Fixes the fork-exec/wait race condition for ForkExec
as well, by making it use startProcess. This makes the
comment for StartProcess consistent as well.
Further, the passing of Waitmsg data in startProcess
and WaitProcess is protected against possible forks
from outside of ForkExec and StartProcess, which might
cause interference with the Await call.
R=rsc, rminnich, npe, ality
CC=golang-dev
https://golang.org/cl/7128059
On Plan 9, only the parent of a given process can enter its wait
queue. When a Go program tries to fork-exec a child process
and subsequently waits for it to finish, the goroutines doing
these two tasks do not necessarily tie themselves to the same
(or any single) OS thread. In the case that the fork and the wait
system calls happen on different OS threads (say, due to a
goroutine being rescheduled somewhere along the way), the
wait() will either return an error or end up waiting for a
completely different child than was intended.
This change forces the fork and wait syscalls to happen in the
same goroutine and ties that goroutine to its OS thread until
the child exits. The PID of the child is recorded upon fork and
exit, and de-queued once the child's wait message has been read.
The Wait API, then, is translated into a synthetic implementation
that simply waits for the requested PID to show up in the queue
and then reads the associated stats.
R=rsc, rminnich, npe, mirtchovski, ality
CC=golang-dev
https://golang.org/cl/6545051
This change updates CL 6576057 for exceptional cases where
return values from Syscall/RawSyscall functions are used.
The system calls return 32-bit integers. With the recent change
in size of `int' in Go for amd64, the type conversion was not
catching `-1' return values. This change makes the conversion
explicitly `int32'.
R=rsc, r
CC=golang-dev
https://golang.org/cl/6590047
Since NUL usually terminates strings in underlying syscalls, allowing
it when converting string arguments is a security risk, especially
when dealing with filenames. For example, a program might reason that
filename like "/root/..\x00/" is a subdirectory or "/root/" and allow
access to it, while underlying syscall will treat "\x00" as an end of
that string and the actual filename will be "/root/..", which might
be unexpected. Returning EINVAL when string arguments have NUL in
them makes sure this attack vector is unusable.
R=golang-dev, r, bradfitz, fullung, rsc, minux.ma
CC=golang-dev
https://golang.org/cl/6458050
1. Readdirnames was erroneously returning an
empty slice on every invocation.
2. The logic for determining which files to
close before exec was incorrect. If the
set of files to be kept open (provided by
the caller) did not include the files
opened at startup, those files would be
accidentally closed.
I also cleaned up readdupdevice while I was
in the vicinity.
R=golang-dev, seed, rsc
CC=golang-dev
https://golang.org/cl/6016044
This change comes from CL 5536043,
created by Andrey Mirtchovski. His
description follows:
"The plan9 exec child handler does not manage
dup-ed fds from the parent correctly: when a
dup-ed file descriptor appears in the child's fd
list it is closed when first encountered and then
subsequent attempt to dup it later in Pass 2 fails,
resulting in 'fork/exec: fd out of range or not
open'."
R=golang-dev, rminnich, ality
CC=golang-dev, mirtchovski, rsc
https://golang.org/cl/6009046
exec_plan9.go:
. Adjusted return argument to match other changes.
#mksyscall.pl:
. Replaced "err = e1" with "err = NewError(e1)".
* Change abandoned, Russ made a better suggestion involving
syscall_plan9.go.
syscall_plan9.go:
. Removed redundant "err = nil" lines.
. Adjusted //sys lines for mksyscall.pl.
* Replaced "err string" with "err ErrorString" in return arguments.
zsyscall_plan9_386.go:
. This module ought to be generated, but as it exists in the
repository, I rebuilt it and checked that it matched expectations.
Anybody is welcome to remove this from the repository if
they feel it should go, but remember that not all Plan 9
installations have a working Perl.
R=rsc
CC=ality, golang-dev
https://golang.org/cl/5411046
