getlogin_r: fix the type of len

getlogin_r is specified by POSIX to to take a size_t len, not int. Fix our
version to do the same, bump the symbol version due to ABI change and
provide compat.

This was reported to break compilation of Ruby 2.8.

Some discussion about the necessity of the ABI compat did take place in the
review. While many 64-bit platforms would likely be passing it in a 64-bit
register and zero-extended and thus, not notice ABI breakage, some do
sign-extend (e.g. mips).

PR:		247102
Submitted by:	Bertram Scharpf <software@bertram-scharpf.de> (original)
Submitted by:	cem (ABI compat)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D26335

4 files changed, 15 insertions, 5 deletions

diff --git a/include/unistd.h b/include/unistd.h
index 02df2515eaaa..9fa9bebbc4c0 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -399,7 +399,7 @@ int	 ftruncate(int, off_t);
 #endif
 
 #if __POSIX_VISIBLE >= 199506
-int	 getlogin_r(char *, int);
+int	 getlogin_r(char *, size_t);
 #endif
 
 /* 1003.1-2001 */
diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
index e17d74d1a151..718b95e6f82d 100644
--- a/lib/libc/gen/Symbol.map
+++ b/lib/libc/gen/Symbol.map
@@ -156,7 +156,6 @@ FBSD_1.0 {
 	gethostname;
 	getloadavg;
 	getlogin;
-	getlogin_r;
 	setnetgrent;
 	getnetgrent;
 	endnetgrent;
@@ -422,6 +421,7 @@ FBSD_1.5 {
 };
 
 FBSD_1.6 {
+	getlogin_r;
 	memalign;
 	scandir_b;
 	sigandset;
diff --git a/lib/libc/gen/getlogin.c b/lib/libc/gen/getlogin.c
index 3a07ca36bca7..a8bc2fd0688f 100644
--- a/lib/libc/gen/getlogin.c
+++ b/lib/libc/gen/getlogin.c
@@ -58,7 +58,7 @@ getlogin(void)
 }
 
 int
-getlogin_r(char *logname, int namelen)
+getlogin_r(char *logname, size_t namelen)
 {
 	char tmpname[MAXLOGNAME];
 	int	len;
@@ -75,3 +75,13 @@ getlogin_r(char *logname, int namelen)
 	strlcpy(logname, tmpname, len);
 	return (0);
 }
+
+/* FreeBSD 12 and earlier compat. */
+int
+__getlogin_r_fbsd12(char *logname, int namelen)
+{
+	if (namelen < 1)
+		return (ERANGE);
+	return (getlogin_r(logname, namelen));
+}
+__sym_compat(getlogin_r, __getlogin_r_fbsd12, FBSD_1.0);
diff --git a/lib/libc/sys/getlogin.2 b/lib/libc/sys/getlogin.2
index a0c1dd82024b..2d82aea92aa5 100644
--- a/lib/libc/sys/getlogin.2
+++ b/lib/libc/sys/getlogin.2
@@ -28,7 +28,7 @@
 .\"	@(#)getlogin.2	8.1 (Berkeley) 6/9/93
 .\" $FreeBSD$
 .\"
-.Dd June 9, 1993
+.Dd September 9, 2020
 .Dt GETLOGIN 2
 .Os
 .Sh NAME
@@ -44,7 +44,7 @@
 .Fn getlogin void
 .In sys/param.h
 .Ft int
-.Fn getlogin_r "char *name" "int len"
+.Fn getlogin_r "char *name" "size_t len"
 .Ft int
 .Fn setlogin "const char *name"
 .Sh DESCRIPTION