libiscsi: add patch to fix largefile related issues

This commit adds a patch to libiscsi, to fix largefile related issues
occuring in two situations:

 * glibc toolchains, due to the way _FILE_OFFSET_BITS=64 is handled,
   by declaring the *64() functions as aliases to the non-64*() ones.

 * uClibc toolchains without largefile support.

First problem was visible in:

  http://autobuild.buildroot.org/results/b52/b52782c7ada0db098620bd8eceedd7b84515446b/

Second problem was visible in:

  http://autobuild.buildroot.org/results/23c/23c27fc7c4836dfd2527e52d95d5e72905ece7be/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libiscsi/libiscsi-0005-ld_iscsi-fix-largefile-related-issues.patch

@@ -0,0 +1,83 @@
+From b77db7fa6cd00e1412fdd186180996f8d622b275 Mon Sep 17 00:00:00 2001
+From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+Date: Sun, 7 Sep 2014 12:21:04 +0200
+Subject: [PATCH 5/5] ld_iscsi: fix largefile related issues
+
+This commit fixes two related issues in the ld_iscsi example with
+largefile support.
+
+The first issue appears when building libiscsi against the glibc C
+library, with the flags -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
+-D_FILE_OFFSET_BITS=64:
+
+{standard input}: Assembler messages:
+{standard input}:2774: Error: symbol `__fxstat64' is already defined
+{standard input}:2850: Error: symbol `__lxstat64' is already defined
+{standard input}:2938: Error: symbol `__xstat64' is already defined
+
+This is due to the fact that when _FILE_OFFSET_BITS=64 is passed, the
+*64() functions are defined by the C library as aliases to the
+non-64*() functions, because those ones directly support large files
+(i.e 64 bits).
+
+The second issue appears when building libiscsi against the uClibc C
+library, in a configuration that doesn't have largefile support. In
+this case, the ld_iscsi that tries to use stat64 or some other *64()
+functions cannot build, because such functions are not provided by the
+C library. Of course, ld_iscsi does not need to wrap the *64()
+functions in such a situation, because they do not exist.
+
+This commit fixes those problems by enclosing the *64() related code
+of ld_iscsi in the following compile time conditional:
+
+This ensures that the *64() function handling is here only if
+largefile support is available and enabled (_LARGEFILE_SOURCE64) and
+if non-*64() functions are not already 64 bits capable (in which case
+the 64*() functions are just aliases for the non-64*() ones).
+
+See also
+http://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html
+for more details about the meaning of those macros.
+
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+---
+ examples/ld_iscsi.c | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/examples/ld_iscsi.c b/examples/ld_iscsi.c
+index 0cf2724..02f9d25 100644
+--- a/examples/ld_iscsi.c
++++ b/examples/ld_iscsi.c
+@@ -543,6 +543,7 @@ int dup2(int oldfd, int newfd)
+ 	return real_dup2(oldfd, newfd);
+ }
+ 
++#if defined(_LARGEFILE64_SOURCE) && _FILE_OFFSET_BITS != 64
+ 
+ int (*real_fxstat64)(int ver, int fd, struct stat64 *buf);
+ 
+@@ -591,6 +592,7 @@ int __xstat64(int ver, const char *path, struct stat64 *buf)
+ 	return __lxstat64(ver, path, buf);
+ }
+ 
++#endif
+ 
+ static void __attribute__((constructor)) _init(void)
+ {
+@@ -669,6 +671,7 @@ static void __attribute__((constructor)) _init(void)
+ 		exit(10);
+ 	}
+ 
++#if defined(_LARGEFILE64_SOURCE) && _FILE_OFFSET_BITS != 64
+ 	real_fxstat64 = dlsym(RTLD_NEXT, "__fxstat64");
+ 	if (real_fxstat64 == NULL) {
+ 		LD_ISCSI_DPRINTF(0,"Failed to dlsym(__fxstat64)");
+@@ -683,4 +686,5 @@ static void __attribute__((constructor)) _init(void)
+ 	if (real_xstat64 == NULL) {
+ 		LD_ISCSI_DPRINTF(0,"Failed to dlsym(__xstat64)");
+ 	}
++#endif
+ }
+-- 
+2.0.0
+