This adds a "framepointer" GOEXPERIMENT that that makes the amd64
toolchain maintain base pointer chains in the same way that gcc
-fno-omit-frame-pointer does.  Go doesn't use these saved base
pointers, but this does enable external tools like Linux perf and
VTune to unwind Go stacks when collecting system-wide profiles.

This requires support in the compilers to not clobber BP, support in
liblink for generating the BP-saving function prologue and unwinding
epilogue, and support in the runtime to save BPs across preemption, to
skip saved BPs during stack unwinding and, and to adjust saved BPs
during stack moving.

As with other GOEXPERIMENTs, everything from the toolchain to the
runtime must be compiled with this experiment enabled.  To do this,
run make.bash (or all.bash) with GOEXPERIMENT=framepointer.

Change-Id: I4024853beefb9539949e5ca381adfdd9cfada544
Reviewed-on: https://go-review.googlesource.com/2992Reviewed-by: Russ Cox <rsc@golang.org>

Any place that clobbers BP in the runtime can potentially interfere
with frame pointer unwinding with GOEXPERIMENT=framepointer.  This
change eliminates uses of BP in the runtime to address this problem.
We have spare registers everywhere this occurs, so there's no downside
to eliminating BP.  Where possible, this uses the same new register as
the amd64p32 runtime, which doesn't use BP due to restrictions placed
on it by NaCL.

One nice side effect of this is that it will let perf/VTune unwind the
call stack even through a call to systemstack, which will let us get
really good call graphs from the garbage collector.

Change-Id: I0ffa14cb4dd2b613a7049b8ec59df37c52286212
Reviewed-on: https://go-review.googlesource.com/3390Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

m.gcing has become overloaded to mean "don't preempt this g" in
general.  Once the garbage collector is preemptible, the one thing it
*won't* mean is that we're in the garbage collector.

So, rename gcing to "preemptoff" and make it a string giving a reason
that preemption is disabled.  gcing was never set to anything but 0 or
1, so we don't have to worry about there being a stack of reasons.

Change-Id: I4337c29e8e942e7aa4f106fc29597e1b5de4ef46
Reviewed-on: https://go-review.googlesource.com/3660Reviewed-by: Russ Cox <rsc@golang.org>

Commit 656be317 replaced onM with systemstack, but missed updating a
few comments that still referred to onM.  Update these.

Change-Id: I0efb017e9a66ea0adebb6e1da6e518ee11263f69
Reviewed-on: https://go-review.googlesource.com/3664Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

9g generates needlessly complex code for small copies.  There are a
few other things that need to be improved about the copy code, so for
now just note the problem.

Change-Id: I0f1de4b2f9197a2635e27cc4b91ecf7a6c11f457
Reviewed-on: https://go-review.googlesource.com/3665Reviewed-by: Russ Cox <rsc@golang.org>

Change-Id: I278ce47b38ec5732d981aec06b71f9ee5747c3bb
Reviewed-on: https://go-review.googlesource.com/3730Reviewed-by: Alan Donovan <adonovan@google.com>

In stripCommonPrefix, the prefix was correctly calculated in all cases,
except one. That unhandled case is when there are more than 2 lines,
but all lines are blank (other than the first and last lines,
which contain /* and */ respectively).
This change detects that case and correctly sets the prefix calculated
from the last line. This is consistent with the (correct) behavior
that happens when there's at least one non-blank line.
That fixes issue #9751 that occurs for problematic input,
where cmd/gofmt and go/source would insert extra indentation on
every format operation. It also allows go/printer itself to print
such parsed files in an expected way.

Fixes #9751.

Change-Id: Id3dfb945beb59ffad3705085a3c285fca30a5f87
Reviewed-on: https://go-review.googlesource.com/3684Reviewed-by: Robert Griesemer <gri@golang.org>

Since CL 3676, the TestMkdirAllAtSlash test
depends on syscall.EROFS, which isn't defined
on Plan 9.

This change works around this issue by
defining a system dependent isReadonlyError
function.

Change-Id: If972fd2fe4828ee3bcb8537ea7f4ba29f7a87619
Reviewed-on: https://go-review.googlesource.com/3696Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #9738.

