6 files changed, 439 insertions, 9 deletions
diff --git a/Makefile b/Makefile
index ab7279b..944358f 100644
--- a/Makefile
+++ b/Makefile
@@ -6,14 +6,14 @@ CFLAGS = -Wall -O3 -fomit-frame-pointer -Isrc
 ifeq ($(BUILD_SHARED),yes)
        TARGETS += libdl.dll
-        SHFLAGS += -Wl,--out-implib,libdl.dll.a -DSHARED
+        SHFLAGS += -Wl,--out-implib,libdl.dll.a
        INSTALL += shared-install
-        TESTS   += test.exe
+        TESTS   += test.exe test-dladdr.exe
 endif
 ifeq ($(BUILD_STATIC),yes)
        TARGETS += libdl.a
        INSTALL += static-install
-        TESTS   += test-static.exe
+        TESTS   += test-static.exe test-dladdr-static.exe
 endif
 ifeq ($(BUILD_MSVC),yes)
    TARGETS += libdl.lib
@@ -32,7 +32,7 @@ libdl.a: $(SOURCES)
        $(RANLIB) $@
 libdl.dll: $(SOURCES)
-        $(CC) $(CFLAGS) $(SHFLAGS) -shared -o $@ $^
+        $(CC) $(CFLAGS) $(SHFLAGS) -DDLFCN_WIN32_SHARED -shared -o $@ $^
 libdl.lib: libdl.dll
        $(LIBCMD) /machine:i386 /def:libdl.def
@@ -64,6 +64,12 @@ test.exe: tests/test.c $(TARGETS)
 test-static.exe: tests/test.c $(TARGETS)
        $(CC) $(CFLAGS) -o $@ $< libdl.a
+test-dladdr.exe: tests/test-dladdr.c $(TARGETS)
+        $(CC) $(CFLAGS) -DDLFCN_WIN32_SHARED -o $@ $< libdl.dll.a
+test-dladdr-static.exe: tests/test-dladdr.c $(TARGETS)
+        $(CC) $(CFLAGS) -o $@ $< libdl.a
 testdll.dll: tests/testdll.c
        $(CC) $(CFLAGS) -shared -o $@ $^
@@ -81,6 +87,7 @@ clean::
                src/dlfcn.o \
                libdl.dll libdl.a libdl.def libdl.dll.a libdl.lib libdl.exp \
                tmptest.c tmptest.dll \
+                test-dladdr.exe test-dladdr-static.exe \
                test.exe test-static.exe testdll.dll testdll2.dll testdll3.dll
 distclean: clean
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d5296b1..27f9030 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,15 +1,20 @@
 set(headers dlfcn.h)
 set(sources dlfcn.c)
-if (BUILD_SHARED_LIBS)
-  add_definitions(-DSHARED)
-endif (BUILD_SHARED_LIBS)
 add_library(dl ${sources})
 # Correctly export the location of installed includes in the target
 target_include_directories(dl INTERFACE $<INSTALL_INTERFACE:include>)
+# dot not add -D<target>_EXPORTS
+set_target_properties(dl PROPERTIES DEFINE_SYMBOL "")
+# set shared mode for compiling library and propagate mode to cmake clients
+if (BUILD_SHARED_LIBS)
+    target_compile_definitions(dl PUBLIC DLFCN_WIN32_SHARED)
+endif (BUILD_SHARED_LIBS)
 install (TARGETS dl EXPORT dlfcn-win32-targets
                    RUNTIME DESTINATION bin
                    LIBRARY DESTINATION lib${LIB_SUFFIX}
diff --git a/src/dlfcn.c b/src/dlfcn.c
index 3251661..5dd1ccf 100644
--- a/src/dlfcn.c
+++ b/src/dlfcn.c
@@ -3,6 +3,7 @@
 * Copyright (c) 2007 Ramiro Polla
 * Copyright (c) 2015 Tiancheng "Timothy" Gu
 * Copyright (c) 2019 Pali Rohár <pali.rohar@gmail.com>
+ * Copyright (c) 2020 Ralf Habacker <ralf.habacker@freenet.de>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
@@ -45,7 +46,7 @@
 #endif
 #endif
-#ifdef SHARED
+#ifdef DLFCN_WIN32_SHARED
 #define DLFCN_WIN32_EXPORTS
 #endif
 #include "dlfcn.h"
@@ -222,6 +223,7 @@ static BOOL MyEnumProcessModules( HANDLE hProcess, HMODULE *lphModule, DWORD cb,
    return EnumProcessModulesPtr( hProcess, lphModule, cb, lpcbNeeded );
 }
+DLFCN_EXPORT
