dyncall: dynload/dynload_syms_mach-o.c comparison

comparison dynload/dynload_syms_mach-o.c @ 219:912efa3cfd4b

- mach-o symbol iteration stability fixes

author	Tassilo Philipp
date	Tue, 11 Apr 2017 09:37:14 +0200
parents	87c695673522
children	94dc0bdd7dbe

comparison

equal deleted inserted replaced

-:cb56f077fd37
+:912efa3cfd4b
 /*
 Package: dyncall
 Library: dynload
 File: dynload/dynload_syms_mach-o.c
 Description:
 License:
 Copyright (c) 2007-2015 Olivier Chafik <olivier.chafik@gmail.com>,
-2017 refactored for stability, API consistency
+2017 refactored completely for stability, API
-and portability by Tassilo Philipp.
+consistency and portability by Tassilo Philipp.
 Permission to use, copy, modify, and distribute this software for any
 purpose with or without fee is hereby granted, provided that the above
 copyright notice and this permission notice appear in all copies.
 */
 /*
 dynamic symbol resolver for Mach-O
 */
 #include "dynload.h"
 #include <dlfcn.h>
 #include <string.h>
 #if defined(ARCH_X64) || defined(ARCH_PPC64) || defined(ARCH_ARM64) //@@@ use dyncall_macros.h
 #define MACH_HEADER_TYPE mach_header_64
+#define SEGMENT_COMMAND segment_command_64
 #define NLIST_TYPE nlist_64
 #else
 #define MACH_HEADER_TYPE mach_header
 #define NLIST_TYPE nlist
+#define SEGMENT_COMMAND segment_command
 #endif
 struct DLSyms_
 {
 DLSyms* dlSymsInit(const char* libPath)
 {
 	DLLib* pLib;
 	DLSyms* pSyms;
-	uint32_t iImage, nImages;
+	uint32_t i, n;
 	struct stat st0;
+	const struct MACH_HEADER_TYPE* pHeader = NULL;
 	if(stat(libPath, &st0) == -1)
 		return NULL;
 	pLib = dlLoadLibrary(libPath);
 	if(!pLib)
 		return NULL;
-	// Loop over all dynamically linked images.
+	// Loop over all dynamically linked images to find ours.
-	for (iImage = 0, nImages = _dyld_image_count(); iImage < nImages; iImage++)
+	for(i = 0, n = _dyld_image_count(); i < n; ++i)
 	{
 		struct stat st1;
-		const char* name = _dyld_get_image_name(iImage);
+		const char* name = _dyld_get_image_name(i);
 		if(name && (stat(name, &st1) != -1))
 		{
 			// Don't rely on name comparison alone, as libPath might be relative, symlink, differently
 			// cased, etc., but compare inode number with the one of the mapped dyld image.
-			if (st0.st_ino == st1.st_ino/*!strcmp(name, libPath)*/)
+			if(st0.st_ino == st1.st_ino/*!strcmp(name, libPath)*/)
 			{
-				const struct MACH_HEADER_TYPE* pHeader = (const struct MACH_HEADER_TYPE*) _dyld_get_image_header(iImage);
+				pHeader = (const struct MACH_HEADER_TYPE*) _dyld_get_image_header(i);
-				const char* pBase = ((const char*)pHeader);
+				break; // found header
-				if (pHeader->filetype != MH_DYLIB)
-					return NULL;
-				if (pHeader->flags & MH_SPLIT_SEGS)
-					return NULL;
-				if (pHeader)
-				{
-					uint32_t iCmd, nCmds = pHeader->ncmds;
-					const struct load_command* cmd = (const struct load_command*)(pBase + sizeof(struct MACH_HEADER_TYPE));
-					for (iCmd = 0; iCmd < nCmds; iCmd++)
-					{
-						if (cmd->cmd == LC_SYMTAB)
-						{
-							const struct symtab_command* scmd = (const struct symtab_command*)cmd;
-							pSyms = (DLSyms*)( dlAllocMem(sizeof(DLSyms)) );
-							pSyms->symbolCount  = scmd->nsyms;
-							pSyms->pStringTable = pBase + scmd->stroff;
