/*

 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 completely for stability, API
                           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.

   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

*/



/*

 dynamic symbol resolver for Mach-O

*/

#include "dynload.h"
#include "dynload_alloc.h"
#include "../autovar/autovar_ARCH.h"

#include <mach-o/dyld.h>
#include <mach-o/nlist.h>
#include <sys/stat.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_
{
	DLLib*                   pLib;
	const char*              pStringTable;
	const struct NLIST_TYPE* pSymbolTable;
	uint32_t                 symbolCount;
};


DLSyms* dlSymsInit(const char* libPath)
{
	DLLib* pLib;
	DLSyms* pSyms;
	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 to find ours.
	for(i = 0, n = _dyld_image_count(); i < n; ++i)
	{
		struct stat st1;
		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)*/)
			{
				pHeader = (const struct MACH_HEADER_TYPE*) _dyld_get_image_header(i);
				break; // found header
			}
		}
	}

	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)
{
	if(pSyms) {
		dlFreeLibrary(pSyms->pLib);
		dlFreeMem(pSyms);
	}
}

int dlSymsCount(DLSyms* pSyms)
{
	return pSyms ? pSyms->symbolCount : 0;
}


const char* dlSymsName(DLSyms* pSyms, int index)
{
	const struct NLIST_TYPE* nl;
	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;

	// 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 name - handles lookup of indirect names.
	return &pSyms->pStringTable[t == N_INDR ? nl->n_value : nl->n_un.n_strx];
}


const char* dlSymsNameFromValue(DLSyms* pSyms, void* value)
{
	Dl_info info;
	if (!dladdr(value, &info) || (value != info.dli_saddr))
		return NULL;

	return info.dli_sname;
}