install: Always use a temporary file.

Previously, we would only use a temporary file if explicitly asked to
with the `-S` option, and even then, only if the target file already
existed.  This meant that an outside observer looking for the target
file might see a partial file, and might see the file disappear and
then reappear.

With this patch, we always use a temporary file, ensuring atomicity.
The downside is slightly increased disk usage.  The upside is never
having to worry about, for instance, cron jobs randomly failing if
they happen to run simultaneously with `make installworld`.

The `-S` option is retained, partly for compatibility, and partly
to control the use of `fsync(2)`, which has a non-negligible cost
(approximately 10% increase in wall time for `make installworld`).

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	0mp, brooks, imp, markj
Differential Revision:	https://reviews.freebsd.org/D44742

(cherry picked from commit e5035d08578e372d40b4e2d4c3574b7583549bd6)

install: Simplify path construction.

There's no need to copy the path twice to split it into base and dir.
We simply call `basename()` first, then handle the two trivial cases in
which it isn't safe to call `dirname()`.

While here, add an early check that the destination is not an empty
string.  This would always fail eventually, so it may as well fail
right away.  Also add a test case for this shortcut.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D44743

(cherry picked from commit 17dc7017d7375b3463d65adffe1eb980b0f86795)

install: Remove the mmap(2) option.

We already removed it from cp(1) over a year ago but never followed up
here.  Do so now, for the same reasons: significant complexity for
little to no benefit.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D44809

(cherry picked from commit a0439a1b820fa0e742c00d095f5f5c06f5f19432)

install: Assorted nitpickery.

* Use `errc()` instead of manually setting `errno` before calling `err()`.
* Change one warning into a fatal error.
* Drop some unnecessary casts.
* `strlcat()` bounds checks were off-by-one.  This does not matter in
  practice because the subsequent code renders an overrun harmless.
* We were passing `SSIZE_MAX` to `copy_file_range()` instead of the
  requested size.  This only matters if we're asked to install a file
  which is still being written to while we are copying it.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D44810

(cherry picked from commit 000a533e6d1db9878296b32d1cc212e11a2cc718)

3 files changed, 142 insertions, 304 deletions

diff --git a/usr.bin/xinstall/install.1 b/usr.bin/xinstall/install.1
index 346b0f428121..193892c4a2b9 100644
--- a/usr.bin/xinstall/install.1
+++ b/usr.bin/xinstall/install.1
@@ -27,7 +27,7 @@
 .\"
 .\"	From: @(#)install.1	8.1 (Berkeley) 6/6/93
 .\"
-.Dd August 4, 2022
+.Dd April 16, 2024
 .Dt INSTALL 1
 .Os
 .Sh NAME
@@ -227,16 +227,18 @@ Copy the file, as if the
 except if the target file does not already exist or is different,
 then preserve the access and modification times of the source file.
 .It Fl S
-Safe copy.
-Normally,
+Flush each file to disk after copying.
+This has a non-negligible impact on performance, but reduces the risk
+of being left with a partial file if the system crashes or loses power
+shortly after
 .Nm
-unlinks an existing target before installing the new file.
-With the
+runs.
+.Pp
+Historically,
 .Fl S
-flag a temporary file is used and then renamed to be
-the target.
-The reason this is safer is that if the copy or
-rename fails, the existing target is left untouched.
+also enabled the use of temporary files to ensure atomicity when
+replacing an existing target.
+Temporary files are no longer optional.
 .It Fl s
 .Nm
 exec's the command
@@ -302,15 +304,7 @@ Ports Collection.
 .Sh FILES
 .Bl -tag -width "INS@XXXXXX" -compact
 .It Pa INS@XXXXXX
-If either
-.Fl S
-option is specified, or the
-.Fl C
-or
-.Fl p
-option is used in conjunction with the
-.Fl s
-option, temporary files named
+Temporary files named
 .Pa INS@XXXXXX ,
 where
 .Pa XXXXXX
@@ -333,7 +327,6 @@ The default was changed to copy in
 .Xr cp 1 ,
 .Xr mv 1 ,
 .Xr strip 1 ,
-.Xr mmap 2 ,
 .Xr getgrnam 3 ,
 .Xr getpwnam 3 ,
 .Xr chown 8
diff --git a/usr.bin/xinstall/tests/install_test.sh b/usr.bin/xinstall/tests/install_test.sh
index cbe95f0dfbf3..b35706521ec3 100755
--- a/usr.bin/xinstall/tests/install_test.sh
+++ b/usr.bin/xinstall/tests/install_test.sh
@@ -25,6 +25,13 @@
 #
 #
 