Change-Id: Iab75de2d78335d4e31c3dce6a0e1826d8cddf5f3
Reviewed-on: https://go-review.googlesource.com/3690Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

Change-Id: Iea4221186325783db2029b07af1409015ddeda99
Reviewed-on: https://go-review.googlesource.com/3695Reviewed-by: Dave Cheney <dave@cheney.net>

This is a followup to CL 3676.

Rather than silently returning from the test, a pass,
use the Skip facility to mark the test as skipped.

Change-Id: I90d237e770150bf8d69f14fb09874e70894a7f86
Reviewed-on: https://go-review.googlesource.com/3682Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

On some systems (e.g. ChromeOS), / is mounted read-only.
This results in error code syscall.EROFS, which I guess
is just as valid as syscall.EACCES for this test.

Change-Id: I9188d5437a1b5ac1daa9c68b95b8dcb447666ca3
Reviewed-on: https://go-review.googlesource.com/3676Reviewed-by: Ian Lance Taylor <iant@golang.org>

No other functional changes.

Change-Id: I7e0bb7452c6a265535297ec7ce6a629f1aff695c
Reviewed-on: https://go-review.googlesource.com/3674Reviewed-by: Alan Donovan <adonovan@google.com>

No other functional changes.

Change-Id: I8be1fc488caa4f3d4c00afcb8c00475bfcd10709
Reviewed-on: https://go-review.googlesource.com/3673Reviewed-by: Alan Donovan <adonovan@google.com>

No other functional changes.

Change-Id: If0d9e6208d53478e70d991b6926ea196b2cccf2e
Reviewed-on: https://go-review.googlesource.com/3672Reviewed-by: Alan Donovan <adonovan@google.com>

No functional changes.

Change-Id: Ibbb705b167603d30467f3ebb83a3bb39845306a5
Reviewed-on: https://go-review.googlesource.com/3671Reviewed-by: Alan Donovan <adonovan@google.com>

Change-Id: I1eaebf956a69e0958201cc5e0a9beefa062c71e1
Reviewed-on: https://go-review.googlesource.com/3454Reviewed-by: Alan Donovan <adonovan@google.com>

Change-Id: I257211f10b334eb4828be96cd434d588bfb1a378
Reviewed-on: https://go-review.googlesource.com/3605Reviewed-by: Rob Pike <r@golang.org>

Fixes #9629

Change-Id: I66091003b97742ca6d857fe51d609833ab727216
Reviewed-on: https://go-review.googlesource.com/3023Reviewed-by: Rob Pike <r@golang.org>

Fixes #9656

Change-Id: I1158636683492ef12eeafb12e257d205026adc3f
Reviewed-on: https://go-review.googlesource.com/3175Reviewed-by: Minux Ma <minux@golang.org>

These are no longer used by anything.

Change-Id: I50c971418b07cafc983242833a196ba2028a2723
Reviewed-on: https://go-review.googlesource.com/3603Reviewed-by: Rob Pike <r@golang.org>

Another attempt to fix the arm build by moving the include of signal.h
to cmd/lex.c, unless we are building on plan9.

Obviously if we had a plan9/arm builder this would probably not work, but
this is only a temporary measure until the c2go transition is complete.

Change-Id: I7f8ae27349b2e7a09c55db03e02a01939159a268
Reviewed-on: https://go-review.googlesource.com/3566Reviewed-by: Russ Cox <rsc@golang.org>

The following line in sysFree:
n += (n + memRound) &^ memRound
doubles value of n (n += n).
Which is wrong and can lead to memory corruption.

Fixes #9712

Change-Id: I3c141b71da11e38837c09408cf4f1d22e8f7f36e
Reviewed-on: https://go-review.googlesource.com/3602Reviewed-by: David du Colombier <0intro@gmail.com>

Change-Id: I8c7fcc7705070bc9979e39d08a4c9b2870087a08
Reviewed-on: https://go-review.googlesource.com/3500Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

Change-Id: I32cad7358f5bfd8e107179653bdc55a69fbe772a
Reviewed-on: https://go-review.googlesource.com/3579Reviewed-by: Russ Cox <rsc@golang.org>

REG_R0 etc are defined in <ucontext.h> on ARM systems.
Possible use of uninitialized n in 8g/reg.c.

