pstore: Add decompression support to pstore

Based on the flag 'compressed' set or not, pstore will decompress the
data returning a plain text file. If decompression fails for a particular
record it will have the compressed data in the file which can be
decompressed with 'openssl' command line tool.

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 51 insertions, 2 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 6418eb77d64b..76bc5c12c0cf 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -162,6 +162,36 @@ error:
         return ret;
 }
 
+/* Derived from logfs_uncompress */
+static int pstore_decompress(void *in, void *out, size_t inlen, size_t outlen)
+{
+        int err, ret;
+
+        ret = -EIO;
+        err = zlib_inflateInit(&stream);
+        if (err != Z_OK)
+                goto error;
+
+        stream.next_in = in;
+        stream.avail_in = inlen;
+        stream.total_in = 0;
+        stream.next_out = out;
+        stream.avail_out = outlen;
+        stream.total_out = 0;
+
+        err = zlib_inflate(&stream, Z_FINISH);
+        if (err != Z_STREAM_END)
+                goto error;
+
+        err = zlib_inflateEnd(&stream);
+        if (err != Z_OK)
+                goto error;
+
+        ret = stream.total_out;
+error:
+        return ret;
+}
+
 static void allocate_buf_for_compression(void)
 {
         size_t size;
@@ -429,6 +459,7 @@ void pstore_get_records(int quiet)
         struct timespec         time;
         int                     failed = 0, rc;
         bool                    compressed;
+        int                     unzipped_len = -1;
 
         if (!psi)
                 return;
@@ -439,10 +470,28 @@ void pstore_get_records(int quiet)
 
         while ((size = psi->read(&id, &type, &count, &time, &buf, &compressed,
                                 psi)) > 0) {
+                if (compressed && (type == PSTORE_TYPE_DMESG)) {
+                        if (big_oops_buf)
+                                unzipped_len = pstore_decompress(buf,
+                                                        big_oops_buf, size,
+                                                        big_oops_buf_sz);
+
+                        if (unzipped_len > 0) {
+                                buf = big_oops_buf;
+                                size = unzipped_len;
+                        } else {
+                                pr_err("pstore: decompression failed;"
+                                        "returned %d\n", unzipped_len);
+                        }
+                }
                 rc = pstore_mkfile(type, psi->name, id, count, buf,
                                   (size_t)size, time, psi);
-                kfree(buf);
-                buf = NULL;
+                if (unzipped_len < 0) {
+                        /* Free buffer other than big oops */
+                        kfree(buf);
+                        buf = NULL;
+                } else
+                        unzipped_len = -1;
                 if (rc && (rc != -EEXIST || !quiet))
                         failed++;
         }