+atf_test_case copy_to_empty
+copy_to_empty_body() {
+	printf 'test\n123\r456\r\n789\0z' >testf
+	atf_check -s not-exit:0 -e match:"empty string" \
+	    install testf ""
+}
+
 copy_to_nonexistent_with_opts() {
 	printf 'test\n123\r456\r\n789\0z' >testf
 	atf_check install "$@" testf copyf
@@ -497,6 +504,7 @@ set_optional_exec_body()
 }
 
 atf_init_test_cases() {
+	atf_add_test_case copy_to_empty
 	atf_add_test_case copy_to_nonexistent
 	atf_add_test_case copy_to_nonexistent_safe
 	atf_add_test_case copy_to_nonexistent_comparing
diff --git a/usr.bin/xinstall/xinstall.c b/usr.bin/xinstall/xinstall.c
index f1fe1a969377..efd37150246b 100644
--- a/usr.bin/xinstall/xinstall.c
+++ b/usr.bin/xinstall/xinstall.c
@@ -42,10 +42,6 @@ static char sccsid[] = "@(#)xinstall.c	8.1 (Berkeley) 7/21/93";
 #endif /* not lint */
 #endif
 
-#include <sys/cdefs.h>
-#include <sys/param.h>
-#include <sys/mman.h>
-#include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/wait.h>
@@ -157,7 +153,6 @@ static char *destdir, *digest, *fflags, *metafile, *tags;
 static int	compare(int, const char *, size_t, int, const char *, size_t,
 		    char **);
 static char	*copy(int, const char *, int, const char *, off_t);
-static int	create_newfile(const char *, int, struct stat *);
 static int	create_tempfile(const char *, char *, size_t);
 static char	*quiet_mktemp(char *template);
 static char	*digest_file(const char *);
@@ -173,7 +168,6 @@ static void	metadata_log(const char *, const char *, struct timespec *,
 		    const char *, const char *, off_t);
 static int	parseid(const char *, id_t *);
 static int	strip(const char *, int, const char *, char **);
-static int	trymmap(size_t);
 static void	usage(void);
 
 int
@@ -341,10 +335,6 @@ main(int argc, char *argv[])
 		}
 	}
 
-	/* need to make a temp copy so we can compare stripped version */
-	if (docompare && dostrip)
-		safecopy = 1;
-
 	/* get group and owner id's */
 	if (group != NULL && !dounpriv) {
 		if (gid_from_group(group, &gid) == -1) {
@@ -393,8 +383,8 @@ main(int argc, char *argv[])
 				err(EX_OSERR, "%s vanished", to_name);
 			if (S_ISLNK(to_sb.st_mode)) {
 				if (argc != 2) {
-					errno = ENOTDIR;
-					err(EX_USAGE, "%s", to_name);
+					errc(EX_CANTCREAT, ENOTDIR, "%s",
+					    to_name);
 				}
 				install(*argv, to_name, fset, iflags);
 				exit(EX_OK);
@@ -420,14 +410,13 @@ main(int argc, char *argv[])
 	if (!no_target && !dolink) {
 		if (stat(*argv, &from_sb))
 			err(EX_OSERR, "%s", *argv);
-		if (!S_ISREG(to_sb.st_mode)) {
-			errno = EFTYPE;
-			err(EX_OSERR, "%s", to_name);
-		}
+		if (!S_ISREG(to_sb.st_mode))
+			errc(EX_CANTCREAT, EFTYPE, "%s", to_name);
 		if (to_sb.st_dev == from_sb.st_dev &&
-		    to_sb.st_ino == from_sb.st_ino)
-			errx(EX_USAGE, 
-			    "%s and %s are the same file", *argv, to_name);
+		    to_sb.st_ino == from_sb.st_ino) {
+			errx(EX_USAGE, "%s and %s are the same file",
+			    *argv, to_name);
+		}
 	}
 	install(*argv, to_name, fset, iflags);
 	exit(EX_OK);
@@ -585,7 +574,7 @@ do_link(const char *from_name, const char *to_name,
 	char tmpl[MAXPATHLEN];
 	int ret;
 
