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mirror of https://git.FreeBSD.org/src.git synced 2024-12-25 11:37:56 +00:00
freebsd/sys/kern/kern_exec.c
Gleb Smirnoff b0cd20172d A change to KPI of vm_pager_get_pages() and underlying VOP_GETPAGES().
o With new KPI consumers can request contiguous ranges of pages, and
  unlike before, all pages will be kept busied on return, like it was
  done before with the 'reqpage' only. Now the reqpage goes away. With
  new interface it is easier to implement code protected from race
  conditions.

  Such arrayed requests for now should be preceeded by a call to
  vm_pager_haspage() to make sure that request is possible. This
  could be improved later, making vm_pager_haspage() obsolete.

  Strenghtening the promises on the business of the array of pages
  allows us to remove such hacks as swp_pager_free_nrpage() and
  vm_pager_free_nonreq().

o New KPI accepts two integer pointers that may optionally point at
  values for read ahead and read behind, that a pager may do, if it
  can. These pages are completely owned by pager, and not controlled
  by the caller.

  This shifts the UFS-specific readahead logic from vm_fault.c, which
  should be file system agnostic, into vnode_pager.c. It also removes
  one VOP_BMAP() request per hard fault.

Discussed with:	kib, alc, jeff, scottl
Sponsored by:	Nginx, Inc.
Sponsored by:	Netflix
2015-12-16 21:30:45 +00:00

1619 lines
40 KiB
C

/*-
* Copyright (c) 1993, David Greenman
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_capsicum.h"
#include "opt_hwpmc_hooks.h"
#include "opt_ktrace.h"
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/systm.h>
#include <sys/eventhandler.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sysproto.h>
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/filedesc.h>
#include <sys/fcntl.h>
#include <sys/acct.h>
#include <sys/exec.h>
#include <sys/imgact.h>
#include <sys/imgact_elf.h>
#include <sys/wait.h>
#include <sys/malloc.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/pioctl.h>
#include <sys/namei.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/sf_buf.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/shm.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/stat.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vm_pager.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <machine/reg.h>
#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_execexit_func_t dtrace_fasttrap_exec;
#endif
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE1(proc, kernel, , exec, "char *");
SDT_PROBE_DEFINE1(proc, kernel, , exec__failure, "int");
SDT_PROBE_DEFINE1(proc, kernel, , exec__success, "char *");
MALLOC_DEFINE(M_PARGS, "proc-args", "Process arguments");
int coredump_pack_fileinfo = 1;
SYSCTL_INT(_kern, OID_AUTO, coredump_pack_fileinfo, CTLFLAG_RWTUN,
&coredump_pack_fileinfo, 0,
"Enable file path packing in 'procstat -f' coredump notes");
int coredump_pack_vmmapinfo = 1;
SYSCTL_INT(_kern, OID_AUTO, coredump_pack_vmmapinfo, CTLFLAG_RWTUN,
&coredump_pack_vmmapinfo, 0,
"Enable file path packing in 'procstat -v' coredump notes");
static int sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS);
static int sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS);
static int sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS);
static int do_execve(struct thread *td, struct image_args *args,
struct mac *mac_p);
/* XXX This should be vm_size_t. */
SYSCTL_PROC(_kern, KERN_PS_STRINGS, ps_strings, CTLTYPE_ULONG|CTLFLAG_RD,
NULL, 0, sysctl_kern_ps_strings, "LU", "");
/* XXX This should be vm_size_t. */
SYSCTL_PROC(_kern, KERN_USRSTACK, usrstack, CTLTYPE_ULONG|CTLFLAG_RD|
CTLFLAG_CAPRD, NULL, 0, sysctl_kern_usrstack, "LU", "");
SYSCTL_PROC(_kern, OID_AUTO, stackprot, CTLTYPE_INT|CTLFLAG_RD,
NULL, 0, sysctl_kern_stackprot, "I", "");
u_long ps_arg_cache_limit = PAGE_SIZE / 16;
SYSCTL_ULONG(_kern, OID_AUTO, ps_arg_cache_limit, CTLFLAG_RW,
&ps_arg_cache_limit, 0, "");
static int disallow_high_osrel;
SYSCTL_INT(_kern, OID_AUTO, disallow_high_osrel, CTLFLAG_RW,
&disallow_high_osrel, 0,
"Disallow execution of binaries built for higher version of the world");
static int map_at_zero = 0;
SYSCTL_INT(_security_bsd, OID_AUTO, map_at_zero, CTLFLAG_RWTUN, &map_at_zero, 0,
"Permit processes to map an object at virtual address 0.");
static int
sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS)
{
struct proc *p;
int error;
p = curproc;
#ifdef SCTL_MASK32
if (req->flags & SCTL_MASK32) {
unsigned int val;
val = (unsigned int)p->p_sysent->sv_psstrings;
error = SYSCTL_OUT(req, &val, sizeof(val));
} else
#endif
error = SYSCTL_OUT(req, &p->p_sysent->sv_psstrings,
sizeof(p->p_sysent->sv_psstrings));
return error;
}
static int
sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS)
{
struct proc *p;
int error;
p = curproc;
#ifdef SCTL_MASK32
if (req->flags & SCTL_MASK32) {
unsigned int val;
val = (unsigned int)p->p_sysent->sv_usrstack;
error = SYSCTL_OUT(req, &val, sizeof(val));
} else
#endif
error = SYSCTL_OUT(req, &p->p_sysent->sv_usrstack,
sizeof(p->p_sysent->sv_usrstack));
return error;
}
static int
sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS)
{
struct proc *p;
p = curproc;
return (SYSCTL_OUT(req, &p->p_sysent->sv_stackprot,
sizeof(p->p_sysent->sv_stackprot)));
}
/*
* Each of the items is a pointer to a `const struct execsw', hence the
* double pointer here.
