xref: /src/sys/kern/exec_elf32.c

/*	$NetBSD: exec_elf32.c,v 1.14 1996/10/07 18:24:48 cgd Exp $	*/

/*
 * Copyright (c) 1996 Christopher G. Demetriou
 * Copyright (c) 1994 Christos Zoulas
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* If not included by exec_elf64.c, ELFSIZE won't be defined. */
#ifndef ELFSIZE
#define	ELFSIZE		32
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/exec.h>
#include <sys/exec_elf.h>
#include <sys/fcntl.h>
#include <sys/syscall.h>
#include <sys/signalvar.h>
#include <sys/mount.h>
#include <sys/stat.h>

#include <sys/mman.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_map.h>

#include <machine/cpu.h>
#include <machine/reg.h>
#include <machine/exec.h>

#ifdef COMPAT_LINUX
#include <compat/linux/linux_exec.h>
#endif

#ifdef COMPAT_SVR4
#include <compat/svr4/svr4_exec.h>
#endif

#define	CONCAT(x,y)	__CONCAT(x,y)
#define	ELFNAME(x)	CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
#define	ELFNAME2(x,y)	CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
#define	ELFNAMEEND(x)	CONCAT(x,CONCAT(_elf,ELFSIZE))
#define	ELFDEFNNAME(x)	CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))

static int ELFNAME(check_header) __P((Elf_Ehdr *, int));
static int ELFNAME(load_file) __P((struct proc *, struct exec_package *,
	    char *, struct exec_vmcmd_set *, u_long *, struct elf_args *,
	    Elf_Addr *));
static void ELFNAME(load_psection) __P((struct exec_vmcmd_set *,
	struct vnode *, Elf_Phdr *, Elf_Addr *, u_long *, int *));

extern char sigcode[], esigcode[];
#ifdef SYSCALL_DEBUG
extern char *syscallnames[];
#endif

struct emul ELFNAMEEND(emul_netbsd) = {
	"netbsd",
	NULL,
	sendsig,
	SYS_syscall,
	SYS_MAXSYSCALL,
	sysent,
#ifdef SYSCALL_DEBUG
	syscallnames,
#else
	NULL,
#endif
	ELF_AUX_ENTRIES * sizeof(AuxInfo),
	ELFNAME(copyargs),
	setregs,
	sigcode,
	esigcode,
};

int (*ELFNAME(probe_funcs)[]) __P((struct proc *, struct exec_package *,
    Elf_Ehdr *, char *, Elf_Addr *)) = {
#if defined(COMPAT_SVR4) && (ELFSIZE == 32)
	ELFNAME2(svr4,probe),			/* XXX not 64-bit safe */
#endif
#if defined(COMPAT_LINUX) && (ELFSIZE == 32)
	ELFNAME2(linux,probe),			/* XXX not 64-bit safe */
#endif
};

#define ELF_ALIGN(a, b) ((a) & ~((b) - 1))

/*
 * Copy arguments onto the stack in the normal way, but add some
 * extra information in case of dynamic binding.
 */
void *
ELFNAME(copyargs)(pack, arginfo, stack, argp)
	struct exec_package *pack;
	struct ps_strings *arginfo;
	void *stack;
	void *argp;
{
	size_t len;
	AuxInfo ai[ELF_AUX_ENTRIES], *a;
	struct elf_args *ap;

	stack = copyargs(pack, arginfo, stack, argp);
	if (!stack)
		return NULL;

	/*
	 * Push extra arguments on the stack needed by dynamically
	 * linked binaries
	 */
	if ((ap = (struct elf_args *) pack->ep_emul_arg)) {
		a = ai;

		a->au_id = AUX_phdr;
		a->au_v = ap->arg_phaddr;
		a++;

		a->au_id = AUX_phent;
		a->au_v = ap->arg_phentsize;
		a++;

		a->au_id = AUX_phnum;
		a->au_v = ap->arg_phnum;
		a++;

		a->au_id = AUX_pagesz;
		a->au_v = NBPG;
		a++;

		a->au_id = AUX_base;
		a->au_v = ap->arg_interp;
		a++;

		a->au_id = AUX_flags;
		a->au_v = 0;
		a++;

		a->au_id = AUX_entry;
		a->au_v = ap->arg_entry;
		a++;

		a->au_id = AUX_null;
		a->au_v = 0;
		a++;

		free((char *) ap, M_TEMP);
		pack->ep_emul_arg = NULL;
		len = ELF_AUX_ENTRIES * sizeof (AuxInfo);
		if (copyout(ai, stack, len))
			return NULL;
		stack += len;
	}
	return stack;
}

