Two memory allocator bug fixes.

- efence is not maintaining the proper heap metadata
  to make eventual memory reuse safe, so use SysFault.

- now that our heap PageSize is 8k but most hardware
  uses 4k pages, SysAlloc and SysReserve results must be
  explicitly aligned. Do that in a few more call sites and
  document this fact in malloc.h.

Fixes #7448.

LGTM=iant
R=golang-codereviews, josharian, iant
CC=dvyukov, golang-codereviews
https://golang.org/cl/71750048

cmd/5c/txt.c was missing from CL 72010043.

LGTM=bradfitz
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/72220043

Replaces CL 70000043.

Introduce linkarchinit() from cmd/ld.

For cmd/6c, switch to the amd64p32 linker model if we are building under nacl/amd64p32.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/72010043

I've just needed the G status on fault to debug runtime bug.
For some reason we print everything except header here.
Make it more informative and consistent.

R=rsc
CC=golang-codereviews
https://golang.org/cl/67870056

warning: pkg/runtime/mgc0.c:2352 format mismatch p UVLONG, arg 2
warning: pkg/runtime/mgc0.c:2352 format mismatch p UVLONG, arg 3

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71950044

Implement custom assembly thunks for hot race calls (memory accesses and function entry/exit).
The thunks extract caller pc, verify that the address is in heap or global and switch to g0 stack.

Before:
ok  	regexp	3.692s
ok  	compress/bzip2	9.461s
ok  	encoding/json	6.380s
After:
ok  	regexp	2.229s (-40%)
ok  	compress/bzip2	4.703s (-50%)
ok  	encoding/json	3.629s (-43%)

For comparison, normal non-race build:
ok  	regexp	0.348s
ok  	compress/bzip2	0.304s
ok  	encoding/json	0.661s
Race build:
ok  	regexp	2.229s (+540%)
ok  	compress/bzip2	4.703s (+1447%)
ok  	encoding/json	3.629s (+449%)

Also removes some race-related special cases from cgocall and scheduler.
In long-term it will allow to remove cyclic runtime/race dependency on cmd/cgo.

Fixes #4249.
Fixes #7460.
Update #6508
Update #6688

R=iant, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/55100044

Fixes #7196

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, iant
https://golang.org/cl/69970052

NOT A LANGUAGE CHANGE.

Fixes #7073.

LGTM=r
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/68840045

LGTM=khr
R=khr
CC=golang-codereviews, rsc
https://golang.org/cl/69870054

It was caused by mstats.heap_alloc skew.
Fixes #7430.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, rsc
https://golang.org/cl/69870055

Currently it fails on second and subsequent runs (when using -cpu=1,2,4) as:
--- FAIL: TestUseProxy-4 (0.00 seconds)
proxy_test.go:109: useProxy(barbaz.net) = true, want false
proxy_test.go:109: useProxy(foobar.com) = true, want false
proxy_test.go:109: useProxy(www.foobar.com) = true, want false

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://golang.org/cl/71940044

Fixes #7459.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/71060044

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71950043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71940043

Tested GOARM=6 on Raspberry Pi, and I found only a few tests that
use sub-normal numbers fails. I have a patch to NetBSD kernel pending
that fixes this issue (NetBSD kernel doesn't allow us to disable the
Flush-to-Zero feature).

LGTM=jsing
R=golang-codereviews, jsing
CC=golang-codereviews
https://golang.org/cl/70730043

LGTM=jsing
R=golang-codereviews, jsing
CC=golang-codereviews
https://golang.org/cl/70720043

The underlying type of the predeclared type error is not itself,
but the interface it is defined as.

Fixes #7444.

LGTM=r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/71790044

Fixes #7449.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71610044

To be enabled by https://golang.org/cl/71230045/

Update #7442

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/69860056

I missed this one in codereview.appspot.com/70010050
Same thing, but different test.

Fixes windows-amd64-race and likely other Windows
machines failing like:
http://build.golang.org/log/0382bf0048bf5835a51a8a902df5c6fc73cd7ff5

LGTM=adg
R=rsc, adg
CC=golang-codereviews
https://golang.org/cl/71770043

CLA links are now redirects. Use new URLs instead.

Also, use https:// links for all Google sites where
the http version just redirects to https anyway.
(That's all links on the page, as it turns out)

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/69980051

Also add it to doc/go1.3.txt.

Update #7289

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/71740043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71670043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71700043

Fixes #7289.

LGTM=bradfitz
R=golang-codereviews, r, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/52660047

Generated by addca.

R=gobot
CC=golang-codereviews
https://golang.org/cl/71570044

Fixes the syscall test.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71470043

This documents the implemented behavior of both
gc and gccgo as an implementation restriction.

NOT A LANGUAGE CHANGE.

Fixes #5425.

