Add Sys.dlpath() to map strings or dlopen handles to absolute pathnames

Currently implemented for OSX and Linux only

base/sysinfo.jl

@@ -12,7 +12,8 @@ export  CPU_CORES,
         free_memory,
         total_memory,
         shlib_ext,
-        shlib_list
+        shlib_list,
+        dlpath
 
 import ..Base: WORD_SIZE, OS_NAME, ARCH, MACHINE
 import ..Base: show, uv_error
@@ -192,4 +193,12 @@ function shlib_list()
     dynamic_libraries
 end
 
+function dlpath( handle::Ptr{Void} )
+    return bytestring(ccall( :jl_pathname_for_handle, Ptr{Uint8}, (Ptr{Void},), handle ))
+end
+
+function dlpath( libname::String )
+    return dlpath( dlopen(libname) )
+end
+
 end

src/sys.c

@@ -13,6 +13,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 #include <sys/mman.h>
+#include <dlfcn.h>
 #endif
 #include <errno.h>
 #include <signal.h>
@@ -24,6 +25,15 @@ char *dirname(char *);
 #endif
 #include <fcntl.h>
 
+#ifdef __APPLE__
+#include <mach-o/dyld.h>
+#include <mach-o/nlist.h>
+#endif
+
+#ifdef _OS_LINUX_
+#include <link.h>
+#endif
+
 #define __STDC_CONSTANT_MACROS
 #define __STDC_LIMIT_MACROS
 #include <llvm-c/Target.h>
@@ -517,3 +527,100 @@ DLLEXPORT long jl_SC_CLK_TCK(void)
     return 0;
 #endif
 }
+
+// Dynamic Library interrogation
+
+#ifdef __APPLE__
+// This code gratefully lifted from: http://stackoverflow.com/questions/20481058
+#ifdef __LP64__
+typedef struct mach_header_64 mach_header_t;
+typedef struct segment_command_64 segment_command_t;
+typedef struct nlist_64 nlist_t;
+#else
+typedef struct mach_header mach_header_t;
+typedef struct segment_command segment_command_t;
+typedef struct nlist nlist_t;
+#endif
+
+static const char * first_external_symbol_for_image(const mach_header_t *header)
+{
+    Dl_info info;
+    if (dladdr(header, &info) == 0)
+        return NULL;
+
+    segment_command_t *seg_linkedit = NULL;
+    segment_command_t *seg_text = NULL;
+    struct symtab_command *symtab = NULL;
+
+    struct load_command *cmd = (struct load_command *)((intptr_t)header + sizeof(mach_header_t));
+    for (uint32_t i = 0; i < header->ncmds; i++, cmd = (struct load_command *)((intptr_t)cmd + cmd->cmdsize))
+    {
+        switch(cmd->cmd)
+        {
+            case LC_SEGMENT:
+            case LC_SEGMENT_64:
+                if (!strcmp(((segment_command_t *)cmd)->segname, SEG_TEXT))
+                    seg_text = (segment_command_t *)cmd;
+                else if (!strcmp(((segment_command_t *)cmd)->segname, SEG_LINKEDIT))
+                    seg_linkedit = (segment_command_t *)cmd;
+                break;
+
+            case LC_SYMTAB:
+                symtab = (struct symtab_command *)cmd;
+                break;
+        }
+    }
+
+    if ((seg_text == NULL) || (seg_linkedit == NULL) || (symtab == NULL))
+        return NULL;
+
+    intptr_t file_slide = ((intptr_t)seg_linkedit->vmaddr - (intptr_t)seg_text->vmaddr) - seg_linkedit->fileoff;
+    intptr_t strings = (intptr_t)header + (symtab->stroff + file_slide);
+    nlist_t *sym = (nlist_t *)((intptr_t)header + (symtab->symoff + file_slide));
+
+    for (uint32_t i = 0; i < symtab->nsyms; i++, sym++)
+    {
+        if ((sym->n_type & N_EXT) != N_EXT || !sym->n_value)
+            continue;
+
+        return (const char *)strings + sym->n_un.n_strx;
+    }
+
+    return NULL;
+}
+#endif
+
+
+// Takes a handle (as returned from dlopen()) and returns the absolute path to the image loaded
+DLLEXPORT const char * jl_pathname_for_handle(uv_lib_t * uv_lib)
+{
+    if( !uv_lib )
+        return NULL;
+
+    void * handle = uv_lib->handle;
+#ifdef __APPLE__
+    for (int32_t i = _dyld_image_count(); i >= 0 ; i--) {
+        const char *first_symbol = first_external_symbol_for_image((const mach_header_t *)_dyld_get_image_header(i));
+        if (first_symbol && strlen(first_symbol) > 1) {
+            handle = (void *)((intptr_t)handle | 1); // in order to trigger findExportedSymbol instead of findExportedSymbolInImageOrDependentImages. See `dlsym` implementation at http://opensource.apple.com/source/dyld/dyld-239.3/src/dyldAPIs.cpp
+            first_symbol++; // in order to remove the leading underscore
+            void *address = dlsym(handle, first_symbol);
+            Dl_info info;
+            if (dladdr(address, &info))
+                return info.dli_fname;
+        }
+    }
+#endif
+
+#ifdef _OS_LINUX_
+    struct link_map * map;
+    dlinfo( handle, RTLD_DI_LINKMAP, &map );
+    if (map)
+        return map->l_name;
+#endif
+
+#ifdef _OS_WINDOWS_
+    // Not supported yet...
+#endif
+    return NULL;
+}