-	if (safecopy && target_sb != NULL) {
+	if (target_sb != NULL) {
 		(void)snprintf(tmpl, sizeof(tmpl), "%s.inst.XXXXXX", to_name);
 		/* This usage is safe. */
 		if (quiet_mktemp(tmpl) == NULL)
@@ -632,7 +621,7 @@ do_symlink(const char *from_name, const char *to_name,
 {
 	char tmpl[MAXPATHLEN];
 
-	if (safecopy && target_sb != NULL) {
+	if (target_sb != NULL) {
 		(void)snprintf(tmpl, sizeof(tmpl), "%s.inst.XXXXXX", to_name);
 		/* This usage is safe. */
 		if (quiet_mktemp(tmpl) == NULL)
@@ -675,8 +664,10 @@ static void
 makelink(const char *from_name, const char *to_name,
     const struct stat *target_sb)
 {
-	char	src[MAXPATHLEN], dst[MAXPATHLEN], lnk[MAXPATHLEN];
-	struct stat	to_sb;
+	char src[MAXPATHLEN], dst[MAXPATHLEN], lnk[MAXPATHLEN];
+	char *to_name_copy, *d, *ld, *ls, *s;
+	const char *base, *dir;
+	struct stat to_sb;
 
 	/* Try hard links first. */
 	if (dolink & (LN_HARD|LN_MIXED)) {
@@ -737,8 +728,6 @@ makelink(const char *from_name, const char *to_name,
 	}
 
 	if (dolink & LN_RELATIVE) {
-		char *to_name_copy, *cp, *d, *ld, *ls, *s;
-
 		if (*from_name != '/') {
 			/* this is already a relative link */
 			do_symlink(from_name, to_name, target_sb);
@@ -758,17 +747,23 @@ makelink(const char *from_name, const char *to_name,
 		to_name_copy = strdup(to_name);
 		if (to_name_copy == NULL)
 			err(EX_OSERR, "%s: strdup", to_name);
-		cp = dirname(to_name_copy);
-		if (realpath(cp, dst) == NULL)
-			err(EX_OSERR, "%s: realpath", cp);
-		/* .. and add the last component. */
-		if (strcmp(dst, "/") != 0) {
-			if (strlcat(dst, "/", sizeof(dst)) > sizeof(dst))
+		base = basename(to_name_copy);
+		if (base == to_name_copy) {
+			/* destination is a file in cwd */
+			(void)strlcpy(dst, "./", sizeof(dst));
+		} else if (base == to_name_copy + 1) {
+			/* destination is a file in the root */
+			(void)strlcpy(dst, "/", sizeof(dst));
+		} else {
+			/* all other cases: safe to call dirname() */
+			dir = dirname(to_name_copy);
+			if (realpath(dir, dst) == NULL)
+				err(EX_OSERR, "%s: realpath", dir);
+			if (strcmp(dst, "/") != 0 &&
+			    strlcat(dst, "/", sizeof(dst)) >= sizeof(dst))
 				errx(1, "resolved pathname too long");
 		}
-		strcpy(to_name_copy, to_name);
-		cp = basename(to_name_copy);
-		if (strlcat(dst, cp, sizeof(dst)) > sizeof(dst))
+		if (strlcat(dst, base, sizeof(dst)) >= sizeof(dst))
 			errx(1, "resolved pathname too long");
 		free(to_name_copy);
 
@@ -821,7 +816,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 	struct stat from_sb, temp_sb, to_sb;
 	struct timespec tsb[2];
 	int devnull, files_match, from_fd, serrno, stripped, target;
-	int tempcopy, temp_fd, to_fd;
+	int temp_fd, to_fd;
 	char backup[MAXPATHLEN], *p, pathbuf[MAXPATHLEN], tempfile[MAXPATHLEN];
 	char *digestresult;
 
