Change-Id: I0fcb79f471cdb8b464924d9b04c675f120861f67
Reviewed-on: https://go-review.googlesource.com/c/go/+/539835
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: shuang cui <imcusg@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
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For #65355
Change-Id: I5fefe30dcb520159de565e61dafc74a740fc8730
Reviewed-on: https://go-review.googlesource.com/c/go/+/559715
Reviewed-by: Michael Pratt <mpratt@google.com>
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The fchmodat2 syscall was added in Linux kernel 6.6. Mirror the
implementation in golang.org/x/sys/unix.Fchmodat (CL 539635) and use
fchmodat2 in Fchmodat if flags are given. It will return ENOSYS on older
kernels (or EINVAL or any other bogus error in some container
implementations).
Also update ztypes_linux_$GOARCH.go for all linux platforms to add
_AT_EMPTY_PATH. It was added to linux/types in CL 407694 but was only
updated for linux/loong64 at that time.
Updates #61636
Change-Id: I863d06e35cd366f1cf99052e9f77c22ab8168b3f
Reviewed-on: https://go-review.googlesource.com/c/go/+/540435
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
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Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Changes trailing-NUL-counting behavior for abstract addresses
starting with the NUL character to be the same as abstract
addresses starting with the @ character.
For #63579.
Change-Id: I206e4d0d808396998cb7d92a9e26dda854cb1248
GitHub-Last-Rev: 0ff0a9c938
GitHub-Pull-Request: golang/go#63580
Reviewed-on: https://go-review.googlesource.com/c/go/+/535776
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Reviewed-by: Ian Lance Taylor <iant@google.com>
Currently we are bootstrapping with Go 1.20, origRlimitNofile can
be changed to atomic.Pointer[Rlimit].
Change-Id: I00ce9d1a9030bd5dbd34e3dc6c4e38683a87be86
GitHub-Last-Rev: f2ccdb3841
GitHub-Pull-Request: golang/go#63274
Reviewed-on: https://go-review.googlesource.com/c/go/+/531516
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Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Add PidFD support, so that if the PidFD pointer in SysProcAttr is not
nil, ForkExec (and thus all its users) obtains a pidfd from the kernel
during clone(), and writes the result (or -1, if the functionality
is not supported by the kernel) into *PidFD.
The functionality to get pidfd is implemented for both clone3 and clone.
For the latter, an extra argument to rawVforkSyscall is needed, thus the
change in asm files.
Add a trivial test case checking the obtained pidfd can be used to send
a signal to a process, using pidfd_send_signal. To test clone3 code path,
add a flag available to tests only.
Updates #51246.
Change-Id: I2212b69e1a657163c31b4a6245b076bc495777a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/520266
Auto-Submit: Ian Lance Taylor <iant@google.com>
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Fix spelling errors discovered using https://github.com/codespell-project/codespell. Errors in data files and vendored packages are ignored.
Change-Id: I83c7818222f2eea69afbd270c15b7897678131dc
GitHub-Last-Rev: 3491615b1b
GitHub-Pull-Request: golang/go#60758
Reviewed-on: https://go-review.googlesource.com/c/go/+/502576
Auto-Submit: Michael Pratt <mpratt@google.com>
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In the ptrace system call, most of the newer architectures (e.g. arm64,riscv64,loong64)
do not provide support for the command PTRACE_{GET, SET}REGS.
The Linux kernel 2.6.33-rc7[1] introduces support for the command PTRACE_{GET,SET}REGSET,
which exports different types of register sets depending on the NT_* types, completely
overriding the functionality provided by PTRACE_{GET,SET}REGS.
[1] https://lore.kernel.org/all/20100211195614.886724710@sbs-t61.sc.intel.com/Fixes#60679.
Change-Id: I8c2671d64a7ecd654834740f4f1e1e50c00edcae
Reviewed-on: https://go-review.googlesource.com/c/go/+/501756
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Auto-Submit: Ian Lance Taylor <iant@google.com>
If we increased the NOFILE rlimit when starting the program,
restore the original rlimit when forking a child process.
