diff --git a/usr.bin/gcore/Makefile b/usr.bin/gcore/Makefile
index 664813febb92..7f6a3eed905a 100644
--- a/usr.bin/gcore/Makefile
+++ b/usr.bin/gcore/Makefile
@@ -1,7 +1,8 @@
 #	@(#)Makefile	8.1 (Berkeley) 6/6/93
 
 PROG=	gcore
-SRCS=	gcore.c
+SRCS=	elfcore.c gcore.c
+CFLAGS+=-Wall
 DPADD=	${LIBKVM}
 LDADD=	-lkvm
 
diff --git a/usr.bin/gcore/aoutcore.c b/usr.bin/gcore/aoutcore.c
index 8ab7b0bdbe61..c191a0aa2a68 100644
--- a/usr.bin/gcore/aoutcore.c
+++ b/usr.bin/gcore/aoutcore.c
@@ -42,7 +42,7 @@ static const char copyright[] =
 static char sccsid[] = "@(#)gcore.c	8.2 (Berkeley) 9/23/93";
 #endif
 static const char rcsid[] =
-	"$Id: gcore.c,v 1.9 1998/09/14 10:09:30 des Exp $";
+	"$Id: gcore.c,v 1.10 1998/10/14 16:16:50 jdp Exp $";
 #endif /* not lint */
 
 /*
@@ -81,7 +81,7 @@ static const char rcsid[] =
 
 void	core __P((int, int, struct kinfo_proc *));
 void	datadump __P((int, int, struct proc *, u_long, int));
-void	usage __P((void));
+void	usage __P((void)) __dead2;
 void	userdump __P((int, struct proc *, u_long, int));
 
 kvm_t *kd;
@@ -97,11 +97,12 @@ main(argc, argv)
 	char *argv[];
 {
 	register struct proc *p;
-	struct kinfo_proc *ki;
+	struct kinfo_proc *ki = NULL;
 	struct exec exec;
 	int ch, cnt, efd, fd, pid, sflag, uid;
 	char *binfile, *corefile;
 	char errbuf[_POSIX2_LINE_MAX], fname[MAXPATHLEN + 1];
+	int is_aout;
 
 	sflag = 0;
 	corefile = NULL;
@@ -137,27 +138,53 @@ main(argc, argv)
 		usage();
 	}
 
-	kd = kvm_openfiles(0, 0, 0, O_RDONLY, errbuf);
-	if (kd == NULL)
-		errx(1, "%s", errbuf);
+	efd = open(binfile, O_RDONLY, 0);
+	if (efd < 0)
+		err(1, "%s", binfile);
 
-	uid = getuid();
+	cnt = read(efd, &exec, sizeof(exec));
+	if (cnt != sizeof(exec))
+		errx(1, "%s exec header: %s",
+		    binfile, cnt > 0 ? strerror(EIO) : strerror(errno));
+	if (!N_BADMAG(exec)) {
+		is_aout = 1;
+		/*
+		 * This legacy a.out support uses the kvm interface instead
+		 * of procfs.
+		 */
+		kd = kvm_openfiles(0, 0, 0, O_RDONLY, errbuf);
+		if (kd == NULL)
+			errx(1, "%s", errbuf);
 
-	ki = kvm_getprocs(kd, KERN_PROC_PID, pid, &cnt);
-	if (ki == NULL || cnt != 1)
-		errx(1, "%d: not found", pid);
+		uid = getuid();
 
-	p = &ki->kp_proc;
-	if (ki->kp_eproc.e_pcred.p_ruid != uid && uid != 0)
-		errx(1, "%d: not owner", pid);
+		ki = kvm_getprocs(kd, KERN_PROC_PID, pid, &cnt);
+		if (ki == NULL || cnt != 1)
+			errx(1, "%d: not found", pid);
 
-	if (p->p_stat == SZOMB)
-		errx(1, "%d: zombie", pid);
+		p = &ki->kp_proc;
+		if (ki->kp_eproc.e_pcred.p_ruid != uid && uid != 0)
+			errx(1, "%d: not owner", pid);
 
