Index: include/unistd.h
===================================================================
--- include/unistd.h
+++ include/unistd.h
@@ -431,6 +431,7 @@
 int	faccessat(int, const char *, int, int);
 int	fchownat(int, const char *, uid_t, gid_t, int);
 int	fexecve(int, char *const [], char *const []);
+int	fldexec(int, int, char *const [], char *const []);
 int	linkat(int, const char *, int, const char *, int);
 ssize_t	readlinkat(int, const char * __restrict, char * __restrict, size_t);
 int	symlinkat(const char *, int, const char *);
Index: lib/libc/sys/Makefile.inc
===================================================================
--- lib/libc/sys/Makefile.inc
+++ lib/libc/sys/Makefile.inc
@@ -364,7 +364,7 @@
 	cpuset.2 cpuset_setid.2
 MLINKS+=cpuset_getaffinity.2 cpuset_setaffinity.2
 MLINKS+=dup.2 dup2.2
-MLINKS+=execve.2 fexecve.2
+MLINKS+=execve.2 fexecve.2 fldexec.2
 MLINKS+=extattr_get_file.2 extattr.2 \
 	extattr_get_file.2 extattr_delete_fd.2 \
 	extattr_get_file.2 extattr_delete_file.2 \
Index: lib/libc/sys/Symbol.map
===================================================================
--- lib/libc/sys/Symbol.map
+++ lib/libc/sys/Symbol.map
@@ -330,6 +330,7 @@
 	fchmodat;
 	fchownat;
 	fexecve;
+	fldexec;
 	fstatat;
 	futimesat;
 	jail_get;
Index: lib/libc/sys/execve.2
===================================================================
--- lib/libc/sys/execve.2
+++ lib/libc/sys/execve.2
@@ -33,7 +33,8 @@
 .Os
 .Sh NAME
 .Nm execve ,
-.Nm fexecve
+.Nm fexecve,
+.Nm fldexec
 .Nd execute a file
 .Sh LIBRARY
 .Lb libc
Index: sys/compat/freebsd32/syscalls.master
===================================================================
--- sys/compat/freebsd32/syscalls.master
+++ sys/compat/freebsd32/syscalls.master
@@ -1081,3 +1081,5 @@
 				    id_t id, \
 				    const struct vm_domain_policy *policy); }
 550	AUE_FSYNC	NOPROTO	{ int fdatasync(int fd); }
+551	AUE_NULL	STD	{ int fldexec(int rtld, int bin, char **argv, \
+				    char **envv); }
Index: sys/kern/capabilities.conf
===================================================================
--- sys/kern/capabilities.conf
+++ sys/kern/capabilities.conf
@@ -176,6 +176,7 @@
 ## such as disallowing privilege escalation.
 ##
 fexecve
+fldexec
 
 ##
 ## Allow flock(2), subject to capability rights.
Index: sys/kern/imgact_elf.c
===================================================================
--- sys/kern/imgact_elf.c
+++ sys/kern/imgact_elf.c
@@ -87,8 +87,10 @@
 static int __elfN(check_header)(const Elf_Ehdr *hdr);
 static Elf_Brandinfo *__elfN(get_brandinfo)(struct image_params *imgp,
     const char *interp, int interp_name_len, int32_t *osrel);
-static int __elfN(load_file)(struct proc *p, const char *file, u_long *addr,
+static int __elfN(load_file)(struct proc *p, struct vnode *vp, u_long *addr,
     u_long *entry, size_t pagesize);
+static int __elfN(load_path)(struct proc *p, const char *path, u_long *addr,
+	u_long *entry, size_t pagesize);
 static int __elfN(load_section)(struct image_params *imgp, vm_offset_t offset,
     caddr_t vmaddr, size_t memsz, size_t filsz, vm_prot_t prot,
     size_t pagesize);
@@ -616,17 +618,15 @@
  * the entry point for the loaded file.
  */
 static int
-__elfN(load_file)(struct proc *p, const char *file, u_long *addr,
+__elfN(load_file)(struct proc *p, struct vnode *vp, u_long *addr,
 	u_long *entry, size_t pagesize)
 {
 	struct {
-		struct nameidata nd;
 		struct vattr attr;
 		struct image_params image_params;
 	} *tempdata;
 	const Elf_Ehdr *hdr = NULL;
 	const Elf_Phdr *phdr = NULL;
-	struct nameidata *nd;
 	struct vattr *attr;
 	struct image_params *imgp;
 	vm_prot_t prot;
@@ -634,17 +634,7 @@
 	u_long base_addr = 0;
 	int error, i, numsegs;
 
