readelflib1.c

linux下用PCMCIA无线网卡虚拟无线AP的程序源码

	int flags;
	char header[4096];
	unsigned long dynamic_info[24];
	int *lpnt;
	unsigned long libaddr;
	unsigned long minvma = 0xffffffff, maxvma = 0;

	int i;
	int infile;

	/* If this file is already loaded, skip this step */
	tpnt = _dl_check_hashed_files(libname);
	if (tpnt)
		return tpnt;

	/* If we are in secure mode (i.e. a setu/gid binary using LD_PRELOAD),
	   we don't load the library if it isn't setuid. */

	if (secure) {
		struct stat st;

		if (_dl_stat(libname, &st) || !(st.st_mode & S_ISUID))
			return NULL;
	}

	libaddr = 0;
	infile = _dl_open(libname, O_RDONLY);
	if (infile < 0) {
#if 0
		/*
		 * NO!  When we open shared libraries we may search several paths.
		 * it is inappropriate to generate an error here.
		 */
		_dl_dprintf(2, "%s: can't open '%s'\n", _dl_progname, libname);
#endif
		_dl_internal_error_number = DL_ERROR_NOFILE;
		return NULL;
	}

	_dl_read(infile, header, sizeof(header));
	epnt = (elfhdr *) header;
	if (epnt->e_ident[0] != 0x7f ||
		epnt->e_ident[1] != 'E' || 
		epnt->e_ident[2] != 'L' || 
		epnt->e_ident[3] != 'F') 
	{
		_dl_dprintf(2, "%s: '%s' is not an ELF file\n", _dl_progname,
					 libname);
		_dl_internal_error_number = DL_ERROR_NOTELF;
		_dl_close(infile);
		return NULL;
	};

	if ((epnt->e_type != ET_DYN) || (epnt->e_machine != MAGIC1 
#ifdef MAGIC2
		    && epnt->e_machine != MAGIC2
#endif
		)) 
	{
		_dl_internal_error_number = 
		    (epnt->e_type != ET_DYN ? DL_ERROR_NOTDYN : DL_ERROR_NOTMAGIC);
		_dl_dprintf(2, "%s: '%s' is not an ELF executable for " ELF_TARGET 
			"\n", _dl_progname, libname);
		_dl_close(infile);
		return NULL;
	};

	ppnt = (elf_phdr *) & header[epnt->e_phoff];

	piclib = 1;
	for (i = 0; i < epnt->e_phnum; i++) {

		if (ppnt->p_type == PT_DYNAMIC) {
			if (dynamic_addr)
				_dl_dprintf(2, "%s: '%s' has more than one dynamic section\n", 
					_dl_progname, libname);
			dynamic_addr = ppnt->p_vaddr;
			dynamic_size = ppnt->p_filesz;
		};

		if (ppnt->p_type == PT_LOAD) {
			/* See if this is a PIC library. */
			if (i == 0 && ppnt->p_vaddr > 0x1000000) {
				piclib = 0;
				minvma = ppnt->p_vaddr;
			}
			if (piclib && ppnt->p_vaddr < minvma) {
				minvma = ppnt->p_vaddr;
			}
			if (((unsigned long) ppnt->p_vaddr + ppnt->p_memsz) > maxvma) {
				maxvma = ppnt->p_vaddr + ppnt->p_memsz;
			}
		}
		ppnt++;
	};

	maxvma = (maxvma + 0xfffU) & ~0xfffU;
	minvma = minvma & ~0xffffU;

	flags = MAP_PRIVATE /*| MAP_DENYWRITE */ ;
	if (!piclib)
		flags |= MAP_FIXED;

	status = (char *) _dl_mmap((char *) (piclib ? 0 : minvma), 
		maxvma - minvma, PROT_NONE, flags | MAP_ANONYMOUS, -1, 0);
	if (_dl_mmap_check_error(status)) {
		_dl_dprintf(2, "%s: can't map '/dev/zero'\n", _dl_progname);
		_dl_internal_error_number = DL_ERROR_MMAP_FAILED;
		_dl_close(infile);
		return NULL;
	};
	libaddr = (unsigned long) status;
	flags |= MAP_FIXED;

	/* Get the memory to store the library */
	ppnt = (elf_phdr *) & header[epnt->e_phoff];

	for (i = 0; i < epnt->e_phnum; i++) {
		if (ppnt->p_type == PT_LOAD) {

			/* See if this is a PIC library. */
			if (i == 0 && ppnt->p_vaddr > 0x1000000) {
				piclib = 0;
				/* flags |= MAP_FIXED; */
			}



			if (ppnt->p_flags & PF_W) {
				unsigned long map_size;
				char *cpnt;

				status = (char *) _dl_mmap((char *) ((piclib ? libaddr : 0) + 
					(ppnt->p_vaddr & 0xfffff000)), (ppnt->p_vaddr & 0xfff) 
					+ ppnt->p_filesz, LXFLAGS(ppnt->p_flags), flags, infile, 
					ppnt->p_offset & 0x7ffff000);

				if (_dl_mmap_check_error(status)) {
					_dl_dprintf(2, "%s: can't map '%s'\n", 
						_dl_progname, libname);
					_dl_internal_error_number = DL_ERROR_MMAP_FAILED;
					_dl_munmap((char *) libaddr, maxvma - minvma);
					_dl_close(infile);
					return NULL;
				};

				/* Pad the last page with zeroes. */
				cpnt = (char *) (status + (ppnt->p_vaddr & 0xfff) +
							  ppnt->p_filesz);
				while (((unsigned long) cpnt) & 0xfff)
					*cpnt++ = 0;

