# HG changeset patch
# User Tassilo Philipp
# Date 1573039973 -3600
# Node ID b2e4e23d995369e05ce2a313dd2974fcaec5a454
# Parent  73b5b9e224e237377419049ff3b65db8356c0517
- stop using dlinfo() on glibc platforms but use dl_iterate_phdr() instead, as former's implementation is nothing more than a fancy cast and thus dangerously assuming that every provided handle is valid
- dynload_plain test
  * now testing getting exec's path
  * workdir independent

diff -r 73b5b9e224e2 -r b2e4e23d9953 ChangeLog
--- a/ChangeLog	Tue Nov 05 15:19:16 2019 +0100
+++ b/ChangeLog	Wed Nov 06 12:32:53 2019 +0100
@@ -7,6 +7,9 @@
   o support for soft-float MIPS o32 & n64 (big- and little-endian, each)
 dynload:
   o added UTF-8 support for pathnames on windows
+  o reliability/stability fix for dlGetLibraryPath() on glibc based platforms (avoiding
+    internal use of glibc's bad impl of dlinfo() which doesn't do any error checking at all)
+  o support for dlGetLibraryPath() on glibc platforms with glibc vesions <= 2.3.3
 doc:
   o more detail in support matrix for bi-endian platforms
 tests:
diff -r 73b5b9e224e2 -r b2e4e23d9953 dynload/dynload_unix.c
--- a/dynload/dynload_unix.c	Tue Nov 05 15:19:16 2019 +0100
+++ b/dynload/dynload_unix.c	Wed Nov 06 12:32:53 2019 +0100
@@ -38,7 +38,12 @@
 
 #include <string.h>
 
-#if defined(__GLIBC__) /* to access dlinfo */
+#if defined(__GLIBC__)
+/* @@@ version check glibc correctly... dl_iterate_phdr(): glibc ver >= 2.2.4*/
+#if (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 3)
+#  define DL_USE_GLIBC_ITER_PHDR
+#endif
+/* to access dl_iterate_phdr(), and related w/ glibc */
 #  define _GNU_SOURCE
 #  define __USE_GNU
 #endif
@@ -69,20 +74,23 @@
 
 
 
-/* for dlopen-based dlGetLibraryPath impls below, prefer RTLD_NOLOAD */
-/* that merely checks lib names */
+/* for dlopen-based dlGetLibraryPath impls below, prefer RTLD_NOLOAD that
+ * merely checks lib names */
 #if defined(RTLD_NOLOAD)
-#  define RTLD_LIGHTEST RTLD_NOLOAD
+#  define RTLD_LIGHTEST RTLD_LAZY|RTLD_NOLOAD
 #else
 #  define RTLD_LIGHTEST RTLD_LAZY
 #endif
 
 
-/* code for dlGetLibraryPath is platform specific - if dlinfo() exists use */
-/* that: check for RTLD_DI_LINKMAP (#define for dlinfo()), or if GNU C Lib */
-/* is used (where RTLD_DI_LINKMAP is an enum), or by OS (dlinfo comes from */
-/* Solaris), etc. */
-#if defined(RTLD_DI_LINKMAP) || defined(OS_SunOS) || defined(__GLIBC__) /* @@@ dlinfo() was introduced in glibc 2.3.3 (in 2003), somehow check for that, also */
+/* code for dlGetLibraryPath() is platform specific */
+
+/* if dlinfo() exists use it (except on glibc, where it exists since version
+ * 2.3.3, but its implementation is dangerous, as no checks are done whether
+ * the handle is valid, thus rendering the returned values useless): check for
+ * RTLD_DI_LINKMAP which is a #define for dlinfo() on most supported targets,
+ * or specifically check the OS (e.g. dlinfo() is originally from Solaris) */
+#if (defined(RTLD_DI_LINKMAP) || defined(OS_SunOS)) && !defined(DL_USE_GLIBC_ITER_PHDR)
 