/*
 * elf_check_header():
 *
 * Check header for validity; return 0 of ok ENOEXEC if error
 */
static int
ELFNAME(check_header)(eh, type)
	Elf_Ehdr *eh;
	int type;
{

	if (bcmp(eh->e_ident, Elf_e_ident, Elf_e_siz) != 0)
		return ENOEXEC;

	switch (eh->e_machine) {

	ELFDEFNNAME(MACHDEP_ID_CASES)

	default:
		return ENOEXEC;
	}

	if (eh->e_type != type)
		return ENOEXEC;

	return 0;
}

/*
 * elf_load_psection():
 *
 * Load a psection at the appropriate address
 */
static void
ELFNAME(load_psection)(vcset, vp, ph, addr, size, prot)
	struct exec_vmcmd_set *vcset;
	struct vnode *vp;
	Elf_Phdr *ph;
	Elf_Addr *addr;
	u_long *size;
	int *prot;
{
	u_long uaddr, msize, psize, rm, rf;
	long diff, offset;

	/*
         * If the user specified an address, then we load there.
         */
	if (*addr != ELFDEFNNAME(NO_ADDR)) {
		if (ph->p_align > 1) {
			*addr = ELF_ALIGN(*addr + ph->p_align, ph->p_align);
			uaddr = ELF_ALIGN(ph->p_vaddr, ph->p_align);
		} else
			uaddr = ph->p_vaddr;
		diff = ph->p_vaddr - uaddr;
	} else {
		*addr = uaddr = ph->p_vaddr;
		if (ph->p_align > 1)
			*addr = ELF_ALIGN(uaddr, ph->p_align);
		diff = uaddr - *addr;
	}

	*prot |= (ph->p_flags & Elf_pf_r) ? VM_PROT_READ : 0;
	*prot |= (ph->p_flags & Elf_pf_w) ? VM_PROT_WRITE : 0;
	*prot |= (ph->p_flags & Elf_pf_x) ? VM_PROT_EXECUTE : 0;

	offset = ph->p_offset - diff;
	*size = ph->p_filesz + diff;
	msize = ph->p_memsz + diff;
	psize = round_page(*size);

	if ((ph->p_flags & Elf_pf_w) != 0) {
		/*
		 * Because the pagedvn pager can't handle zero fill of the last
		 * data page if it's not page aligned we map the last page
		 * readvn.
		 */
		psize = trunc_page(*size);
		NEW_VMCMD(vcset, vmcmd_map_pagedvn, psize, *addr, vp,
		    offset, *prot);
		if(psize != *size)
			NEW_VMCMD(vcset, vmcmd_map_readvn, *size - psize,
			    *addr + psize, vp, offset + psize, *prot);
	} else
		NEW_VMCMD(vcset, vmcmd_map_pagedvn, psize, *addr, vp,
		    offset, *prot);

	/*
         * Check if we need to extend the size of the segment
         */
	rm = round_page(*addr + msize);
	rf = round_page(*addr + *size);

	if (rm != rf) {
		NEW_VMCMD(vcset, vmcmd_map_zero, rm - rf, rf, NULLVP, 0, *prot);
		*size = msize;
	}
}

/*
 * elf_read_from():
 *
 *	Read from vnode into buffer at offset.
 */
int
ELFNAME(read_from)(p, vp, off, buf, size)
	struct vnode *vp;
	u_long off;
	struct proc *p;
	caddr_t buf;
	int size;
{
	int error;
	int resid;

	if ((error = vn_rdwr(UIO_READ, vp, buf, size,
			     off, UIO_SYSSPACE, 0, p->p_ucred,
			     &resid, p)) != 0)
		return error;
	/*
         * See if we got all of it
         */
	if (resid != 0)
		return ENOEXEC;
	return 0;
}

/*
 * elf_load_file():
 *
 * Load a file (interpreter/library) pointed to by path
 * [stolen from coff_load_shlib()]. Made slightly generic
 * so it might be used externally.
 */
static int
ELFNAME(load_file)(p, epp, path, vcset, entry, ap, last)
	struct proc *p;
	struct exec_package *epp;
	char *path;
	struct exec_vmcmd_set *vcset;
	u_long *entry;
	struct elf_args	*ap;
	Elf_Addr *last;
{
	int error, i;
	struct nameidata nd;
	struct vnode *vp;
	struct vattr attr;
	Elf_Ehdr eh;
	Elf_Phdr *ph = NULL;
	u_long phsize;
	char *bp = NULL;
	Elf_Addr addr = *last;

	bp = path;
	/*
         * 1. open file
         * 2. read filehdr
         * 3. map text, data, and bss out of it using VM_*
         */
	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, path, p);
	if ((error = namei(&nd)) != 0)
		return error;
	vp = nd.ni_vp;

	/* check for regular file */
	if (vp->v_type != VREG) {
		error = EACCES;
		goto badunlock;
	}

        /* get attributes */
	if ((error = VOP_GETATTR(vp, &attr, p->p_ucred, p)) != 0)
		goto badunlock;