-#ifdef CAPABILITY_MODE
-	/*
-	 * XXXJA: This check can go away once we are sufficiently confident
-	 * that the checks in namei() are correct.
-	 */
-	if (IN_CAPABILITY_MODE(curthread))
-		return (ECAPMODE);
-#endif
-
 	tempdata = malloc(sizeof(*tempdata), M_TEMP, M_WAITOK);
-	nd = &tempdata->nd;
 	attr = &tempdata->attr;
 	imgp = &tempdata->image_params;
 
@@ -657,14 +647,7 @@
 	imgp->image_header = NULL;
 	imgp->object = NULL;
 	imgp->execlabel = NULL;
-
-	NDINIT(nd, LOOKUP, LOCKLEAF | FOLLOW, UIO_SYSSPACE, file, curthread);
-	if ((error = namei(nd)) != 0) {
-		nd->ni_vp = NULL;
-		goto fail;
-	}
-	NDFREE(nd, NDF_ONLY_PNBUF);
-	imgp->vp = nd->ni_vp;
+	imgp->vp = vp;
 
 	/*
 	 * Check permissions, modes, uid, etc on the file, and "open" it.
@@ -681,9 +664,9 @@
 	 * Also make certain that the interpreter stays the same, so set
 	 * its VV_TEXT flag, too.
 	 */
-	VOP_SET_TEXT(nd->ni_vp);
+	VOP_SET_TEXT(vp);
 
-	imgp->object = nd->ni_vp->v_object;
+	imgp->object = vp->v_object;
 
 	hdr = (const Elf_Ehdr *)imgp->image_header;
 	if ((error = __elfN(check_header)(hdr)) != 0)
@@ -736,17 +719,47 @@
 	if (imgp->firstpage)
 		exec_unmap_first_page(imgp);
 
-	if (nd->ni_vp)
-		vput(nd->ni_vp);
-
+	vput(vp);
 	free(tempdata, M_TEMP);
 
 	return (error);
 }
 
+/*
+ * Load a file into memory as specified by a path.
+ */
+static int
+__elfN(load_path)(struct proc *p, const char *path, u_long *addr,
+	u_long *entry, size_t pagesize)
+{
+	struct nameidata nd;
+	struct vnode *vp = NULL;
+	int error;
+
+#ifdef CAPABILITY_MODE
+	/*
+	 * XXXJA: This check can go away once we are sufficiently confident
+	 * that the checks in namei() are correct.
+	 */
+	if (IN_CAPABILITY_MODE(curthread))
+		return (ECAPMODE);
+#endif
+
+	NDINIT(&nd, LOOKUP, LOCKLEAF | FOLLOW, UIO_SYSSPACE, path, curthread);
+	error = namei(&nd);
+	vp = nd.ni_vp;
+	NDFREE(&nd, NDF_ONLY_PNBUF);
+	if (error != 0) {
+		return (error);
+	}
+
+	return __elfN(load_file)(p, vp, addr, entry, pagesize);
+}
+
 static int
 __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp)
 {
+	cap_rights_t rights;
 	struct thread *td;
 	const Elf_Ehdr *hdr;
 	const Elf_Phdr *phdr;
@@ -760,7 +773,7 @@
 	u_long text_size, data_size, total_size, text_addr, data_addr;
 	u_long seg_size, seg_addr, addr, baddr, et_dyn_addr, entry, proghdr;
 	int32_t osrel;
-	int error, i, n, interp_name_len, have_interp;
+	int error, i, n, interp_fd, interp_name_len, have_interp;
 
 	hdr = (const Elf_Ehdr *)imgp->image_header;
 
