add support for loading lzma compressed kernels

This patch allows one to load a lzma compressed kernel using kexec -l.
As I wanted the lzma code to be very similar to the existing
zlib slurp_decompress I took lzread and associated routines
from the cpio lzma support. Tested on my x86 laptop using the
following commands:

lzma e bzImage bzImage.lzma
kexec -l bzImage.lzma

Having lzma support is particularly useful on some embedded
systems on which we have the kernel already lzma compressed
and available on a mtd partition.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Simon Horman <horms@verge.net.au>

1 files changed, 78 insertions, 0 deletions

diff --git a/kexec/zlib.c b/kexec/zlib.c
new file mode 100644
index 0000000..3968494
--- /dev/null
+++ b/kexec/zlib.c
@@ -0,0 +1,78 @@
+#include "kexec-zlib.h"
+#ifdef HAVE_LIBZ
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <zlib.h>
+
+#include "kexec.h"
+
+char *zlib_decompress_file(const char *filename, off_t *r_size)
+{
+	gzFile fp;
+	int errnum;
+	const char *msg;
+	char *buf;
+	off_t size, allocated;
+	ssize_t result;
+
+	if (!filename) {
+		*r_size = 0;
+		return 0;
+	}
+	fp = gzopen(filename, "rb");
+	if (fp == 0) {
+		msg = gzerror(fp, &errnum);
+		if (errnum == Z_ERRNO) {
+			msg = strerror(errno);
+		}
+		fprintf(stderr, "Cannot open `%s': %s\n", filename, msg);
+		return NULL;
+	}
+	size = 0;
+	allocated = 65536;
+	buf = xmalloc(allocated);
+	do {
+		if (size == allocated) {
+			allocated <<= 1;
+			buf = xrealloc(buf, allocated);
+		}
+		result = gzread(fp, buf + size, allocated - size);
+		if (result < 0) {
+			if ((errno == EINTR) || (errno == EAGAIN))
+				continue;
+
+			msg = gzerror(fp, &errnum);
+			if (errnum == Z_ERRNO) {
+				msg = strerror(errno);
+			}
+			die ("read on %s of %ld bytes failed: %s\n",
+				filename, (allocated - size) + 0UL, msg);
+		}
+		size += result;
+	} while(result > 0);
+	result = gzclose(fp);
+	if (result != Z_OK) {
+		msg = gzerror(fp, &errnum);
+		if (errnum == Z_ERRNO) {
+			msg = strerror(errno);
+		}
+		die ("Close of %s failed: %s\n", filename, msg);
+	}
+	*r_size =  size;
+	return buf;
+}
+#else
+char *zlib_decompress_file(const char *filename, off_t *r_size)
+{
+	return NULL;
+}
+#endif /* HAVE_ZLIB */