-	if (p->p_flag & P_WEXIT)
-		errx(1, "%d: process exiting", pid);
-	if (p->p_flag & P_SYSTEM)	/* Swapper or pagedaemon. */
-		errx(1, "%d: system process", pid);
+		if (p->p_stat == SZOMB)
+			errx(1, "%d: zombie", pid);
+
+		if (p->p_flag & P_WEXIT)
+			errx(1, "%d: process exiting", pid);
+		if (p->p_flag & P_SYSTEM)	/* Swapper or pagedaemon. */
+			errx(1, "%d: system process", pid);
+		if (exec.a_text != ptoa(ki->kp_eproc.e_vm.vm_tsize))
+			errx(1, "The executable %s does not belong to"
+			    " process %d!\n"
+			    "Text segment size (in bytes): executable %d,"
+			    " process %d", binfile, pid, exec.a_text, 
+			     ptoa(ki->kp_eproc.e_vm.vm_tsize));
+		data_offset = N_DATOFF(exec);
+	} else if (IS_ELF(*(Elf_Ehdr *)&exec)) {
+		is_aout = 0;
+		close(efd);
+	} else
+		errx(1, "Invalid executable file");
 
 	if (corefile == NULL) {
 		(void)snprintf(fname, sizeof(fname), "core.%d", pid);
@@ -167,36 +194,13 @@ main(argc, argv)
 	if (fd < 0)
 		err(1, "%s", corefile);
 
-	efd = open(binfile, O_RDONLY, 0);
-	if (efd < 0)
-		err(1, "%s", binfile);
-
-	cnt = read(efd, &exec, sizeof(exec));
-	if (cnt != sizeof(exec))
-		errx(1, "%s exec header: %s",
-		    binfile, cnt > 0 ? strerror(EIO) : strerror(errno));
-	if (N_BADMAG(exec)) {
-		const Elf_Ehdr *ehdr = (const Elf_Ehdr *)&exec;
-
-		if (IS_ELF(*ehdr))
-			errx(1, "ELF executables are not supported yet");
-		errx(1, "Invalid executable file");
-	}
-
-	/* check the text segment size of the executable and the process */
-	if (exec.a_text != ptoa(ki->kp_eproc.e_vm.vm_tsize))
-		errx(1, 
-		     "The executable %s does not belong to process %d!\n"
-		     "Text segment size (in bytes): executable %d, process %d",
-		     binfile, pid, exec.a_text, 
-		     ptoa(ki->kp_eproc.e_vm.vm_tsize));
-
-	data_offset = N_DATOFF(exec);
-
 	if (sflag && kill(pid, SIGSTOP) < 0)
 		err(1, "%d: stop signal", pid);
 
-	core(efd, fd, ki);
+	if (is_aout)
+		core(efd, fd, ki);
+	else
+		elf_coredump(fd, pid);
 