	/*
	 * Check mount point.  Though we're not trying to exec this binary,
	 * we will be executing code from it, so if the mount point (or
	 * tracing) disallows execution or set-id-ness, we punt or kill
	 * the set-id.
	 */
	if (vp->v_mount->mnt_flag & MNT_NOEXEC) {
		error = EACCES;
		goto badunlock;
	}
	if (vp->v_mount->mnt_flag & MNT_NOSUID)
		epp->ep_vap->va_mode &= ~(VSUID | VSGID);

	/*
	 * Similarly, if it's not marked as executable, we don't allow
	 * it to be used.  For root we have to see if any exec bit on.
	 */
	if ((error = VOP_ACCESS(vp, VEXEC, p->p_ucred, p)) != 0)
		goto badunlock;
	if ((attr.va_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0) {
		error = EACCES;
		goto badunlock;
	}

#ifdef notyet /* XXX cgd 960926 */
	XXX cgd 960926: (maybe) VOP_OPEN it (and VOP_CLOSE in copyargs?)
#endif
	VOP_UNLOCK(vp);

	if ((error = ELFNAME(read_from)(p, vp, 0, (caddr_t) &eh,
				    sizeof(eh))) != 0)
		goto bad;

	if ((error = ELFNAME(check_header)(&eh, Elf_et_dyn)) != 0)
		goto bad;

	phsize = eh.e_phnum * sizeof(Elf_Phdr);
	ph = (Elf_Phdr *) malloc(phsize, M_TEMP, M_WAITOK);

	if ((error = ELFNAME(read_from)(p, vp, eh.e_phoff,
	    (caddr_t) ph, phsize)) != 0)
		goto bad;

	/*
         * Load all the necessary sections
         */
	for (i = 0; i < eh.e_phnum; i++) {
		u_long size = 0;
		int prot = 0;

		switch (ph[i].p_type) {
		case Elf_pt_load:
			ELFNAME(load_psection)(vcset, vp, &ph[i], &addr,
						&size, &prot);
			/* If entry is within this section it must be text */
			if (eh.e_entry >= ph[i].p_vaddr &&
			    eh.e_entry < (ph[i].p_vaddr + size)) {
				*entry = addr + eh.e_entry;
				ap->arg_interp = addr;
			}
			addr += size;
			break;

		case Elf_pt_dynamic:
		case Elf_pt_phdr:
		case Elf_pt_note:
			break;

		default:
			break;
		}
	}

	free((char *) ph, M_TEMP);
	*last = addr;
	vrele(vp);
	return 0;

badunlock:
	VOP_UNLOCK(vp);

bad:
	if (ph != NULL)
		free((char *) ph, M_TEMP);
#ifdef notyet /* XXX cgd 960926 */
	(maybe) VOP_CLOSE it
#endif
	vrele(vp);
	return error;
}

/*
 * exec_elf_makecmds(): Prepare an Elf binary's exec package
 *
 * First, set of the various offsets/lengths in the exec package.
 *
 * Then, mark the text image busy (so it can be demand paged) or error
 * out if this is not possible.  Finally, set up vmcmds for the
 * text, data, bss, and stack segments.
 */
int
ELFNAME2(exec,makecmds)(p, epp)
	struct proc *p;
	struct exec_package *epp;
{
	Elf_Ehdr *eh = epp->ep_hdr;
	Elf_Phdr *ph, *pp;
	Elf_Addr phdr = 0, pos = 0;
	int error, i, n, nload;
	char interp[MAXPATHLEN];
	u_long phsize;

	if (epp->ep_hdrvalid < sizeof(Elf_Ehdr))
		return ENOEXEC;

	if (ELFNAME(check_header)(eh, Elf_et_exec))
		return ENOEXEC;

	/*
         * check if vnode is in open for writing, because we want to
         * demand-page out of it.  if it is, don't do it, for various
         * reasons
         */
	if (epp->ep_vp->v_writecount != 0) {
#ifdef DIAGNOSTIC
		if (epp->ep_vp->v_flag & VTEXT)
			panic("exec: a VTEXT vnode has writecount != 0\n");
#endif
		return ETXTBSY;
	}
	/*
         * Allocate space to hold all the program headers, and read them
         * from the file
         */
	phsize = eh->e_phnum * sizeof(Elf_Phdr);
	ph = (Elf_Phdr *) malloc(phsize, M_TEMP, M_WAITOK);

	if ((error = ELFNAME(read_from)(p, epp->ep_vp, eh->e_phoff,
	    (caddr_t) ph, phsize)) != 0)
		goto bad;

	epp->ep_tsize = ELFDEFNNAME(NO_ADDR);
	epp->ep_dsize = ELFDEFNNAME(NO_ADDR);

	interp[0] = '\0';

	for (i = 0; i < eh->e_phnum; i++) {
		pp = &ph[i];
		if (pp->p_type == Elf_pt_interp) {
			if (pp->p_filesz >= sizeof(interp))
				goto bad;
			if ((error = ELFNAME(read_from)(p, epp->ep_vp, pp->p_offset,
				      (caddr_t) interp, pp->p_filesz)) != 0)
				goto bad;
			break;
		}
	}