For #46279
Change-Id: Ia5d2af9ef435e5932965c15eec2e428d2130d230
Reviewed-on: https://go-review.googlesource.com/c/go/+/476097
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Ian Lance Taylor <iant@google.com>
The function was added since go1.17, which is the minimum version for
bootstraping now.
Change-Id: I08b55c3639bb9ff042aabfcdcfbdf2993032ba6b
Reviewed-on: https://go-review.googlesource.com/c/go/+/471436
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
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The existing ptrace wrapper accepts pointer argument as an uintptr which
often points to the memory allocated in Go. This violates unsafe.Pointer safety
rules.
Fixes#58387
Change-Id: Iab12122c495953f94ea00c2a61654a818a464205
Reviewed-on: https://go-review.googlesource.com/c/go/+/470299
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Auto-Submit: Dmitri Goutnik <dgoutnik@gmail.com>
CL 416115 added using faccessat2(2) from syscall.Faccessat on Linux
(which is the only true way to implement AT_EACCESS flag handing),
if available. If not available, it uses some heuristics to mimic the
kernel behavior, mostly taken from glibc (see CL 126415).
Next, CL 414824 added using the above call (via unix.Eaccess) to
exec.LookPath in order to check if the binary can really be executed.
As a result, in a very specific scenario, described below,
syscall.Faccessat (and thus exec.LookPath) mistakenly tells that the
binary can not be executed, while in reality it can be. This makes
this bug a regression in Go 1.20.
This scenario involves all these conditions:
- no faccessat2 support available (i.e. either Linux kernel < 5.8,
or a seccomp set up to disable faccessat2);
- the current user is not root (i.e. geteuid() != 0);
- CAP_DAC_OVERRIDE capability is set for the current process;
- the file to be executed does not have executable permission
bit set for either the current EUID or EGID;
- the file to be executed have at least one executable bit set.
Unfortunately, this set of conditions was observed in the wild -- a
container run as a non-root user with the binary file owned by root with
executable permission set for a user only [1]. Essentially it means it
is not as rare as it may seem.
Now, CAP_DAC_OVERRIDE essentially makes the kernel bypass most of the
checks, so execve(2) and friends work the same was as for root user,
i.e. if at least one executable bit it set, the permission to execute
is granted (see generic_permission() function in the Linux kernel).
Modify the code to check for CAP_DAC_OVERRIDE and mimic the kernel
behavior for permission checks.
[1] https://github.com/opencontainers/runc/issues/3715Fixes#58552.
Change-Id: I82a7e757ab3fd3d0193690a65c3b48fee46ff067
Reviewed-on: https://go-review.googlesource.com/c/go/+/468735
Reviewed-by: Damien Neil <dneil@google.com>
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Reviewed-by: Ian Lance Taylor <iant@google.com>
The Android seccomp policy does not allow faccessat2, so attempting to
use it results in a SIGSYS. Avoid it and go straight to the fallback.
Fixes#57393.
Change-Id: I8d4e12a6f46cea5642d3b5b5a02c682529882f29
Reviewed-on: https://go-review.googlesource.com/c/go/+/458495
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Changkun Ou <mail@changkun.de>
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Our minimum Linux version is 2.6.32, and the accept4 system call was
introduced in 2.6.28, so we use accept4 everywhere. Unfortunately,
it turns out that the accept4 system call was only added to
linux-arm in 2.6.36, so for linux-arm only we need to try the accept4
system call and then fall back to accept if it doesn't work.
The code we use on linux-arm is the code we used in Go 1.17.
On non-arm platforms we continue using the simpler code introduced
in Go 1.18.