*/
static const struct execsw **execsw;
#ifndef _SYS_SYSPROTO_H_
struct execve_args {
char *fname;
char **argv;
char **envv;
};
#endif
int
sys_execve(struct thread *td, struct execve_args *uap)
{
struct image_args args;
struct vmspace *oldvmspace;
int error;
error = pre_execve(td, &oldvmspace);
if (error != 0)
return (error);
error = exec_copyin_args(&args, uap->fname, UIO_USERSPACE,
uap->argv, uap->envv);
if (error == 0)
error = kern_execve(td, &args, NULL);
post_execve(td, error, oldvmspace);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct fexecve_args {
int fd;
char **argv;
char **envv;
}
#endif
int
sys_fexecve(struct thread *td, struct fexecve_args *uap)
{
struct image_args args;
struct vmspace *oldvmspace;
int error;
error = pre_execve(td, &oldvmspace);
if (error != 0)
return (error);
error = exec_copyin_args(&args, NULL, UIO_SYSSPACE,
uap->argv, uap->envv);
if (error == 0) {
args.fd = uap->fd;
error = kern_execve(td, &args, NULL);
}
post_execve(td, error, oldvmspace);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct __mac_execve_args {
char *fname;
char **argv;
char **envv;
struct mac *mac_p;
};
#endif
int
sys___mac_execve(struct thread *td, struct __mac_execve_args *uap)
{
#ifdef MAC
struct image_args args;
struct vmspace *oldvmspace;
int error;
error = pre_execve(td, &oldvmspace);
if (error != 0)
return (error);
error = exec_copyin_args(&args, uap->fname, UIO_USERSPACE,
uap->argv, uap->envv);
if (error == 0)
error = kern_execve(td, &args, uap->mac_p);
post_execve(td, error, oldvmspace);
return (error);
#else
return (ENOSYS);
#endif
}
int
pre_execve(struct thread *td, struct vmspace **oldvmspace)
{
struct proc *p;
int error;
KASSERT(td == curthread, ("non-current thread %p", td));
error = 0;
p = td->td_proc;
if ((p->p_flag & P_HADTHREADS) != 0) {
PROC_LOCK(p);
if (thread_single(p, SINGLE_BOUNDARY) != 0)
error = ERESTART;
PROC_UNLOCK(p);
}
KASSERT(error != 0 || (td->td_pflags & TDP_EXECVMSPC) == 0,
("nested execve"));
*oldvmspace = p->p_vmspace;
return (error);
}
void
post_execve(struct thread *td, int error, struct vmspace *oldvmspace)
{
struct proc *p;
KASSERT(td == curthread, ("non-current thread %p", td));
p = td->td_proc;
if ((p->p_flag & P_HADTHREADS) != 0) {
PROC_LOCK(p);
/*
* If success, we upgrade to SINGLE_EXIT state to
* force other threads to suicide.
*/
if (error == 0)
thread_single(p, SINGLE_EXIT);
else
thread_single_end(p, SINGLE_BOUNDARY);
PROC_UNLOCK(p);
}
if ((td->td_pflags & TDP_EXECVMSPC) != 0) {
KASSERT(p->p_vmspace != oldvmspace,
("oldvmspace still used"));
vmspace_free(oldvmspace);
td->td_pflags &= ~TDP_EXECVMSPC;
}
}
/*
* XXX: kern_execve has the astonishing property of not always returning to
* the caller. If sufficiently bad things happen during the call to
* do_execve(), it can end up calling exit1(); as a result, callers must
* avoid doing anything which they might need to undo (e.g., allocating
* memory).
*/
int
kern_execve(struct thread *td, struct image_args *args, struct mac *mac_p)
{
AUDIT_ARG_ARGV(args->begin_argv, args->argc,
args->begin_envv - args->begin_argv);
AUDIT_ARG_ENVV(args->begin_envv, args->envc,
args->endp - args->begin_envv);
return (do_execve(td, args, mac_p));
}
/*
* In-kernel implementation of execve(). All arguments are assumed to be
* userspace pointers from the passed thread.
*/
static int
do_execve(td, args, mac_p)
struct thread *td;
struct image_args *args;
struct mac *mac_p;
{
struct proc *p = td->td_proc;
struct nameidata nd;
struct ucred *newcred = NULL, *oldcred;
struct uidinfo *euip = NULL;
register_t *stack_base;
int error, i;
struct image_params image_params, *imgp;
struct vattr attr;
int (*img_first)(struct image_params *);
struct pargs *oldargs = NULL, *newargs = NULL;
struct sigacts *oldsigacts, *newsigacts;
#ifdef KTRACE
struct vnode *tracevp = NULL;
struct ucred *tracecred = NULL;
#endif
struct vnode *oldtextvp = NULL, *newtextvp;
cap_rights_t rights;
int credential_changing;
int textset;
#ifdef MAC
struct label *interpvplabel = NULL;
int will_transition;
#endif
#ifdef HWPMC_HOOKS
struct pmckern_procexec pe;
#endif
static const char fexecv_proc_title[] = "(fexecv)";
imgp = &image_params;
/*
* Lock the process and set the P_INEXEC flag to indicate that
* it should be left alone until we're done here. This is
* necessary to avoid race conditions - e.g. in ptrace() -
* that might allow a local user to illicitly obtain elevated
* privileges.
*/
PROC_LOCK(p);
KASSERT((p->p_flag & P_INEXEC) == 0,
("%s(): process already has P_INEXEC flag", __func__));
p->p_flag |= P_INEXEC;
PROC_UNLOCK(p);
/*
* Initialize part of the common data
*/
bzero(imgp, sizeof(*imgp));
imgp->proc = p;
imgp->attr = &attr;
imgp->args = args;
#ifdef MAC
error = mac_execve_enter(imgp, mac_p);
if (error)
goto exec_fail;
#endif
/*
* Translate the file name. namei() returns a vnode pointer
* in ni_vp amoung other things.
