libgo: update to go1.9

[official-gcc.git] / libgo / go / runtime / traceback_gccgo.go

// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Traceback support for gccgo.
// The actual traceback code is written in C.

package runtime

import (
        "runtime/internal/sys"
        _ "unsafe" // for go:linkname
)

func printcreatedby(gp *g) {
        // Show what created goroutine, except main goroutine (goid 1).
        pc := gp.gopc
        tracepc := pc // back up to CALL instruction for funcfileline.
        entry := funcentry(tracepc)
        if entry != 0 && tracepc > entry {
                tracepc -= sys.PCQuantum
        }
        function, file, line := funcfileline(tracepc, -1)
        if function != "" && showframe(function, gp) && gp.goid != 1 {
                print("created by ", function, "\n")
                print("\t", file, ":", line)
                if entry != 0 && pc > entry {
                        print(" +", hex(pc-entry))
                }
                print("\n")
        }
}

// tracebackg is used to collect stack traces from other goroutines.
type tracebackg struct {
        gp     *g
        locbuf [_TracebackMaxFrames]location
        c      int
}

// location is a location in the program, used for backtraces.
type location struct {
        pc       uintptr
        filename string
        function string
        lineno   int
}

//extern runtime_callers
func c_callers(skip int32, locbuf *location, max int32, keepThunks bool) int32

// callers returns a stack trace of the current goroutine.
// The gc version of callers takes []uintptr, but we take []location.
func callers(skip int, locbuf []location) int {
        n := c_callers(int32(skip), &locbuf[0], int32(len(locbuf)), false)
        return int(n)
}

// traceback prints a traceback of the current goroutine.
// This differs from the gc version, which is given pc, sp, lr and g and
// can print a traceback of any goroutine.
func traceback(skip int32) {
        var locbuf [100]location
        c := c_callers(skip+1, &locbuf[0], int32(len(locbuf)), false)
        printtrace(locbuf[:c], getg())
        printcreatedby(getg())
}

// printtrace prints a traceback from locbuf.
func printtrace(locbuf []location, gp *g) {
        for i := range locbuf {
                if showframe(locbuf[i].function, gp) {
                        name := locbuf[i].function
                        if name == "runtime.gopanic" {
                                name = "panic"
                        }
                        print(name, "\n\t", locbuf[i].filename, ":", locbuf[i].lineno, "\n")
                }
        }
}

// showframe returns whether to print a frame in a traceback.
// name is the function name.
func showframe(name string, gp *g) bool {
        g := getg()
        if g.m.throwing > 0 && gp != nil && (gp == g.m.curg || gp == g.m.caughtsig.ptr()) {
                return true
        }

        // Gccgo can trace back through C functions called via cgo.
        // We want to print those in the traceback.
        // But unless GOTRACEBACK > 1 (checked below), still skip
        // internal C functions and cgo-generated functions.
        if name != "" && !contains(name, ".") && !hasprefix(name, "__go_") && !hasprefix(name, "_cgo_") {
                return true
        }

        level, _, _ := gotraceback()

        // Special case: always show runtime.gopanic frame, so that we can
        // see where a panic started in the middle of a stack trace.
        // See golang.org/issue/5832.
        // __go_panic is the current gccgo name.
        if name == "runtime.gopanic" || name == "__go_panic" {
                return true
        }

        return level > 1 || contains(name, ".") && (!hasprefix(name, "runtime.") || isExportedRuntime(name))
}

// isExportedRuntime reports whether name is an exported runtime function.
// It is only for runtime functions, so ASCII A-Z is fine.
func isExportedRuntime(name string) bool {
        const n = len("runtime.")
        return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z'
}

var gStatusStrings = [...]string{
        _Gidle:      "idle",
        _Grunnable:  "runnable",
        _Grunning:   "running",
        _Gsyscall:   "syscall",
        _Gwaiting:   "waiting",
        _Gdead:      "dead",
        _Gcopystack: "copystack",
}

func goroutineheader(gp *g) {
        gpstatus := readgstatus(gp)

        isScan := gpstatus&_Gscan != 0
        gpstatus &^= _Gscan // drop the scan bit

        // Basic string status
        var status string
        if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) {
                status = gStatusStrings[gpstatus]
        } else {
                status = "???"
        }

        // Override.
        if gpstatus == _Gwaiting && gp.waitreason != "" {
                status = gp.waitreason
        }

        // approx time the G is blocked, in minutes
        var waitfor int64
        if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 {
                waitfor = (nanotime() - gp.waitsince) / 60e9
        }
        print("goroutine ", gp.goid, " [", status)
        if isScan {
                print(" (scan)")
        }
        if waitfor >= 1 {
                print(", ", waitfor, " minutes")
        }
        if gp.lockedm != nil {
                print(", locked to thread")
        }
        print("]:\n")
}

// isSystemGoroutine reports whether the goroutine g must be omitted in
// stack dumps and deadlock detector.
func isSystemGoroutine(gp *g) bool {
        return gp.isSystemGoroutine
}

func tracebackothers(me *g) {
        var tb tracebackg
        tb.gp = me

        // The getTraceback function will modify me's stack context.
        // Preserve it in case we have been called via systemstack.
        context := me.context
        stackcontext := me.stackcontext

        level, _, _ := gotraceback()

        // Show the current goroutine first, if we haven't already.
        g := getg()
        gp := g.m.curg
        if gp != nil && gp != me {
                print("\n")
                goroutineheader(gp)
                gp.traceback = &tb
                getTraceback(me, gp)
                printtrace(tb.locbuf[:tb.c], nil)
                printcreatedby(gp)
        }

        lock(&allglock)
        for _, gp := range allgs {
                if gp == me || gp == g.m.curg || readgstatus(gp) == _Gdead || isSystemGoroutine(gp) && level < 2 {
                        continue
                }
                print("\n")
                goroutineheader(gp)

                // gccgo's only mechanism for doing a stack trace is
                // _Unwind_Backtrace.  And that only works for the
                // current thread, not for other random goroutines.
                // So we need to switch context to the goroutine, get
                // the backtrace, and then switch back.
                //
                // This means that if g is running or in a syscall, we
                // can't reliably print a stack trace.  FIXME.

                // Note: gp.m == g.m occurs when tracebackothers is
                // called from a signal handler initiated during a
                // systemstack call. The original G is still in the
                // running state, and we want to print its stack.
                if gp.m != g.m && readgstatus(gp)&^_Gscan == _Grunning {
                        print("\tgoroutine running on other thread; stack unavailable\n")
                        printcreatedby(gp)
                } else if readgstatus(gp)&^_Gscan == _Gsyscall {
                        print("\tin C code; stack unavailable\n")
                        printcreatedby(gp)
                } else {
                        gp.traceback = &tb
                        getTraceback(me, gp)
                        printtrace(tb.locbuf[:tb.c], nil)
                        printcreatedby(gp)
                }
        }
        unlock(&allglock)

        me.context = context
        me.stackcontext = stackcontext
}