@@ -810,6 +823,10 @@
 			break;
 		case PT_INTERP:
 			/* Path to interpreter */
+			if (interp != NULL) {
+				/* fldexec() is overriding the interpreter */
+				break;
+			}
 			if (phdr[i].p_filesz > MAXPATHLEN) {
 				uprintf("Invalid PT_INTERP\n");
 				error = ENOEXEC;
@@ -1007,12 +1024,32 @@
 	if (interp != NULL) {
 		have_interp = FALSE;
 		VOP_UNLOCK(imgp->vp, 0);
+		if ((interp_fd = imgp->args->interpreter) != -1) {
+			/* fldexec() is overriding the interpreter */
+			error = fgetvp_exec(td, interp_fd,
+			    cap_rights_init(&rights, CAP_FEXECVE), &imgp->vp);
+			if (error) {
+				uprintf("failed getting interpreter from FD %d",
+					interp_fd);
+				goto ret;
+			}
+
+			error = vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
+			if (error) {
+				goto ret;
+			}
+
+			error = __elfN(load_file)(imgp->proc, imgp->vp, &addr,
+			    &imgp->entry_addr, sv->sv_pagesize);
+			if (error == 0)
+				have_interp = TRUE;
+		}
 		if (brand_info->emul_path != NULL &&
 		    brand_info->emul_path[0] != '\0') {
 			path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 			snprintf(path, MAXPATHLEN, "%s%s",
 			    brand_info->emul_path, interp);
-			error = __elfN(load_file)(imgp->proc, path, &addr,
+			error = __elfN(load_path)(imgp->proc, path, &addr,
 			    &imgp->entry_addr, sv->sv_pagesize);
 			free(path, M_TEMP);
 			if (error == 0)
@@ -1021,13 +1058,13 @@
 		if (!have_interp && newinterp != NULL &&
 		    (brand_info->interp_path == NULL ||
 		    strcmp(interp, brand_info->interp_path) == 0)) {
-			error = __elfN(load_file)(imgp->proc, newinterp, &addr,
+			error = __elfN(load_path)(imgp->proc, newinterp, &addr,
 			    &imgp->entry_addr, sv->sv_pagesize);
 			if (error == 0)
 				have_interp = TRUE;
 		}
 		if (!have_interp) {
-			error = __elfN(load_file)(imgp->proc, interp, &addr,
+			error = __elfN(load_path)(imgp->proc, interp, &addr,
 			    &imgp->entry_addr, sv->sv_pagesize);
 		}
 		vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
Index: sys/kern/init_sysent.c
===================================================================
--- sys/kern/init_sysent.c
+++ sys/kern/init_sysent.c
@@ -3,7 +3,6 @@
  *
  * DO NOT EDIT-- this file is automatically generated.
  * $FreeBSD$
- * created from FreeBSD: head/sys/kern/syscalls.master 310638 2016-12-27 20:21:11Z jhb
  */
 
 #include "opt_compat.h"
Index: sys/kern/kern_exec.c
===================================================================
--- sys/kern/kern_exec.c
+++ sys/kern/kern_exec.c
@@ -249,6 +249,35 @@
 }
 
 #ifndef _SYS_SYSPROTO_H_
+struct fldexec_args {
+	int	interpreter;
+	int	fd;
+	char	**argv;
+	char	**envv;
+}
+#endif
+int
+sys_fldexec(struct thread *td, struct fldexec_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.interpreter = uap->interpreter;
+		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;
@@ -1169,6 +1198,11 @@
 		return (EFAULT);
 
 	/*
+	 * Don't override the imgact-specified interpreter by default.
+	 */
+	args->interpreter = -1;
+
+	/*
 	 * Allocate demand-paged memory for the file name, argument, and
 	 * environment strings.
 	 */
Index: sys/kern/syscalls.c
===================================================================
--- sys/kern/syscalls.c
+++ sys/kern/syscalls.c
@@ -3,7 +3,6 @@
  *
  * DO NOT EDIT-- this file is automatically generated.
  * $FreeBSD$
- * created from FreeBSD: head/sys/kern/syscalls.master 310638 2016-12-27 20:21:11Z jhb
  */
 
 const char *syscallnames[] = {
Index: sys/kern/syscalls.master
===================================================================
--- sys/kern/syscalls.master
+++ sys/kern/syscalls.master
@@ -995,6 +995,8 @@
 				    id_t id, const struct \
 				    vm_domain_policy_entry *policy); }
 550	AUE_FSYNC	STD	{ int fdatasync(int fd); }
+551	AUE_NULL	STD	{ int fldexec(int interpreter, int fd, \
+				    char **argv, char **envv); }
 