*
* XXXAUDIT: It would be desirable to also audit the name of the
* interpreter if this is an interpreted binary.
*/
if (args->fname != NULL) {
NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | FOLLOW | SAVENAME
| AUDITVNODE1, UIO_SYSSPACE, args->fname, td);
}
SDT_PROBE1(proc, kernel, , exec, args->fname);
interpret:
if (args->fname != NULL) {
#ifdef CAPABILITY_MODE
/*
* While capability mode can't reach this point via direct
* path arguments to execve(), we also don't allow
* interpreters to be used in capability mode (for now).
* Catch indirect lookups and return a permissions error.
*/
if (IN_CAPABILITY_MODE(td)) {
error = ECAPMODE;
goto exec_fail;
}
#endif
error = namei(&nd);
if (error)
goto exec_fail;
newtextvp = nd.ni_vp;
imgp->vp = newtextvp;
} else {
AUDIT_ARG_FD(args->fd);
/*
* Descriptors opened only with O_EXEC or O_RDONLY are allowed.
*/
error = fgetvp_exec(td, args->fd,
cap_rights_init(&rights, CAP_FEXECVE), &newtextvp);
if (error)
goto exec_fail;
vn_lock(newtextvp, LK_EXCLUSIVE | LK_RETRY);
AUDIT_ARG_VNODE1(newtextvp);
imgp->vp = newtextvp;
}
/*
* Check file permissions (also 'opens' file)
*/
error = exec_check_permissions(imgp);
if (error)
goto exec_fail_dealloc;
imgp->object = imgp->vp->v_object;
if (imgp->object != NULL)
vm_object_reference(imgp->object);
/*
* Set VV_TEXT now so no one can write to the executable while we're
* activating it.
*
* Remember if this was set before and unset it in case this is not
* actually an executable image.
*/
textset = VOP_IS_TEXT(imgp->vp);
VOP_SET_TEXT(imgp->vp);
error = exec_map_first_page(imgp);
if (error)
goto exec_fail_dealloc;
imgp->proc->p_osrel = 0;
/*
* If the current process has a special image activator it
* wants to try first, call it. For example, emulating shell
* scripts differently.
*/
error = -1;
if ((img_first = imgp->proc->p_sysent->sv_imgact_try) != NULL)
error = img_first(imgp);
/*
* Loop through the list of image activators, calling each one.
* An activator returns -1 if there is no match, 0 on success,
* and an error otherwise.
*/
for (i = 0; error == -1 && execsw[i]; ++i) {
if (execsw[i]->ex_imgact == NULL ||
execsw[i]->ex_imgact == img_first) {
continue;
}
error = (*execsw[i]->ex_imgact)(imgp);
}
if (error) {
if (error == -1) {
if (textset == 0)
VOP_UNSET_TEXT(imgp->vp);
error = ENOEXEC;
}
goto exec_fail_dealloc;
}
/*
* Special interpreter operation, cleanup and loop up to try to
* activate the interpreter.
*/
if (imgp->interpreted) {
exec_unmap_first_page(imgp);
/*
* VV_TEXT needs to be unset for scripts. There is a short
* period before we determine that something is a script where
* VV_TEXT will be set. The vnode lock is held over this
* entire period so nothing should illegitimately be blocked.
*/
VOP_UNSET_TEXT(imgp->vp);
/* free name buffer and old vnode */
if (args->fname != NULL)
NDFREE(&nd, NDF_ONLY_PNBUF);
#ifdef MAC
mac_execve_interpreter_enter(newtextvp, &interpvplabel);
#endif
if (imgp->opened) {
VOP_CLOSE(newtextvp, FREAD, td->td_ucred, td);
imgp->opened = 0;
}
vput(newtextvp);
vm_object_deallocate(imgp->object);
imgp->object = NULL;
/* set new name to that of the interpreter */
NDINIT(&nd, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME,
UIO_SYSSPACE, imgp->interpreter_name, td);
args->fname = imgp->interpreter_name;
goto interpret;
}
/*
* NB: We unlock the vnode here because it is believed that none
* of the sv_copyout_strings/sv_fixup operations require the vnode.
*/
VOP_UNLOCK(imgp->vp, 0);
/*
* Do the best to calculate the full path to the image file.
*/
if (imgp->auxargs != NULL &&
((args->fname != NULL && args->fname[0] == '/') ||
vn_fullpath(td, imgp->vp, &imgp->execpath, &imgp->freepath) != 0))
imgp->execpath = args->fname;
if (disallow_high_osrel &&
P_OSREL_MAJOR(p->p_osrel) > P_OSREL_MAJOR(__FreeBSD_version)) {
error = ENOEXEC;
uprintf("Osrel %d for image %s too high\n", p->p_osrel,
imgp->execpath != NULL ? imgp->execpath : "<unresolved>");
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
goto exec_fail_dealloc;
}
/* ABI enforces the use of Capsicum. Switch into capabilities mode. */
if (SV_PROC_FLAG(p, SV_CAPSICUM))
sys_cap_enter(td, NULL);
/*
* Copy out strings (args and env) and initialize stack base
*/
if (p->p_sysent->sv_copyout_strings)
stack_base = (*p->p_sysent->sv_copyout_strings)(imgp);
else
stack_base = exec_copyout_strings(imgp);
/*
* If custom stack fixup routine present for this process
* let it do the stack setup.
* Else stuff argument count as first item on stack
*/
if (p->p_sysent->sv_fixup != NULL)
(*p->p_sysent->sv_fixup)(&stack_base, imgp);
else
suword(--stack_base, imgp->args->argc);
if (args->fdp != NULL) {
/* Install a brand new file descriptor table. */
fdinstall_remapped(td, args->fdp);
args->fdp = NULL;
} else {
/*
* Keep on using the existing file descriptor table. For
* security and other reasons, the file descriptor table
* cannot be shared after an exec.