 void *dlopen( const char *file, int mode )
 {
    HMODULE hModule;
@@ -329,6 +331,7 @@ void *dlopen( const char *file, int mode )
    return (void *) hModule;
 }
+DLFCN_EXPORT
 int dlclose( void *handle )
 {
    HMODULE hModule = (HMODULE) handle;
@@ -353,6 +356,7 @@ int dlclose( void *handle )
 }
 __declspec(noinline) /* Needed for _ReturnAddress() */
+DLFCN_EXPORT
 void *dlsym( void *handle, const char *name )
 {
    FARPROC symbol;
@@ -460,6 +464,7 @@ end:
    return *(void **) (&symbol);
 }
+DLFCN_EXPORT
 char *dlerror( void )
 {
    /* If this is the second consecutive call to dlerror, return NULL */
@@ -474,7 +479,212 @@ char *dlerror( void )
    return error_buffer;
 }
-#ifdef SHARED
+/* See https://docs.microsoft.com/en-us/archive/msdn-magazine/2002/march/inside-windows-an-in-depth-look-into-the-win32-portable-executable-file-format-part-2
+ * for details */
+/* Get specific image section */
+static BOOL get_image_section( HMODULE module, int index, void **ptr, DWORD *size )
+{
+    IMAGE_DOS_HEADER *dosHeader;
+    IMAGE_OPTIONAL_HEADER *optionalHeader;
+    dosHeader = (IMAGE_DOS_HEADER *) module;
+    if( dosHeader->e_magic != 0x5A4D )
+        return FALSE;
+    optionalHeader = (IMAGE_OPTIONAL_HEADER *) ( (BYTE *) module + dosHeader->e_lfanew + 24 );
+    if( optionalHeader->Magic != IMAGE_NT_OPTIONAL_HDR_MAGIC )
+        return FALSE;
+    if( index < 0 || index > IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR )
+        return FALSE;
+    if( optionalHeader->DataDirectory[index].Size == 0 || optionalHeader->DataDirectory[index].VirtualAddress == 0 )
+        return FALSE;
+    if( size != NULL )
+        *size = optionalHeader->DataDirectory[index].Size;
+    *ptr = (void *)( (BYTE *) module + optionalHeader->DataDirectory[index].VirtualAddress );
+    return TRUE;
+}
+/* Return symbol name for a given address */
+static const char *get_symbol_name( HMODULE module, IMAGE_IMPORT_DESCRIPTOR *iid, void *addr, void **func_address )
+{
+    int i;
+    void *candidateAddr = NULL;
+    const char *candidateName = NULL;
+    BYTE *base = (BYTE *) module; /* Required to have correct calculations */
+    for( i = 0; iid[i].Characteristics != 0 && iid[i].FirstThunk != 0; i++ )
+    {
+        IMAGE_THUNK_DATA *thunkILT = (IMAGE_THUNK_DATA *)( base + iid[i].Characteristics );
+        IMAGE_THUNK_DATA *thunkIAT = (IMAGE_THUNK_DATA *)( base + iid[i].FirstThunk );
+        for( ; thunkILT->u1.AddressOfData != 0; thunkILT++, thunkIAT++ )
+        {
+            IMAGE_IMPORT_BY_NAME *nameData;
+            if( IMAGE_SNAP_BY_ORDINAL( thunkILT->u1.Ordinal ) )
+                continue;
+            if( (void *) thunkIAT->u1.Function > addr || candidateAddr >= (void *) thunkIAT->u1.Function )
+                continue;
+            candidateAddr = (void *) thunkIAT->u1.Function;
+            nameData = (IMAGE_IMPORT_BY_NAME *)( base + (ULONG_PTR) thunkILT->u1.AddressOfData );
+            candidateName = (const char *) nameData->Name;
+        }
+    }
+    *func_address = candidateAddr;
+    return candidateName;
+}
+static BOOL is_valid_address( void *addr )
+{
+    MEMORY_BASIC_INFORMATION info;
+    SIZE_T result;
+    if( addr == NULL )
+        return FALSE;
+    /* check valid pointer */
+    result = VirtualQuery( addr, &info, sizeof( info ) );