 	if (sflag && kill(pid, SIGCONT) < 0)
 		err(1, "%d: continue signal", pid);
diff --git a/usr.bin/gcore/elfcore.c b/usr.bin/gcore/elfcore.c
new file mode 100644
index 000000000000..10538418d877
--- /dev/null
+++ b/usr.bin/gcore/elfcore.c
@@ -0,0 +1,513 @@
+/*-
+ * Copyright (c) 1998 John D. Polstra
+ * 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.
+ *
+ *	$Id$
+ */
+
+#include <sys/param.h>
+#include <sys/lock.h>
+#include <sys/procfs.h>
+#include <vm/vm_param.h>
+#include <vm/vm.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+#include <vm/vm_prot.h>
+#include <elf.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "extern.h"
+
+/*
+ * Code for generating ELF core dumps.
+ */
+
+typedef void (*segment_callback)(vm_map_entry_t, void *);
+
+/* Closure for cb_put_phdr(). */
+struct phdr_closure {
+	Elf_Phdr *phdr;		/* Program header to fill in */
+	Elf_Off offset;		/* Offset of segment in core file */
+};
+
+/* Closure for cb_size_segment(). */
+struct sseg_closure {
+	int count;		/* Count of writable segments. */
+	size_t size;		/* Total size of all writable segments. */
+};
+
+static void cb_put_phdr(vm_map_entry_t, void *);
+static void cb_size_segment(vm_map_entry_t, void *);
+static void each_writable_segment(vm_map_entry_t, segment_callback,
+    void *closure);
+static void elf_corehdr(int fd, pid_t, vm_map_entry_t, int numsegs,
+    void *hdr, size_t hdrsize);
+static void elf_puthdr(vm_map_entry_t, void *, size_t *,
+    const prstatus_t *, const prfpregset_t *, const prpsinfo_t *, int numsegs);
+static void elf_putnote(void *dst, size_t *off, const char *name, int type,
+    const void *desc, size_t descsz);
+static void freemap(vm_map_entry_t);
+static void readhdrinfo(pid_t, prstatus_t *, prfpregset_t *, prpsinfo_t *);
+static vm_map_entry_t readmap(pid_t);
+
+/*
+ * Write an ELF coredump for the given pid to the given fd.
+ */
+void
+elf_coredump(int fd, pid_t pid)
+{
+	vm_map_entry_t map;
+	struct sseg_closure seginfo;
+	void *hdr;
+	size_t hdrsize;
+	char memname[64];
+	int memfd;
+	Elf_Phdr *php;
+	int i;
+
+	/* Get the program's memory map. */
+	map = readmap(pid);
+
+	/* Size the program segments. */
+	seginfo.count = 0;
+	seginfo.size = 0;
+	each_writable_segment(map, cb_size_segment, &seginfo);
+
+	/*
+	 * Calculate the size of the core file header area by making
+	 * a dry run of generating it.  Nothing is written, but the
+	 * size is calculated.
+	 */
+	hdrsize = 0;
+	elf_puthdr(map, (void *)NULL, &hdrsize,
+	    (const prstatus_t *)NULL, (const prfpregset_t *)NULL,
+	    (const prpsinfo_t *)NULL, seginfo.count);
+
+	/*
+	 * Allocate memory for building the header, fill it up,
+	 * and write it out.
+	 */
+	hdr = malloc(hdrsize);
+	if ((hdr = malloc(hdrsize)) == NULL)
+		errx(1, "out of memory");
+	elf_corehdr(fd, pid, map, seginfo.count, hdr, hdrsize);
+
+	/* Write the contents of all of the writable segments. */
+	snprintf(memname, sizeof memname, "/proc/%d/mem", pid);
+	if ((memfd = open(memname, O_RDONLY)) == -1)
+		err(1, "cannot open %s", memname);
+
+	php = (Elf_Phdr *)((char *)hdr + sizeof(Elf_Ehdr)) + 1;
+	for (i = 0;  i < seginfo.count;  i++) {
+		int nleft = php->p_filesz;
+
+		lseek(memfd, (off_t)php->p_vaddr, SEEK_SET);
+		while (nleft > 0) {
+			char buf[8*1024];
+			int nwant;
+			int ngot;
+
+			nwant = nleft;
+			if (nwant > sizeof buf)
+				nwant = sizeof buf;
