recover4 allocates 16 pages of memory via mmap, makes a 4 page hole in it with
munmap, allocates another 16 pages of memory via normal allocation and then
tries to copy from one to the other. For some reason on arm64 (but no other
platform I have tested) the second allocation sometimes causes the runtime to
ask the kernel for 4 additional pages of memory -- which the kernel satisfies
by remapping the pages that were just unmapped!

Moving the second allocation before the munmap fixes this behaviour, I can run
recover4 tens of thousands of times without failure with this fix vs a failure
rate of ~0.5% before.

Fixes #12549

Change-Id: I490b895b606897e4f7f25b1b51f5d485a366fffb
Reviewed-on: https://go-review.googlesource.com/14632Reviewed-by: Dave Cheney <dave@cheney.net>

Found with https://github.com/remyoudompheng/go-misc/deadcode:

deadcode: walk.go:2228:1: applywritebarrier_bv is unused
deadcode: subr.go:355:1: gethunk is unused
deadcode: subr.go:1991:1: localexpr is unused
deadcode: dcl.go:82:1: poptodcl is unused
deadcode: swt.go:810:1: dumpcase is unused
deadcode: esc.go:251:1: satAdd8 is unused
deadcode: esc.go:387:1: outputsPerTag is unused
deadcode: obj.go:190:1: duint64 is unused
deadcode: obj.go:287:1: dstringptr is unused
deadcode: plive.go:95:1: xmalloc is unused
deadcode: plive.go:119:1: freeblock is unused

followed by

deadcode: go.go:633:1: hunk is unused
deadcode: go.go:635:1: nhunk is unused
deadcode: go.go:637:1: thunk is unused

after 'gethunk' was removed.

Some dead code in bv.go, mparith3.go, and dcl.go was left as is.

Passes go build -a -toolexec 'toolstash -cmp' std cmd.

Change-Id: Ia63519adedc8650d7095572ddd454fd923d3204d
Reviewed-on: https://go-review.googlesource.com/14610Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Remove several uses of stringsCompare.

Passes go build -a -toolexec 'toolstash -cmp' std cmd.

Change-Id: I3f2323df2ad8c03bad77e0a91d6e2e714803705b
Reviewed-on: https://go-review.googlesource.com/14556Reviewed-by: Dave Cheney <dave@cheney.net>

Fixes #12629.

Change-Id: Iee96dc4f806a38f3cd8e065b8d0d5f682bb7e29b
Reviewed-on: https://go-review.googlesource.com/14597Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This has been the root cause of a number of crashes caused by
fuzz throwing modem noise at the assembler, which in turn attempts
to print diagnostics but instead just gets crashes.

Fixes #12627.

Change-Id: I72c2da79d8eb240e1a37aa6140454c552b05e0f1
Reviewed-on: https://go-review.googlesource.com/14595Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #11600.

Change-Id: I8871d4e525168fed35115855483a237bbd6e5445
Reviewed-on: https://go-review.googlesource.com/14596Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This adds a test that debug/dwarf can read the skeleton DWARF data
from a split DWARF image (though it doesn't currently support piecing
the external DWARF data back together). This should work because
there's nothing particularly different about skeleton DWARF data, but
previously failed because of poor handling of unrecognized attributes.

Updates #12592.

Change-Id: I2fc5f4679883b05ebd7ec9f0b5c398a758181a32
Reviewed-on: https://go-review.googlesource.com/14542Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: jcd . <jcd@golang.org>

Currently, if the .debug_abbrev section of an ELF file contains
attributes that aren't known to the dwarf package and that have form
formSecOffset, the dwarf package will fail to open the DWARF data with
an error like "decoding dwarf section abbrev at offset 0x17: cannot
determine class of unknown attribute with formSecOffset". For the most
part, the class is implied by the form encoded in the abbrev section,
but formSecOffset can imply many different DWARF classes. Hence,
debug/dwarf disambiguates these using a table of known attributes.
However, it will reject the entire image if it encounters an attribute
it can't determine the class of. This is particularly unfortunate
because the caller may never even uses the offending attribute.

Fix this by introducing a ClassUnknown attribute class to use as a
fallback in these cases. This allows the dwarf package to load the
DWARF data and isolates the problem to just the affected attributes.

Fixes #12592.

