[Powerpc-utils-devel] [PATCH] nvram: fix endian issue when using the partition length

[Cédric Le G. <cl...@fr...>]

From: Cedric Le Goater <cl...@fr...>

The nvram is in big endian order. The partition length needs to be
byte-swapped when it is read or written on little endian machines.

Signed-off-by: Cedric Le Goater <cl...@fr...>
---
 src/nvram.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/nvram.c b/src/nvram.c
index 8d567fa..d062c30 100644
--- a/src/nvram.c
+++ b/src/nvram.c
@@ -44,6 +44,8 @@
 #include <getopt.h>
 #include <inttypes.h>
 #include <zlib.h>
+#include <endian.h>
+#include <byteswap.h>
 
 #include "nvram.h"
 
@@ -407,6 +409,16 @@ parse_of_common(char *data, int data_len, char *outname, char *outval)
     return p - data;
 }
 
+static inline unsigned short
+nvram_swap_short(unsigned short length)
+{
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+	return bswap_16(length);
+#else
+	return length;
+#endif
+}
+
 /**
  * nvram_parse_partitions
  * @brief fill in the nvram structure with data from nvram 
@@ -439,6 +451,7 @@ nvram_parse_partitions(struct nvram *nvram)
 	c_sum = checksum(phead);
 	if (c_sum != phead->checksum)
 	    warn_msg("this partition checksum should be %02x!\n", c_sum);
+	phead->length = nvram_swap_short(phead->length);
 	p_start += phead->length * NVRAM_BLOCK_SIZE;
     }
 
@@ -484,7 +497,8 @@ nvram_find_fd_partition(struct nvram *nvram, char *name)
 	if (! strncmp(phead.name, name, sizeof(phead.name)))
 	    found = 1;
 	else {
-	    int offset = phead.length * NVRAM_BLOCK_SIZE - len;
+	    int offset =
+		    nvram_swap_short(phead.length) * NVRAM_BLOCK_SIZE - len;
 	    if (lseek(nvram->fd, offset, SEEK_CUR) == -1) {
 	        err_msg("seek error in file %s: %s\n", nvram->filename,
 			strerror(errno));
@@ -1337,6 +1351,7 @@ update_of_config_var(struct nvram *nvram, char *config_var, char *pname)
 
     /* make sure the new config var will fit into the partition and add it */
     new_phead = (struct partition_header *)new_part;
+    new_phead->length = nvram_swap_short(new_phead->length);
     new_part_offset = new_part + (data_offset - (char *)phead);
     new_part_end = new_part + part_size;
 
-- 
1.7.10.4