LGTM=rsc, r, iant
R=r, iant, rsc, ken
CC=golang-codereviews
https://golang.org/cl/71430043

Essentialy for running tests without a working cmd/go.
While we're at it, also fix a typo.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/70640043

During the glob decoding process interface values are set to concrete
values after a test for assignability. If the assignability test fails
a slightly vague error message is produced. While technically accurate
the error message does not clearly describe the problem.

Rewrite the error message to include the usage of the word assignable,
which makes it clear the concrete value type is not assignable to the
interface value type.

Fixes #6467.

LGTM=r
R=golang-codereviews, rsc, r
CC=golang-codereviews
https://golang.org/cl/71590043

LGTM=rsc
R=golang-codereviews, josharian, dave, iant, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/47870043

Recently NetBSD starts to enforce this, and refuses to execute
the program if n is larger than the sum of entry sizes.

Before:
$ readelf -n ../bin/go.old
Notes at offset 0x00000bd0 with length 0x00000019:
  Owner         Data size       Description
  NetBSD                0x00000004      NT_VERSION (version)
readelf: Warning: corrupt note found at offset 18 into core notes
readelf: Warning:  type: 0, namesize: 00000000, descsize: 00000000
$ readelf -n ../bin/go
Notes at offset 0x00000bd0 with length 0x00000018:
Owner         Data size       Description
NetBSD                0x00000004      NT_VERSION (version)

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/70710043

Add CgoFiles to the covered files when building
with cover support.

LGTM=rsc
R=golang-codereviews, gobot, r, rsc
CC=golang-codereviews
https://golang.org/cl/34680044

Apparently, the Windows routines sometimes fail to generate output.
Copy the Unix stdio-based implementations instead.

Suggested by Pietro Gagliardi in CL 65280043 but that CL
seems to have been abandoned.

Fixes #7242.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71550044

Fixes #5793.

LGTM=rsc
R=rsc, adonovan, dave
CC=golang-codereviews
https://golang.org/cl/13367051

Update #6882.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/69860055

32-bit Windows uses "structured exception handling" (SEH) to
handle hardware faults: that there is a per-thread linked list
of fault handlers maintained in user space instead of
something like Unix's signal handlers. The structures in the
linked list are required to live on the OS stack, and the
usual discipline is that the function that pushes a record
(allocated from the current stack frame) onto the list pops
that record before returning. Not to pop the entry before
returning creates a dangling pointer error: the list head
points to a stack frame that no longer exists.

Go pushes an SEH record in the top frame of every OS thread,
and that record suffices for all Go execution on that thread,
at least until cgo gets involved.

If we call into C using cgo, that called C code may push its
own SEH records, but by the convention it must pop them before
returning back to the Go code. We assume it does, and that's
fine.

If the C code calls back into Go, we want the Go SEH handler
to become active again, not whatever C has set up. So
runtime.callbackasm1, which handles a call from C back into
Go, pushes a new SEH record before calling the Go code and
pops it when the Go code returns. That's also fine.

It can happen that when Go calls C calls Go like this, the
inner Go code panics. We allow a defer in the outer Go to
recover the panic, effectively wiping not only the inner Go
frames but also the C calls. This sequence was not popping the
SEH stack up to what it was before the cgo calls, so it was
creating the dangling pointer warned about above. When
eventually the m stack was used enough to overwrite the
dangling SEH records, the SEH chain was lost, and any future
panic would not end up in Go's handler.

The bug in TestCallbackPanic and friends was thus creating a
situation where TestSetPanicOnFault - which causes a hardware
fault - would not find the Go fault handler and instead crash
the binary.

Add checks to TestCallbackPanicLocked to diagnose the mistake
in that test instead of leaving a bad state for another test
case to stumble over.

Fix bug by restoring SEH chain during deferred "endcgo"
cleanup.

This bug is likely present in Go 1.2.1, but since it depends
on Go calling C calling Go, with the inner Go panicking and
the outer Go recovering the panic, it seems not important
enough to bother fixing before Go 1.3. Certainly no one has
complained.

Fixes #7470.

LGTM=alex.brainman
R=golang-codereviews, alex.brainman
CC=golang-codereviews, iant, khr
https://golang.org/cl/71440043

Regenerate z-files for DragonFly BSD 3.6.

F_DUP_FD_CLOEXEC is now supported, so remove the zero value constant
from types_dragonfly.go so that we use the generated value from the
z-files.

LGTM=mikioh.mikioh
R=golang-codereviews, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/70080047

The format of the DragonFly BSD syscalls.master file has changed
slightly - update mksysnum_dragonfly.pl to match.

LGTM=mikioh.mikioh
R=golang-codereviews, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/71460044

Disable the "udp" to IPv6 unicast address on the loopback interface
test under DragonFly BSD. This currently returns a local address of
0.0.0.1, rather than an IPv6 address with zone identifier.

Update #7473

LGTM=mikioh.mikioh
R=golang-codereviews, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/71500044