Change-Id: I6e8ce83a6515ca2b779ed8a344a25432db629cc2
Reviewed-on: https://go-review.googlesource.com/3578Reviewed-by: Russ Cox <rsc@golang.org>

There are no D_ names anymore.

Change-Id: Id3f1ce5efafb93818e5fd16c47ff48bbf61b5339
Reviewed-on: https://go-review.googlesource.com/3520Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

Change-Id: I55afed0eabf3c38e72ff105294782ac36446b66b
Reviewed-on: https://go-review.googlesource.com/3519Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

Change-Id: I19ed283962aa0221cf806307bde9ea0773a1bfd4
Reviewed-on: https://go-review.googlesource.com/3518Reviewed-by: Austin Clements <austin@google.com>

Change-Id: I5535582660da3504663c6cba2637da132c65a400
Reviewed-on: https://go-review.googlesource.com/3517Reviewed-by: Austin Clements <austin@google.com>

Change-Id: I06762d4fb3bb2616087339b6ae1eb5267a39c46a
Reviewed-on: https://go-review.googlesource.com/3516Reviewed-by: Austin Clements <austin@google.com>

Change-Id: Ia6f8badca56565b9df80c8dbe28c47f6cf7e653f
Reviewed-on: https://go-review.googlesource.com/3515Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>

Change-Id: Idda476b71ae23f7b73fe63f062cf3531c1268eb3
Reviewed-on: https://go-review.googlesource.com/3514Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>
Reviewed-by: Dave Cheney <dave@cheney.net>

headstr(Hlinux) was reporting "android",
making for some confusing error messages.

Change-Id: I437095bee7cb2143aa37c91cf786f3a3581ae7b9
Reviewed-on: https://go-review.googlesource.com/3513Reviewed-by: Austin Clements <austin@google.com>

In addition to duplicating the logic, the old code was
clearing the line number, which led to missing source line
information in the -S output.

Also fix nopout, which was incomplete.

Change-Id: Ic2b596a2f9ec2fe85642ebe125cca8ef38c83085
Reviewed-on: https://go-review.googlesource.com/3512Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Dave Cheney <dave@cheney.net>

- certain code paths were appending to the string without first clearing it.
- some prints were using spaces instead of tabs

Change-Id: I7a3d38289c8206682baf8942abf5a9950a56b449
Reviewed-on: https://go-review.googlesource.com/3511Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Dave Cheney <dave@cheney.net>

cmd/go doesn't complain (this is an open issue), but go/types does

Change-Id: I2caec1f7aec991a9500d2c3504c29e4ab718c138
Reviewed-on: https://go-review.googlesource.com/3541Reviewed-by: Alan Donovan <adonovan@google.com>

Set gcscanvalid=false after you have cased to _Grunning.
If you do it before the cas and the atomicstatus races to a scan state,
the scan will set gcscanvalid=true and we will be _Grunning
with gcscanvalid==true which is not a good thing.

Change-Id: Ie53ea744a5600392b47da91159d985fe6fe75961
Reviewed-on: https://go-review.googlesource.com/3510Reviewed-by: Austin Clements <austin@google.com>

Yet another leftover from C: parfor took a func value for the
callback, casted it to an unsafe.Pointer for storage, and then casted
it back to a func value to call it.  This is unnecessary, so just
store the body as a func value.  Beyond general cleanup, this also
eliminates the last use of unsafe in parfor.

Change-Id: Ia904af7c6c443ba75e2699835aee8e9a39b26dd8
Reviewed-on: https://go-review.googlesource.com/3396Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

Prior to the conversion of the runtime to Go, this void* was
necessary to get closure information in to C callbacks.  There
are no more C callbacks and parfor is perfectly capable of
invoking a Go closure now, so eliminate ctx and all of its
unsafe-ness.  (Plus, the runtime currently doesn't use ctx for
anything.)

Change-Id: I39fc53b7dd3d7f660710abc76b0d831bfc6296d8
Reviewed-on: https://go-review.googlesource.com/3395Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>