Adding accept4 to the ARM Linux kernel was:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=21d93e2e29722d7832f61cc56d73fb953ee6578eFixes#57333
Change-Id: I6680cb54dd4d3514a6887dda8906e6708c64459d
Reviewed-on: https://go-review.googlesource.com/c/go/+/457995
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
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Run-TryBot: Ian Lance Taylor <iant@google.com>
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Implement CLONE_INTO_CGROUP feature, allowing to put a child in a
specified cgroup in a clean and simple way. Note that the feature only
works for cgroup v2, and requires Linux kernel 5.7 or newer.
Using the feature requires a new syscall, clone3. Currently this is the
only reason to use clone3, but the code is structured in a way so that
other cases may be easily added in the future.
Add a test case.
While at it, try to simplify the syscall calling code in
forkAndExecInChild1, which became complicated over time because:
1. It was using either rawVforkSyscall or RawSyscall6 depending on
whether CLONE_NEWUSER was set.
2. On Linux/s390, the first two arguments to clone(2) system call are
swapped (which deserved a mention in Linux ABI hall of shame). It
was worked around in rawVforkSyscall on s390, but had to be
implemented via a switch/case when using RawSyscall6, making the code
less clear.
Let's
- modify rawVforkSyscall to have two arguments (which is also required
for clone3);
- remove the arguments workaround from s390 asm, instead implementing
arguments swap in the caller (which still looks ugly but at least
it's done once and is clearly documented now);
- use rawVforkSyscall for all cases (since it is essentially similar to
RawSyscall6, except for having less parameters, not returning r2, and
saving/restoring the return address before/after syscall on 386 and
amd64).
Updates #51246.
Change-Id: Ifcd418ebead9257177338ffbcccd0bdecb94474e
Reviewed-on: https://go-review.googlesource.com/c/go/+/417695
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
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Linux kernel 5.8 added the faccessat2 syscall taking a flags argument.
Attempt to use it in Faccessat and fall back to the existing
implementation mimicking glibc faccessat.
Do not export the new syscall value so we keep syscall API intact.
Part of this commit is generated by:
GOOS=linux ./mkall.sh -syscalls zsyscall_linux_*.go
This is similar to [1] amended by [2]. Required for [3].
[1] https://go-review.googlesource.com/c/sys/+/246537
[2] https://go-review.googlesource.com/c/sys/+/246817
[3] https://go-review.googlesource.com/c/go/+/414824
Co-authored-by: Tobias Klauser <tklauser@distanz.ch>
Change-Id: Ib7fe5ba853c15d92e869df9a16b56b79b96e43a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/416115
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Most newer architectures (e.g. arm64, riscv64, loong64) don't provide the
epoll_create syscall. Some systems (e.g. Android) block it even if it
were available. In the kernel, the epoll_create syscall is implemented
[1] the same way EpollCreate is implemented in this package for
platforms without the epoll_create syscall. The epoll_create1 syscall is
available since Linux kernel 2.6.27 and the minimum required kernel
version is 2.6.32 since Go 1.18 (see #45964). Thus, avoid the separate
wrapper and consistently implement EpollCreate using EpollCreate1.
[1] https://elixir.bootlin.com/linux/v5.15-rc1/source/fs/eventpoll.c#L2006
The same change was already done in CL 349809 for golang.org/x/sys/unix.
For #45964
Change-Id: I5463b208aa7ae236fa2c175d6d3ec6568f1840b0
Reviewed-on: https://go-review.googlesource.com/c/go/+/411594
Reviewed-by: Bryan Mills <bcmills@google.com>
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Excluding vendor and testdata.
CL 384268 already reformatted most, but these slipped past.
The struct in the doc comment in debug/dwarf/type.go
was fixed up by hand to indent the first and last lines as well.
For #51082.
Change-Id: Iad020f83aafd671ff58238fe491907e85923d0c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/407137
Run-TryBot: Russ Cox <rsc@golang.org>
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RawSyscall is used in a variety of rather unsafe conditions, such as
after fork in forkAndExecInChild1. Disable race instrumentation to avoid
calling TSAN in unsafe conditions.