Change-Id: I766227b136e9757f8b89c0b3ab8e9ddea899d94f
Reviewed-on: https://go-review.googlesource.com/14541Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: jcd . <jcd@golang.org>

The current code prints an error message and then tries to carry on.
This is not helpful for Go users: they see a message that means
nothing and that they can do nothing about.  In the only known case of
this message, in issue 11498, the best guess is that the netpoll code
went into an infinite loop.  Instead of doing that, crash the program.

Fixes #11498.

Change-Id: Idda3456c5b708f0df6a6b56c5bb4e796bbc39d7c
Reviewed-on: https://go-review.googlesource.com/12047Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

Aeshash currently computes the hash of the empty string as
hash("", seed) = seed.  This is bad because the hash of a compound
object with empty strings in it doesn't include information about
where those empty strings were.  For instance [2]string{"", "foo"}
and [2]string{"foo", ""} might get the same hash.

Fix this by returning a scrambled seed instead of the seed itself.
With this fix, we can remove the scrambling done by the generated
array hash routines.

The test also rejects hash("", seed) = 0, if we ever thought
it would be a good idea to try that.

The fallback hash is already OK in this regard.

Change-Id: Iaedbaa5be8d6a246dc7e9383d795000e0f562037
Reviewed-on: https://go-review.googlesource.com/14129Reviewed-by: jcd . <jcd@golang.org>

Updates #11241

Change-Id: If71f651f3b8aca432c91314358b93f195217d9ec
Reviewed-on: https://go-review.googlesource.com/14317Reviewed-by: Robert Griesemer <gri@golang.org>

Change-Id: I7de85034d499a9f859ab37d56463073f5cb29b35
Reviewed-on: https://go-review.googlesource.com/14592Reviewed-by: Rob Pike <r@golang.org>

More protection against random input bytes.

Fixes #12614.

Change-Id: Ie9f817de1376a10bb80b22ecee3bae4f1d26cc6c
Reviewed-on: https://go-review.googlesource.com/14563Reviewed-by: Andrew Gerrand <adg@golang.org>

There was no verification in Funcs that the map had valid names,
which meant that the error could only be caught when parsing
the template that tried to use them. Fix this by validating the names
in Funcs and panicking before parsing if there is a bad name.

This is arguably an API change, since it didn't trigger a panic
before, but Funcs did already panic if the function itself was no
good, so I argue it's an acceptable change to add more sanity
checks.

Fixes #9685.

Change-Id: Iabf1d0602c49d830f3ed71ca1ccc7eb9a5521ff5
Reviewed-on: https://go-review.googlesource.com/14562Reviewed-by: Andrew Gerrand <adg@golang.org>

Cleaning along the way:
-convert variable types from int to bool
-remove unnecessary functions
-remove unnecessary type conversion
-remove unnecessary variable declarations
-transform struct{string,string} with lookup to map[string]string

This change passes go build -toolexec 'toolstash -cmp' -a std.

Change-Id: I259728fe4afd7f23b67f08fab856ce0abee57b21
Reviewed-on: https://go-review.googlesource.com/14435Reviewed-by: Ian Lance Taylor <iant@golang.org>

They added no value.

Change-Id: I9e690379d2dfd983266de0ea5231f2b57c8b1517
Reviewed-on: https://go-review.googlesource.com/14568Reviewed-by: Ian Lance Taylor <iant@golang.org>

CL 13166 skipped external tests on freebsd/arm with the rationale
that the cmd/go tests are not architecture dependent.

This CL does the same for linux/arm to help linux/arm users who are
building Go on platforms like the Raspberry Pi where ./all.bash
frequently times out due to a lack of resources.

Change-Id: Iae1a25b63b74200da3f1b5637da0fa5c2dceeb83
Reviewed-on: https://go-review.googlesource.com/13342Reviewed-by: Ian Lance Taylor <iant@golang.org>

Windows amd64 requires all syscall callers to provide room for first
4 parameters on stack. We do that for all our syscalls, except inside
of usleep2. In https://codereview.appspot.com/7563043#msg3 rsc says:

"We don't need the stack alignment and first 4 parameters on amd64
because it's just a system call, not an ordinary function call."

He seems to be wrong on both counts. But alignment is already fixed.
Fix parameter space now too.

Fixes #12444

Change-Id: I66a2a18d2f2c3846e3aa556cc3acc8ec6240bea0
Reviewed-on: https://go-review.googlesource.com/14282Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #12437.