+			ngot = read(memfd, buf, nwant);
+			if (ngot == -1)
+				err(1, "read from %s", memname);
+			if (ngot < nwant)
+				errx(1, "short read from %s:"
+				    " wanted %d, got %d\n", nwant, ngot);
+			ngot = write(fd, buf, nwant);
+			if (ngot == -1)
+				err(1, "write of segment %d failed", i);
+			if (ngot != nwant)
+				errx(1, "short write");
+			nleft -= nwant;
+		}
+		php++;
+	}
+	close(memfd);
+	free(hdr);
+	freemap(map);
+}
+
+/*
+ * A callback for each_writable_segment() to write out the segment's
+ * program header entry.
+ */
+static void
+cb_put_phdr(vm_map_entry_t entry, void *closure)
+{
+	struct phdr_closure *phc = (struct phdr_closure *)closure;
+	Elf_Phdr *phdr = phc->phdr;
+
+	phc->offset = round_page(phc->offset);
+
+	phdr->p_type = PT_LOAD;
+	phdr->p_offset = phc->offset;
+	phdr->p_vaddr = entry->start;
+	phdr->p_paddr = 0;
+	phdr->p_filesz = phdr->p_memsz = entry->end - entry->start;
+	phdr->p_align = PAGE_SIZE;
+	phdr->p_flags = 0;
+	if (entry->protection & VM_PROT_READ)
+		phdr->p_flags |= PF_R;
+	if (entry->protection & VM_PROT_WRITE)
+		phdr->p_flags |= PF_W;
+	if (entry->protection & VM_PROT_EXECUTE)
+		phdr->p_flags |= PF_X;
+
+	phc->offset += phdr->p_filesz;
+	phc->phdr++;
+}
+
+/*
+ * A callback for each_writable_segment() to gather information about
+ * the number of segments and their total size.
+ */
+static void
+cb_size_segment(vm_map_entry_t entry, void *closure)
+{
+	struct sseg_closure *ssc = (struct sseg_closure *)closure;
+
+	ssc->count++;
+	ssc->size += entry->end - entry->start;
+}
+
+/*
+ * For each segment in the given memory map, call the given function
+ * with a pointer to the map entry and some arbitrary caller-supplied
+ * data.
+ */
+static void
+each_writable_segment(vm_map_entry_t map, segment_callback func, void *closure)
+{
+	vm_map_entry_t entry;
+
+	for (entry = map;  entry != NULL;  entry = entry->next)
+		(*func)(entry, closure);
+}
+
+/*
+ * Write the core file header to the file, including padding up to
+ * the page boundary.
+ */
+static void
+elf_corehdr(int fd, pid_t pid, vm_map_entry_t map, int numsegs, void *hdr,
+    size_t hdrsize)
+{
+	size_t off;
+	prstatus_t status;
+	prfpregset_t fpregset;
+	prpsinfo_t psinfo;
+
+	/* Gather the information for the header. */
+	readhdrinfo(pid, &status, &fpregset, &psinfo);
+
+	/* Fill in the header. */
+	memset(hdr, 0, hdrsize);
+	off = 0;
+	elf_puthdr(map, hdr, &off, &status, &fpregset, &psinfo, numsegs);
+
+	/* Write it to the core file. */
+	if (write(fd, hdr, hdrsize) == -1)
+		err(1, "write");
+}
+
+/*
+ * Generate the ELF coredump header into the buffer at "dst".  "dst" may
+ * be NULL, in which case the header is sized but not actually generated.
+ */
+static void
+elf_puthdr(vm_map_entry_t map, void *dst, size_t *off, const prstatus_t *status,
+    const prfpregset_t *fpregset, const prpsinfo_t *psinfo, int numsegs)
+{
+	size_t ehoff;
+	size_t phoff;
+	size_t noteoff;
+	size_t notesz;
+
+	ehoff = *off;
+	*off += sizeof(Elf_Ehdr);
+
+	phoff = *off;
+	*off += (numsegs + 1) * sizeof(Elf_Phdr);
+
+	noteoff = *off;
+	elf_putnote(dst, off, "FreeBSD", NT_PRSTATUS, status,
+	    sizeof *status);
+	elf_putnote(dst, off, "FreeBSD", NT_FPREGSET, fpregset,
+	    sizeof *fpregset);
+	elf_putnote(dst, off, "FreeBSD", NT_PRPSINFO, psinfo,
+	    sizeof *psinfo);
+	notesz = *off - noteoff;
+
+	/* Align up to a page boundary for the program segments. */