For #51087
Change-Id: I47c35e6f0768c77ddab99010ea0404c45ad2f1da
Reviewed-on: https://go-review.googlesource.com/c/go/+/402914
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This is an exact copy of CL 388478 after fixing #52472 in CL 401654.
For #51087
For #52472
Change-Id: I6c6bd7ddcab1512c682e6b44f61c7bcde97f5c58
Reviewed-on: https://go-review.googlesource.com/c/go/+/401655
Run-TryBot: Michael Pratt <mpratt@google.com>
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This is a re-do of CL 388477, fixing #52472.
It is unsafe to call syscall.RawSyscall from syscall.Syscall with
-coverpkg=all and -race. This is because:
1. Coverage adds a sync/atomic call in RawSyscall to increment the
coverage counter.
2. Race mode instruments sync/atomic calls with TSAN runtime calls. TSAN
eventually calls runtime.racecallbackfunc, which expects
getg().m.p != 0, which is no longer true after entersyscall().
cmd/go actually avoids adding coverage instrumention to package runtime
in race mode entirely to avoid these kinds of problems. Rather than also
excluding all of syscall for this one function, work around by calling
RawSyscall6 instead, which avoids coverage instrumention both by being
written in assembly and in package runtime/*.
For #51087Fixes#52472
Change-Id: Iaffd27df03753020c4716059a455d6ca7b62f347
Reviewed-on: https://go-review.googlesource.com/c/go/+/401654
Run-TryBot: Michael Pratt <mpratt@google.com>
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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>
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The Faccessat call checks the user, group, or other permission bits of a
file to see if the calling process can access it. The test to see if the
group permissions should be used was made with the wrong group id, using
the process's group id rather than the file's group id. Fix this to use
the correct group id.
No test since we cannot easily change file permissions when not running
as root and the test is meaningless if running as root.
For #52313
Change-Id: I4e2c84754b0af7830b40fd15dedcbc58374d75ee
Reviewed-on: https://go-review.googlesource.com/c/go/+/399539
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
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A future change to gofmt will rewrite
// Doc comment.
//go:foo
to
// Doc comment.
//
//go:foo
Apply that change preemptively to all comments (not necessarily just doc comments).
For #51082.
Change-Id: Iffe0285418d1e79d34526af3520b415a12203ca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/384260
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
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Since Linux kernel 2.6.36, the pathname returned by the getcwd() system
call can be prefixed with the string "(unreachable)" in some cases [1].
Getcwd should return an absolute path, and doing otherwise is a
conformance issue; it also can be dangerous, since the path returned
can be an existing relative path.
Fix by returning ENOENT in case the path is not absolute. This is
essentially the same as what glibc does (since [2]).
[1] https://man7.org/linux/man-pages/man2/getcwd.2.html#BUGS
[2] https://sourceware.org/git/?p=glibc.git;a=commit;h=52a713fdd0a30e1bd79818e2e3c4ab44ddca1a94
Change-Id: I444c80eb3c836ff7d32c64c8b65d5112fa8c710f
Reviewed-on: https://go-review.googlesource.com/c/go/+/387174
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
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In issue 50113, we see that a thread blocked in a system call can result
in a hang of AllThreadsSyscall. To resolve this, we must send a signal
to these threads to knock them out of the system call long enough to run
the per-thread syscall.
Stepping back, if we need to send signals anyway, it should be possible
to implement this entire mechanism on top of signals. This CL does so,
vastly simplifying the mechanism, both as a direct result of
newly-unnecessary code as well as some ancillary simplifications to make
things simpler to follow.
Major changes:
* The rest of the mechanism is moved to os_linux.go, with fields in mOS
instead of m itself.
* 'Fixup' fields and functions are renamed to 'perThreadSyscall' so they
are more precise about their purpose.
