work around libselinux.so issue

This issue came up in the real world because apparently libselinux.so.1 does an fopen in a constructor function. Big Thanks to Mike Shal (http://sourceware.org/ml/libc-help/2009-06/msg00000.html ) [Made some cosmetic changes -JP] Fixes: GitHub issues #1 and #2 Signed-off-by: Julius Plenz <julius@plenz.com>

work around libselinux.so issue
e6df5f64 · Aleksandr · Julius Plenz · 5de2538b · e6df5f64
Commit e6df5f64 authored Oct 16, 2012 by Aleksandr Committed by Julius Plenz Oct 16, 2012
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Showing with 22 additions and 6 deletions

nocache.c nocache.c +22 -6

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--- a/nocache.c
+++ b/nocache.c
@@ -8,6 +8,7 @@
 #include <dlfcn.h>
 #include <string.h>
 #include <pthread.h>
+#include <errno.h>

 #include "fcntl_helpers.h"

@@ -185,17 +186,32 @@ int close(int fd)
 FILE *fopen(const char *path, const char *mode)
 {
    int fd;
-    FILE *fp;
-    if((fp = _original_fopen(path, mode)) != NULL)
-        if((fd = fileno(fp)) != -1)
-            store_pageinfo(fd);
+    FILE *fp = NULL;
+
+    if(!_original_fopen)
+       _original_fopen = (FILE *(*)(const char *, const char *)) dlsym(RTLD_NEXT, "fopen");
+
+    if(_original_fopen) {
+        if((fp = _original_fopen(path, mode)) != NULL)
+            if((fd = fileno(fp)) != -1)
+                store_pageinfo(fd);
+    }
+
    return fp;
 }

 int fclose(FILE *fp)
 {
-    free_unclaimed_pages(fileno(fp));
-    return _original_fclose(fp);
+    if(!_original_fclose)
+        _original_fclose = (int (*)(FILE *)) dlsym(RTLD_NEXT, "fclose");
+
+    if(_original_fclose) {
+       free_unclaimed_pages(fileno(fp));
+       return _original_fclose(fp);
+    }
+
+    errno = EFAULT;
+    return EOF;
 }

 static void store_pageinfo(int fd)