*/
fdunshare(td);
/* close files on exec */
fdcloseexec(td);
}
/*
* Malloc things before we need locks.
*/
i = imgp->args->begin_envv - imgp->args->begin_argv;
/* Cache arguments if they fit inside our allowance */
if (ps_arg_cache_limit >= i + sizeof(struct pargs)) {
newargs = pargs_alloc(i);
bcopy(imgp->args->begin_argv, newargs->ar_args, i);
}
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
/*
* For security and other reasons, signal handlers cannot
* be shared after an exec. The new process gets a copy of the old
* handlers. In execsigs(), the new process will have its signals
* reset.
*/
if (sigacts_shared(p->p_sigacts)) {
oldsigacts = p->p_sigacts;
newsigacts = sigacts_alloc();
sigacts_copy(newsigacts, oldsigacts);
} else {
oldsigacts = NULL;
newsigacts = NULL; /* satisfy gcc */
}
PROC_LOCK(p);
if (oldsigacts)
p->p_sigacts = newsigacts;
oldcred = p->p_ucred;
/* Stop profiling */
stopprofclock(p);
/* reset caught signals */
execsigs(p);
/* name this process - nameiexec(p, ndp) */
bzero(p->p_comm, sizeof(p->p_comm));
if (args->fname)
bcopy(nd.ni_cnd.cn_nameptr, p->p_comm,
min(nd.ni_cnd.cn_namelen, MAXCOMLEN));
else if (vn_commname(newtextvp, p->p_comm, sizeof(p->p_comm)) != 0)
bcopy(fexecv_proc_title, p->p_comm, sizeof(fexecv_proc_title));
bcopy(p->p_comm, td->td_name, sizeof(td->td_name));
#ifdef KTR
sched_clear_tdname(td);
#endif
/*
* mark as execed, wakeup the process that vforked (if any) and tell
* it that it now has its own resources back
*/
p->p_flag |= P_EXEC;
if ((p->p_flag2 & P2_NOTRACE_EXEC) == 0)
p->p_flag2 &= ~P2_NOTRACE;
if (p->p_flag & P_PPWAIT) {
p->p_flag &= ~(P_PPWAIT | P_PPTRACE);
cv_broadcast(&p->p_pwait);
}
/*
* Implement image setuid/setgid.
*
* Don't honor setuid/setgid if the filesystem prohibits it or if
* the process is being traced.
*
* We disable setuid/setgid/etc in compatibility mode on the basis
* that most setugid applications are not written with that
* environment in mind, and will therefore almost certainly operate
* incorrectly. In principle there's no reason that setugid
* applications might not be useful in capability mode, so we may want
* to reconsider this conservative design choice in the future.
*
* XXXMAC: For the time being, use NOSUID to also prohibit
* transitions on the file system.
*/
credential_changing = 0;
credential_changing |= (attr.va_mode & S_ISUID) && oldcred->cr_uid !=
attr.va_uid;
credential_changing |= (attr.va_mode & S_ISGID) && oldcred->cr_gid !=
attr.va_gid;
#ifdef MAC
will_transition = mac_vnode_execve_will_transition(oldcred, imgp->vp,
interpvplabel, imgp);
credential_changing |= will_transition;
#endif
if (credential_changing &&
#ifdef CAPABILITY_MODE
((oldcred->cr_flags & CRED_FLAG_CAPMODE) == 0) &&
#endif
(imgp->vp->v_mount->mnt_flag & MNT_NOSUID) == 0 &&
(p->p_flag & P_TRACED) == 0) {
/*
* Turn off syscall tracing for set-id programs, except for
* root. Record any set-id flags first to make sure that
* we do not regain any tracing during a possible block.
*/
setsugid(p);
#ifdef KTRACE
if (p->p_tracecred != NULL &&
priv_check_cred(p->p_tracecred, PRIV_DEBUG_DIFFCRED, 0))
ktrprocexec(p, &tracecred, &tracevp);
#endif
/*
* Close any file descriptors 0..2 that reference procfs,
* then make sure file descriptors 0..2 are in use.
*
* Both fdsetugidsafety() and fdcheckstd() may call functions
* taking sleepable locks, so temporarily drop our locks.
*/
PROC_UNLOCK(p);
VOP_UNLOCK(imgp->vp, 0);
fdsetugidsafety(td);
error = fdcheckstd(td);
if (error != 0)
goto done1;
newcred = crdup(oldcred);
euip = uifind(attr.va_uid);
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
PROC_LOCK(p);
/*
* Set the new credentials.
*/
if (attr.va_mode & S_ISUID)
change_euid(newcred, euip);
if (attr.va_mode & S_ISGID)
change_egid(newcred, attr.va_gid);
#ifdef MAC
if (will_transition) {
mac_vnode_execve_transition(oldcred, newcred, imgp->vp,
interpvplabel, imgp);
}
#endif
/*
* Implement correct POSIX saved-id behavior.
*
* XXXMAC: Note that the current logic will save the
* uid and gid if a MAC domain transition occurs, even
* though maybe it shouldn't.
*/
change_svuid(newcred, newcred->cr_uid);
change_svgid(newcred, newcred->cr_gid);
proc_set_cred(p, newcred);
} else {
if (oldcred->cr_uid == oldcred->cr_ruid &&
oldcred->cr_gid == oldcred->cr_rgid)
p->p_flag &= ~P_SUGID;
/*
* Implement correct POSIX saved-id behavior.
*
* XXX: It's not clear that the existing behavior is
* POSIX-compliant. A number of sources indicate that the
* saved uid/gid should only be updated if the new ruid is
* not equal to the old ruid, or the new euid is not equal
* to the old euid and the new euid is not equal to the old
* ruid. The FreeBSD code always updates the saved uid/gid.
* Also, this code uses the new (replaced) euid and egid as
* the source, which may or may not be the right ones to use.
