sys_read(fd, buf, size);
 
-#ifdef CONFIG_RD_GZIP
-        /*
-         * If it matches the gzip magic numbers, return 0
-         */
-        if (buf[0] == 037 && ((buf[1] == 0213) || (buf[1] == 0236))) {
-                printk(KERN_NOTICE
-                       "RAMDISK: Compressed image found at block %d\n",
-                       start_block);
-                *decompressor = gunzip;
-                nblocks = 0;
-                goto done;
-        }
-#endif
-
-#ifdef CONFIG_RD_BZIP2
-        /*
-         * If it matches the bzip2 magic numbers, return -1
-         */
-        if (buf[0] == 0x42 && (buf[1] == 0x5a)) {
-                printk(KERN_NOTICE
-                       "RAMDISK: Bzipped image found at block %d\n",
-                       start_block);
-                *decompressor = bunzip2;
-                nblocks = 0;
-                goto done;
-        }
-#endif
-
-#ifdef CONFIG_RD_LZMA
-        /*
-         * If it matches the lzma magic numbers, return -1
-         */
-        if (buf[0] == 0x5d && (buf[1] == 0x00)) {
-                printk(KERN_NOTICE
-                       "RAMDISK: Lzma image found at block %d\n",
-                       start_block);
-                *decompressor = unlzma;
-                nblocks = 0;
-                goto done;
+        for (cf = compressed_formats; cf->decompressor; cf++) {
+                if (buf[0] == cf->magic[0] && buf[1] == cf->magic[1]) {
+                        printk(KERN_NOTICE
+                               "RAMDISK: %s image found at block %d\n",
+                               cf->name, start_block);
+                        *decompressor = cf->decompressor;
+                        nblocks = 0;
+                        goto done;
+                }
         }
-#endif
 
         /* romfs is at block zero too */
         if (romfsb->word0 == ROMSB_WORD0 &&
@@ -165,7 +153,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor)
         printk(KERN_NOTICE
                "RAMDISK: Couldn't find valid RAM disk image starting at %d.\n",
                start_block);
-        
+
 done:
         sys_lseek(fd, start_block * BLOCK_SIZE, 0);
         kfree(buf);
@@ -224,7 +212,7 @@ int __init rd_load_image(char *from)
                        nblocks, rd_blocks);
                 goto done;
         }
-                
+
         /*
          * OK, time to copy in the data
          */