+    if( result == 0 || info.AllocationBase == NULL || info.AllocationProtect == 0 || info.AllocationProtect == PAGE_NOACCESS )
+        return FALSE;
+    return TRUE;
+}
+/* Return state if address points to an import thunk
+ *
+ * An import thunk is setup with a 'jmp' instruction followed by an
+ * absolute address (32bit) or relative offset (64bit) pointing into
+ * the import address table (iat), which is partially maintained by
+ * the runtime linker.
+ */
+static BOOL is_import_thunk( void *addr )
+{
+    return *(short *) addr == 0x25ff ? TRUE : FALSE;
+}
+/* Return adress from the import address table (iat),
+ * if the original address points to a thunk table entry.
+ */
+static void *get_address_from_import_address_table( void *iat, DWORD iat_size, void *addr )
+{
+    BYTE *thkp = (BYTE *) addr;
+    /* Get offset from thunk table (after instruction 0xff 0x25)
+     *   4018c8 <_VirtualQuery>: ff 25 4a 8a 00 00
+     */
+    ULONG offset = *(ULONG *)( thkp + 2 );
+#ifdef _WIN64
+    /* On 64 bit the offset is relative
+     *      4018c8:   ff 25 4a 8a 00 00    jmpq    *0x8a4a(%rip)    # 40a318 <__imp_VirtualQuery>
+     * And can be also negative (MSVC in WDK)
+     *   100002f20:   ff 25 3a e1 ff ff    jmpq   *-0x1ec6(%rip)    # 0x100001060
+     * So cast to signed LONG type
+     */
+    BYTE *ptr = (BYTE *)( thkp + 6 + (LONG) offset );
+#else
+    /* On 32 bit the offset is absolute
+     *   4019b4:    ff 25 90 71 40 00    jmp    *0x40719
+     */
+    BYTE *ptr = (BYTE *) offset;
+#endif
+    if( !is_valid_address( ptr ) || ptr < (BYTE *) iat || ptr > (BYTE *) iat + iat_size )
+        return NULL;
+    return *(void **) ptr;
+}
+/* Holds module filename */
+static char module_filename[2*MAX_PATH];
+static BOOL fill_module_info( void *addr, Dl_info *info )
+{
+    HMODULE hModule;
+    DWORD dwSize;
+    if( !GetModuleHandleExA( GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, addr, &hModule ) || hModule == NULL )
+        return FALSE;
+    dwSize = GetModuleFileNameA( hModule, module_filename, sizeof( module_filename ) );
+    if( dwSize == 0 || dwSize == sizeof( module_filename ) )
+        return FALSE;
+    info->dli_fbase = (void *) hModule;
+    info->dli_fname = module_filename;
+    return TRUE;
+}
+DLFCN_EXPORT
+int dladdr( void *addr, Dl_info *info )
+{
+    void *realAddr, *funcAddress = NULL;
+    HMODULE hModule;
+    IMAGE_IMPORT_DESCRIPTOR *iid;
+    DWORD iidSize = 0;
+    if( addr == NULL || info == NULL )
+        return 0;
+    hModule = GetModuleHandleA( NULL );
+    if( hModule == NULL )
+        return 0;
+    if( !is_valid_address( addr ) )
+        return 0;
+    realAddr = addr;
+    if( !get_image_section( hModule, IMAGE_DIRECTORY_ENTRY_IMPORT, (void **) &iid, &iidSize ) )
+        return 0;
+    if( is_import_thunk( addr ) )
+    {
+        void *iat;
+        void *iatAddr = NULL;
+        DWORD iatSize = 0;
+        if( !get_image_section( hModule, IMAGE_DIRECTORY_ENTRY_IAT, &iat, &iatSize ) )
+        {
+            /* Fallback for cases where the iat is not defined,
+             * for example i586-mingw32msvc-gcc */
+            if( iid == NULL || iid->Characteristics == 0 || iid->FirstThunk == 0 )
+                return 0;
+            iat = (void *)( (BYTE *) hModule + iid->FirstThunk );
