delta/go-git.git/src/runtime/sys_linux_arm64.s, branch dev.go2go

runtime: make nanotime1 reentrant

2020-08-10T18:06:04+00:00

Currently, nanotime1 (and walltime1) is not reentrant, in that it
sets m.vdsoSP at entry and clears it at exit. If a signal lands
in between, and nanotime1 is called from the signal handler, it
will clear m.vdsoSP while we are still in nanotime1. If (in the
unlikely event) it is signaled again, m.vdsoSP will be wrong,
which may cause the stack unwinding code to crash.

This CL makes it reentrant, by saving/restoring the previous
vdsoPC and vdsoSP, instead of setting it to 0 at exit.

TODO: have some way to test?

Change-Id: I9ee53b251f1d8a5a489c71d4b4c0df1dee70c3e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/246763
Run-TryBot: Cherry Zhang 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor

runtime: use CBZ/CBNZ in linux/arm64 assembly code

2020-03-03T09:29:47+00:00

Replace compare and branch on zero/non-zero instructions in linux/arm64
assembly files with CBZ/CBNZ.

Change-Id: I4dbf56678f85827e83b5863804368bc28a4603b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/209617
Run-TryBot: Tobias Klauser 
TryBot-Result: Gobot Gobot 
Reviewed-by: Tobias Klauser

runtime: use FP offsets for pipe/pipe2 on freebsd/arm64 and linux/arm64

2020-01-08T14:58:33+00:00

This is more readable and less error-prone than using RSP offsets.

Suggested during review of CL 212765.

Change-Id: I070190abeeac8eae5dbd414407602619d9d57422
Reviewed-on: https://go-review.googlesource.com/c/go/+/213577
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Cherry Zhang

runtime: correct setNonblock on linux/arm64

2020-01-07T02:56:05+00:00

The current code uses EOR (exclusive OR), which will result in the O_NONBLOCK
flag being toggled rather than being set. Other implementations use OR, hence
this is likely a bug.

Change-Id: I5dafa9c572452070bd37789c8a731ad6d04a86cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/212766
Run-TryBot: Ian Lance Taylor 
Reviewed-by: Cherry Zhang 
Reviewed-by: Ian Lance Taylor 
TryBot-Result: Gobot Gobot

runtime: don't save G during VDSO if we're handling signal

2019-11-11T15:16:05+00:00

On some platforms (currently ARM and ARM64), when calling into
VDSO we store the G to the gsignal stack, if there is one, so if
we receive a signal during VDSO we can find the G.

If we receive a signal during VDSO, and within the signal handler
we call nanotime again (e.g. when handling profiling signal),
we'll save/clear the G slot on the gsignal stack again, which
clobbers the original saved G. If we receive a second signal
during the same VDSO execution, we will fetch a nil G, which will
lead to bad things such as deadlock.

Don't save G if we're calling VDSO code from the gsignal stack.
Saving G is not necessary as we won't receive a nested signal.

Fixes #35473.

Change-Id: Ibfd8587a3c70c2f1533908b056e81b94d75d65a5
Reviewed-on: https://go-review.googlesource.com/c/go/+/206397
Run-TryBot: Cherry Zhang 
TryBot-Result: Gobot Gobot 
Reviewed-by: Bryan C. Mills

runtime: don't fetch G from signal stack when using cgo

2019-11-05T18:58:41+00:00

When using cgo, we save G to TLS, and when a signal happens, we
load G from TLS in sigtramp. This should give us a valid G. Don't
try to fetch from the signal stack. In particular, C code may
change the signal stack or call our signal handler directly (e.g.
TSAN), so we are not necessarily running on the original gsignal
stack where we saved G.

Also skip saving G on the signal stack when using cgo.

Updates #35249.

Change-Id: I40749ce6682709bd4ebfdfd9f23bd0f317fc197d
Reviewed-on: https://go-review.googlesource.com/c/go/+/204519
Reviewed-by: Ian Lance Taylor

runtime: M-targeted signals for Linux

2019-10-26T02:52:25+00:00

We'll add a test once all of the POSIX platforms are done.

For #10958, #24543.

Change-Id: If7e3f14e8391791364877629bf415d9f8e788b0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/201401
Run-TryBot: Austin Clements 
Reviewed-by: Cherry Zhang

runtime: save/fetch g register during VDSO on ARM and ARM64

2019-10-23T22:59:54+00:00

On ARM and ARM64, during a VDSO call, the g register may be
temporarily clobbered by the VDSO code. If a signal is received
during the execution of VDSO code, we may not find a valid g
reading the g register. In CL 192937, we conservatively assume
g is nil. But this approach has a problem: we cannot handle
the signal in this case. Further, if the signal is not a
profiling signal, we'll call badsignal, which calls needm, which
wants to get an extra m, but we don't have one in a non-cgo
binary, which cuases the program to hang.

This is even more of a problem with async preemption, where we
will receive more signals than before. I ran into this problem
while working on async preemption support on ARM64.

In this CL, before making a VDSO call, we save the g on the
gsignal stack. When we receive a signal, we will be running on
the gsignal stack, so we can fetch the g from there and move on.

We probably want to do the same for PPC64. Currently we rely on
that the VDSO code doesn't actually clobber the g register, but
this is not guaranteed and we don't have control with.

Idea from discussion with Dan Cross and Austin.

Should fix #34391.

Change-Id: Idbefc5e4c2f4373192c2be797be0140ae08b26e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/202759
Run-TryBot: Cherry Zhang 
Reviewed-by: Austin Clements

runtime: change read and write to return negative errno value

2019-10-21T14:07:34+00:00

The internal read and write functions used to return -1 on error;
change them to return a negative errno value instead.
This will be used by later CLs in this series.

For most targets this is a simplification, although for ones that call
into libc it is a complication.

Updates #27707

Change-Id: Id02bf9487f03e7e88e4f2b85e899e986738697ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/171823
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Michael Knyszek

runtime: define nonblockingPipe

2019-10-20T21:15:55+00:00

This requires defining pipe, pipe2, and setNonblock for various platforms.

The new function is currently only used on AIX. It will be used by
later CLs in this series.

Updates #27707

Change-Id: Id2f987b66b4c66a3ef40c22484ff1d14f58e9b31
Reviewed-on: https://go-review.googlesource.com/c/go/+/171822
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Michael Knyszek 
Reviewed-by: Brad Fitzpatrick