I've been writing some code which involves syncing files (like
rsync) and it became apparent that under Linux I could read
modification times (os.Lstat) with nanosecond precision but
only write them with microsecond precision. This difference
in precision is rather annoying when trying to discover
whether files need syncing or not!
I've patched syscall and os to increases the accuracy of of
os.Chtimes for Linux and Windows. This involved exposing the
utimensat system call under Linux and a bit of extra code
under Windows. I decided not to expose the "at" bit of the
system call as it is impossible to replicate under Windows, so
the patch adds syscall.Utimens() to all architectures along
with a ImplementsUtimens flag.
If the utimensat syscall isn't available (utimensat was added
to Linux in 2.6.22, Released, 8 July 2007) then it silently
falls back to the microsecond accuracy version it uses now.
The improved accuracy for Windows should be good for all
versions of Windows.
Unfortunately Darwin doesn't seem to have a utimensat system
call that I could find so I couldn't implement it there. The
BSDs do, but since they share their syscall implementation
with Darwin I couldn't figure out how to define a syscall for
*BSD and not Darwin. I've left this as a TODO in the code.
In the process I implemented the missing methods for Timespec
under Windows which I needed which just happened to round out
the Timespec API for all platforms!
------------------------------------------------------------
Test code: http://play.golang.org/p/1xnGuYOi4b
Linux Before (1000 ns precision)
$ ./utimetest.linux.before z
Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST
Reading mtime 1344937903123457000: 2012-08-14 10:51:43.123457 +0100 BST
Linux After (1 ns precision)
$ ./utimetest.linux.after z
Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST
Reading mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST
Windows Before (1000 ns precision)
X:\>utimetest.windows.before.exe c:\Test.txt
Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 GMTDT
Reading mtime 1344937903123456000: 2012-08-14 10:51:43.123456 +0100 GMTDT
Windows After (100 ns precision)
X:\>utimetest.windows.after.exe c:\Test.txt
Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 GMTDT
Reading mtime 1344937903123456700: 2012-08-14 10:51:43.1234567 +0100 GMTDT
R=golang-dev, alex.brainman, rsc, bradfitz
CC=golang-dev
https://golang.org/cl/6905057
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 CL fixes code that incorrectly assumes that int is 32 bits wide.
Specifically, the socketpair system call expects a pointer to a pair
of int32s, not a pair of ints. Fix this inside the wrappers without
changing the APIs.
Update #2188.
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6552063
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
This syscall was inadvertently exported when fixing
Getrlimit/Setrlimit on 32-bit platforms.
R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/6458051
CL 3075041 says ARM is not little-endian, but my test suggests otherwise.
My test program is:
package main
import ("fmt"; "syscall"; "os")
func main() {
err := syscall.Fallocate(1, 1/*FALLOC_FL_KEEP_SIZE*/, 0, int64(40960));
fmt.Fprintln(os.Stderr, err)
}
Without this CL, ./test > testfile will show: file too large; and strace shows:
fallocate(1, 01, 0, 175921860444160) = -1 EFBIG (File too large)
With this CL, ./test > testfile will show: <nil>; and strace shows:
fallocate(1, 01, 0, 40960) = 0
Quoting rsc:
"[It turns out that] ARM syscall ABI requires 64-bit arguments to use an
(even, odd) register pair, not an (odd, even) pair. Switching to "big-endian"
worked because it ended up using the high 32-bits (always zero in the tests
we had) as the padding word, because the 64-bit argument was the last one,
and because we fill in zeros for the rest of the system call arguments, up to
six. So it happened to work."
I updated mksyscall_linux.pl to accommodate the register pair ABI requirement,
and removed all hand-tweaked syscall routines in favor of the auto-generated
ones. These including: Ftruncate, Truncate, Pread and Pwrite.
Some recent Linux/ARM distributions do not bundle kernel asm headers,
so instead we always get latest asm/unistd.h from git.kernel.org (just like
what we do for FreeBSD).
R=ken, r, rsc, r, dave, iant
CC=golang-dev
https://golang.org/cl/5726051
Restore package os/signal, with new API:
Notify replaces Incoming, allowing clients
to ask for certain signals only. Also, signals
go to everyone who asks, not just one client.
This could plausibly move into package os now
that there are no magic side effects as a result
of the import.
Update runtime for new API: move common Unix
signal handling code into signal_unix.c.
(It's so easy to do this now that we don't have
to edit Makefiles!)
Tested on darwin,linux 386,amd64.
Fixes#1266.
R=r, dsymonds, bradfitz, iant, borman
CC=golang-dev
https://golang.org/cl/3749041
You could argue for changing all the others, but
Linux is outvoted, and the only time it matters
is when newfd==-1, in which case you can call Dup.
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5650073
Notably, the "data" argument should be nil if no options are
given, or (at least) the cgroup filesystem will refuse to
mount.
R=bradfitz, rsc
CC=golang-dev
https://golang.org/cl/5147047
* tweak mksyscall*.pl to be more gofmt-compatible.
* add mkall.sh -syscalls option.
* add sys/mman.h constants on OS X
R=r, eds, niemeyer
CC=golang-dev
https://golang.org/cl/4369044
Permit system calls to be designated as non-blocking, meaning
that we simply call them without involving the scheduler.
This change by itself is mostly performance neutral. In
combination with a following change to the net package there
is a performance advantage.
R=rsc, dfc, r2, iant2, rsc1
CC=golang-dev
https://golang.org/cl/4278055
Note that, while the final argument of mount(2) is a void*, in
practice all filesystem implementations treat it as a string
of comma-separated mount options.
R=bradfitzgo, bradfitzwork
CC=golang-dev
https://golang.org/cl/4247070
The published interface is the simple version of the syscall,
allowing all reboot functions except for the esoteric
LINUX_REBOOT_CMD_RESTART2.
R=golang-dev, bradfitzgo, bradfitzwork
CC=golang-dev
https://golang.org/cl/4256060
Regenerate zsyscall_linux_*.go files with recent changes to
mksyscall.sh.
Add socketpair to syscall_linux_amd64.go; for some reason it
was in the generated file but not in the source file.
R=rsc, r2
CC=golang-dev
https://golang.org/cl/2190044
Besides being more correct, it protects against people accidentally
exchanging the permission and open mode arguments to Open.
R=rsc
CC=golang-dev
https://golang.org/cl/1904045
SETSID does return an errno - any reason why it has been done this
way in zsyscall_linux_* ? Otherwise it should be the same as darwin.
From SETSID(2) on my Linux box:
ERRORS
On error, -1 is returned, and errno is set.
Fixes#730
R=rsc
CC=golang-dev
https://golang.org/cl/878047
parsing and printing to new syntax.
Use -oldparser to parse the old syntax,
use -oldprinter to print the old syntax.
2) Change default gofmt formatting settings
to use tabs for indentation only and to use
spaces for alignment. This will make the code
alignment insensitive to an editor's tabwidth.
Use -spaces=false to use tabs for alignment.
3) Manually changed src/exp/parser/parser_test.go
so that it doesn't try to parse the parser's
source files using the old syntax (they have
new syntax now).
4) gofmt -w src misc test/bench
4th set of files.
R=rsc
CC=golang-dev
https://golang.org/cl/180049