@@ -835,10 +830,8 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 		if (!dolink) {
 			if (stat(from_name, &from_sb))
 				err(EX_OSERR, "%s", from_name);
-			if (!S_ISREG(from_sb.st_mode)) {
-				errno = EFTYPE;
-				err(EX_OSERR, "%s", from_name);
-			}
+			if (!S_ISREG(from_sb.st_mode))
+				errc(EX_OSERR, EFTYPE, "%s", from_name);
 		}
 		/* Build the target path. */
 		if (flags & DIRECTORY) {
@@ -852,32 +845,18 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 	} else {
 		devnull = 1;
 	}
+	if (*to_name == '\0')
+		errx(EX_USAGE, "destination cannot be an empty string");
 
 	target = (lstat(to_name, &to_sb) == 0);
 
 	if (dolink) {
-		if (target && !safecopy) {
-			if (to_sb.st_mode & S_IFDIR && rmdir(to_name) == -1)
-				err(EX_OSERR, "%s", to_name);
-#if HAVE_STRUCT_STAT_ST_FLAGS
-			if (to_sb.st_flags & NOCHANGEBITS)
-				(void)chflags(to_name,
-				    to_sb.st_flags & ~NOCHANGEBITS);
-#endif
-			unlink(to_name);
-		}
 		makelink(from_name, to_name, target ? &to_sb : NULL);
 		return;
 	}
 
-	if (target && !S_ISREG(to_sb.st_mode) && !S_ISLNK(to_sb.st_mode)) {
-		errno = EFTYPE;
-		warn("%s", to_name);
-		return;
-	}
-
-	/* Only copy safe if the target exists. */
-	tempcopy = safecopy && target;
+	if (target && !S_ISREG(to_sb.st_mode) && !S_ISLNK(to_sb.st_mode))
+		errc(EX_CANTCREAT, EFTYPE, "%s", to_name);
 
 	if (!devnull && (from_fd = open(from_name, O_RDONLY, 0)) < 0)
 		err(EX_OSERR, "%s", from_name);
@@ -899,40 +878,32 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 	}
 
 	if (!files_match) {
-		if (tempcopy) {
-			to_fd = create_tempfile(to_name, tempfile,
-			    sizeof(tempfile));
-			if (to_fd < 0)
-				err(EX_OSERR, "%s", tempfile);
-		} else {
-			if ((to_fd = create_newfile(to_name, target,
-			    &to_sb)) < 0)
-				err(EX_OSERR, "%s", to_name);
-			if (verbose)
-				(void)printf("install: %s -> %s\n",
-				    from_name, to_name);
-		}
+		to_fd = create_tempfile(to_name, tempfile,
+		    sizeof(tempfile));
+		if (to_fd < 0)
+			err(EX_OSERR, "%s", tempfile);
 		if (!devnull) {
-			if (dostrip)
-			    stripped = strip(tempcopy ? tempfile : to_name,
-				to_fd, from_name, &digestresult);
-			if (!stripped)
-			    digestresult = copy(from_fd, from_name, to_fd,
-				tempcopy ? tempfile : to_name, from_sb.st_size);
+			if (dostrip) {
+				stripped = strip(tempfile, to_fd, from_name,
+				    &digestresult);
+			}
+			if (!stripped) {
+				digestresult = copy(from_fd, from_name, to_fd,
+				    tempfile, from_sb.st_size);
+			}
 		}
 	}
 
 	if (dostrip) {
 		if (!stripped)
-			(void)strip(tempcopy ? tempfile : to_name, to_fd,
-			    NULL, &digestresult);
+			(void)strip(tempfile, to_fd, NULL, &digestresult);
 
 		/*
 		 * Re-open our fd on the target, in case
 		 * we did not strip in-place.
 		 */
 		close(to_fd);
-		to_fd = open(tempcopy ? tempfile : to_name, O_RDONLY, 0);
+		to_fd = open(tempfile, O_RDONLY, 0);
 		if (to_fd < 0)
 			err(EX_OSERR, "stripping %s", to_name);
 	}
@@ -976,16 +947,16 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 		digestresult = digest_file(tempfile);
 
