In CL 6350, Brad fixed the following system calls
to use the program-wide workding directory:

- bind
- chdir
- create
- open
- remove
- stat
- umount
- wstat

However, Russ Cox pointed out that the mount
system call should be fixed as well.

Change-Id: I6139ed11ba449f18c46e95269f4d0e51be7cec48
Reviewed-on: https://go-review.googlesource.com/6385Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

On Plan 9, the pwd is apparently per-thread not per process. That
means different goroutines saw different current directories, even
changing within a goroutine as they were scheduled.

Instead, track the the process-wide pwd protected by a mutex in the
syscall package and set the current goroutine thread's pwd to the
correct once at critical points.

Fixes #9428

Change-Id: I928e90886355be4a95c2be834f5883e2b50fc0cf
Reviewed-on: https://go-review.googlesource.com/6350Reviewed-by: David du Colombier <0intro@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Given:

        p := alloc()
        fn_taking_ptr(p)

p is NOT recorded as live at the call to fn_taking_ptr:
it's not needed by the code following the call.
p was passed to fn_taking_ptr, and fn_taking_ptr must keep
it alive as long as it needs it.
In practice, fn_taking_ptr will keep its own arguments live
for as long as the function is executing.

But if instead you have:

        p := alloc()
        i := uintptr(unsafe.Pointer(p))
        fn_taking_int(i)

p is STILL NOT recorded as live at the call to fn_taking_int:
it's not needed by the code following the call.
fn_taking_int is responsible for keeping its own arguments
live, but fn_taking_int is written to take an integer, so even
though fn_taking_int does keep its argument live, that argument
does not keep the allocated memory live, because the garbage
collector does not dereference integers.

The shorter form:

        p := alloc()
        fn_taking_int(uintptr(unsafe.Pointer(p)))

and the even shorter form:

        fn_taking_int(uintptr(unsafe.Pointer(alloc())))

are both the same as the 3-line form above.

syscall.Syscall is like fn_taking_int: it is written to take a list
of integers, and yet those integers are sometimes pointers.
If there is no other copy of those pointers being kept live,
the memory they point at may be garbage collected during
the call to syscall.Syscall.

This is happening on Solaris: for whatever reason, the timing
is such that the garbage collector manages to free the string
argument to the open(2) system call before the system call
has been invoked.

Change the system call wrappers to insert explicit references
that will keep the allocations alive in the original frame
(and therefore preserve the memory) until after syscall.Syscall
has returned.

Should fix Solaris flakiness.

This is not a problem for cgo, because cgo wrappers have
correctly typed arguments.

LGTM=iant, khr, aram, rlh
R=iant, khr, bradfitz, aram, rlh
CC=dvyukov, golang-codereviews, r
https://golang.org/cl/139360044

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

Also remove arch-specific Go files in the Plan 9 syscall package

LGTM=0intro
R=0intro, dave
CC=ality, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/112720043

for GOOS in darwin freebsd linux nacl netbsd openbsd plan9 solaris windows
do
        for GOARCH in 386 amd64 amd64p32 arm
        do
                go vet
        done
done

These are all real mistakes being corrected, but none
of them should be able to cause problems today
due to the NOSPLIT on the functions.

However, vet has also identified a few important problems.
I'm sending this CL to get rid of the trivial 'go vet' results
before attacking the real ones.

LGTM=r
R=golang-codereviews, r, bradfitz
CC=golang-codereviews
https://golang.org/cl/95460046

The compiler change is an ugly hack.
We can do better.

««« original CL description
syscall: mark arguments to Syscall as noescape
Heap arguments to "async" syscalls will break when/if we have moving GC anyway.
With this change is must not break until moving GC, because a user must
reference the object in Go to preserve liveness. Otherwise the code is broken already.
Reduces number of leaked params from 125 to 36 on linux.

R=golang-codereviews, mikioh.mikioh, bradfitz
CC=cshapiro, golang-codereviews, khr, rsc
https://golang.org/cl/45930043
»»»

R=golang-codereviews, r
CC=bradfitz, dvyukov, golang-codereviews
https://golang.org/cl/53870043

Heap arguments to "async" syscalls will break when/if we have moving GC anyway.
With this change is must not break until moving GC, because a user must
reference the object in Go to preserve liveness. Otherwise the code is broken already.
Reduces number of leaked params from 125 to 36 on linux.

R=golang-codereviews, mikioh.mikioh, bradfitz
CC=cshapiro, golang-codereviews, khr, rsc
https://golang.org/cl/45930043

Fixes #5567.