*/
if (oldcred->cr_svuid != oldcred->cr_uid ||
oldcred->cr_svgid != oldcred->cr_gid) {
PROC_UNLOCK(p);
VOP_UNLOCK(imgp->vp, 0);
newcred = crdup(oldcred);
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
PROC_LOCK(p);
change_svuid(newcred, newcred->cr_uid);
change_svgid(newcred, newcred->cr_gid);
proc_set_cred(p, newcred);
}
}
/*
* Store the vp for use in procfs. This vnode was referenced by namei
* or fgetvp_exec.
*/
oldtextvp = p->p_textvp;
p->p_textvp = newtextvp;
#ifdef KDTRACE_HOOKS
/*
* Tell the DTrace fasttrap provider about the exec if it
* has declared an interest.
*/
if (dtrace_fasttrap_exec)
dtrace_fasttrap_exec(p);
#endif
/*
* Notify others that we exec'd, and clear the P_INEXEC flag
* as we're now a bona fide freshly-execed process.
*/
KNOTE_LOCKED(&p->p_klist, NOTE_EXEC);
p->p_flag &= ~P_INEXEC;
/* clear "fork but no exec" flag, as we _are_ execing */
p->p_acflag &= ~AFORK;
/*
* Free any previous argument cache and replace it with
* the new argument cache, if any.
*/
oldargs = p->p_args;
p->p_args = newargs;
newargs = NULL;
#ifdef HWPMC_HOOKS
/*
* Check if system-wide sampling is in effect or if the
* current process is using PMCs. If so, do exec() time
* processing. This processing needs to happen AFTER the
* P_INEXEC flag is cleared.
*
* The proc lock needs to be released before taking the PMC
* SX.
*/
if (PMC_SYSTEM_SAMPLING_ACTIVE() || PMC_PROC_IS_USING_PMCS(p)) {
PROC_UNLOCK(p);
VOP_UNLOCK(imgp->vp, 0);
pe.pm_credentialschanged = credential_changing;
pe.pm_entryaddr = imgp->entry_addr;
PMC_CALL_HOOK_X(td, PMC_FN_PROCESS_EXEC, (void *) &pe);
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
} else
PROC_UNLOCK(p);
#else /* !HWPMC_HOOKS */
PROC_UNLOCK(p);
#endif
/* Set values passed into the program in registers. */
if (p->p_sysent->sv_setregs)
(*p->p_sysent->sv_setregs)(td, imgp,
(u_long)(uintptr_t)stack_base);
else
exec_setregs(td, imgp, (u_long)(uintptr_t)stack_base);
vfs_mark_atime(imgp->vp, td->td_ucred);
SDT_PROBE1(proc, kernel, , exec__success, args->fname);
VOP_UNLOCK(imgp->vp, 0);
done1:
/*
* Free any resources malloc'd earlier that we didn't use.
*/
if (euip != NULL)
uifree(euip);
if (newcred != NULL)
crfree(oldcred);
/*
* Handle deferred decrement of ref counts.
*/
if (oldtextvp != NULL)
vrele(oldtextvp);
#ifdef KTRACE
if (tracevp != NULL)
vrele(tracevp);
if (tracecred != NULL)
crfree(tracecred);
#endif
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
pargs_drop(oldargs);
pargs_drop(newargs);
if (oldsigacts != NULL)
sigacts_free(oldsigacts);
exec_fail_dealloc:
/*
* free various allocated resources
*/
if (imgp->firstpage != NULL)
exec_unmap_first_page(imgp);
if (imgp->vp != NULL) {
if (args->fname)
NDFREE(&nd, NDF_ONLY_PNBUF);
if (imgp->opened)
VOP_CLOSE(imgp->vp, FREAD, td->td_ucred, td);
if (error != 0)
vput(imgp->vp);
else
VOP_UNLOCK(imgp->vp, 0);
}
if (imgp->object != NULL)
vm_object_deallocate(imgp->object);
free(imgp->freepath, M_TEMP);
if (error == 0) {
PROC_LOCK(p);
td->td_dbgflags |= TDB_EXEC;
PROC_UNLOCK(p);
/*
* Stop the process here if its stop event mask has
* the S_EXEC bit set.