 	/*
-	 * Move the new file into place if doing a safe copy
-	 * and the files are different (or just not compared).
+	 * Move the new file into place if the files are different (or
+	 * just not compared).
 	 */
-	if (tempcopy && !files_match) {
+	if (!files_match) {
 #if HAVE_STRUCT_STAT_ST_FLAGS
 		/* Try to turn off the immutable bits. */
 		if (to_sb.st_flags & NOCHANGEBITS)
 			(void)chflags(to_name, to_sb.st_flags & ~NOCHANGEBITS);
 #endif
-		if (dobackup) {
+		if (target && dobackup) {
 			if ((size_t)snprintf(backup, MAXPATHLEN, "%s%s", to_name,
 			    suffix) != strlen(to_name) + strlen(suffix)) {
 				unlink(tempfile);
@@ -1124,86 +1095,62 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 	int to_fd, const char *to_name __unused, size_t to_len,
 	char **dresp)
 {
-	char *p, *q;
 	int rv;
-	int do_digest, done_compare;
+	int do_digest;
 	DIGEST_CTX ctx;
 
-	rv = 0;
 	if (from_len != to_len)
 		return 1;
 
 	do_digest = (digesttype != DIGEST_NONE && dresp != NULL &&
 	    *dresp == NULL);
 	if (from_len <= MAX_CMP_SIZE) {
+		static char *buf, *buf1, *buf2;
+		static size_t bufsize;
+		int n1, n2;
+
 		if (do_digest)
 			digest_init(&ctx);
-		done_compare = 0;
-		if (trymmap(from_len) && trymmap(to_len)) {
-			p = mmap(NULL, from_len, PROT_READ, MAP_SHARED,
-			    from_fd, (off_t)0);
-			if (p == MAP_FAILED)
-				goto out;
-			q = mmap(NULL, from_len, PROT_READ, MAP_SHARED,
-			    to_fd, (off_t)0);
-			if (q == MAP_FAILED) {
-				munmap(p, from_len);
-				goto out;
-			}
 
-			rv = memcmp(p, q, from_len);
-			if (do_digest)
-				digest_update(&ctx, p, from_len);
-			munmap(p, from_len);
-			munmap(q, from_len);
-			done_compare = 1;
+		if (buf == NULL) {
+			/*
+			 * Note that buf and bufsize are static. If
+			 * malloc() fails, it will fail at the start
+			 * and not copy only some files.
+			 */
+			if (sysconf(_SC_PHYS_PAGES) > PHYSPAGES_THRESHOLD)
+				bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
+			else
+				bufsize = BUFSIZE_SMALL;
+			buf = malloc(bufsize * 2);
+			if (buf == NULL)
+				err(1, "Not enough memory");
+			buf1 = buf;
+			buf2 = buf + bufsize;
 		}
-	out:
-		if (!done_compare) {
-			static char *buf, *buf1, *buf2;
-			static size_t bufsize;
-			int n1, n2;
-
-			if (buf == NULL) {
-				/*
-				 * Note that buf and bufsize are static. If
-				 * malloc() fails, it will fail at the start
-				 * and not copy only some files.
-				 */
-				if (sysconf(_SC_PHYS_PAGES) >
-				    PHYSPAGES_THRESHOLD)
-					bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
+		rv = 0;
+		lseek(from_fd, 0, SEEK_SET);
+		lseek(to_fd, 0, SEEK_SET);
+		while (rv == 0) {
+			n1 = read(from_fd, buf1, bufsize);
+			if (n1 == 0)
+				break;		/* EOF */
+			else if (n1 > 0) {
+				n2 = read(to_fd, buf2, n1);
+				if (n2 == n1)
+					rv = memcmp(buf1, buf2, n1);
 				else
-					bufsize = BUFSIZE_SMALL;
-				buf = malloc(bufsize * 2);
-				if (buf == NULL)
-					err(1, "Not enough memory");
-				buf1 = buf;
-				buf2 = buf + bufsize;
-			}
-			rv = 0;
-			lseek(from_fd, 0, SEEK_SET);
-			lseek(to_fd, 0, SEEK_SET);
-			while (rv == 0) {
-				n1 = read(from_fd, buf1, bufsize);
-				if (n1 == 0)
-					break;		/* EOF */
-				else if (n1 > 0) {
-					n2 = read(to_fd, buf2, n1);
-					if (n2 == n1)
-						rv = memcmp(buf1, buf2, n1);
-					else
-						rv = 1;	/* out of sync */
-				} else
-					rv = 1;		/* read failure */
-				if (do_digest)
-					digest_update(&ctx, buf1, n1);
-			}
-			lseek(from_fd, 0, SEEK_SET);
-			lseek(to_fd, 0, SEEK_SET);
+					rv = 1;	/* out of sync */
+			} else
+				rv = 1;		/* read failure */
+			if (do_digest)
+				digest_update(&ctx, buf1, n1);
 		}
-	} else
+		lseek(from_fd, 0, SEEK_SET);
+		lseek(to_fd, 0, SEEK_SET);
+	} else {
 		rv = 1;	/* don't bother in this case */
+	}
 