Change-Id: I5463970a6259527003eb0e12903a338cc78e0683
Reviewed-on: https://go-review.googlesource.com/14564Reviewed-by: Chris Manghane <cmang@golang.org>

Glibc uses some special signals for special thread operations.  These
signals will be used in programs that use cgo and invoke certain glibc
functions, such as setgid.  In order for this to work, these signals
need to not be masked by any thread.  Before this change, they were
being masked by programs that used os/signal.Notify, because it
carefully masks all non-thread-specific signals in all threads so that a
dedicated thread will collect and report those signals (see ensureSigM
in signal1_unix.go).

This change adds the two glibc special signals to the set of signals
that are unmasked in each thread.

Fixes #12498.

Change-Id: I797d71a099a2169c186f024185d44a2e1972d4ad
Reviewed-on: https://go-review.googlesource.com/14297Reviewed-by: David Crawshaw <crawshaw@golang.org>

This puts the _Root* indexes in a more friendly order and tweaks
markrootSpans to use a for-range loop instead of its own indexing.

Change-Id: I2c18d55c9a673ea396b6424d51ef4997a1a74825
Reviewed-on: https://go-review.googlesource.com/14548Reviewed-by: Rick Hudson <rlh@golang.org>

Commit 0e6a6c51 removed readyExecute a long time ago, but left behind
the g.readyg field that was used by readyExecute. Remove this now
unused field.

Change-Id: I41b87ad2b427974d256ec7a7f6d4bdc2ce8a13bb
Reviewed-on: https://go-review.googlesource.com/13111Reviewed-by: Rick Hudson <rlh@golang.org>

This is a cleanup following cc8f5441, which was a minimal change to fix
issue #11617. This consolidates the two places in mSpan_Sweep that
update sweepgen. Previously this was necessary because sweepgen must
be updated before freeing the span, but we freed large spans early.
Now we free large spans later, so there's no need to duplicate the
sweepgen update. This also means large spans can take advantage of the
sweepgen sanity checking performed for other spans.

Change-Id: I23b79dbd9ec81d08575cd307cdc0fa6b20831768
Reviewed-on: https://go-review.googlesource.com/12451Reviewed-by: Rick Hudson <rlh@golang.org>

Marking of span roots can represent a significant fraction of the time
spent in mark termination. Simply traversing the span list takes about
1ms per GB of heap and if there are a large number of finalizers (for
example, for network connections), it may take much longer.

Improve the situation by splitting the span scan into 128 subtasks
that can be executed in parallel and load balanced by the markroots
parallel for. This lets the GC balance this job across the Ps.

A better solution is to do this during concurrent mark, or to improve
it algorithmically, but this is a simple change with a lot of bang for
the buck.

This was suggested by Rhys Hiltner.

Updates #11485.

Change-Id: I8b281adf0ba827064e154a1b6cc32d4d8031c03c
Reviewed-on: https://go-review.googlesource.com/13112Reviewed-by: Keith Randall <khr@golang.org>

The call to hash the trace stack reversed the "seed" and "size"
arguments to memhash and, hence, always called memhash with a 0 size,
which dutifully returned a hash value that depended only on the number
of PCs in the stack and not their values. As a result, all stacks were
put in to a very subset of the 8,192 buckets.

Fix this by passing these arguments in the correct order.

Change-Id: I67cd29312f5615c7ffa23e205008dd72c6b8af62
Reviewed-on: https://go-review.googlesource.com/13613Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

Passes go build -a -toolexec 'toolstash -cmp' std cmd

Change-Id: Ief4613cfb341172a85e3a894f44fb2bb308c7b55
Reviewed-on: https://go-review.googlesource.com/14554
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

Fixes #12606

Change-Id: Ib68cb20108ad35c3dd96e606649c4c8f9c0f085c
Reviewed-on: https://go-review.googlesource.com/14571Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Id07811a25bf4aa3ff834e7254a3dfb04522b2926
Reviewed-on: https://go-review.googlesource.com/14174Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

Fixes #11959

This test runs 100 concurrent callbacks from C to Go consuming 100
operating system threads, which at 8mb a piece (the default on linux/arm)
would reserve over 800mb of address space. This would frequently
cause the test to fail on platforms with ~1gb of ram, such as the
raspberry pi.

This change reduces the thread stack allocation to 256kb, a number picked
at random, but at 1/32th the previous size, should allow the test to
pass successfully on all platforms.