*/
STOPEVENT(p, S_EXEC, 0);
goto done2;
}
exec_fail:
/* we're done here, clear P_INEXEC */
PROC_LOCK(p);
p->p_flag &= ~P_INEXEC;
PROC_UNLOCK(p);
SDT_PROBE1(proc, kernel, , exec__failure, error);
done2:
#ifdef MAC
mac_execve_exit(imgp);
mac_execve_interpreter_exit(interpvplabel);
#endif
exec_free_args(args);
if (error && imgp->vmspace_destroyed) {
/* sorry, no more process anymore. exit gracefully */
exit1(td, 0, SIGABRT);
/* NOT REACHED */
}
#ifdef KTRACE
if (error == 0)
ktrprocctor(p);
#endif
return (error);
}
int
exec_map_first_page(imgp)
struct image_params *imgp;
{
int rv, i, after, initial_pagein;
vm_page_t ma[VM_INITIAL_PAGEIN];
vm_object_t object;
if (imgp->firstpage != NULL)
exec_unmap_first_page(imgp);
object = imgp->vp->v_object;
if (object == NULL)
return (EACCES);
VM_OBJECT_WLOCK(object);
#if VM_NRESERVLEVEL > 0
vm_object_color(object, 0);
#endif
ma[0] = vm_page_grab(object, 0, VM_ALLOC_NORMAL);
if (ma[0]->valid != VM_PAGE_BITS_ALL) {
if (!vm_pager_has_page(object, 0, NULL, &after)) {
vm_page_lock(ma[0]);
vm_page_free(ma[0]);
vm_page_unlock(ma[0]);
vm_page_xunbusy(ma[0]);
VM_OBJECT_WUNLOCK(object);
return (EIO);
}
initial_pagein = min(after, VM_INITIAL_PAGEIN);
KASSERT(initial_pagein <= object->size,
("%s: initial_pagein %d object->size %ju",
__func__, initial_pagein, (uintmax_t )object->size));
for (i = 1; i < initial_pagein; i++) {
if ((ma[i] = vm_page_next(ma[i - 1])) != NULL) {
if (ma[i]->valid)
break;
if (vm_page_tryxbusy(ma[i]))
break;
} else {
ma[i] = vm_page_alloc(object, i,
VM_ALLOC_NORMAL | VM_ALLOC_IFNOTCACHED);
if (ma[i] == NULL)
break;
}
}
initial_pagein = i;
rv = vm_pager_get_pages(object, ma, initial_pagein, NULL, NULL);
if (rv != VM_PAGER_OK) {
for (i = 0; i < initial_pagein; i++) {
vm_page_lock(ma[i]);
vm_page_free(ma[i]);
vm_page_unlock(ma[i]);
vm_page_xunbusy(ma[i]);
}
VM_OBJECT_WUNLOCK(object);
return (EIO);
}
for (i = 1; i < initial_pagein; i++)
vm_page_readahead_finish(ma[i]);
}
vm_page_xunbusy(ma[0]);
vm_page_lock(ma[0]);
vm_page_hold(ma[0]);
vm_page_activate(ma[0]);
vm_page_unlock(ma[0]);
VM_OBJECT_WUNLOCK(object);
imgp->firstpage = sf_buf_alloc(ma[0], 0);
imgp->image_header = (char *)sf_buf_kva(imgp->firstpage);
return (0);
}
void
exec_unmap_first_page(imgp)
struct image_params *imgp;
{
vm_page_t m;
if (imgp->firstpage != NULL) {
m = sf_buf_page(imgp->firstpage);
sf_buf_free(imgp->firstpage);
imgp->firstpage = NULL;
vm_page_lock(m);
vm_page_unhold(m);
vm_page_unlock(m);
}
}
/*
* Destroy old address space, and allocate a new stack
* The new stack is only SGROWSIZ large because it is grown
* automatically in trap.c.
*/
int
exec_new_vmspace(imgp, sv)
struct image_params *imgp;
struct sysentvec *sv;
{
int error;
struct proc *p = imgp->proc;
struct vmspace *vmspace = p->p_vmspace;
vm_object_t obj;
struct rlimit rlim_stack;
vm_offset_t sv_minuser, stack_addr;
vm_map_t map;
u_long ssiz;
imgp->vmspace_destroyed = 1;
imgp->sysent = sv;
/* May be called with Giant held */
EVENTHANDLER_INVOKE(process_exec, p, imgp);
/*
* Blow away entire process VM, if address space not shared,
* otherwise, create a new VM space so that other threads are
* not disrupted
*/
map = &vmspace->vm_map;
if (map_at_zero)
sv_minuser = sv->sv_minuser;
else
sv_minuser = MAX(sv->sv_minuser, PAGE_SIZE);
if (vmspace->vm_refcnt == 1 && vm_map_min(map) == sv_minuser &&
vm_map_max(map) == sv->sv_maxuser) {
shmexit(vmspace);
pmap_remove_pages(vmspace_pmap(vmspace));
vm_map_remove(map, vm_map_min(map), vm_map_max(map));
} else {
error = vmspace_exec(p, sv_minuser, sv->sv_maxuser);
if (error)
return (error);
vmspace = p->p_vmspace;
map = &vmspace->vm_map;
}
/* Map a shared page */
obj = sv->sv_shared_page_obj;
if (obj != NULL) {
vm_object_reference(obj);
error = vm_map_fixed(map, obj, 0,
sv->sv_shared_page_base, sv->sv_shared_page_len,
VM_PROT_READ | VM_PROT_EXECUTE,
VM_PROT_READ | VM_PROT_EXECUTE,
MAP_INHERIT_SHARE | MAP_ACC_NO_CHARGE);
if (error) {
vm_object_deallocate(obj);
return (error);
}
}
/* Allocate a new stack */
if (imgp->stack_sz != 0) {
ssiz = trunc_page(imgp->stack_sz);
PROC_LOCK(p);
lim_rlimit_proc(p, RLIMIT_STACK, &rlim_stack);
PROC_UNLOCK(p);
if (ssiz > rlim_stack.rlim_max)
ssiz = rlim_stack.rlim_max;
if (ssiz > rlim_stack.rlim_cur) {
rlim_stack.rlim_cur = ssiz;
kern_setrlimit(curthread, RLIMIT_STACK, &rlim_stack);
}
} else if (sv->sv_maxssiz != NULL) {
ssiz = *sv->sv_maxssiz;
} else {
ssiz = maxssiz;
}
stack_addr = sv->sv_usrstack - ssiz;
error = vm_map_stack(map, stack_addr, (vm_size_t)ssiz,
obj != NULL && imgp->stack_prot != 0 ? imgp->stack_prot :
sv->sv_stackprot,
VM_PROT_ALL, MAP_STACK_GROWS_DOWN);
if (error)
return (error);
/*
* vm_ssize and vm_maxsaddr are somewhat antiquated concepts, but they
* are still used to enforce the stack rlimit on the process stack.
*/
vmspace->vm_ssize = sgrowsiz >> PAGE_SHIFT;
vmspace->vm_maxsaddr = (char *)stack_addr;
return (0);
}
/*
* Copy out argument and environment strings from the old process address
* space into the temporary string buffer.
*/
int
exec_copyin_args(struct image_args *args, char *fname,
enum uio_seg segflg, char **argv, char **envv)
{
u_long argp, envp;
int error;
size_t length;
bzero(args, sizeof(*args));
if (argv == NULL)
return (EFAULT);
/*
* Allocate demand-paged memory for the file name, argument, and
* environment strings.
*/
error = exec_alloc_args(args);
if (error != 0)
return (error);
/*
* Copy the file name.