 	if (do_digest) {
 		if (rv == 0)
@@ -1236,65 +1183,6 @@ create_tempfile(const char *path, char *temp, size_t tsize)
 }
 
 /*
- * create_newfile --
- *	create a new file, overwriting an existing one if necessary
- */
-static int
-create_newfile(const char *path, int target, struct stat *sbp)
-{
-	char backup[MAXPATHLEN];
-	int saved_errno = 0;
-	int newfd;
-
-	if (target) {
-		/*
-		 * Unlink now... avoid ETXTBSY errors later.  Try to turn
-		 * off the append/immutable bits -- if we fail, go ahead,
-		 * it might work.
-		 */
-#if HAVE_STRUCT_STAT_ST_FLAGS
-		if (sbp->st_flags & NOCHANGEBITS)
-			(void)chflags(path, sbp->st_flags & ~NOCHANGEBITS);
-#endif
-
-		if (dobackup) {
-			if ((size_t)snprintf(backup, MAXPATHLEN, "%s%s",
-			    path, suffix) != strlen(path) + strlen(suffix)) {
-				saved_errno = errno;
-#if HAVE_STRUCT_STAT_ST_FLAGS
-				if (sbp->st_flags & NOCHANGEBITS)
-					(void)chflags(path, sbp->st_flags);
-#endif
-				errno = saved_errno;
-				errx(EX_OSERR, "%s: backup filename too long",
-				    path);
-			}
-			(void)snprintf(backup, MAXPATHLEN, "%s%s",
-			    path, suffix);
-			if (verbose)
-				(void)printf("install: %s -> %s\n",
-				    path, backup);
-			if (rename(path, backup) < 0) {
-				saved_errno = errno;
-#if HAVE_STRUCT_STAT_ST_FLAGS
-				if (sbp->st_flags & NOCHANGEBITS)
-					(void)chflags(path, sbp->st_flags);
-#endif
-				errno = saved_errno;
-				err(EX_OSERR, "rename: %s to %s", path, backup);
-			}
-		} else
-			if (unlink(path) < 0)
-				saved_errno = errno;
-	}
-
-	newfd = open(path, O_CREAT | O_RDWR | O_TRUNC, S_IRUSR | S_IWUSR);
-	if (newfd < 0 && saved_errno != 0)
-		errno = saved_errno;
-	return newfd;
-}
-
-/*
  * copy --
  *	copy from one file to another
  */
@@ -1306,77 +1194,52 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 	static size_t bufsize;
 	int nr, nw;
 	int serrno;
-	char *p;
-	int done_copy;
 	DIGEST_CTX ctx;
 
 	/* Rewind file descriptors. */
-	if (lseek(from_fd, (off_t)0, SEEK_SET) == (off_t)-1)
+	if (lseek(from_fd, 0, SEEK_SET) < 0)
 		err(EX_OSERR, "lseek: %s", from_name);
-	if (lseek(to_fd, (off_t)0, SEEK_SET) == (off_t)-1)
+	if (lseek(to_fd, 0, SEEK_SET) < 0)
 		err(EX_OSERR, "lseek: %s", to_name);
 
 	digest_init(&ctx);
 