+	*off = round_page(*off);
+
+	if (dst != NULL) {
+		Elf_Ehdr *ehdr;
+		Elf_Phdr *phdr;
+		struct phdr_closure phc;
+
+		/*
+		 * Fill in the ELF header.
+		 */
+		ehdr = (Elf_Ehdr *)((char *)dst + ehoff);
+		ehdr->e_ident[EI_MAG0] = ELFMAG0;
+		ehdr->e_ident[EI_MAG1] = ELFMAG1;
+		ehdr->e_ident[EI_MAG2] = ELFMAG2;
+		ehdr->e_ident[EI_MAG3] = ELFMAG3;
+		ehdr->e_ident[EI_CLASS] = ELF_CLASS;
+		ehdr->e_ident[EI_DATA] = ELF_DATA;
+		ehdr->e_ident[EI_VERSION] = EV_CURRENT;
+		ehdr->e_ident[EI_PAD] = 0;
+		strncpy(ehdr->e_ident + EI_BRAND, "FreeBSD",
+		    EI_NIDENT - EI_BRAND);
+		ehdr->e_type = ET_CORE;
+		ehdr->e_machine = ELF_ARCH;
+		ehdr->e_version = EV_CURRENT;
+		ehdr->e_entry = 0;
+		ehdr->e_phoff = phoff;
+		ehdr->e_flags = 0;
+		ehdr->e_ehsize = sizeof(Elf_Ehdr);
+		ehdr->e_phentsize = sizeof(Elf_Phdr);
+		ehdr->e_phnum = numsegs + 1;
+		ehdr->e_shentsize = sizeof(Elf_Shdr);
+		ehdr->e_shnum = 0;
+		ehdr->e_shstrndx = SHN_UNDEF;
+
+		/*
+		 * Fill in the program header entries.
+		 */
+		phdr = (Elf_Phdr *)((char *)dst + phoff);
+
+		/* The note segement. */
+		phdr->p_type = PT_NOTE;
+		phdr->p_offset = noteoff;
+		phdr->p_vaddr = 0;
+		phdr->p_paddr = 0;
+		phdr->p_filesz = notesz;
+		phdr->p_memsz = 0;
+		phdr->p_flags = 0;
+		phdr->p_align = 0;
+		phdr++;
+
+		/* All the writable segments from the program. */
+		phc.phdr = phdr;
+		phc.offset = *off;
+		each_writable_segment(map, cb_put_phdr, &phc);
+	}
+}
+
+/*
+ * Emit one note section to "dst", or just size it if "dst" is NULL.
+ */
+static void
+elf_putnote(void *dst, size_t *off, const char *name, int type,
+    const void *desc, size_t descsz)
+{
+	Elf_Note note;
+
+	note.n_namesz = strlen(name) + 1;
+	note.n_descsz = descsz;
+	note.n_type = type;
+	if (dst != NULL)
+		bcopy(&note, (char *)dst + *off, sizeof note);
+	*off += sizeof note;
+	if (dst != NULL)
+		bcopy(name, (char *)dst + *off, note.n_namesz);
+	*off += roundup2(note.n_namesz, sizeof(Elf_Size));
+	if (dst != NULL)
+		bcopy(desc, (char *)dst + *off, note.n_descsz);
+	*off += roundup2(note.n_descsz, sizeof(Elf_Size));
+}
+
+/*
+ * Free the memory map.
+ */
+static void
+freemap(vm_map_entry_t map)
+{
+	while (map != NULL) {
+		vm_map_entry_t next = map->next;
+		free(map);
+		map = next;
+	}
+}
+
+/*
+ * Read the process information necessary to fill in the core file's header.
+ */
+static void
+readhdrinfo(pid_t pid, prstatus_t *status, prfpregset_t *fpregset,
+    prpsinfo_t *psinfo)
+{
+	char name[64];
+	char line[256];
+	int fd;
+	int i;
+	int n;
+
+	memset(status, 0, sizeof *status);
+	status->pr_version = PRSTATUS_VERSION;
+	status->pr_statussz = sizeof(prstatus_t);
+	status->pr_gregsetsz = sizeof(gregset_t);
+	status->pr_fpregsetsz = sizeof(fpregset_t);
+	status->pr_osreldate = __FreeBSD_version;
+	status->pr_pid = pid;
+
+	memset(fpregset, 0, sizeof *fpregset);
+
+	memset(psinfo, 0, sizeof *psinfo);
+	psinfo->pr_version = PRPSINFO_VERSION;
+	psinfo->pr_psinfosz = sizeof(prpsinfo_t);
+
+	/* Read the general registers. */
+	snprintf(name, sizeof name, "/proc/%d/regs", pid);
+	if ((fd = open(name, O_RDONLY)) == -1)
+		err(1, "cannot open %s", name);
+	if ((n = read(fd, &status->pr_reg, sizeof status->pr_reg)) == -1)
+		err(1, "read error from %s", name);
+	if (n < sizeof status->pr_reg)
+		errx(1, "short read from %s: wanted %u, got %d", name,
