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2014-11-11[dev.cc] runtime: convert panic and stack code from C to GoRuss Cox
The conversion was done with an automated tool and then modified only as necessary to make it compile and run. [This CL is part of the removal of C code from package runtime. See golang.org/s/dev.cc for an overview.] LGTM=r R=r, dave CC=austin, dvyukov, golang-codereviews, iant, khr https://golang.org/cl/166520043
2014-10-07runtime: clear Defer.panic before removing from G.defer listRuss Cox
Another dangling stack pointer in a cached structure. Same as SudoG.elem and SudoG.selectdone. Definitely a fix, and the new test in freedefer makes the crash reproducible, but probably not a complete fix. I have seen one dangling pointer in a Defer.panic even after this fix; I cannot see where it could be coming from. I think this will fix the solaris build. I do not think this will fix the occasional failure on the darwin build. TBR=khr R=khr CC=golang-codereviews https://golang.org/cl/155080043
2014-10-07runtime: zero pointer-looking scalararg valuesKeith Randall
I have a CL which at every gc looks through data and bss sections for nonpointer data (according to gc maps) that looks like a pointer. These are potential missing roots. The only thing it finds are begnign, storing stack pointers into m0.scalararg[1] and never cleaning them up. Let's clean them up now so the test CL passes all.bash cleanly. The test CL can't be checked in because we might store pointer-looking things in nonpointer data by accident. LGTM=iant R=golang-codereviews, iant, khr CC=golang-codereviews https://golang.org/cl/153210043
2014-09-16runtime: use traceback to traverse defer structuresRuss Cox
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
2014-09-09runtime: assume precisestack, copystack, StackCopyAlways, ScanStackByFramesRuss Cox
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
2014-09-08liblink, runtime: diagnose and fix C code running on Go stackRuss Cox
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
2014-09-08build: move package sources from src/pkg to srcRuss Cox
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.