[PATCH] binutils/windmc: Parse input correctly on big endian hosts

[PATCH] binutils/windmc: Parse input correctly on big endian hosts

[Richard W.M. Jones]

On big endian hosts (eg. s390x) the windmc tool fails to parse even
trivial files:

  $ cat test.mc
  ;
  $ ./binutils/windmc ./test.mc
  In test.mc at line 1: parser: syntax error.
  In test.mc at line 1: fatal: syntax error.

The tool starts by reading the input as Windows CP1252 and then
converting it internally into an array of UTF-16LE, which it then
processes as an array of unsigned short (typedef unichar).

There are lots of ways this is wrong, but in the specific case of big
endian machines the little endian pairs of bytes are byte-swapped.

For example, the ';' character in the input above is first converted
to UTF16-LE byte sequence { 0x3b, 0x00 }, which is then cast to
unsigned short.  On a big endian machine the first unichar appears to
be 0x3b00.  The lexer is unable to recognize this as the comment
character ((unichar)';') and so parsing fails.

The simple fix is to convert the input to UTF-16BE on big endian
machines (and do the reverse conversion when writing the output).

Fixes: https://sourceware.org/bugzilla/show_bug.cgi?id=31283
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 binutils/winduni.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/binutils/winduni.c b/binutils/winduni.c
index 5b659764948..9406ca577a9 100644
--- a/binutils/winduni.c
+++ b/binutils/winduni.c
@@ -45,6 +45,19 @@
 #include <iconv.h>
 #endif
 
+/* Best effort attempt to find out if we're running on a big endian
+ * system (only old ppc64 and s390x these days).  Assume little endian
+ * if the macros are not defined.  On big endian, unichar will be a
+ * big endian short.
+ */
+#if defined(__BYTE_ORDER__) && \
+    defined(__ORDER_BIG_ENDIAN__) && \
+    __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define IS_LITTLE_ENDIAN 0
+#else
+#define IS_LITTLE_ENDIAN 1
+#endif
+
 static rc_uint_type wind_WideCharToMultiByte (rc_uint_type, const unichar *, char *, rc_uint_type);
 static rc_uint_type wind_MultiByteToWideChar (rc_uint_type, const char *, unichar *, rc_uint_type);
 static int unichar_isascii (const unichar *, rc_uint_type);
@@ -771,7 +784,8 @@ wind_MultiByteToWideChar (rc_uint_type cp, const char *mb,
 
   if (!mb || !iconv_name)
     return 0;
-  iconv_t cd = iconv_open ("UTF-16LE", iconv_name);
+  iconv_t cd = iconv_open (IS_LITTLE_ENDIAN ? "UTF-16LE" : "UTF-16BE",
+			   iconv_name);
 
   while (1)
     {
@@ -844,7 +858,8 @@ wind_WideCharToMultiByte (rc_uint_type cp, const unichar *u, char *mb, rc_uint_t
 
   if (!u || !iconv_name)
     return 0;
-  iconv_t cd = iconv_open (iconv_name, "UTF-16LE");
+  iconv_t cd = iconv_open (iconv_name,
+			   IS_LITTLE_ENDIAN ? "UTF-16LE" : "UTF-16BE");
 
   while (1)
     {
-- 
2.43.0

Re: [PATCH] binutils/windmc: Parse input correctly on big endian hosts

[Richard W.M. Jones]

On Wed, Jan 24, 2024 at 11:20:05AM +0000, Richard W.M. Jones wrote:
> +/* Best effort attempt to find out if we're running on a big endian
> + * system (only old ppc64 and s390x these days).  Assume little endian
> + * if the macros are not defined.  On big endian, unichar will be a
> + * big endian short.
> + */
> +#if defined(__BYTE_ORDER__) && \
> +    defined(__ORDER_BIG_ENDIAN__) && \
> +    __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> +#define IS_LITTLE_ENDIAN 0
> +#else
> +#define IS_LITTLE_ENDIAN 1
> +#endif

I just found a thread about how to find host endianness:

https://sourceware.org/pipermail/binutils/2024-January/131506.html

so I'll rework this patch, except v2 soon.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v