+		    sizeof status->pr_reg, n);
+	close(fd);
+
+	/* Read the floating point registers. */
+	snprintf(name, sizeof name, "/proc/%d/fpregs", pid);
+	if ((fd = open(name, O_RDONLY)) == -1)
+		err(1, "cannot open %s", name);
+	if ((n = read(fd, fpregset, sizeof *fpregset)) == -1)
+		err(1, "read error from %s", name);
+	if (n < sizeof *fpregset)
+		errx(1, "short read from %s: wanted %u, got %d", name,
+		    sizeof *fpregset, n);
+	close(fd);
+
+	/* Read and parse the process status. */
+	snprintf(name, sizeof name, "/proc/%d/status", pid);
+	if ((fd = open(name, O_RDONLY)) == -1)
+		err(1, "cannot open %s", name);
+	if ((n = read(fd, line, sizeof line - 1)) == -1)
+		err(1, "read error from %s", name);
+	if (n > MAXCOMLEN)
+		n = MAXCOMLEN;
+	for (i = 0;  i < n && line[i] != ' ';  i++)
+		psinfo->pr_fname[i] = line[i];
+	strncpy(psinfo->pr_psargs, psinfo->pr_fname, PRARGSZ);
+	close(fd);
+}
+
+/*
+ * Read the process's memory map using procfs, and return a list of
+ * VM map entries.  Only the non-device read/writable segments are
+ * returned.  The map entries in the list aren't fully filled in; only
+ * the items we need are present.
+ */
+static vm_map_entry_t
+readmap(pid_t pid)
+{
+	char mapname[64];
+	int mapfd;
+	ssize_t mapsize;
+	size_t bufsize;
+	char *mapbuf;
+	int pos;
+	vm_map_entry_t map;
+	vm_map_entry_t *linkp;
+
+	snprintf(mapname, sizeof mapname, "/proc/%d/map", pid);
+	if ((mapfd = open(mapname, O_RDONLY)) == -1)
+		err(1, "cannot open %s", mapname);
+
+	/*
+	 * Procfs requires (for consistency) that the entire memory map
+	 * be read with a single read() call.  Start with a reasonbly sized
+	 * buffer, and double it until it is big enough.
+	 */
+	bufsize = 8 * 1024;
+	mapbuf = NULL;
+	for ( ; ; ) {
+		if ((mapbuf = realloc(mapbuf, bufsize)) == NULL)
+			errx(1, "out of memory");
+		mapsize = read(mapfd, mapbuf, bufsize);
+		if (mapsize != -1 || errno != EFBIG)
+			break;
+		bufsize *= 2;
+		/* This lseek shouldn't be necessary, but it is. */
+		lseek(mapfd, (off_t)0, SEEK_SET);
+	}
+	if (mapsize == -1)
+		err(1, "read error from %s", mapname);
+	if (mapsize == 0)
+		errx(1, "empty map file %s", mapname);
+	close(mapfd);
+
+	pos = 0;
+	map = NULL;
+	linkp = &map;
+	while (pos < mapsize) {
+		vm_map_entry_t ent;
+		vm_offset_t start;
+		vm_offset_t end;
+		char prot[4];
+		char type[16];
+		int n;
+		int len;
+
+		len = 0;
+		n = sscanf(mapbuf + pos, "%x %x %*d %*d %*d %3[-rwx]"
+		    " %*d %*d %*x %*s %*s %16s%*[\n]%n",
+		    &start, &end, prot, type, &len);
+		if (n != 4)
+			errx(1, "ill-formed line in %s", mapname);
+		pos += len;
+
+		/* Ignore segments of the wrong kind, and unwritable ones */
+		if (strncmp(prot, "rw", 2) != 0 ||
+		    (strcmp(type, "default") != 0 &&
+		    strcmp(type, "vnode") != 0 &&
+		    strcmp(type, "swap") != 0))
+			continue;
+
+		if ((ent = (vm_map_entry_t)calloc(1, sizeof *ent)) == NULL)
+			errx(1, "out of memory");
+		ent->start = start;
+		ent->end = end;
+		ent->protection = VM_PROT_READ | VM_PROT_WRITE;
+		if (prot[2] == 'x')
+		    ent->protection |= VM_PROT_EXECUTE;
+
+		*linkp = ent;
+		linkp = &ent->next;
+	}
+	free(mapbuf);
+	return map;
+}
diff --git a/usr.bin/gcore/extern.h b/usr.bin/gcore/extern.h
index 3dccafe70845..f157e531a5f3 100644
--- a/usr.bin/gcore/extern.h
+++ b/usr.bin/gcore/extern.h
@@ -33,5 +33,9 @@
  *	@(#)extern.h	8.1 (Berkeley) 6/6/93
  */
 
