If we increased the NOFILE rlimit when starting the program,
restore the original rlimit when forking a child process.
In CL 393354 the os package was changed to raise the open file rlimit
at program start. That code is not inherently tied to the os package.
This CL moves it into the syscall package.
This is a backport of CLs 476096 and 476097 from trunk.
For #46279Fixes#59064
Change-Id: Ib813de896de0a5d28fa2b29afdf414a89fbe7b2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/478659
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
An Apple engineer suggests that since __fork is not public API,
it would be better to use a different fix. With the benefit of source code,
they suggest using xpc_date_create_from_current instead of
xpc_atfork_child. The latter sets some flags that disable certain
functionality for the remainder of the process lifetime (expecting exec),
while the former should do the necessary setup.
Reverting the __fork fix in order to prepare a clean fix based
on CL 451735 using xpc_date_create_from_current.
This reverts commit c61d322d5f.
Change-Id: I2da293ff537237ffd2d40ad756d827c95c84635b
Reviewed-on: https://go-review.googlesource.com/c/go/+/460475
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Issues #33565 and #56784 were caused by hangs in the child process
after fork, while it ran atfork handlers that ran into slow paths that
didn't work in the child.
CL 451735 worked around those two issues by calling a couple functions
at startup to try to warm up those child paths. That mostly worked,
but it broke programs using cgo with certain macOS frameworks (#57263).
CL 459175 reverted CL 451735.
This CL introduces a different fix: bypass the atfork child handlers
entirely. For a general fork call where the child and parent are both
meant to keep executing the original program, atfork handlers can be
necessary to fix any state that would otherwise be tied to the parent
process. But Go only uses fork as preparation for exec, and it takes
care to limit what it attempts to do in the child between the fork and
exec. In particular it doesn't use any of the things that the macOS
atfork handlers are trying to fix up (malloc, xpc, others). So we can
use the low-level fork system call (__fork) instead of the
atfork-wrapped one.
The full list of functions that can be called in a child after fork in
exec_libc2.go is:
- ptrace
- setsid
- setpgid
- getpid
- ioctl
- chroot
- setgroups
- setgid
- setuid
- chdir
- dup2
- fcntl
- close
- execve
- write
- exit
I disassembled all of these while attached to a hung exec.test binary
and confirmed that nearly all of them are making direct kernel calls,
not using anything that the atfork handler needs to fix up.
The exceptions are ioctl, fcntl, and exit.
The ioctl and fcntl implementations do some extra work around the
kernel call but don't call any other functions, so they should still
be OK. (If not, we could use __ioctl and __fcntl instead, but without
a good reason, we should keep using the standard entry points.)
The exit implementation calls atexit handlers. That is almost
certainly inappropriate in a failed fork child, so this CL changes
that call to __exit on darwin. To avoid making unnecessary changes at
this point in the release cycle, this CL leaves OpenBSD calling plain
exit, even though that is probably a bug in the OpenBSD port
(filed #57446).
Fixes#33565.
Fixes#56784.
Fixes#57263.
Change-Id: I26812c26a72bdd7fcf72ec41899ba11cf6b9c4ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/459176
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Change-Id: Iae290216687fd1ce8be720600157fb78cc2446d0
GitHub-Last-Rev: 4fba64ecb1
GitHub-Pull-Request: golang/go#55959
Reviewed-on: https://go-review.googlesource.com/c/go/+/436881
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Direct syscalls should no longer be used on darwin. Instead, directly
call libc's msync when using Go ≥ 1.20 for bootstrap.
For #54265
Change-Id: Ie3f1e6ccd1a06e7f0ddd88cdef5067393a69e8db
Reviewed-on: https://go-review.googlesource.com/c/go/+/430336
Reviewed-by: Ian Lance Taylor <iant@google.com>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Updates #54854
Change-Id: Ibaf4eea14a6259cdbca79e9e95db1602966f18e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/428176
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Future CLs will be changing the provenance of these functions. Move the
declarations to the individual OS files now so that future CLs can
change only 1 OS at a time rather than changing all at once.
For #51087
Change-Id: I5e1bca71e670263d8c0faa586c1b6b4de1a114b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/388474
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Fixes#51618
Change-Id: Ife894d8c313dce8c4929f40fa0ac90a069f77a89
Reviewed-on: https://go-review.googlesource.com/c/go/+/391954
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Use dup3(oldfd, newfd, O_CLOEXEC) to atomically duplicate the file
descriptor and mark is as close-on-exec instead of dup2 & fcntl.
