Re: [PATCH] lsprop: Fixes to work correctly when built little endian

On 01/07/2013 08:12 PM, Benjamin Herrenschmidt wrote:

On Mon, 2013-01-07 at 15:23 +1100, Michael Ellerman wrote:

quoted

Add and use dt_swap_int() to byte swap on little endian.

Also declare buf as unsigned char, so that we don't sign extend when
printing values from it.

Signed-off-by: Michael Ellerman <redacted>
---

Ben, based on your patch, can you add your s-o-b? :
  https://lists.ozlabs.org/pipermail/linuxppc-dev/2008-May/056088.html

I didn't know powerpc-utils required sob's :-)

Not technically, it's more a CYA thing. It (hopefully) keeps big blue legal
happy, which keeps me happy.

-Nathan

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

quoted

---
 src/lsprop.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/lsprop.c b/src/lsprop.c
index 5969a97..38a8fa5 100644
--- a/src/lsprop.c
+++ b/src/lsprop.c

@@ -13,11 +13,22 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <dirent.h>
+#include <endian.h>
+#include <byteswap.h>
+
+static inline unsigned int dt_swap_int(unsigned int data)
+{
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+	return bswap_32(data);
+#else
+	return data;
+#endif
+}
 
 int recurse;
 int maxbytes = 128;
 int words_per_line = 0;
-char *buf;
+unsigned char *buf;
 
 void lsprop(FILE *f, char *name);
 void lsdir(char *name);

@@ -183,7 +194,7 @@ void lsprop(FILE *f, char *name)
     } else if ((n & 3) == 0) {
 	nw = n >> 2;
 	if (nw == 1) {
-	    i = *(int *)buf;
+	    i = dt_swap_int(*(int *)buf);
 	    printf(" %.8x", i);
 	    if (i > -0x10000 && !(i >= 0 && i <= 9))
 		printf(" (%d)", i);

@@ -201,7 +212,7 @@ void lsprop(FILE *f, char *name)
 		if (i != 0)
 		    printf("\n\t\t");
 		for (j = 0; j < npl && i + j < nw; ++j)
-		    printf(" %.8x", ((unsigned int *)buf)[i+j]);
+		    printf(" %.8x", dt_swap_int(((unsigned int *)buf)[i+j]));
 	    }
 	}
     } else {

-- 
-Nathan