binfmt_elf.c

linux下内存管理源代码。。。精、简、强!

	retval = -ENOEXEC;
	/* First of all, some simple consistency checks */
	if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
		goto out;

	if (elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN)
		goto out;
	if (!elf_check_arch(&elf_ex))
		goto out;
	if (!bprm->file->f_op||!bprm->file->f_op->mmap)
		goto out;

	/* Now read in all of the header information */

	retval = -ENOMEM;
	size = elf_ex.e_phentsize * elf_ex.e_phnum;
	if (size > 65536)
		goto out;
	elf_phdata = (struct elf_phdr *) kmalloc(size, GFP_KERNEL);
	if (!elf_phdata)
		goto out;

	retval = kernel_read(bprm->file, elf_ex.e_phoff, (char *) elf_phdata, size);
	if (retval < 0)
		goto out_free_ph;

	retval = get_unused_fd();
	if (retval < 0)
		goto out_free_ph;
	get_file(bprm->file);
	fd_install(elf_exec_fileno = retval, bprm->file);

	elf_ppnt = elf_phdata;
	elf_bss = 0;
	elf_brk = 0;

	start_code = ~0UL;
	end_code = 0;
	start_data = 0;
	end_data = 0;

	for (i = 0; i < elf_ex.e_phnum; i++) {
		if (elf_ppnt->p_type == PT_INTERP) {
			retval = -EINVAL;
		  	if (elf_interpreter)
				goto out_free_dentry;

			/* This is the program interpreter used for
			 * shared libraries - for now assume that this
			 * is an a.out format binary
			 */

			retval = -ENOMEM;
			elf_interpreter = (char *) kmalloc(elf_ppnt->p_filesz,
							   GFP_KERNEL);
			if (!elf_interpreter)
				goto out_free_file;

			retval = kernel_read(bprm->file, elf_ppnt->p_offset,
					   elf_interpreter,
					   elf_ppnt->p_filesz);
			if (retval < 0)
				goto out_free_interp;
			/* If the program interpreter is one of these two,
			 * then assume an iBCS2 image. Otherwise assume
			 * a native linux image.
			 */
			if (strcmp(elf_interpreter,"/usr/lib/libc.so.1") == 0 ||
			    strcmp(elf_interpreter,"/usr/lib/ld.so.1") == 0)
				ibcs2_interpreter = 1;
#if 0
			printk("Using ELF interpreter %s\n", elf_interpreter);
#endif
#ifdef __sparc__
			if (ibcs2_interpreter) {
				unsigned long old_pers = current->personality;
				struct exec_domain *old_domain = current->exec_domain;
				struct exec_domain *new_domain;
				struct fs_struct *old_fs = current->fs, *new_fs;
				get_exec_domain(old_domain);
				atomic_inc(&old_fs->count);

				set_personality(PER_SVR4);
				interpreter = open_exec(elf_interpreter);

				new_domain = current->exec_domain;
				new_fs = current->fs;
				current->personality = old_pers;
				current->exec_domain = old_domain;
				current->fs = old_fs;
				put_exec_domain(new_domain);
				put_fs_struct(new_fs);
			} else
#endif
			{
				interpreter = open_exec(elf_interpreter);
			}
			retval = PTR_ERR(interpreter);
			if (IS_ERR(interpreter))
				goto out_free_interp;
			retval = kernel_read(interpreter, 0, bprm->buf, BINPRM_BUF_SIZE);
			if (retval < 0)
				goto out_free_dentry;

			/* Get the exec headers */
			interp_ex = *((struct exec *) bprm->buf);
			interp_elf_ex = *((struct elfhdr *) bprm->buf);
		}
		elf_ppnt++;
	}

	/* Some simple consistency checks for the interpreter */
	if (elf_interpreter) {
		interpreter_type = INTERPRETER_ELF | INTERPRETER_AOUT;

		/* Now figure out which format our binary is */
		if ((N_MAGIC(interp_ex) != OMAGIC) &&
		    (N_MAGIC(interp_ex) != ZMAGIC) &&
		    (N_MAGIC(interp_ex) != QMAGIC))
			interpreter_type = INTERPRETER_ELF;

		if (memcmp(interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
			interpreter_type &= ~INTERPRETER_ELF;

		retval = -ELIBBAD;
		if (!interpreter_type)
			goto out_free_dentry;

		/* Make sure only one type was selected */
		if ((interpreter_type & INTERPRETER_ELF) &&
		     interpreter_type != INTERPRETER_ELF) {
			printk(KERN_WARNING "ELF: Ambiguous type, using ELF\n");
			interpreter_type = INTERPRETER_ELF;
		}
	}

