diff options
| author | наб <nabijaczleweli@nabijaczleweli.xyz> | 2023-07-18 01:31:17 +0200 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2023-07-18 13:33:57 +0200 |
| commit | 114ed1505678640c456533d8e2b4436a52afc7f4 (patch) | |
| tree | cf74ccf52a99c358f01d68e94c82a228fdae6bdf | |
| parent | 7f19730b07068ba871da501f498f06d26530882a (diff) | |
grantpt.3: It's a no-op on modern glibc and other UNIXes; HISTORYise
FreeBSD, OpenBSD, and Linux (/dev/ptmx) do all intialisation in open(2),
and grantpt(3) is a no-op (that checks whether the fd is a pty, except
on musl).
The illumos gate and NetBSD do a ioctl (and, indeed, illumos-gate commit
facf4a8d7b59fde89a8662b4f4c73a758e6c402c ("PSARC/2003/246 Filesystem
Driven Device Naming"), which kills pt_chmod, notes that it's been
"6464196 bfu should remove pt_chmod, obsoleted by /dev filesystem").
glibc 2.33 completely kills BSD PTY support on Linux
(Debian hasn't configured with them on any architecture since 2007:
https://bugs.debian.org/338404
and even earlier on some arches; they're really just trivia under
Linux ‒ this may be better served stuffed into HISTORY as an explainer
for the SIGCHLD thing, since regardless of the "version", the behaviour
is well-defined and consistent).
There really aren't many cohesive "versions" of this ‒ indeed, so long
as grantpt(3) exists it behaves precisely as described here ‒
inasmuch as different systems, historically, had different ptys,
and thus different implementations. These are all but trivia.
Cc: Jakub Wilk <jwilk@jwilk.net>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
| -rw-r--r-- | man3/grantpt.3 | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/man3/grantpt.3 b/man3/grantpt.3 index a19172a3e..949f70de9 100644 --- a/man3/grantpt.3 +++ b/man3/grantpt.3 @@ -83,18 +83,6 @@ T} Thread safety MT-Safe locale .hy .ad .sp 1 -.SH VERSIONS -Many systems implement this function via a set-user-ID helper binary -called "pt_chown". -On Linux systems with a devpts filesystem (present since Linux 2.2), -the kernel normally sets the correct ownership and permissions -for the pseudoterminal slave when the master is opened -.RB ( posix_openpt (3)), -so that nothing must be done by -.BR grantpt (). -Thus, no such helper binary is required -(and indeed it is configured to be absent during the -glibc build that is typical on many systems). .SH STANDARDS POSIX.1-2008. .SH HISTORY @@ -103,6 +91,16 @@ POSIX.1-2001. .PP This is part of the UNIX 98 pseudoterminal support, see .BR pts (4). +.PP +Historical systems implemented this function via a set-user-ID helper binary +called "pt_chown". +glibc on Linux before glibc 2.33 could do so as well, +in order to support configurations with only BSD pseudoterminals; +this support has been removed. +On modern systems this is either a no-op +\[em]with permissions configured on pty allocation, as is the case on Linux\[em] +or an +.BR ioctl (2). .SH SEE ALSO .BR open (2), .BR posix_openpt (3), |