+            /* We assume that in this case iid and iat's are in linear order */
+            iatSize = iidSize - (DWORD) ( (BYTE *) iat - (BYTE *) iid );
+        }
+        iatAddr = get_address_from_import_address_table( iat, iatSize, addr );
+        if( iatAddr == NULL )
+            return 0;
+        realAddr = iatAddr;
+    }
+    if( !fill_module_info( realAddr, info ) )
+        return 0;
+    info->dli_sname = get_symbol_name( hModule, iid, realAddr, &funcAddress );
+    info->dli_saddr = !info->dli_sname ? NULL : funcAddress ? funcAddress : realAddr;
+    return 1;
+}
+#ifdef DLFCN_WIN32_SHARED
 BOOL WINAPI DllMain( HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved )
 {
    (void) hinstDLL;
diff --git a/src/dlfcn.h b/src/dlfcn.h
index 9ddbba3..164216f 100644
--- a/src/dlfcn.h
+++ b/src/dlfcn.h
@@ -28,9 +28,13 @@
 extern "C" {
 #endif
+#if defined(DLFCN_WIN32_SHARED)
 #if defined(DLFCN_WIN32_EXPORTS)
 #   define DLFCN_EXPORT __declspec(dllexport)
 #else
+#   define DLFCN_EXPORT __declspec(dllimport)
+#endif
+#else
 #   define DLFCN_EXPORT
 #endif
@@ -59,6 +63,15 @@ extern "C" {
 /* Specifies the next object after this one that defines name. */
 #define RTLD_NEXT       ((void *)-1)
+/* Structure filled in by dladdr() */
+typedef struct dl_info
+{
+   const char *dli_fname;  /* Filename of defining object (thread unsafe and reused on every call to dladdr) */
+   void       *dli_fbase;  /* Load address of that object */
+   const char *dli_sname;  /* Name of nearest lower symbol */
+   void       *dli_saddr;  /* Exact value of nearest symbol */
+} Dl_info;
 /* Open a symbol table handle. */
 DLFCN_EXPORT void *dlopen(const char *file, int mode);
@@ -71,6 +84,9 @@ DLFCN_EXPORT void *dlsym(void *handle, const char *name);
 /* Get diagnostic information. */
 DLFCN_EXPORT char *dlerror(void);
+/* Translate address to symbolic information (no POSIX standard) */
+DLFCN_EXPORT int dladdr(void *addr, Dl_info *info);
 #ifdef __cplusplus
 }
 #endif
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 5fc6c44..f0871e5 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -9,9 +9,17 @@ target_link_libraries(testdll2 dl)
 add_library(testdll3 SHARED testdll3.c)
 set_target_properties(testdll3 PROPERTIES PREFIX "")
+add_executable(test-dladdr test-dladdr.c)
+target_link_libraries(test-dladdr dl)
+if(UNIX)
+    set_target_properties(test-dladdr PROPERTIES COMPILE_FLAGS "-Wl,--export-dynamic -fpie")
+endif()
+install(TARGETS test-dladdr EXPORT dlfcn-win32-targets RUNTIME DESTINATION bin)
 add_executable(t_dlfcn test.c)
 target_link_libraries(t_dlfcn dl)
 if(RUN_TESTS)
    add_test(NAME t_dlfcn COMMAND ${WRAPPER} $<TARGET_FILE:t_dlfcn> WORKING_DIRECTORY $<TARGET_FILE_DIR:t_dlfcn>)
+    add_test(NAME test-dladdr COMMAND ${WRAPPER} $<TARGET_FILE:test-dladdr> WORKING_DIRECTORY $<TARGET_FILE_DIR:test-dladdr>)
 endif()
diff --git a/tests/test-dladdr.c b/tests/test-dladdr.c
new file mode 100644
index 0000000..57914cb
--- /dev/null
+++ b/tests/test-dladdr.c
@@ -0,0 +1,184 @@
+/* On Unix like os compile with "-Wl,--export-dynamic -fpie" (default with cmake) */
+/* required for non Windows builds, must be set in front of the first system include */
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+static int verbose = 0;
+typedef enum {
+    Pass = 1,
+    PassWithoutSymbol = 2,