	/* OK, we are done with that, now set up the arg stuff,
	   and then start this sucker up */

	if (!bprm->sh_bang) {
		char * passed_p;

		if (interpreter_type == INTERPRETER_AOUT) {
		  sprintf(passed_fileno, "%d", elf_exec_fileno);
		  passed_p = passed_fileno;

		  if (elf_interpreter) {
		    retval = copy_strings_kernel(1,&passed_p,bprm);
			if (retval)
				goto out_free_dentry; 
		    bprm->argc++;
		  }
		}
	}

	/* Flush all traces of the currently running executable */
	retval = flush_old_exec(bprm);
	if (retval)
		goto out_free_dentry;

	/* OK, This is the point of no return */
	current->mm->start_data = 0;
	current->mm->end_data = 0;
	current->mm->end_code = 0;
	current->mm->mmap = NULL;
	current->flags &= ~PF_FORKNOEXEC;
	elf_entry = (unsigned long) elf_ex.e_entry;

	/* Do this immediately, since STACK_TOP as used in setup_arg_pages
	   may depend on the personality.  */
	SET_PERSONALITY(elf_ex, ibcs2_interpreter);

	/* Do this so that we can load the interpreter, if need be.  We will
	   change some of these later */
	current->mm->rss = 0;
	setup_arg_pages(bprm); /* XXX: check error */
	current->mm->start_stack = bprm->p;

	/* Try and get dynamic programs out of the way of the default mmap
	   base, as well as whatever program they might try to exec.  This
	   is because the brk will follow the loader, and is not movable.  */

	load_bias = ELF_PAGESTART(elf_ex.e_type==ET_DYN ? ELF_ET_DYN_BASE : 0);

	/* Now we do a little grungy work by mmaping the ELF image into
	   the correct location in memory.  At this point, we assume that
	   the image should be loaded at fixed address, not at a variable
	   address. */

	old_fs = get_fs();
	set_fs(get_ds());
	for(i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum; i++, elf_ppnt++) {
		int elf_prot = 0, elf_flags;
		unsigned long vaddr;

		if (elf_ppnt->p_type != PT_LOAD)
			continue;

		if (elf_ppnt->p_flags & PF_R) elf_prot |= PROT_READ;
		if (elf_ppnt->p_flags & PF_W) elf_prot |= PROT_WRITE;
		if (elf_ppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;

		elf_flags = MAP_PRIVATE|MAP_DENYWRITE|MAP_EXECUTABLE;

		vaddr = elf_ppnt->p_vaddr;
		if (elf_ex.e_type == ET_EXEC || load_addr_set) {
			elf_flags |= MAP_FIXED;
		}

		error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt, elf_prot, elf_flags);

		if (!load_addr_set) {
			load_addr_set = 1;
			load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset);
			if (elf_ex.e_type == ET_DYN) {
				load_bias += error -
				             ELF_PAGESTART(load_bias + vaddr);
				load_addr += error;
			}
		}
		k = elf_ppnt->p_vaddr;
		if (k < start_code) start_code = k;
		if (start_data < k) start_data = k;

		k = elf_ppnt->p_vaddr + elf_ppnt->p_filesz;

		if (k > elf_bss)
			elf_bss = k;
		if ((elf_ppnt->p_flags & PF_X) && end_code <  k)
			end_code = k;
		if (end_data < k)
			end_data = k;
		k = elf_ppnt->p_vaddr + elf_ppnt->p_memsz;
		if (k > elf_brk)
			elf_brk = k;
	}
	set_fs(old_fs);

	elf_entry += load_bias;
	elf_bss += load_bias;
	elf_brk += load_bias;
	start_code += load_bias;
	end_code += load_bias;
	start_data += load_bias;
	end_data += load_bias;

	if (elf_interpreter) {
		if (interpreter_type == INTERPRETER_AOUT)
			elf_entry = load_aout_interp(&interp_ex,
						     interpreter);
		else
			elf_entry = load_elf_interp(&interp_elf_ex,
						    interpreter,
						    &interp_load_addr);

		allow_write_access(interpreter);
		fput(interpreter);
		kfree(elf_interpreter);

		if (elf_entry == ~0UL) {
			printk(KERN_ERR "Unable to load interpreter\n");
			kfree(elf_phdata);
			send_sig(SIGSEGV, current, 0);
			return 0;
		}
	}

	kfree(elf_phdata);

	if (interpreter_type != INTERPRETER_AOUT)
		sys_close(elf_exec_fileno);

	set_binfmt(&elf_format);

	compute_creds(bprm);
	current->flags &= ~PF_FORKNOEXEC;
	bprm->p = (unsigned long)
	  create_elf_tables((char *)bprm->p,
			bprm->argc,
			bprm->envc,
			(interpreter_type == INTERPRETER_ELF ? &elf_ex : NULL),
			load_addr, load_bias,
			interp_load_addr,
			(interpreter_type == INTERPRETER_AOUT ? 0 : 1));
	/* N.B. passed_fileno might not be initialized? */
	if (interpreter_type == INTERPRETER_AOUT)
		current->mm->arg_start += strlen(passed_fileno) + 1;
	current->mm->start_brk = current->mm->brk = elf_brk;
	current->mm->end_code = end_code;
	current->mm->start_code = start_code;
	current->mm->start_data = start_data;
	current->mm->end_data = end_data;
	current->mm->start_stack = bprm->p;

