Function do_execve

freebsd/kern/kern_exec.c:360–972

* In-kernel implementation of execve(). All arguments are assumed to be * userspace pointers from the passed thread. */

 * userspace pointers from the passed thread.
 */
static int
do_execve(struct thread *td, struct image_args *args, struct mac *mac_p,
    struct vmspace *oldvmspace)
{
	struct proc *p = td->td_proc;
	struct nameidata nd;
	struct ucred *oldcred;
	struct uidinfo *euip = NULL;
	uintptr_t stack_base;
	struct image_params image_params, *imgp;
	struct vattr attr;
	int (*img_first)(struct image_params *);
	struct pargs *oldargs = NULL, *newargs = NULL;
	struct sigacts *oldsigacts = NULL, *newsigacts = NULL;
#ifdef KTRACE
	struct vnode *tracevp = NULL;
	struct ucred *tracecred = NULL;
#endif
	struct vnode *oldtextvp = NULL, *newtextvp;
	int credential_changing;
#ifdef MAC
	struct label *interpvplabel = NULL;
	int will_transition;
#endif
#ifdef HWPMC_HOOKS
	struct pmckern_procexec pe;
#endif
	int error, i, orig_osrel;
	uint32_t orig_fctl0;
	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;
	oldcred = p->p_ucred;
	orig_osrel = p->p_osrel;
	orig_fctl0 = p->p_fctl0;

#ifdef MAC