* Rather than getting passed a closure, doAllThreadsSyscall takes the
syscall number and arguments. This avoids a lot of hairy behavior:
* The closure may potentially only be live in fields in the M,
hidden from the GC. Not necessary with no closure.
* The need to loan out the race context. A direct RawSyscall6 call
does not require any race context.
* The closure previously conditionally panicked in strange
locations, like a signal handler. Now we simply throw.
* All manual fixup synchronization with mPark, sysmon, templateThread,
sigqueue, etc is gone. The core approach is much simpler:
doAllThreadsSyscall sends a signal to every thread in allm, which
executes the system call from the signal handler. We use (SIGRTMIN +
1), aka SIGSETXID, the same signal used by glibc for this purpose. As
such, we are careful to only handle this signal on non-cgo binaries.
Synchronization with thread creation is a key part of this CL. The
comment near the top of doAllThreadsSyscall describes the required
synchronization semantics and how they are achieved.
Note that current use of allocmLock protects the state mutations of allm
that are also protected by sched.lock. allocmLock is used instead of
sched.lock simply to avoid holding sched.lock for so long.
Fixes#50113
Change-Id: Ic7ea856dc66cf711731540a54996e08fc986ce84
Reviewed-on: https://go-review.googlesource.com/c/go/+/383434
Reviewed-by: Austin Clements <austin@google.com>
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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
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These were identical. This is a preliminary step
towards remove allocs per UDP receive.
Change-Id: I83106cd3f1fe4bc5bae2d1b0ebd23eedd820abed
Reviewed-on: https://go-review.googlesource.com/c/go/+/361258
Trust: Josh Bleecher Snyder <josharian@gmail.com>
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These were identical. This is a preliminary step
towards remove allocs per UDP send.
Change-Id: I21e1264c7d4747baa626ddb93afff4c1cf225d13
Reviewed-on: https://go-review.googlesource.com/c/go/+/361256
Trust: Josh Bleecher Snyder <josharian@gmail.com>
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Most architectures currently already implement Pipe using the pipe2
syscall. Only 386, amd64 and mips{,le} still use the pipe syscall.
However, some systems (e.g. Android seccomp policies) block that
syscall, see #40828 for an example.
The pipe2 syscall was added in Linux kernel version 2.6.27. The minimum
required Linux kernel version for Go 1.18 will be changed to 2.6.32
per #45964 so it is possible to unify the implementation of Pipe using
the pipe2 syscall.
For #45964
Change-Id: I8ed6a391300c95f3107b4ec6b27d320e42fb535b
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The minimum required Linux kernel version for Go 1.18 will be changed to
2.6.32, see #45964. The current minimum required version is 2.6.23 and
accept4 was added in 2.6.28, so the fallback to accept in Accept on
Linux can be removed.
For #45964
Change-Id: I78fc4e5b58417bbc540912c9dbf1b1b3db888fea
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The minimum required Linux kernel version for Go 1.18 will be changed to
2.6.32, see #45964. The current minimum required version is 2.6.23 and
utimensat was added in 2.6.22, so the fallback isn't even necessary for
the current minimum supported version. Remove the fallback to utimes.
For #45964
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Android seems to block the accept syscall in newer versions. Use accept4
instead on kernel versions that support it (Linux 2.6.28 and newer) and
fall back to accept on ENOSYS.
Fixes#45767
Change-Id: If190ace0e0213207fdaf6eeb79a5543ef18456de
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This replaces five implementations scattered across low level packages.
(And I plan to use it in a sixth soon.)
Three of the five were byte-for-byte identical.
Change-Id: I3bbbeeac63723a487986c912b604e10ad1e042f4
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This change fixes two failng tests on linux-ppc64x:
- TestAllThreadsSyscall() exposed a real bug in the ppc64x support:
- It turns out that the r2 syscall return value is not defined
on all architectures. Notably linux-ppc64x so address that by
introducing a private architectural constant in the syscall
package, archHonorsR2: true if r2 has a determanistic value.