+    PassWithDifferentAddress = 3,
+    Fail = 0,
+    NoInfo = -1,
+} ExpectedResult;
+typedef void (* func) (void);
+static void print_dl_info( Dl_info *info, char *prefix, char *suffix )
+{
+    printf( "%sfilename: %s base: %p symbol name: '%s' addr: %p%s", prefix, info->dli_fname, info->dli_fbase, info->dli_sname, info->dli_saddr, suffix );
+}
+/**
+ * @brief check information returned by dladdr
+ * @param hint text describing what to test
+ * @param addr address to check
+ * @param addrsym
+ * @param expected check against expected result
+ * @return 0 check passed
+ * @return 1 check failed
+ */
+static int check_dladdr( const char *hint, void *addr, char *addrsym, ExpectedResult expected_result )
+{
+    Dl_info info;
+    int result = dladdr( addr, &info );
+    int passed = 0;
+    if (!result)
+    {
+        passed = expected_result == NoInfo || expected_result == Fail;
+    }
+    else
+    {
+        int sym_match  = info.dli_sname && strcmp( addrsym, info.dli_sname ) == 0;
+        int addr_match  = addr == info.dli_saddr;
+        passed = (expected_result == Pass && sym_match && addr_match)
+                 || (expected_result == PassWithoutSymbol && addr_match && !info.dli_sname)
+                 || (expected_result == PassWithDifferentAddress && sym_match && !addr_match)
+                 || (expected_result == Fail && (!sym_match || !addr_match));
+    }
+    printf( "checking '%s' - address %p which should have symbol '%s' -> %s%s", hint, addr, addrsym, passed ? "passed" : "failed", verbose || !passed ? " " : "\n" );
+    if( verbose || !passed )
+    {
+        if( !result )
+            printf( "(could not get symbol information for address %p)\n", addr );
+        else
+            print_dl_info( &info, "(", ")\n");
+    }
+    return !passed;
+}
+#ifdef _WIN32
+/**
+ * @brief check address from a symbol located in a shared lilbrary
+ * @param hint text describing what to test
+ * @param libname libray to get the address from
+ * @param addrsym symbol to get the address for
+ * @param should_match result should match the given values
+ * @return 0 check passed
+ * @return 1 check failed
+ * @return 2 failed to open library
+ * @return 3 failed to get symbol address
+ */
+static int check_dladdr_by_dlopen( const char *hint, char *libname, char *sym, int should_match )
+{
+    void *library = NULL;
+    void *addr = NULL;
+    int result;
+    library = dlopen( libname, RTLD_GLOBAL );
+    if ( library == NULL )
+    {
+        fprintf( stderr, "could not open '%s'\n", libname );
+        return 2;
+    }
+    addr = dlsym( library, sym );
+    if ( !addr ) {
+        fprintf( stderr, "could not get address from library '%s' for symbol '%s'\n", libname, sym );
+        return 3;
+    }
+    result = check_dladdr( hint, addr, sym, should_match );
+    dlclose( library );
+    return result;
+}
+#endif
+#ifdef _WIN32
+#include <windows.h>
+#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
+/* hide warning "reclared without 'dllimport' attribute" */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wattributes"
+#elif defined(_MSC_VER)
+/* disable warning C4273 inconsistent dll linkage */
+#pragma warning(push)
+#pragma warning(disable: 4273)
+#endif
+/*
+ * Windows API functions decorated with WINBASEAPI are imported from iat.