+#include <sys/types.h>
+#include <kvm.h>
+
 void	err __P((int, const char *, ...));
+void	elf_coredump __P((int, pid_t));
 void	md_core __P((kvm_t *, int, struct kinfo_proc *));
diff --git a/usr.bin/gcore/gcore.c b/usr.bin/gcore/gcore.c
index 8ab7b0bdbe61..c191a0aa2a68 100644
--- a/usr.bin/gcore/gcore.c
+++ b/usr.bin/gcore/gcore.c
@@ -42,7 +42,7 @@ static const char copyright[] =
 static char sccsid[] = "@(#)gcore.c	8.2 (Berkeley) 9/23/93";
 #endif
 static const char rcsid[] =
-	"$Id: gcore.c,v 1.9 1998/09/14 10:09:30 des Exp $";
+	"$Id: gcore.c,v 1.10 1998/10/14 16:16:50 jdp Exp $";
 #endif /* not lint */
 
 /*
@@ -81,7 +81,7 @@ static const char rcsid[] =
 
 void	core __P((int, int, struct kinfo_proc *));
 void	datadump __P((int, int, struct proc *, u_long, int));
-void	usage __P((void));
+void	usage __P((void)) __dead2;
 void	userdump __P((int, struct proc *, u_long, int));
 
 kvm_t *kd;
@@ -97,11 +97,12 @@ main(argc, argv)
 	char *argv[];
 {
 	register struct proc *p;
-	struct kinfo_proc *ki;
+	struct kinfo_proc *ki = NULL;
 	struct exec exec;
 	int ch, cnt, efd, fd, pid, sflag, uid;
 	char *binfile, *corefile;
 	char errbuf[_POSIX2_LINE_MAX], fname[MAXPATHLEN + 1];
+	int is_aout;
 
 	sflag = 0;
 	corefile = NULL;
@@ -137,27 +138,53 @@ main(argc, argv)
 		usage();
 	}
 
-	kd = kvm_openfiles(0, 0, 0, O_RDONLY, errbuf);
-	if (kd == NULL)
-		errx(1, "%s", errbuf);
+	efd = open(binfile, O_RDONLY, 0);
+	if (efd < 0)
+		err(1, "%s", binfile);
 
-	uid = getuid();
+	cnt = read(efd, &exec, sizeof(exec));
+	if (cnt != sizeof(exec))
+		errx(1, "%s exec header: %s",
+		    binfile, cnt > 0 ? strerror(EIO) : strerror(errno));
+	if (!N_BADMAG(exec)) {
+		is_aout = 1;
+		/*
+		 * This legacy a.out support uses the kvm interface instead
+		 * of procfs.
+		 */
+		kd = kvm_openfiles(0, 0, 0, O_RDONLY, errbuf);
+		if (kd == NULL)
+			errx(1, "%s", errbuf);
 