 ; Please copy any additions and changes to the following compatability tables:
 ; sys/compat/freebsd32/syscalls.master
Index: sys/kern/systrace_args.c
===================================================================
--- sys/kern/systrace_args.c
+++ sys/kern/systrace_args.c
@@ -3324,6 +3324,16 @@
 		*n_args = 1;
 		break;
 	}
+	/* fldexec */
+	case 551: {
+		struct fldexec_args *p = params;
+		iarg[0] = p->interpreter; /* int */
+		iarg[1] = p->fd; /* int */
+		uarg[2] = (intptr_t) p->argv; /* char ** */
+		uarg[3] = (intptr_t) p->envv; /* char ** */
+		*n_args = 4;
+		break;
+	}
 	default:
 		*n_args = 0;
 		break;
@@ -8854,6 +8864,25 @@
 			break;
 		};
 		break;
+	/* fldexec */
+	case 551:
+		switch(ndx) {
+		case 0:
+			p = "int";
+			break;
+		case 1:
+			p = "int";
+			break;
+		case 2:
+			p = "userland char **";
+			break;
+		case 3:
+			p = "userland char **";
+			break;
+		default:
+			break;
+		};
+		break;
 	default:
 		break;
 	};
@@ -10770,6 +10799,11 @@
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
+	/* fldexec */
+	case 551:
+		if (ndx == 0 || ndx == 1)
+			p = "int";
+		break;
 	default:
 		break;
 	};
Index: sys/sys/imgact.h
===================================================================
--- sys/sys/imgact.h
+++ sys/sys/imgact.h
@@ -50,6 +50,7 @@
 	int stringspace;	/* space left in arg & env buffer */
 	int argc;		/* count of argument strings */
 	int envc;		/* count of environment strings */
+	int interpreter;	/* descriptor of interpreter to override with */
 	int fd;			/* file descriptor of the executable */
 	struct filedesc *fdp;	/* new file descriptor table */
 };
Index: sys/sys/syscall.h
===================================================================
--- sys/sys/syscall.h
+++ sys/sys/syscall.h
@@ -3,7 +3,7 @@
  *
  * DO NOT EDIT-- this file is automatically generated.
  * $FreeBSD$
- * created from FreeBSD: head/sys/kern/syscalls.master 310638 2016-12-27 20:21:11Z jhb
+ * created fromFreeBSD$
  */
 
 #define	SYS_syscall	0
@@ -468,4 +468,5 @@
 #define	SYS_numa_getaffinity	548
 #define	SYS_numa_setaffinity	549
 #define	SYS_fdatasync	550
-#define	SYS_MAXSYSCALL	551
+#define	SYS_fldexec	551
+#define	SYS_MAXSYSCALL	552
Index: sys/sys/syscall.mk
===================================================================
--- sys/sys/syscall.mk
+++ sys/sys/syscall.mk
@@ -1,7 +1,7 @@
 # FreeBSD system call object files.
 # DO NOT EDIT-- this file is automatically generated.
 # $FreeBSD$
-# created from FreeBSD: head/sys/kern/syscalls.master 310638 2016-12-27 20:21:11Z jhb
+# created fromFreeBSD$
 MIASM =  \
 	syscall.o \
 	exit.o \
@@ -395,4 +395,5 @@
 	utimensat.o \
 	numa_getaffinity.o \
 	numa_setaffinity.o \
-	fdatasync.o
+	fdatasync.o \
+	fldexec.o
Index: sys/sys/sysproto.h
===================================================================
--- sys/sys/sysproto.h
+++ sys/sys/sysproto.h
@@ -3,7 +3,7 @@
  *
  * DO NOT EDIT-- this file is automatically generated.
  * $FreeBSD$
- * created from FreeBSD: head/sys/kern/syscalls.master 310638 2016-12-27 20:21:11Z jhb
+ * created fromFreeBSD$
  */
 
 #ifndef _SYS_SYSPROTO_H_
@@ -1786,6 +1786,12 @@
 struct fdatasync_args {
 	char fd_l_[PADL_(int)]; int fd; char fd_r_[PADR_(int)];
 };
+struct fldexec_args {
+	char interpreter_l_[PADL_(int)]; int interpreter; char interpreter_r_[PADR_(int)];
+	char fd_l_[PADL_(int)]; int fd; char fd_r_[PADR_(int)];
+	char argv_l_[PADL_(char **)]; char ** argv; char argv_r_[PADR_(char **)];
+	char envv_l_[PADL_(char **)]; char ** envv; char envv_r_[PADR_(char **)];
+};
 int	nosys(struct thread *, struct nosys_args *);
 void	sys_sys_exit(struct thread *, struct sys_exit_args *);
 int	sys_fork(struct thread *, struct fork_args *);
@@ -2172,6 +2178,7 @@
 int	sys_numa_getaffinity(struct thread *, struct numa_getaffinity_args *);
 int	sys_numa_setaffinity(struct thread *, struct numa_setaffinity_args *);
 int	sys_fdatasync(struct thread *, struct fdatasync_args *);
+int	sys_fldexec(struct thread *, struct fldexec_args *);
 
 #ifdef COMPAT_43
 
@@ -2949,6 +2956,7 @@
 #define	SYS_AUE_numa_getaffinity	AUE_NULL
 #define	SYS_AUE_numa_setaffinity	AUE_NULL
 #define	SYS_AUE_fdatasync	AUE_FSYNC
+#define	SYS_AUE_fldexec	AUE_NULL
 
 #undef PAD_
 #undef PADL_