pstore: Add compression support to pstore

Add compression support to pstore which will help in capturing more data.
Initially, pstore will make a call to kmsg_dump with a bigger buffer
and will pass the size of bigger buffer to kmsg_dump and then compress
the data to registered buffer of registered size.

In case compression fails, pstore will capture the uncompressed
data by making a call again to kmsg_dump with registered_buffer
of registered size.

Pstore will indicate the data is compressed or not with a flag
in the write callback.

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, 139 insertions, 9 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 20fa686f80fa..56218cb35267 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -26,6 +26,7 @@
 #include <linux/console.h>
 #include <linux/module.h>
 #include <linux/pstore.h>
+#include <linux/zlib.h>
 #include <linux/string.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
@@ -65,6 +66,15 @@ struct pstore_info *psinfo;
 
 static char *backend;
 
+/* Compression parameters */
+#define COMPR_LEVEL 6
+#define WINDOW_BITS 12
+#define MEM_LEVEL 4
+static struct z_stream_s stream;
+
+static char *big_oops_buf;
+static size_t big_oops_buf_sz;
+
 /* How much of the console log to snapshot */
 static unsigned long kmsg_bytes = 10240;
 
@@ -117,6 +127,91 @@ bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
 }
 EXPORT_SYMBOL_GPL(pstore_cannot_block_path);
 
+/* Derived from logfs_compress() */
+static int pstore_compress(const void *in, void *out, size_t inlen,
+                                                        size_t outlen)
+{
+        int err, ret;
+
+        ret = -EIO;
+        err = zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
+                                                MEM_LEVEL, Z_DEFAULT_STRATEGY);
+        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_deflate(&stream, Z_FINISH);
+        if (err != Z_STREAM_END)
+                goto error;
+
+        err = zlib_deflateEnd(&stream);
+        if (err != Z_OK)
+                goto error;
+
+        if (stream.total_out >= stream.total_in)
+                goto error;
+
+        ret = stream.total_out;
+error:
+        return ret;
+}
+
+static void allocate_buf_for_compression(void)
+{
+        size_t size;
+
+        big_oops_buf_sz = (psinfo->bufsize * 100) / 45;
+        big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
+        if (big_oops_buf) {
+                size = max(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
+                        zlib_inflate_workspacesize());
+                stream.workspace = kmalloc(size, GFP_KERNEL);
+                if (!stream.workspace) {
+                        pr_err("pstore: No memory for compression workspace; "
+                                "skipping compression\n");
+                        kfree(big_oops_buf);
+                        big_oops_buf = NULL;
+                }
+        } else {
+                pr_err("No memory for uncompressed data; "
+                        "skipping compression\n");
+                stream.workspace = NULL;
+        }
+
+}
+
+/*
+ * Called when compression fails, since the printk buffer
+ * would be fetched for compression calling it again when
+ * compression fails would have moved the iterator of
+ * printk buffer which results in fetching old contents.
+ * Copy the recent messages from big_oops_buf to psinfo->buf
+ */
+static size_t copy_kmsg_to_buffer(int hsize, size_t len)
+{
+        size_t total_len;
+        size_t diff;
+
+        total_len = hsize + len;
+
+        if (total_len > psinfo->bufsize) {
+                diff = total_len - psinfo->bufsize + hsize;
+                memcpy(psinfo->buf, big_oops_buf, hsize);
+                memcpy(psinfo->buf + hsize, big_oops_buf + diff,
+                                        psinfo->bufsize - hsize);
+                total_len = psinfo->bufsize;
+        } else
+                memcpy(psinfo->buf, big_oops_buf, total_len);
+
+        return total_len;
+}
+
 /*
  * callback from kmsg_dump. (s2,l2) has the most recently
  * written bytes, older bytes are in (s1,l1). Save as much
@@ -148,23 +243,56 @@ static void pstore_dump(struct kmsg_dumper *dumper,
                 char *dst;
                 unsigned long size;
                 int hsize;
+                int zipped_len = -1;
                 size_t len;
-                bool compressed = false;
+                bool compressed;
+                size_t total_len;
 
-                dst = psinfo->buf;
-                hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount, part);
-                size = psinfo->bufsize - hsize;
-                dst += hsize;
+                if (big_oops_buf) {
+                        dst = big_oops_buf;
+                        hsize = sprintf(dst, "%s#%d Part%d\n", why,
+                                                        oopscount, part);
+                        size = big_oops_buf_sz - hsize;
 
-                if (!kmsg_dump_get_buffer(dumper, true, dst, size, &len))
-                        break;
+                        if (!kmsg_dump_get_buffer(dumper, true, dst + hsize,
+                                                                size, &len))
+                                break;
+
+                        zipped_len = pstore_compress(dst, psinfo->buf,
+                                                hsize + len, psinfo->bufsize);
+
+                        if (zipped_len > 0) {
+                                compressed = true;
+                                total_len = zipped_len;
+                        } else {
+                                pr_err("pstore: compression failed for Part %d"
+                                        " returned %d\n", part, zipped_len);
+                                pr_err("pstore: Capture uncompressed"
+                                        " oops/panic report of Part %d\n", part);
+                                compressed = false;
+                                total_len = copy_kmsg_to_buffer(hsize, len);
+                        }
+                } else {
+                        dst = psinfo->buf;
+                        hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount,
+                                                                        part);
+                        size = psinfo->bufsize - hsize;
+                        dst += hsize;
+
+                        if (!kmsg_dump_get_buffer(dumper, true, dst,
+                                                                size, &len))
+                                break;
+
+                        compressed = false;
+                        total_len = hsize + len;
+                }
 
                 ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
-                                    oopscount, compressed, hsize + len, psinfo);
+                                    oopscount, compressed, total_len, psinfo);
                 if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
                         pstore_new_entry = 1;
 
-                total += hsize + len;
+                total += total_len;
                 part++;
         }
         if (pstore_cannot_block_path(reason)) {
@@ -262,6 +390,8 @@ int pstore_register(struct pstore_info *psi)
                 return -EINVAL;
         }
 
+        allocate_buf_for_compression();
+
         if (pstore_is_mounted())
                 pstore_get_records(0);