	/* Calling set_brk effectively mmaps the pages that we need
	 * for the bss and break sections
	 */
	set_brk(elf_bss, elf_brk);

	padzero(elf_bss);

#if 0
	printk("(start_brk) %lx\n" , (long) current->mm->start_brk);
	printk("(end_code) %lx\n" , (long) current->mm->end_code);
	printk("(start_code) %lx\n" , (long) current->mm->start_code);
	printk("(start_data) %lx\n" , (long) current->mm->start_data);
	printk("(end_data) %lx\n" , (long) current->mm->end_data);
	printk("(start_stack) %lx\n" , (long) current->mm->start_stack);
	printk("(brk) %lx\n" , (long) current->mm->brk);
#endif

	if ( current->personality == PER_SVR4 )
	{
		/* Why this, you ask???  Well SVr4 maps page 0 as read-only,
		   and some applications "depend" upon this behavior.
		   Since we do not have the power to recompile these, we
		   emulate the SVr4 behavior.  Sigh.  */
		/* N.B. Shouldn't the size here be PAGE_SIZE?? */
		down(&current->mm->mmap_sem);
		error = do_mmap(NULL, 0, 4096, PROT_READ | PROT_EXEC,
				MAP_FIXED | MAP_PRIVATE, 0);
		up(&current->mm->mmap_sem);
	}

#ifdef ELF_PLAT_INIT
	/*
	 * The ABI may specify that certain registers be set up in special
	 * ways (on i386 %edx is the address of a DT_FINI function, for
	 * example.  This macro performs whatever initialization to
	 * the regs structure is required.
	 */
	ELF_PLAT_INIT(regs);
#endif

	start_thread(regs, elf_entry, bprm->p);
	if (current->ptrace & PT_PTRACED)
		send_sig(SIGTRAP, current, 0);
	retval = 0;
out:
	return retval;

	/* error cleanup */
out_free_dentry:
	allow_write_access(interpreter);
	fput(interpreter);
out_free_interp:
	if (elf_interpreter)
		kfree(elf_interpreter);
out_free_file:
	sys_close(elf_exec_fileno);
out_free_ph:
	kfree(elf_phdata);
	goto out;
}

/* This is really simpleminded and specialized - we are loading an
   a.out library that is given an ELF header. */

static int load_elf_library(struct file *file)
{
	struct elf_phdr *elf_phdata;
	unsigned long elf_bss = 0, bss, len, k;
	int retval, error, i, j;
	struct elfhdr elf_ex;

	error = -ENOEXEC;
	retval = kernel_read(file, 0, (char *) &elf_ex, sizeof(elf_ex));
	if (retval != sizeof(elf_ex))
		goto out;

	if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
		goto out;

	/* First of all, some simple consistency checks */
	if (elf_ex.e_type != ET_EXEC || elf_ex.e_phnum > 2 ||
	   !elf_check_arch(&elf_ex) || !file->f_op || !file->f_op->mmap)
		goto out;

	/* Now read in all of the header information */

	j = sizeof(struct elf_phdr) * elf_ex.e_phnum;
	if (j > ELF_MIN_ALIGN)
		goto out;

	error = -ENOMEM;
	elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL);
	if (!elf_phdata)
		goto out;

	/* N.B. check for error return?? */
	retval = kernel_read(file, elf_ex.e_phoff, (char *) elf_phdata,
			   sizeof(struct elf_phdr) * elf_ex.e_phnum);

	error = -ENOEXEC;
	for (j = 0, i = 0; i<elf_ex.e_phnum; i++)
		if ((elf_phdata + i)->p_type == PT_LOAD) j++;
	if (j != 1)
		goto out_free_ph;

	while (elf_phdata->p_type != PT_LOAD) elf_phdata++;

	/* Now use mmap to map the library into memory. */
	down(&current->mm->mmap_sem);
	error = do_mmap(file,
			ELF_PAGESTART(elf_phdata->p_vaddr),
			(elf_phdata->p_filesz +
			 ELF_PAGEOFFSET(elf_phdata->p_vaddr)),
			PROT_READ | PROT_WRITE | PROT_EXEC,
			MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
			(elf_phdata->p_offset -
			 ELF_PAGEOFFSET(elf_phdata->p_vaddr)));
	up(&current->mm->mmap_sem);
	if (error != ELF_PAGESTART(elf_phdata->p_vaddr))
		goto out_free_ph;

	k = elf_phdata->p_vaddr + elf_phdata->p_filesz;