The dup3 system call first appeared in OpenBSD 5.7.
Change-Id: Ic06c2c7089dcdbd931ee24e5e8c316879d81474e
Reviewed-on: https://go-review.googlesource.com/c/go/+/389974
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Generally speaking Go functions make no guarantees
about what has happened to result parameters on error,
and Pipe is no exception: callers should avoid looking at
p if Pipe returns an error.
However, we had a bug in which ForkExec was using the
content of p after a failed Pipe, and others may too.
As a robustness fix, make Pipe avoid writing to p on failure.
Updates #50057
Change-Id: Ie8955025dbd20702fabadc9bbe1d1a5ac0f36305
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1291271
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/370577
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Trust: Russ Cox <rsc@golang.org>
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Reviewed-by: Alex Rakoczy <alex@golang.org>
Add utimensat as a wrapper around the libc function of the same name.
utimensat was added in macOS 10.13 which is the minimum supported
release since Go 1.17 dropped support for macOS 10.12.
This also allows to drop the fallback to setattrlistTimes which was
used to set timestamps with nanosecond resolution before utimensat could
be used, see #22528 and CL 74952.
Updates #22528
Change-Id: I87b6a76acf1d642ceede9254f7d9d06dddc3fd71
Reviewed-on: https://go-review.googlesource.com/c/go/+/358274
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
In CL 288092 we made Darwin syscall wrappers as ABIInternal, so
their addresses taken from Go using funcPC are the actual function
entries, not the wrappers.
As we introduced internal/abi.FuncPCABIxxx intrinsics, use that.
And change the assembly functions back to ABI0.
Do it on OpenBSD as well, as OpenBSD and Darwin share code
generator.
Change-Id: I408120795f7fc826637c867394248f8f373906bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/313230
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Allows emitting errors about ineffectual //go:linkname directives.
In particular, this exposed: a typo in os2_aix.go; redundant (but
harmless) directives for libc_pipe in both os3_solaris.go and
syscall2_solaris.go; and a bunch of useless //go:linkname directives
in macOS wrapper code.
However, because there's also ineffectual directives in the vendored
macOS code from x/sys, that can't be an error just yet. So instead we
print a warning (including a heads up that it will be promoted to an
error in Go 1.17) to prevent backsliding while we fix and re-vendor
that code.
Passes toolstash-check.
Change-Id: I59badeab5df0d8b3abfd14c6066e9bb00e840f73
Reviewed-on: https://go-review.googlesource.com/c/go/+/273986
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Directly wrap the getcwd implementation provided by libSystem.dylib on
darwin and use it to implement Getwd like on the BSDs. This allows to
drop the custom implementation using getAttrList and to merge the
implementation of Getwd for darwin and the BSDs in syscall_bsd.go.
Same as CL 257497 did for golang.org/x/sys/unix
Change-Id: If30390c4c17cd463bb8fdcb5465f40d6fa11f391
Reviewed-on: https://go-review.googlesource.com/c/go/+/257637
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This was disabled due to a report that the App Store rejects the symbol
__sysctl. However, we use the sysctl symbol, which is fine. The __sysctl
symbol is used by x/sys/unix, which needs fixing instead. So, this
commit reenables sysctl on iOS, so that things like net.InterfaceByName
can work again.
This reverts CL 193843, CL 193844, CL 193845, and CL 193846.
Fixes#35101
Updates #34133
Updates #35103
Change-Id: Ib8eb9f87b81db24965b0de29d99eb52887c7c60a
Reviewed-on: https://go-review.googlesource.com/c/go/+/202778
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
It is forbidden by App Store.
Fixes#31628
Change-Id: Ie6d14a524ee55b57af8db685f3a79f474733add5
Reviewed-on: https://go-review.googlesource.com/c/go/+/182297
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
getfsstat64 is deprecated but not yet caught by the App Store checks.
Use the supported getfsstat$INODE64 form instead to ensure forward
compatibility.
Change-Id: I0d97e8a8b254debb3de1cfcb3778dbed3702c249
Reviewed-on: https://go-review.googlesource.com/c/go/+/174200
Run-TryBot: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Keith Randall <khr@golang.org>
Some libc functions are suffixed with "$INODE64" on macOS.
Unfortunately, the iOS simulator doesn't have the suffixes, so we can't
use GOARCH to distinguish the two platform.
Add linker support for adding the suffix, using the macho platform
to determine whether it is needed.