-	ki = kvm_getprocs(kd, KERN_PROC_PID, pid, &cnt);
-	if (ki == NULL || cnt != 1)
-		errx(1, "%d: not found", pid);
+		uid = getuid();
 
-	p = &ki->kp_proc;
-	if (ki->kp_eproc.e_pcred.p_ruid != uid && uid != 0)
-		errx(1, "%d: not owner", pid);
+		ki = kvm_getprocs(kd, KERN_PROC_PID, pid, &cnt);
+		if (ki == NULL || cnt != 1)
+			errx(1, "%d: not found", pid);
 
-	if (p->p_stat == SZOMB)
-		errx(1, "%d: zombie", pid);
+		p = &ki->kp_proc;
+		if (ki->kp_eproc.e_pcred.p_ruid != uid && uid != 0)
+			errx(1, "%d: not owner", pid);
 
-	if (p->p_flag & P_WEXIT)
-		errx(1, "%d: process exiting", pid);
-	if (p->p_flag & P_SYSTEM)	/* Swapper or pagedaemon. */
-		errx(1, "%d: system process", pid);
+		if (p->p_stat == SZOMB)
+			errx(1, "%d: zombie", pid);
+
+		if (p->p_flag & P_WEXIT)
+			errx(1, "%d: process exiting", pid);
+		if (p->p_flag & P_SYSTEM)	/* Swapper or pagedaemon. */
+			errx(1, "%d: system process", pid);
+		if (exec.a_text != ptoa(ki->kp_eproc.e_vm.vm_tsize))
+			errx(1, "The executable %s does not belong to"
+			    " process %d!\n"
+			    "Text segment size (in bytes): executable %d,"
+			    " process %d", binfile, pid, exec.a_text, 
+			     ptoa(ki->kp_eproc.e_vm.vm_tsize));
+		data_offset = N_DATOFF(exec);
+	} else if (IS_ELF(*(Elf_Ehdr *)&exec)) {
+		is_aout = 0;
+		close(efd);
+	} else
+		errx(1, "Invalid executable file");
 
 	if (corefile == NULL) {
 		(void)snprintf(fname, sizeof(fname), "core.%d", pid);
@@ -167,36 +194,13 @@ main(argc, argv)
 	if (fd < 0)
 		err(1, "%s", corefile);
 
-	efd = open(binfile, O_RDONLY, 0);
-	if (efd < 0)
-		err(1, "%s", binfile);
-
-	cnt = read(efd, &exec, sizeof(exec));
-	if (cnt != sizeof(exec))
-		errx(1, "%s exec header: %s",
-		    binfile, cnt > 0 ? strerror(EIO) : strerror(errno));
-	if (N_BADMAG(exec)) {
-		const Elf_Ehdr *ehdr = (const Elf_Ehdr *)&exec;
-
-		if (IS_ELF(*ehdr))
-			errx(1, "ELF executables are not supported yet");
-		errx(1, "Invalid executable file");
-	}
-
-	/* check the text segment size of the executable and the process */
-	if (exec.a_text != ptoa(ki->kp_eproc.e_vm.vm_tsize))
-		errx(1, 
-		     "The executable %s does not belong to process %d!\n"
-		     "Text segment size (in bytes): executable %d, process %d",
-		     binfile, pid, exec.a_text, 
-		     ptoa(ki->kp_eproc.e_vm.vm_tsize));
-
-	data_offset = N_DATOFF(exec);
-
 	if (sflag && kill(pid, SIGSTOP) < 0)
 		err(1, "%d: stop signal", pid);
 
-	core(efd, fd, ki);
+	if (is_aout)
+		core(efd, fd, ki);
+	else
+		elf_coredump(fd, pid);
 
 	if (sflag && kill(pid, SIGCONT) < 0)
 		err(1, "%d: continue signal", pid);