*/
if (fname != NULL) {
args->fname = args->buf;
error = (segflg == UIO_SYSSPACE) ?
copystr(fname, args->fname, PATH_MAX, &length) :
copyinstr(fname, args->fname, PATH_MAX, &length);
if (error != 0)
goto err_exit;
} else
length = 0;
args->begin_argv = args->buf + length;
args->endp = args->begin_argv;
args->stringspace = ARG_MAX;
/*
* extract arguments first
*/
for (;;) {
error = fueword(argv++, &argp);
if (error == -1) {
error = EFAULT;
goto err_exit;
}
if (argp == 0)
break;
error = copyinstr((void *)(uintptr_t)argp, args->endp,
args->stringspace, &length);
if (error != 0) {
if (error == ENAMETOOLONG)
error = E2BIG;
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->argc++;
}
args->begin_envv = args->endp;
/*
* extract environment strings
*/
if (envv) {
for (;;) {
error = fueword(envv++, &envp);
if (error == -1) {
error = EFAULT;
goto err_exit;
}
if (envp == 0)
break;
error = copyinstr((void *)(uintptr_t)envp,
args->endp, args->stringspace, &length);
if (error != 0) {
if (error == ENAMETOOLONG)
error = E2BIG;
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->envc++;
}
}
return (0);
err_exit:
exec_free_args(args);
return (error);
}
int
exec_copyin_data_fds(struct thread *td, struct image_args *args,
const void *data, size_t datalen, const int *fds, size_t fdslen)
{
struct filedesc *ofdp;
const char *p;
int *kfds;
int error;
memset(args, '\0', sizeof(*args));
ofdp = td->td_proc->p_fd;
if (datalen >= ARG_MAX || fdslen > ofdp->fd_lastfile + 1)
return (E2BIG);
error = exec_alloc_args(args);
if (error != 0)
return (error);
args->begin_argv = args->buf;
args->stringspace = ARG_MAX;
if (datalen > 0) {
/*
* Argument buffer has been provided. Copy it into the
* kernel as a single string and add a terminating null
* byte.
*/
error = copyin(data, args->begin_argv, datalen);
if (error != 0)
goto err_exit;
args->begin_argv[datalen] = '\0';
args->endp = args->begin_argv + datalen + 1;
args->stringspace -= datalen + 1;
/*
* Traditional argument counting. Count the number of
* null bytes.
*/
for (p = args->begin_argv; p < args->endp; ++p)
if (*p == '\0')
++args->argc;
} else {
/* No argument buffer provided. */
args->endp = args->begin_argv;
}
/* There are no environment variables. */
args->begin_envv = args->endp;
/* Create new file descriptor table. */
kfds = malloc(fdslen * sizeof(int), M_TEMP, M_WAITOK);
error = copyin(fds, kfds, fdslen * sizeof(int));
if (error != 0) {
free(kfds, M_TEMP);
goto err_exit;
}
error = fdcopy_remapped(ofdp, kfds, fdslen, &args->fdp);
free(kfds, M_TEMP);
if (error != 0)
goto err_exit;
return (0);
err_exit:
exec_free_args(args);
return (error);
}
/*
* Allocate temporary demand-paged, zero-filled memory for the file name,
* argument, and environment strings. Returns zero if the allocation succeeds
* and ENOMEM otherwise.
*/
int
exec_alloc_args(struct image_args *args)
{
args->buf = (char *)kmap_alloc_wait(exec_map, PATH_MAX + ARG_MAX);
return (args->buf != NULL ? 0 : ENOMEM);
}
void
exec_free_args(struct image_args *args)
{
if (args->buf != NULL) {
kmap_free_wakeup(exec_map, (vm_offset_t)args->buf,
PATH_MAX + ARG_MAX);
args->buf = NULL;
}
if (args->fname_buf != NULL) {
free(args->fname_buf, M_TEMP);
args->fname_buf = NULL;
}
if (args->fdp != NULL)
fdescfree_remapped(args->fdp);
}
/*
* Copy strings out to the new process address space, constructing new arg
* and env vector tables. Return a pointer to the base so that it can be used
* as the initial stack pointer.
*/
register_t *
exec_copyout_strings(imgp)
struct image_params *imgp;
{
int argc, envc;
char **vectp;
char *stringp;
uintptr_t destp;
register_t *stack_base;
struct ps_strings *arginfo;
struct proc *p;
size_t execpath_len;
int szsigcode, szps;
char canary[sizeof(long) * 8];
szps = sizeof(pagesizes[0]) * MAXPAGESIZES;
/*
* Calculate string base and vector table pointers.
* Also deal with signal trampoline code for this exec type.
*/
if (imgp->execpath != NULL && imgp->auxargs != NULL)
execpath_len = strlen(imgp->execpath) + 1;
else
execpath_len = 0;
p = imgp->proc;
szsigcode = 0;
arginfo = (struct ps_strings *)p->p_sysent->sv_psstrings;
if (p->p_sysent->sv_sigcode_base == 0) {
if (p->p_sysent->sv_szsigcode != NULL)
szsigcode = *(p->p_sysent->sv_szsigcode);
}
destp = (uintptr_t)arginfo;
/*
* install sigcode
*/
if (szsigcode != 0) {
destp -= szsigcode;
destp = rounddown2(destp, sizeof(void *));
copyout(p->p_sysent->sv_sigcode, (void *)destp, szsigcode);
}
/*
* Copy the image path for the rtld.
*/
if (execpath_len != 0) {
destp -= execpath_len;
imgp->execpathp = destp;
copyout(imgp->execpath, (void *)destp, execpath_len);
}
/*
* Prepare the canary for SSP.
*/
arc4rand(canary, sizeof(canary), 0);
destp -= sizeof(canary);
imgp->canary = destp;
copyout(canary, (void *)destp, sizeof(canary));
imgp->canarylen = sizeof(canary);
/*
* Prepare the pagesizes array.