	/*
	 * Setup things for native emulation.
	 */
	epp->ep_emul = &ELFNAMEEND(emul_netbsd);
	pos = ELFDEFNNAME(NO_ADDR);

	/*
	 * On the same architecture, we may be emulating different systems.
	 * See which one will accept this executable. This currently only
	 * applies to Linux and SVR4 on the i386.
	 *
	 * Probe functions would normally see if the interpreter (if any)
	 * exists. Emulation packages may possibly replace the interpreter in
	 * interp[] with a changed path (/emul/xxx/<path>), and also
	 * set the ep_emul field in the exec package structure.
	 */
	if ((n = sizeof ELFNAME(probe_funcs) / sizeof ELFNAME(probe_funcs)[0])) {
		error = ENOEXEC;
		for (i = 0; i < n && error; i++)
			error = ELFNAME(probe_funcs)[i](p, epp, eh, interp, &pos);

#ifdef notyet
		/*
		 * We should really use a signature in our native binaries
		 * and have our own probe function for matching binaries,
		 * before trying the emulations. For now, if the emulation
		 * probes failed we default to native.
		 */
		if (error)
			goto bad;
#endif
	}

	/*
         * Load all the necessary sections
         */
	for (i = nload = 0; i < eh->e_phnum; i++) {
		Elf_Addr  addr = ELFDEFNNAME(NO_ADDR);
		u_long size = 0;
		int prot = 0;

		pp = &ph[i];

		switch (ph[i].p_type) {
		case Elf_pt_load:
			/*
			 * XXX
			 * Can handle only 2 sections: text and data
			 */
			if (nload++ == 2)
				goto bad;
			ELFNAME(load_psection)(&epp->ep_vmcmds, epp->ep_vp,
				&ph[i], &addr, &size, &prot);
			/*
			 * Decide whether it's text or data by looking
			 * at the entry point.
			 */
			if (eh->e_entry >= addr && eh->e_entry < (addr + size)){
				epp->ep_taddr = addr;
				epp->ep_tsize = size;
			} else {
				epp->ep_daddr = addr;
				epp->ep_dsize = size;
			}
			break;

		case Elf_pt_shlib:
			error = ENOEXEC;
			goto bad;

		case Elf_pt_interp:
			/* Already did this one */
		case Elf_pt_dynamic:
		case Elf_pt_note:
			break;

		case Elf_pt_phdr:
			/* Note address of program headers (in text segment) */
			phdr = pp->p_vaddr;
			break;

		default:
			/*
			 * Not fatal; we don't need to understand everything.
			 */
			break;
		}
	}

	/*
	 * If no position to load the interpreter was set by a probe
	 * function, pick the same address that a non-fixed mmap(0, ..)
	 * would (i.e. something safely out of the way).
	 */
	if (pos == ELFDEFNNAME(NO_ADDR) &&
	    epp->ep_emul == &ELFNAMEEND(emul_netbsd))
		pos = round_page(epp->ep_daddr + MAXDSIZ);

	/*
         * Check if we found a dynamically linked binary and arrange to load
         * it's interpreter
         */
	if (interp[0]) {
		struct elf_args *ap;

		ap = (struct elf_args *) malloc(sizeof(struct elf_args),
						 M_TEMP, M_WAITOK);
		if ((error = ELFNAME(load_file)(p, epp, interp,
		    &epp->ep_vmcmds, &epp->ep_entry, ap, &pos)) != 0) {
			free((char *) ap, M_TEMP);
			goto bad;
		}
		pos += phsize;
		ap->arg_phaddr = phdr;

		ap->arg_phentsize = eh->e_phentsize;
		ap->arg_phnum = eh->e_phnum;
		ap->arg_entry = eh->e_entry;

		epp->ep_emul_arg = ap;
	} else
		epp->ep_entry = eh->e_entry;

#ifdef ELF_MAP_PAGE_ZERO
	/* Dell SVR4 maps page zero, yeuch! */
	NEW_VMCMD(&epp->ep_vmcmds, vmcmd_map_readvn, NBPG, 0, epp->ep_vp, 0,
	    VM_PROT_READ);
#endif
	free((char *) ph, M_TEMP);
	epp->ep_vp->v_flag |= VTEXT;
	return exec_elf_setup_stack(p, epp);

bad:
	free((char *) ph, M_TEMP);
	kill_vmcmds(&epp->ep_vmcmds);
	return ENOEXEC;
}