R=golang-dev, dave, iant
CC=golang-dev
https://golang.org/cl/10085043

syscall: Use NewError for all system errors and introduce
        some new errors for compatibility with other packages
        and proper error handling in net. Also introduce
        Temporary and Timeout methods on ErrorString.

net: Make errors from dial, accept, listen functions follow the
        OpError standard and discern whether the underlying
        error came from syscall. Since Plan 9 uses a correspondence
        between file and network operations, all system error
        reporting happens through the underlying file operation.
        In Go code, we go through package os for file operations,
        so there is another level of indirection in error types.
        This change allows us to compare the errors with those in
        package syscall, when appropriate.

os: Just use the error string already present in package os,
        instead of calling out to package syscall.

R=rsc, ality, rminnich, bradfitz
CC=golang-dev
https://golang.org/cl/7398054

Separates the implementation of nanotime on 64-bit
version of Plan 9 from that on the 32-bit version.
The former uses a syscall.

R=rsc, rminnich, ality
CC=golang-dev
https://golang.org/cl/7379051

Remove trailing whitespace in comments.
No other changes.

R=r
CC=golang-dev
https://golang.org/cl/6815053

This is a part of a bigger change that adds data race detection feature:
https://golang.org/cl/6456044
The purpose of this patch is to provide coarse-grained synchronization
between all Read() and Write() calls.

R=rsc, bradfitz, alex.brainman
CC=golang-dev
https://golang.org/cl/6610064

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

This set of changes extends the Plan 9 support
to include the AMD64 architecture and should
work on all versions of Plan 9.

R=golang-dev, rminnich, noah.evans, rsc, minux.ma, npe
CC=akskuma, golang-dev, jfflore, noah.evans
https://golang.org/cl/6479052

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

Instead use a new type, "Note", whose underlying
type is just a string.  This change allows us to
remove the exported os.Plan9Note type.

R=bradfitz, seed, rsc
CC=golang-dev
https://golang.org/cl/6015046

syscall.Exit would originally kill only the calling
Go proc, leaving behind other procs in the
same group. This change makes syscall.Exit call
runtime·exit, which due to CL
https://golang.org/cl/5617048
will cleanly exit all the Go procs in the group.

R=golang-dev, rsc, rminnich, remyoudompheng, ality, john
CC=golang-dev, mirtchovski
https://golang.org/cl/6036051

Also fixes plan9 cross-build.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5675073

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5532097

R=rsc, r
CC=golang-dev
https://golang.org/cl/5545048

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

R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/5371092

The environment is needed by package time, which
we want not to depend on os (so that os can use
time.Time), so push down into syscall.

Delete syscall.Sleep, now unnecessary.

The package os environment API is preserved;
it is only the implementation that is moving to syscall.

Delete os.Envs, which was undocumented,
uninitialized on Windows and Plan 9, and
not maintained by Setenv and Clearenv.
Code can call os.Environ instead.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5370091

- syscall (not os) now defines the Errno type.
- the low-level assembly functions Syscall, Syscall6, and so on
  return Errno, not uintptr
- syscall wrappers all return error, not uintptr.

R=golang-dev, mikioh.mikioh, r, alex.brainman
CC=golang-dev
https://golang.org/cl/5372080

R=rsc
CC=golang-dev
https://golang.org/cl/5330067

Plan 9's await() returns '' for nil exit status but programs, most notably gotest,
see this as an error return.

R=rsc
CC=golang-dev
https://golang.org/cl/5305079

All tests enabled by default passes except those in timeout_test.go.

For TestLookupPort, add an entry for "bootps" in /lib/ndb/common
(Plan 9 calls it "bootp"). I've sent out a patch to fix this.

R=paulzhol, rsc, mikioh.mikioh
CC=ality, golang-dev
https://golang.org/cl/4779041

manual changes in src/pkg/go/printer, src/cmd/gofix/signal_test.go
(cd src/cmd/gofix/testdata; gofmt -w *.in *.out)
(cd src/pkg/go/printer; gotest -update)
gofmt -w misc src

runs all tests

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4715041

R=paulzhol, mirtchovski, fshahriar, alex.brainman, r
CC=golang-dev
https://golang.org/cl/4386041

Move mmapper from syscall.go to syscall_unix.go.
Remove Sendfile from syscall_plan9.go.

R=rsc, alex.brainman
CC=golang-dev
https://golang.org/cl/4368060

R=iant
CC=golang-dev
https://golang.org/cl/4553051

R=r, bradfitzwork
CC=golang-dev
https://golang.org/cl/4406044

CC=golang-dev
https://golang.org/cl/3816043