*/
destp -= szps;
destp = rounddown2(destp, sizeof(void *));
imgp->pagesizes = destp;
copyout(pagesizes, (void *)destp, szps);
imgp->pagesizeslen = szps;
destp -= ARG_MAX - imgp->args->stringspace;
destp = rounddown2(destp, sizeof(void *));
/*
* If we have a valid auxargs ptr, prepare some room
* on the stack.
*/
if (imgp->auxargs) {
/*
* 'AT_COUNT*2' is size for the ELF Auxargs data. This is for
* lower compatibility.
*/
imgp->auxarg_size = (imgp->auxarg_size) ? imgp->auxarg_size :
(AT_COUNT * 2);
/*
* The '+ 2' is for the null pointers at the end of each of
* the arg and env vector sets,and imgp->auxarg_size is room
* for argument of Runtime loader.
*/
vectp = (char **)(destp - (imgp->args->argc +
imgp->args->envc + 2 + imgp->auxarg_size)
* sizeof(char *));
} else {
/*
* The '+ 2' is for the null pointers at the end of each of
* the arg and env vector sets
*/
vectp = (char **)(destp - (imgp->args->argc + imgp->args->envc
+ 2) * sizeof(char *));
}
/*
* vectp also becomes our initial stack base
*/
stack_base = (register_t *)vectp;
stringp = imgp->args->begin_argv;
argc = imgp->args->argc;
envc = imgp->args->envc;
/*
* Copy out strings - arguments and environment.
*/
copyout(stringp, (void *)destp, ARG_MAX - imgp->args->stringspace);
/*
* Fill in "ps_strings" struct for ps, w, etc.
*/
suword(&arginfo->ps_argvstr, (long)(intptr_t)vectp);
suword32(&arginfo->ps_nargvstr, argc);
/*
* Fill in argument portion of vector table.
*/
for (; argc > 0; --argc) {
suword(vectp++, (long)(intptr_t)destp);
while (*stringp++ != 0)
destp++;
destp++;
}
/* a null vector table pointer separates the argp's from the envp's */
suword(vectp++, 0);
suword(&arginfo->ps_envstr, (long)(intptr_t)vectp);
suword32(&arginfo->ps_nenvstr, envc);
/*
* Fill in environment portion of vector table.
*/
for (; envc > 0; --envc) {
suword(vectp++, (long)(intptr_t)destp);
while (*stringp++ != 0)
destp++;
destp++;
}
/* end of vector table is a null pointer */
suword(vectp, 0);
return (stack_base);
}
/*
* Check permissions of file to execute.
* Called with imgp->vp locked.
* Return 0 for success or error code on failure.
*/
int
exec_check_permissions(imgp)
struct image_params *imgp;
{
struct vnode *vp = imgp->vp;
struct vattr *attr = imgp->attr;
struct thread *td;
int error, writecount;
td = curthread;
/* Get file attributes */
error = VOP_GETATTR(vp, attr, td->td_ucred);
if (error)
return (error);
#ifdef MAC
error = mac_vnode_check_exec(td->td_ucred, imgp->vp, imgp);
if (error)
return (error);
#endif
/*
* 1) Check if file execution is disabled for the filesystem that
* this file resides on.
* 2) Ensure that at least one execute bit is on. Otherwise, a
* privileged user will always succeed, and we don't want this
* to happen unless the file really is executable.
* 3) Ensure that the file is a regular file.
*/
if ((vp->v_mount->mnt_flag & MNT_NOEXEC) ||
(attr->va_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0 ||
(attr->va_type != VREG))
return (EACCES);
/*
* Zero length files can't be exec'd
*/
if (attr->va_size == 0)
return (ENOEXEC);
/*
* Check for execute permission to file based on current credentials.
*/
error = VOP_ACCESS(vp, VEXEC, td->td_ucred, td);
if (error)
return (error);
/*
* Check number of open-for-writes on the file and deny execution
* if there are any.
*/
error = VOP_GET_WRITECOUNT(vp, &writecount);
if (error != 0)
return (error);
if (writecount != 0)
return (ETXTBSY);
/*
* Call filesystem specific open routine (which does nothing in the
* general case).
*/
error = VOP_OPEN(vp, FREAD, td->td_ucred, td, NULL);
if (error == 0)
imgp->opened = 1;
return (error);
}
/*
* Exec handler registration
*/
int
exec_register(execsw_arg)
const struct execsw *execsw_arg;
{
const struct execsw **es, **xs, **newexecsw;
int count = 2; /* New slot and trailing NULL */
if (execsw)
for (es = execsw; *es; es++)
count++;
newexecsw = malloc(count * sizeof(*es), M_TEMP, M_WAITOK);
if (newexecsw == NULL)
return (ENOMEM);
xs = newexecsw;
if (execsw)
for (es = execsw; *es; es++)
*xs++ = *es;
*xs++ = execsw_arg;
*xs = NULL;
if (execsw)
free(execsw, M_TEMP);
execsw = newexecsw;
return (0);
}
int
exec_unregister(execsw_arg)
const struct execsw *execsw_arg;
{
const struct execsw **es, **xs, **newexecsw;
int count = 1;
if (execsw == NULL)
panic("unregister with no handlers left?\n");
for (es = execsw; *es; es++) {
if (*es == execsw_arg)
break;
}
if (*es == NULL)
return (ENOENT);
for (es = execsw; *es; es++)
if (*es != execsw_arg)
count++;
newexecsw = malloc(count * sizeof(*es), M_TEMP, M_WAITOK);
if (newexecsw == NULL)
return (ENOMEM);
xs = newexecsw;
for (es = execsw; *es; es++)
if (*es != execsw_arg)
*xs++ = *es;
*xs = NULL;
if (execsw)
free(execsw, M_TEMP);
execsw = newexecsw;
return (0);
}