- TestSetuidEtc() was sensitive to /proc/<PID>/status content:
- The amount of padding space has changed with kernel vintage.
- Stress testing revealed a race with /proc files disappearing.
Fixes#42178
Change-Id: Ie6fc0b8f2f94a409ac0e5756e73bfce113274709
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This change adds two new methods for invoking system calls
under Linux: syscall.AllThreadsSyscall() and
syscall.AllThreadsSyscall6().
These system call wrappers ensure that all OSThreads mirror
a common system call. The wrappers serialize execution of the
runtime to ensure no race conditions where any Go code observes
a non-atomic OS state change. As such, the syscalls have
higher runtime overhead than regular system calls, and only
need to be used where such thread (or 'm' in the parlance
of the runtime sources) consistency is required.
The new support is used to enable these functions under Linux:
syscall.Setegid(), syscall.Seteuid(), syscall.Setgroups(),
syscall.Setgid(), syscall.Setregid(), syscall.Setreuid(),
syscall.Setresgid(), syscall.Setresuid() and syscall.Setuid().
They work identically to their glibc counterparts.
Extensive discussion of the background issue addressed in this
patch can be found here:
https://github.com/golang/go/issues/1435
In the case where cgo is used, the C runtime can launch pthreads that
are not managed by the Go runtime. As such, the added
syscall.AllThreadsSyscall*() return ENOTSUP when cgo is enabled.
However, for the 9 syscall.Set*() functions listed above, when cgo is
active, these functions redirect to invoke their C.set*() equivalents
in glibc, which wraps the raw system calls with a nptl:setxid fixup
mechanism. This achieves POSIX semantics for these functions in the
combined Go and C runtime.
As a side note, the glibc/nptl:setxid support (2019-11-30) does not
extend to all security related system calls under Linux so using
native Go (CGO_ENABLED=0) and these AllThreadsSyscall*()s, where
needed, will yield more well defined/consistent behavior over all
threads of a Go program. That is, using the
syscall.AllThreadsSyscall*() wrappers for things like setting state
through SYS_PRCTL and SYS_CAPSET etc.
Fixes#1435
Change-Id: Ib1a3e16b9180f64223196a32fc0f9dce14d9105c
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Follow glibc's implementation and check secondary group memberships
using Getgroups.
No test since we cannot easily change file permissions when not running
as root and the test is meaningless if running as root.
Same as CL 238722 did for x/sys/unix
Updates #39660
Change-Id: I6af50e27b255e33405558947a0ab3dfbc33b2d50
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Reimplement syscall wrappers for linux/arm64 in terms of supported
syscalls (or in case of Ustat make it return ENOSYS) and remove the
manually added SYS_* consts for the deprecated syscalls. Adapted from
golang.org/x/sys/unix where this is already done since CL 119655.
Change-Id: I94ab48a4645924df3822497d0575f1a1573d509f
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On linux/riscv64, the renameat syscall no longer exists and has been
superseded by renameat2. Thus we'll have to use Renameat2 to implement
Renameat on linux/riscv64 for #27532. Prepare for this by moving the
Renameat definition to the GOARCH specific files.
Follow CL 157899 which did the same for golang.org/x/sys/unix
Change-Id: I9670213cc3987df48fee962ddee36915a7785560
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The Linux kernel faccessat system call does not take a flags parameter.
The flag parameter to the C library faccessat function is implemented in C.
The syscall.Faccessat function takes a flags parameter. In older releases
we have passed the flags parameter to the kernel, which ignored it.
In CL 120015 we started returning an error if any flags were set.
That seems clearly better than ignoring them, but it turns out that some
code was using the flags. The code was previously subtly broken.
Now it is obviously broken. That is better, but we can do better still:
we can implement the flags as the C library does. That is what this CL does.
Change-Id: I259bd6f240c3951e939b81c3032dead3d9c567b4
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