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Commit Graph

8 Commits

Author SHA1 Message Date
Russ Cox
54245cba1f runtime: show frames for exported runtime functions
The current Windows build failure happens because by
default runtime frames are excluded from stack traces.
Apparently the Windows breakpoint path dies with an
ordinary panic, while the Unix path dies with a throw.
Breakpoint is a strange function and I don't mind that it's
a little different on the two operating systems.

The panic squelches runtime frames but the throw shows them,
because throw is considered something that shouldn't have
happened at all, so as much detail as possible is wanted.

The runtime exclusion is meant to prevents printing too much noise
about internal runtime details. But exported functions are
not internal details, so show exported functions.
If the program dies because you called runtime.Breakpoint,
it's okay to see that frame.
This makes the Breakpoint test show Breakpoint in the
stack trace no matter how it is handled.

Should fix Windows build.
Tested on Unix by changing Breakpoint to fault instead
of doing a breakpoint.

TBR=brainman
CC=golang-codereviews
https://golang.org/cl/143300043
2014-09-18 20:35:36 -04:00
Russ Cox
f95beae61d runtime: use traceback to traverse defer structures
This makes the GC and the stack copying agree about how
to interpret the defer structures. Previously, only the stack
copying treated them precisely.
This removes an untyped memory allocation and fixes
at least three copystack bugs.

To make sure the GC can find the deferred argument
frame until it has been copied, keep a Defer on the defer list
during its execution.

In addition to making it possible to remove the untyped
memory allocation, keeping the Defer on the list fixes
two races between copystack and execution of defers
(in both gopanic and Goexit). The problem is that once
the defer has been taken off the list, a stack copy that
happens before the deferred arguments have been copied
back to the stack will not update the arguments correctly.
The new tests TestDeferPtrsPanic and TestDeferPtrsGoexit
(variations on the existing TestDeferPtrs) pass now but
failed before this CL.

In addition to those fixes, keeping the Defer on the list
helps correct a dangling pointer error during copystack.
The traceback routines walk the Defer chain to provide
information about where a panic may resume execution.
When the executing Defer was not on the Defer chain
but instead linked from the Panic chain, the traceback
had to walk the Panic chain too. But Panic structs are
on the stack and being updated by copystack.
Traceback's use of the Panic chain while copystack is
updating those structs means that it can follow an
updated pointer and find itself reading from the new stack.
The new stack is usually all zeros, so it sees an incorrect
early end to the chain. The new TestPanicUseStack makes
this happen at tip and dies when adjustdefers finds an
unexpected argp. The new StackCopyPoison mode
causes an earlier bad dereference instead.
By keeping the Defer on the list, traceback can avoid
walking the Panic chain at all,  making it okay for copystack
to update the Panics.

We'd have the same problem for any Defers on the stack.
There was only one: gopanic's dabort. Since we are not
taking the executing Defer off the chain, we can use it
to do what dabort was doing, and then there are no
Defers on the stack ever, so it is okay for traceback to use
the Defer chain even while copystack is executing:
copystack cannot modify the Defer chain.

LGTM=khr
R=khr
CC=dvyukov, golang-codereviews, iant, rlh
https://golang.org/cl/141490043
2014-09-16 10:36:38 -04:00
Russ Cox
d889f5f01e runtime: fix traceback of trap on ARM
The merged traceback was wrong for LR machines,
because traceback didn't pass lr to gentraceback.
Now that we have a test looking at traceback output
for a trap (the test of runtime.Breakpoint),
we caught this.

While we're here, fix a 'set and not used' warning.

Fixes arm build.

TBR=r
R=r
CC=golang-codereviews
https://golang.org/cl/143040043
2014-09-14 20:39:08 +00:00
Russ Cox
e844f53a01 runtime: stop scanning stack frames/args conservatively
The goal here is to commit fully to having precise information
about stack frames. If we need information we don't have,
crash instead of assuming we should scan conservatively.

Since the stack copying assumes fully precise information,
any crashes during garbage collection that are introduced by
this CL are crashes that could have happened during stack
copying instead. Those are harder to find because stacks are
copied much less often than the garbage collector is invoked.

In service of that goal, remove ARGSIZE macros from
asm_*.s, change switchtoM to have no arguments
(it doesn't have any live arguments), and add
args and locals information to some frames that
can call back into Go.

LGTM=khr
R=khr, rlh
CC=golang-codereviews
https://golang.org/cl/137540043
2014-09-12 07:46:11 -04:00
Russ Cox
f0d44dbeaf runtime: look up arg stackmap for makeFuncStub/methodValueStub during traceback
makeFuncStub and methodValueStub are used by reflect as
generic function implementations. Each call might have
different arguments. Extract those arguments from the
closure data instead of assuming it is the same each time.

Because the argument map is now being extracted from the
function itself, we don't need the special cases in reflect.Call
anymore, so delete those.

Fixes an occasional crash seen when stack copying does
not update makeFuncStub's arguments correctly.

Will also help make it safe to require stack maps in the
garbage collector.

Derived from CL 142000044 by khr.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/143890044
2014-09-12 07:29:19 -04:00
Russ Cox
15b76ad94b runtime: assume precisestack, copystack, StackCopyAlways, ScanStackByFrames
Commit to stack copying for stack growth.

We're carrying around a surprising amount of cruft from older schemes.
I am confident that precise stack scans and stack copying are here to stay.

Delete fallback code for when precise stack info is disabled.
Delete fallback code for when copying stacks is disabled.
Delete fallback code for when StackCopyAlways is disabled.
Delete Stktop chain - there is only one stack segment now.
Delete M.moreargp, M.moreargsize, M.moreframesize, M.cret.
Delete G.writenbuf (unrelated, just dead).
Delete runtime.lessstack, runtime.oldstack.
Delete many amd64 morestack variants.
Delete initialization of morestack frame/arg sizes (shortens split prologue!).

Replace G's stackguard/stackbase/stack0/stacksize/
syscallstack/syscallguard/forkstackguard with simple stack
bounds (lo, hi).

Update liblink, runtime/cgo for adjustments to G.

LGTM=khr
R=khr, bradfitz
CC=golang-codereviews, iant, r
https://golang.org/cl/137410043
2014-09-09 13:39:57 -04:00
Russ Cox
c81a0ed3c5 liblink, runtime: diagnose and fix C code running on Go stack
This CL contains compiler+runtime changes that detect C code
running on Go (not g0, not gsignal) stacks, and it contains
corrections for what it detected.

The detection works by changing the C prologue to use a different
stack guard word in the G than Go prologue does. On the g0 and
gsignal stacks, that stack guard word is set to the usual
stack guard value. But on ordinary Go stacks, that stack
guard word is set to ^0, which will make any stack split
check fail. The C prologue then calls morestackc instead
of morestack, and morestackc aborts the program with
a message about running C code on a Go stack.

This check catches all C code running on the Go stack
except NOSPLIT code. The NOSPLIT code is allowed,
so the check is complete. Since it is a dynamic check,
the code must execute to be caught. But unlike the static
checks we've been using in cmd/ld, the dynamic check
works with function pointers and other indirect calls.
For example it caught sigpanic being pushed onto Go
stacks in the signal handlers.

Fixes #8667.

LGTM=khr, iant
R=golang-codereviews, khr, iant
CC=golang-codereviews, r
https://golang.org/cl/133700043
2014-09-08 14:05:23 -04:00
Russ Cox
c007ce824d build: move package sources from src/pkg to src
Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.
2014-09-08 00:08:51 -04:00