While here, add the correct suffix for fdopendir on 386. It's
"$INODE64$UNIX2003", believe it or not. Without the suffix,
GOARCH=386 go test -short syscall
crashes on my Mojave machine.
Fixes#31447
Change-Id: I9bd3de40ece7df62f744bc24cd00909e56b00b78
Reviewed-on: https://go-review.googlesource.com/c/go/+/174199
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Multiple calls to ReadDirent expect to return subsequent
portions of the directory listing. There's no place to store
our progress other than the file descriptor offset.
Fortunately, the file descriptor offset doesn't need to be
a real offset. We can store any int64 we want there.
Fixes#31368
Change-Id: I49e4e0e7ff707d3e96aa5d43e3b0199531013cde
Reviewed-on: https://go-review.googlesource.com/c/go/+/171477
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
fdopendir takes ownership of its file descriptor argument.
Getdirentries shouldn't do that, so dup the file descriptor
before passing to fdopendir.
Fixes#31269
Change-Id: Ie36be8fd6c59eb339dcc9f40228d4191fc1e5850
Reviewed-on: https://go-review.googlesource.com/c/go/+/170698
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Getdirentries is implemented with the __getdirentries64 function
in libSystem.dylib. That function works, but it's on Apple's
can't-be-used-in-an-app-store-application list.
Implement Getdirentries using the underlying fdopendir/readdir_r/closedir.
The simulation isn't faithful, and could be slow, but it should handle
common cases.
Don't use Getdirentries in the stdlib, use fdopendir/readdir_r/closedir
instead (via (*os.File).readdirnames).
Fixes#30933
Update #28984
RELNOTE=yes
Change-Id: Ia6b5d003e5bfe43ba54b1e1d9cfa792cc6511717
Reviewed-on: https://go-review.googlesource.com/c/go/+/168479
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The getdirentries syscall is considered private API on iOS and is
rejected by the App Store submission checks. Replace it with the
fdopendir/readdir_r/closedir syscalls.
Fixes#28984
Change-Id: I73341b124310e9cb34834a95f946769f337ec5b7
Reviewed-on: https://go-review.googlesource.com/c/153338
Reviewed-by: Keith Randall <khr@golang.org>
The stat(2) man page contain this comment about the 64-bit versions
of the system file functions:
"Platforms that were released after these updates only have the
newer variants available to them. These platforms have the macro
_DARWIN_FEATURE_ONLY_64_BIT_INODE defined."
It turns out that on iOS the _DARWIN_FEATURE_ONLY_64_BIT_INODE is
defined and that even though the "64"-postfixed versions are
accessible they are deemed private. Apps that refer to private
API are not admissible on App Store, and after the Go runtime
started using libSystem instead of direct syscalls, the App Store
submission checks reject apps built with Go tip.
The fix is simple: use the non-postfixed versions on iOS.
getdirentries(2) is not changed; it is not available at all on iOS
and needs replacement.
Updates #28984
Change-Id: Icb8d44e271456acaa1913ba486fcf5b569722fa9
Reviewed-on: https://go-review.googlesource.com/c/151938
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Add unexported unlinkat, openat, and fstatat calls, so that
the internal/syscall/unix package can use them.
Change-Id: I1df81ecae6427211dd392ec68c9f020fe131a526
Reviewed-on: https://go-review.googlesource.com/c/148457
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Miscellaneous additional conversions from raw syscalls
to using their libc equivalent.
Update #17490
Change-Id: If9ab22cc1d676c1f20fb161ebf02b0c28f71585d
Reviewed-on: https://go-review.googlesource.com/c/148257
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
There are still some references to the bare Syscall functions
in the stdlib. I will root those out in a following CL.
(This CL is big enough as it is.)
Most are in vendor directories:
cmd/vendor/golang.org/x/sys/unix/
vendor/golang_org/x/net/route/syscall.go
syscall/bpf_bsd.go
syscall/exec_unix.go
syscall/flock.go
Update #17490
Change-Id: I69ab707811530c26b652b291cadee92f5bf5c1a4
Reviewed-on: https://go-review.googlesource.com/c/141639
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
As reported in #26650 and also cautioned on the man page
for fsync on OS X, fsync doesn't properly flush content
to permanent storage, and might cause corruption of data if
the OS crashes or if the drive loses power. Thus it is recommended
to use the F_FULLFSYNC fcntl, which flushes all buffered data to
permanent storage and is important for applications such as
databases that require a strict ordering of writes.