-	done_copy = 0;
-	if (trymmap((size_t)size) &&
-	    (p = mmap(NULL, (size_t)size, PROT_READ, MAP_SHARED,
-		    from_fd, (off_t)0)) != MAP_FAILED) {
-		nw = write(to_fd, p, size);
-		if (nw != size) {
+	if (buf == NULL) {
+		/*
+		 * Note that buf and bufsize are static. If
+		 * malloc() fails, it will fail at the start
+		 * and not copy only some files.
+		 */
+		if (sysconf(_SC_PHYS_PAGES) > PHYSPAGES_THRESHOLD)
+			bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
+		else
+			bufsize = BUFSIZE_SMALL;
+		buf = malloc(bufsize);
+		if (buf == NULL)
+			err(1, "Not enough memory");
+	}
+	while ((nr = read(from_fd, buf, bufsize)) > 0) {
+		if ((nw = write(to_fd, buf, nr)) != nr) {
 			serrno = errno;
 			(void)unlink(to_name);
 			if (nw >= 0) {
 				errx(EX_OSERR,
-     "short write to %s: %jd bytes written, %jd bytes asked to write",
-				    to_name, (uintmax_t)nw, (uintmax_t)size);
+				    "short write to %s: %jd bytes written, "
+				    "%jd bytes asked to write",
+				    to_name, (uintmax_t)nw,
+				    (uintmax_t)size);
 			} else {
 				errno = serrno;
 				err(EX_OSERR, "%s", to_name);
 			}
 		}
-		digest_update(&ctx, p, size);
-		(void)munmap(p, size);
-		done_copy = 1;
+		digest_update(&ctx, buf, nr);
 	}
-	if (!done_copy) {
-		if (buf == NULL) {
-			/*
-			 * Note that buf and bufsize are static. If
-			 * malloc() fails, it will fail at the start
-			 * and not copy only some files.
-			 */
-			if (sysconf(_SC_PHYS_PAGES) >
-			    PHYSPAGES_THRESHOLD)
-				bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
-			else
-				bufsize = BUFSIZE_SMALL;
-			buf = malloc(bufsize);
-			if (buf == NULL)
-				err(1, "Not enough memory");
-		}
-		while ((nr = read(from_fd, buf, bufsize)) > 0) {
-			if ((nw = write(to_fd, buf, nr)) != nr) {
-				serrno = errno;
-				(void)unlink(to_name);
-				if (nw >= 0) {
-					errx(EX_OSERR,
-     "short write to %s: %jd bytes written, %jd bytes asked to write",
-					    to_name, (uintmax_t)nw,
-					    (uintmax_t)size);
-				} else {
-					errno = serrno;
-					err(EX_OSERR, "%s", to_name);
-				}
-			}
-			digest_update(&ctx, buf, nr);
-		}
-		if (nr != 0) {
-			serrno = errno;
-			(void)unlink(to_name);
-			errno = serrno;
-			err(EX_OSERR, "%s", from_name);
-		}
+	if (nr != 0) {
+		serrno = errno;
+		(void)unlink(to_name);
+		errno = serrno;
+		err(EX_OSERR, "%s", from_name);
 	}
 	if (safecopy && fsync(to_fd) == -1) {
 		serrno = errno;
@@ -1600,29 +1463,3 @@ usage(void)
 	exit(EX_USAGE);
 	/* NOTREACHED */
 }
-
-/*
- * trymmap --
- *	return true (1) if mmap should be tried, false (0) if not.
- */
-static int
-trymmap(size_t filesize)
-{
-	/*
-	 * This function existed to skip mmap() for NFS file systems whereas
-	 * nowadays mmap() should be perfectly safe. Nevertheless, using mmap()
-	 * only reduces the number of system calls if we need multiple read()
-	 * syscalls, i.e. if the file size is > MAXBSIZE. However, mmap() is
-	 * more expensive than read() so set the threshold at 4 fewer syscalls.
-	 * Additionally, for larger file size mmap() can significantly increase
-	 * the number of page faults, so avoid it in that case.
-	 *
-	 * Note: the 8MB limit is not based on any meaningful benchmarking
-	 * results, it is simply reusing the same value that was used before
-	 * and also matches bin/cp.
-	 *
-	 * XXX: Maybe we shouldn't bother with mmap() at all, since we use
-	 * MAXBSIZE the syscall overhead of read() shouldn't be too high?
-	 */
-	return (filesize > 4 * MAXBSIZE && filesize < 8 * 1024 * 1024);
-}