 #include <link.h>
 
@@ -90,9 +98,7 @@
 {
   struct link_map* p = NULL;
   int l = -1;
-  /* on some platforms dlinfo() "succeeds" for any handle, returning a */
-  /* legit pointer to a struct w/o any fields set; fail if unset */
-  if(dlinfo(pLib, RTLD_DI_LINKMAP, &p) == 0 && p && p->l_name) {
+  if(dlinfo(pLib, RTLD_DI_LINKMAP, &p) == 0 && p) {
     l = strlen(p->l_name);
     if(l < bufSize) /* l+'\0' <= bufSize */
       strcpy(sOut, p->l_name);
@@ -119,7 +125,7 @@
   /* code. There doesn't seem to be a direct way to query the library path,  */
   /* so "double-load" temporarily all already loaded images (just increases  */
   /* ref count) and compare handles until we found ours. Return the name.    */
-  for(i=_dyld_image_count(); i>0;) /* iterate libs from end, more likely ours */
+  for(i=_dyld_image_count(); i>0;) /* backwards, ours is more likely at end */
   {
     const char* libPath = _dyld_get_image_name(--i);
     void* lib = dlopen(libPath, RTLD_LIGHTEST);
@@ -140,9 +146,10 @@
 }
 
 
-/* OpenBSD >= 3.7 has dl_iterate_phdr(), use it if not explicitly requesting */
-/* to use dladdr()-based guessing (set by configure) -----> */
-#elif defined(OS_OpenBSD) && !defined(DL_DLADDR_TO_LIBPATH)
+/* OpenBSD >= 3.7 has dl_iterate_phdr(), as well as glibc >= 2.2.4, however
+ * skip and use on dladdr()-based guessing if if explicitly requested, e.g. by
+ * ./configure */
+#elif !defined(DL_DLADDR_TO_LIBPATH) && (defined(OS_OpenBSD) || defined(DL_USE_GLIBC_ITER_PHDR))
 
 #include <sys/types.h>
 #include <link.h>
@@ -179,9 +186,16 @@
 }
 
 
+/* glibc with neither dl_iterate_phdr() nor dlinfo() (latter introduced after former) @@@
+#elif defined(__GLIBC__) && !defined(DL_USE_GLIBC_ITER_PHDR)
+
+@@@impl */
+
 /* fallback to dladdr() hack */
 #else
 
+#warning "Using non-optimal code for dlGetLibraryPath() b/c of platform limitations."
+
 /* if nothing else is available, fall back to guessing using dladdr() - this */
 /* might not always work, as it's trying to getit via the _fini() symbol,    */
 /* which is usually defined in ELF files, but not guaranteed                 */
diff -r 73b5b9e224e2 -r b2e4e23d9953 test/dynload_plain/dynload_plain.c
--- a/test/dynload_plain/dynload_plain.c	Tue Nov 05 15:19:16 2019 +0100
+++ b/test/dynload_plain/dynload_plain.c	Wed Nov 06 12:32:53 2019 +0100
@@ -34,6 +34,7 @@
 #else
 #  include <unistd.h>
 #endif
+#include <libgen.h>
 
 
 int strlen_utf8(const char *s)
@@ -58,7 +59,7 @@
 #if defined(DEF_C_DYLIB)
     DEF_C_DYLIB,
 #endif
-	/* fallback guessing if not provided by Makefile */
+    /* fallback guessing if not provided by Makefile */
     "/lib/libc.so",
     "/lib32/libc.so",
     "/lib64/libc.so",
@@ -137,14 +138,24 @@
       printf("path lookup failed as expected with bad lib handle: %d\n", bs == 0);
       r += (bs == 0);
 
+      /* test getting own path */
+      {
+        /* get own exec's path */
+        bs = dlGetLibraryPath(NULL, queriedPath, 200);
+        printf("dynload_plain's own path is: %s\n", queriedPath);
+        r += (bs != 0 && strlen(queriedPath) > 0);
+
+        /* change working dir to where our executable is,  for following test */
+        chdir(dirname(queriedPath));
+      }
+
       /* test UTF-8 path through dummy library that's created by this test's build */
       {
         static const char* pathU8 = "./dynload_plain_\xc3\x9f_test";
-		int nu8c, b;
+        int nu8c, b;
 
-        //cp(pathU8, "/lib/libz.so.6");
         pLib = dlLoadLibrary(pathU8); /* check if we can load a lib with a UTF-8 path */
-        printf("pLib (loaded w/ UTF-8 path %s) handle: %p\n", pathU8, pLib);
+        printf("pLib (loaded w/ UTF-8 path %s with wd being exec's dir) handle: %p\n", pathU8, pLib);
         r += (p != NULL);
 
         if(pLib) {
@@ -220,7 +231,7 @@
   }
 
   /* Check final score of right ones to see if all worked */
-  r = (r == 15);
+  r = (r == 16);
   printf("result: dynload_plain: %d\n", r);
   return !r;
 }