				/* I am not quite sure if this is completely
				 * correct to do or not, but the basic way that
				 * we handle bss segments is that we mmap
				 * /dev/zero if there are any pages left over
				 * that are not mapped as part of the file */

				map_size = (ppnt->p_vaddr + ppnt->p_filesz + 0xfff) & 0xfffff000;
				if (map_size < ppnt->p_vaddr + ppnt->p_memsz)
					status = (char *) _dl_mmap((char *) map_size + 
						(piclib ? libaddr : 0), 
						ppnt->p_vaddr + ppnt->p_memsz - map_size, 
						LXFLAGS(ppnt->p_flags), flags | MAP_ANONYMOUS, -1, 0);
			} else
				status = (char *) _dl_mmap((char *) (ppnt->p_vaddr & 0xfffff000) 
					+ (piclib ? libaddr : 0), (ppnt->p_vaddr & 0xfff) + 
					ppnt->p_filesz, LXFLAGS(ppnt->p_flags), flags, 
					infile, ppnt->p_offset & 0x7ffff000);
			if (_dl_mmap_check_error(status)) {
				_dl_dprintf(2, "%s: can't map '%s'\n", _dl_progname, libname);
				_dl_internal_error_number = DL_ERROR_MMAP_FAILED;
				_dl_munmap((char *) libaddr, maxvma - minvma);
				_dl_close(infile);
				return NULL;
			};

			/* if(libaddr == 0 && piclib) {
			   libaddr = (unsigned long) status;
			   flags |= MAP_FIXED;
			   }; */
		};
		ppnt++;
	};
	_dl_close(infile);

	/* For a non-PIC library, the addresses are all absolute */
	if (piclib) {
		dynamic_addr += (unsigned long) libaddr;
	}

	/* 
	 * OK, the ELF library is now loaded into VM in the correct locations
	 * The next step is to go through and do the dynamic linking (if needed).
	 */

	/* Start by scanning the dynamic section to get all of the pointers */

	if (!dynamic_addr) {
		_dl_internal_error_number = DL_ERROR_NODYNAMIC;
		_dl_dprintf(2, "%s: '%s' is missing a dynamic section\n", 
			_dl_progname, libname);
		return NULL;
	}

	dpnt = (Elf32_Dyn *) dynamic_addr;

	dynamic_size = dynamic_size / sizeof(Elf32_Dyn);
	_dl_memset(dynamic_info, 0, sizeof(dynamic_info));
	for (i = 0; i < dynamic_size; i++) {
		if (dpnt->d_tag > DT_JMPREL) {
			dpnt++;
			continue;
		}
		dynamic_info[dpnt->d_tag] = dpnt->d_un.d_val;
		if (dpnt->d_tag == DT_TEXTREL || SVR4_BUGCOMPAT)
			dynamic_info[DT_TEXTREL] = 1;
		dpnt++;
	};

	/* If the TEXTREL is set, this means that we need to make the pages
	   writable before we perform relocations.  Do this now. They get set back
	   again later. */

	if (dynamic_info[DT_TEXTREL]) {
		ppnt = (elf_phdr *) & header[epnt->e_phoff];
		for (i = 0; i < epnt->e_phnum; i++, ppnt++) {
			if (ppnt->p_type == PT_LOAD && !(ppnt->p_flags & PF_W))
				_dl_mprotect((void *) ((piclib ? libaddr : 0) + 
					    (ppnt->p_vaddr & 0xfffff000)), 
					(ppnt->p_vaddr & 0xfff) + (unsigned long) ppnt->p_filesz, 
					PROT_READ | PROT_WRITE | PROT_EXEC);
		}
	}


	tpnt = _dl_add_elf_hash_table(libname, (char *) libaddr, dynamic_info, 
		dynamic_addr, dynamic_size);

	tpnt->ppnt = (elf_phdr *) (tpnt->loadaddr + epnt->e_phoff);
	tpnt->n_phent = epnt->e_phnum;

	/*
	 * OK, the next thing we need to do is to insert the dynamic linker into
	 * the proper entry in the GOT so that the PLT symbols can be properly
	 * resolved. 
	 */

	lpnt = (int *) dynamic_info[DT_PLTGOT];

	if (lpnt) {
		lpnt = (int *) (dynamic_info[DT_PLTGOT] + ((int) libaddr));
		INIT_GOT(lpnt, tpnt);
	};

	return tpnt;
}

/* Ugly, ugly.  Some versions of the SVr4 linker fail to generate COPY
   relocations for global variables that are present both in the image and
   the shared library.  Go through and do it manually.  If the images
   are guaranteed to be generated by a trustworthy linker, then this
   step can be skipped. */

int _dl_copy_fixups(struct dyn_elf *rpnt)
{
	int goof = 0;
	struct elf_resolve *tpnt;

	if (rpnt->next)
		goof += _dl_copy_fixups(rpnt->next);
	else
		return 0;

	tpnt = rpnt->dyn;

	if (tpnt->init_flag & COPY_RELOCS_DONE)
		return goof;
	tpnt->init_flag |= COPY_RELOCS_DONE;

#ifdef ELF_USES_RELOCA
	goof += _dl_parse_copy_information(rpnt, 
		tpnt->dynamic_info[DT_RELA], tpnt->dynamic_info[DT_RELASZ], 0);

#else
	goof += _dl_parse_copy_information(rpnt, tpnt->dynamic_info[DT_REL], 
		tpnt->dynamic_info[DT_RELSZ], 0);

#endif
	return goof;
}