+ * For testing force linking by import thunk for the following functions
+ */
+HMODULE WINAPI GetModuleHandleA (LPCSTR lpModuleName);
+SIZE_T WINAPI VirtualQuery (LPCVOID lpAddress, PMEMORY_BASIC_INFORMATION lpBuffer, SIZE_T dwLength);
+/* force linking by iat */
+/* WINBASEAPI, which is normally used here, can be overriden by compiler or application, so we cannot use it */
+__declspec(dllimport) HMODULE WINAPI LoadLibraryExA(LPCSTR lpLibFileName, HANDLE hFile, DWORD  dwFlags);
+__declspec(dllimport) int __cdecl atoi(const char *_Str);
+#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
+#pragma GCC diagnostic pop
+#elif defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+#endif
+#ifdef _WIN32
+#define FailOnWin Fail
+#else
+#define FailOnWin Pass
+#endif
+#if defined(_WIN32) && !defined(DLFCN_WIN32_SHARED)
+#define PassOnSharedBuild Fail
+#else
+#define PassOnSharedBuild Pass
+#endif
+#define UNUSED(x) (void)x
+int main(int argc, char **argv)
+{
+    /* points to non reachable address */
+    unsigned char zero_thunk_address[6] = { 0xFF, 0x25, 0x00, 0x00, 0x00, 0x00 };
+    /* points to executable base */
+    unsigned char invalid_thunk_address[6] = { 0xFF, 0x25, 0x00, 0x00, 0x40, 0x00 };
+    /* no import thunk */
+    unsigned char no_import_thunk[6] = { 0xFF, 0x26, 0x00, 0x00, 0x40, 0x00 };
+    int  result = 0;
+    UNUSED(argv);
+    if (argc == 2)
+        verbose = 1;
+    result = check_dladdr( "null pointer", (void*)0, NULL , NoInfo);
+    result |= check_dladdr( "invalid pointer", (void*)0x125, NULL , NoInfo);
+    result |= check_dladdr( "function from dl library", (void*)dladdr, "dladdr" , PassOnSharedBuild );
+    result |= check_dladdr( "function from dl library", (void*)dlopen, "dlopen", PassOnSharedBuild );
+    result |= check_dladdr( "function from glibc/msvcrt library", (void*)atoi, "atoi", Pass );
+    result |= check_dladdr( "function from executable", (void*)main, "main", FailOnWin );
+    result |= check_dladdr( "static function from executable", (void*)print_dl_info, "print_dl_info", Fail );
+    result |= check_dladdr( "address with positive offset", ((char*)atoi)+1, "atoi", PassWithDifferentAddress );
+    result |= check_dladdr( "zero address from import thunk", zero_thunk_address, "", NoInfo );
+    result |= check_dladdr( "invalid address from import thunk", invalid_thunk_address, "", NoInfo );
+    result |= check_dladdr( "no import thunk", no_import_thunk, "", NoInfo );
+#ifdef _WIN32
+    result |= check_dladdr( "last entry in iat", (void*)VirtualQuery, "VirtualQuery", PassWithDifferentAddress );
+    result |= check_dladdr ( "address through import thunk", (void*)GetModuleHandleA, "GetModuleHandleA", PassWithDifferentAddress );
+    result |= check_dladdr_by_dlopen( "address by dlsym", "kernel32.dll", "GetModuleHandleA", Pass );
+    result |= check_dladdr ( "address by image allocation table", (void*)LoadLibraryExA, "LoadLibraryExA", Pass );
+    result |= check_dladdr_by_dlopen( "address by dlsym", "kernel32.dll", "LoadLibraryExA", Pass );
+#endif
+    return result;
+}