Change-Id: I8b8bbab30ea7b2972b3269a6ff91e6fe5bc717af
Reviewed-on: https://go-review.googlesource.com/13731
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Capitanio <capnm9@gmail.com>
Reviewed-by: Minux Ma <minux@golang.org>

It's because runtime links to ntdll, and ntdll exports a couple
incompatible libc functions. We must link to msvcrt first and
then try ntdll.

Fixes #12030.

Change-Id: I0105417bada108da55f5ae4482c2423ac7a92957
Reviewed-on: https://go-review.googlesource.com/14472Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Although bnum was being called with a Bits value, a limitation
of the escape analyser (golang/go#12588) meant that taking the
address of the Bits.b array in the range statement caused the
formal parameter to escape to the heap.

Passing the a pointer to a Bits, as with all the other Bits helper
methods avoids the allocation.

Before:
BenchmarkBnum1-4        20000000                69.6 ns/op            32 B/op          1 allocs/op

After:
BenchmarkBnum1-4        100000000               10.1 ns/op             0 B/op          0 allocs/op

Change-Id: I673bd57ddc032ee67d09474156d795fb1ba72018
Reviewed-on: https://go-review.googlesource.com/14501Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #12578.

Change-Id: I257d70a67609463e24936bc1739285da154be2fe
Reviewed-on: https://go-review.googlesource.com/14531Reviewed-by: Rob Pike <r@golang.org>

The current version of go/printer formats the following code
like this:

	foo.Bar().
		Run(func() {
		do()
	}).
		Set(map[string]interface{}{
		"x": "three",
		"y": 4,
	}).
		Run(
		func() {
			do()
		},
	)

This CL changes the go/printer behaviour to make the code look
like this.

	foo.Bar().
		Run(func() {
			do()
		}).
		Set(map[string]interface{}{
			"x": "three",
			"y": 4,
		}).
		Run(
			func() {
				do()
			},
		)

Fixes #12066.

Change-Id: If0f525dae1a5d45f9ba40534dbb65715d7e8001b
Reviewed-on: https://go-review.googlesource.com/13928Reviewed-by: Robert Griesemer <gri@golang.org>

Fixes #11626.

Change-Id: I1b70c0844473c3b57a53d7cca747ea5cdc68d232
Reviewed-on: https://go-review.googlesource.com/14526
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Simplify slice/map literal expressions.
Caught with gofmt -d -s, fixed with gofmt -w -s

Change-Id: I639cfb02b1f57dea4087863df3995889c9371529
Reviewed-on: https://go-review.googlesource.com/13837Reviewed-by: Andrew Gerrand <adg@golang.org>

Simplify slice/map literal expression.
Caught with gofmt -d -s

Change-Id: I7f38ef9fb528e2fd284bd0f190fbdf4a91956e55
Reviewed-on: https://go-review.googlesource.com/13834Reviewed-by: Andrew Gerrand <adg@golang.org>

Simplify slice/map literal expression.
Caught with gofmt -d -s, fixed with gofmt -w -s

Change-Id: I4472c6003cf66e65f6e69050872ff95c96f01253
Reviewed-on: https://go-review.googlesource.com/13836Reviewed-by: Andrew Gerrand <adg@golang.org>

Simplify slice/map literal expressions.
Caught with gofmt -d -s, fixed with gofmt -w -s
Checked that the result can still be compiled with Go 1.4.

Change-Id: I06bce110bb5f46ee2f45113681294475aa6968bc
Reviewed-on: https://go-review.googlesource.com/13839Reviewed-by: Andrew Gerrand <adg@golang.org>

Simplify slice/map literal expressions.
Caught with gofmt -d -s, fixed with gofmt -w -s
Checked that the result can still be compiled with Go 1.4.

Change-Id: I201cd90fdfb8de2971c46ad7fce64111152b697e
Reviewed-on: https://go-review.googlesource.com/13832Reviewed-by: Andrew Gerrand <adg@golang.org>

One (12466) was an actual logic error, backing up when there was
nothing there. The others were due to continuing to process an
instruction when it cannot work.

Methodically stop assembling an instruction when it's not going to
succeed.

Fixes #12466.
Fixes #12467.
Fixes #12468.

Change-Id: I88c568f2b9c1a8408043b2ac5a78f5e2ffd62abd
Reviewed-on: https://go-review.googlesource.com/14498Reviewed-by: Andrew Gerrand <adg@golang.org>