-							pSyms->pSymbolTable = (struct NLIST_TYPE*)(pBase + scmd->symoff);
-							pSyms->pLib         = pLib;
-							return pSyms;
-						}
-						cmd = (const struct load_command*)(((char*)cmd) + cmd->cmdsize);
-					}
-				}
-				break;
 			}
 		}
 	}
+	if(pHeader && (pHeader->filetype == MH_DYLIB) && !(pHeader->flags & MH_SPLIT_SEGS))
+	{
+		const char* pBase = (const char*)pHeader;
+		uintptr_t slide = 0;
+		const struct load_command* cmd = (const struct load_command*)(pBase + sizeof(struct MACH_HEADER_TYPE));
+		for(i = 0, n = pHeader->ncmds; i < n; ++i, cmd = (const struct load_command*)((const char*)cmd + cmd->cmdsize))
+		{
+			if(cmd->cmd == LC_SEGMENT)
+			{
+				const struct SEGMENT_COMMAND* seg = (struct SEGMENT_COMMAND*)cmd;
+				if((seg->fileoff == 0) && (seg->filesize != 0)) // Count segment sizes to slide over...@@@?
+					slide = (uintptr_t)pHeader - seg->vmaddr;
+				if(strcmp(seg->segname, "__LINKEDIT") == 0)
+					pBase = (const char*)(seg->vmaddr - seg->fileoff + slide); // Adjust pBase depending on __LINKEDIT segment
+			}
+			else if(cmd->cmd == LC_SYMTAB)
+			{
+				const struct symtab_command* scmd = (const struct symtab_command*)cmd;
+				// cmd->cmdsize must be size of struct, otherwise something is off; abort
+				if(cmd->cmdsize != sizeof(struct symtab_command))
+					break;
+				pSyms = (DLSyms*)dlAllocMem(sizeof(DLSyms));
+				pSyms->symbolCount  = scmd->nsyms;
+				pSyms->pStringTable = pBase + scmd->stroff;
+				pSyms->pSymbolTable = (struct NLIST_TYPE*)(pBase + scmd->symoff);
+				pSyms->pLib         = pLib;
+				return pSyms;
+			}
+//@@@ handle also LC_DYSYMTAB
+		}
+	}
+	// Couldn't init syms, so free lib and return error.
+	dlFreeLibrary(pLib);
 	return NULL;
 }
 void dlSymsCleanup(DLSyms* pSyms)
 int dlSymsCount(DLSyms* pSyms)
 {
 	return pSyms ? pSyms->symbolCount : 0;
 }
-static const struct NLIST_TYPE* get_nlist(DLSyms* pSyms, int index)
+const char* dlSymsName(DLSyms* pSyms, int index)
 {
 	const struct NLIST_TYPE* nl;
-	if (!pSyms)
+	unsigned char t;
+//@@@ mach-o ref: http://www.cilinder.be/docs/next/NeXTStep/3.3/nd/DevTools/14_MachO/MachO.htmld/index.html
+	if(!pSyms)
 		return NULL;
 	nl = pSyms->pSymbolTable + index;
-	if (nl->n_un.n_strx <= 1)
-		return NULL; // would be empty string anyway
+	// Mach-O manual: Symbols with an index into the string table of zero
+	// (n_un.n_strx == 0) are defined to have a null ("") name.
+	if(nl->n_un.n_strx == 0)
+		return NULL; //@@@ have return pointer to some static "" string?
+	// Skip undefined symbols. @@@ should we?
+	t = nl->n_type & N_TYPE;
+	if(t == N_UNDF || t == N_PBUD) // @@@ check if N_PBUD is defined, it's not in the NeXT manual, but on Darwin 8.0.1
+		return NULL;
 	//TODO skip more symbols based on nl->n_desc and nl->n_type ?
-	return nl;
-}
+	// Return name - handles lookup of indirect names.
-const char* dlSymsName(DLSyms* pSyms, int index)
+	return &pSyms->pStringTable[t == N_INDR ? nl->n_value : nl->n_un.n_strx];
-{
-	const struct NLIST_TYPE* nl = get_nlist(pSyms, index);
-	return nl ? pSyms->pStringTable + nl->n_un.n_strx : NULL;
 }
 const char* dlSymsNameFromValue(DLSyms* pSyms, void* value)
 {

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comparison dynload/dynload_syms_mach-o.c @ 219:912efa3cfd4b