Also added a note in syscall_darwin.go that syscall.Fsync is
not invoked for os.File.Sync.
Fixes#26650.
Change-Id: Idecd9adbbdd640b9c5b02e73b60ed254c98b48b6
Reviewed-on: https://go-review.googlesource.com/130676
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The syscall package is frozen and we don't want to encourage anyone to
implement these syscalls.
Change-Id: I6b6e33e32a4b097da6012226aa15300735e50e9f
Reviewed-on: https://go-review.googlesource.com/96315
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Mac OS X 10.13 introduced APFS which stores nanosecond resolution
timestamps. The implementation of os.Stat already returns full
resolution timestamps, but os.Chtimes only sets timestamps with
microsecond resolution.
Fix this by using setattrlist on Darwin, which takes a struct timeval
with nanosecond resolution. This is what Mac OS X 10.13 appears uses
to implement utimensat, according to dtruss.
Fixes#22528
Change-Id: I397dabef6b2b73a081382999aa4c4405ab8c6015
Reviewed-on: https://go-review.googlesource.com/74952
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
syscall.Exit and runtime.exit do the same thing.
Why duplicate code?
CL 45115 fixed bug where windows runtime.exit was correct,
but syscall.Exit was broken. So CL 45115 fixed windows
syscall.Exit by calling runtime.exit.
Austin suggested that all OSes should do the same, and
this CL implements his idea.
While making changes, I discovered that nacl syscall.Exit
returned error
func Exit(code int) (err error)
and I changed it into
func Exit(code int)
like all other OSes. I assumed it was a mistake and it
is OK to do because cmd/api does not complain about it.
Also I changed plan9 runtime.exit to accept int32 just
like all other OSes do.
Change-Id: I12f6022ad81406566cf9befcc6edc382eebd413b
Reviewed-on: https://go-review.googlesource.com/66170
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Fixes#21437
Change-Id: I55fbf5114ae1bb7f4aa1a20450e8d5309756cd5b
Reviewed-on: https://go-review.googlesource.com/55430
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
All the BSDs and Solaris support the utimensat syscall, but Darwin
doesn't. Account for that by adding the //sys lines not to
syscall_bsd.go but the individual OS's syscall_*.go files and implement
utimensat on Darwin as just returning ENOSYS, such that UtimesNano will
fall back to use utimes as it currently does unconditionally.
This also adds the previously missing utimensat syscall number for
FreeBSD and Dragonfly.
Fixes#16480
Change-Id: I367454c6168eb1f7150b988fa16cf02abff42f34
Reviewed-on: https://go-review.googlesource.com/55130
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Delete use stub from asm.s, leaving only a dummy file.
Deleting the file causes Windows build to fail.
Fixes#16607
Change-Id: Ic5a55e042e588f1e1bc6605a3d309d1eabdeb288
Reviewed-on: https://go-review.googlesource.com/36716
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Don't panic, crash, or return references to uninitialized memory when
ParseDirent is passed invalid input.
Move common dirent parsing to syscall.go with minimal platform-specific
functions in syscall_$GOOS.go.
Fixes#15653
Change-Id: I5602475e02321fe381064488401c14b33bec6886
Reviewed-on: https://go-review.googlesource.com/23780
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.
This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:
$ perl -i -npe 's,^(\s*// .+[a-z]\.) +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.) +([A-Z])')
$ go test go/doc -update
Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This avoids hanging when a Go program uses a FUSE filesystem and the
dup system call has to close a file descriptor. When dup uses
RawSyscall then the goroutine calling dup will occupy a scheduler slot
(a p structure) during the call, and may block waiting for some other
goroutine to respond to the close call on the FUSE filesystem.
Changing to Syscall avoids the problem. This makes Dup a tiny bit
slower but is quite unlikely to make a difference for any real
programs.
Fixes#10202.
Change-Id: If6490a8f9b3c9cfed6acbfb4bfd1eaeac62ced17
Reviewed-on: https://go-review.googlesource.com/8095
Reviewed-by: Rob Pike <r@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
Ian Lance Taylor
Russ Cox
cui fliter
Tobias Klauser
cuiweixie
Michael Pratt
Cherry Zhang
Matthew Dempsky
Cuong Manh Le
Jason A. Donenfeld
Elias Naur
Keith Randall
Elias Naur
Keith Randall
Emmanuel T Odeke
Evan Jones
Alex Brainman
Yuval Pavel Zholkover
Sameer Ajmani
Damien Neil
Mikio Hara
Brad Fitzpatrick