Index: libexec/rtld-elf/rtld.c
===================================================================
--- libexec/rtld-elf/rtld.c
+++ libexec/rtld-elf/rtld.c
@@ -384,6 +384,7 @@
     caddr_t imgentry;
     char buf[MAXPATHLEN];
     int argc, fd, i, phnum, rtld_argc;
+    int bsdflags;
 #ifdef __powerpc__
     int old_auxv_format = 1;
 #endif
@@ -445,11 +446,15 @@
     main_argc = argc;
     main_argv = argv;
 
-    if (aux_info[AT_BSDFLAGS] != NULL &&
-	(aux_info[AT_BSDFLAGS]->a_un.a_val & ELF_BSDF_SIGFASTBLK) != 0)
-	    ld_fast_sigblock = true;
-
-    trust = !issetugid();
+    bsdflags = 0;
+    if (aux_info[AT_BSDFLAGS] != NULL)
+	bsdflags = aux_info[AT_BSDFLAGS]->a_un.a_val;
+    if ((bsdflags & ELF_BSDF_SIGFASTBLK) != 0)
+	ld_fast_sigblock = true;
+    if ((bsdflags & ELF_BSDF_ISSETUGID_PASSED) != 0)
+	trust = (bsdflags & ELF_BSDF_ISSETUGID) == 0;
+    else
+	trust = !issetugid();
 
     md_abi_variant_hook(aux_info);
 
Index: sys/kern/imgact_elf.c
===================================================================
--- sys/kern/imgact_elf.c
+++ sys/kern/imgact_elf.c
@@ -69,6 +69,7 @@
 #include <sys/sysent.h>
 #include <sys/vnode.h>
 #include <sys/syslog.h>
+#include <sys/syscallsubr.h>
 #include <sys/eventhandler.h>
 #include <sys/user.h>
 
@@ -1332,7 +1333,7 @@
 {
 	Elf_Auxargs *args = (Elf_Auxargs *)imgp->auxargs;
 	Elf_Auxinfo *argarray, *pos;
-	int error;
+	int error, bsdflags;
 
 	argarray = pos = malloc(AT_COUNT * sizeof(*pos), M_TEMP,
 	    M_WAITOK | M_ZERO);
@@ -1371,8 +1372,13 @@
 		AUXARGS_ENTRY(pos, AT_HWCAP, *imgp->sysent->sv_hwcap);
 	if (imgp->sysent->sv_hwcap2 != NULL)
 		AUXARGS_ENTRY(pos, AT_HWCAP2, *imgp->sysent->sv_hwcap2);
-	AUXARGS_ENTRY(pos, AT_BSDFLAGS, __elfN(sigfastblock) ?
-	    ELF_BSDF_SIGFASTBLK : 0);
+	bsdflags = 0;
+	if (__elfN(sigfastblock))
+		bsdflags |= ELF_BSDF_SIGFASTBLK;
+	bsdflags |= ELF_BSDF_ISSETUGID_PASSED;
+	if (kern_issetugid(imgp->proc))
+		bsdflags |= ELF_BSDF_ISSETUGID;
+	AUXARGS_ENTRY(pos, AT_BSDFLAGS, bsdflags);
 	AUXARGS_ENTRY(pos, AT_NULL, 0);
 
 	free(imgp->auxargs, M_TEMP);
Index: sys/kern/kern_prot.c
===================================================================
--- sys/kern/kern_prot.c
+++ sys/kern/kern_prot.c
@@ -1218,6 +1218,21 @@
 	return (error1 ? error1 : error2 ? error2 : error3);
 }
 
+int
+kern_issetugid(struct proc *p)
+
+{
+	/*
+	 * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
+	 * we use P_SUGID because we consider changing the owners as
+	 * "tainting" as well.
+	 * This is significant for procs that start as root and "become"
+	 * a user without an exec - programs cannot know *everything*
+	 * that libc *might* have put in their data segment.
+	 */
+	return ((p->p_flag & P_SUGID) != 0);
+}
+
 #ifndef _SYS_SYSPROTO_H_
 struct issetugid_args {
 	int dummy;
@@ -1229,15 +1244,7 @@
 {
 	struct proc *p = td->td_proc;
 
-	/*
-	 * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
-	 * we use P_SUGID because we consider changing the owners as
-	 * "tainting" as well.
-	 * This is significant for procs that start as root and "become"
-	 * a user without an exec - programs cannot know *everything*
-	 * that libc *might* have put in their data segment.
-	 */
-	td->td_retval[0] = (p->p_flag & P_SUGID) ? 1 : 0;
+	td->td_retval[0] = kern_issetugid(p);
 	return (0);
 }
 
Index: sys/sys/elf_common.h
===================================================================
--- sys/sys/elf_common.h
+++ sys/sys/elf_common.h
@@ -1458,5 +1458,7 @@
 #define	R_X86_64_IRELATIVE	37
 
 #define	ELF_BSDF_SIGFASTBLK	0x0001	/* Kernel supports fast sigblock */
+#define	ELF_BSDF_ISSETUGID_PASSED 0x0002
+#define	ELF_BSDF_ISSETUGID	0x0004	/* The process changed privileges without exec */
 
 #endif /* !_SYS_ELF_COMMON_H_ */
Index: sys/sys/syscallsubr.h
===================================================================
--- sys/sys/syscallsubr.h
+++ sys/sys/syscallsubr.h
@@ -149,6 +149,7 @@
 int	kern_getsockopt(struct thread *td, int s, int level, int name,
 	    void *optval, enum uio_seg valseg, socklen_t *valsize);
 int	kern_ioctl(struct thread *td, int fd, u_long com, caddr_t data);
+int	kern_issetugid(struct proc *p);
 int	kern_jail(struct thread *td, struct jail *j);
 int	kern_jail_get(struct thread *td, struct uio *options, int flags);
 int	kern_jail_set(struct thread *td, struct uio *options, int flags);