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// Copyright 2014 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.
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
// Calling panic with one of the errors below will call errorString.Error
// which will call mallocgc to concatenate strings. That will fail if
// malloc is locked, causing a confusing error message. Throw a better
// error message instead.
func panicCheckMalloc(err error) {
gp := getg()
if gp != nil && gp.m != nil && gp.m.mallocing != 0 {
throw(string(err.(errorString)))
}
}
var indexError = error(errorString("index out of range"))
func panicindex() {
panicCheckMalloc(indexError)
panic(indexError)
}
var sliceError = error(errorString("slice bounds out of range"))
func panicslice() {
panicCheckMalloc(sliceError)
panic(sliceError)
}
var divideError = error(errorString("integer divide by zero"))
func panicdivide() {
panicCheckMalloc(divideError)
panic(divideError)
}
var overflowError = error(errorString("integer overflow"))
func panicoverflow() {
panicCheckMalloc(overflowError)
panic(overflowError)
}
var floatError = error(errorString("floating point error"))
func panicfloat() {
panicCheckMalloc(floatError)
panic(floatError)
}
var memoryError = error(errorString("invalid memory address or nil pointer dereference"))
func panicmem() {
panicCheckMalloc(memoryError)
panic(memoryError)
}
func throwreturn() {
throw("no return at end of a typed function - compiler is broken")
}
func throwinit() {
throw("recursive call during initialization - linker skew")
}
// Create a new deferred function fn with siz bytes of arguments.
// The compiler turns a defer statement into a call to this.
//go:nosplit
func deferproc(siz int32, fn *funcval) { // arguments of fn follow fn
if getg().m.curg != getg() {
// go code on the system stack can't defer
throw("defer on system stack")
}
// the arguments of fn are in a perilous state. The stack map
// for deferproc does not describe them. So we can't let garbage
// collection or stack copying trigger until we've copied them out
// to somewhere safe. The memmove below does that.
// Until the copy completes, we can only call nosplit routines.
sp := getcallersp(unsafe.Pointer(&siz))
argp := uintptr(unsafe.Pointer(&fn)) + unsafe.Sizeof(fn)
callerpc := getcallerpc(unsafe.Pointer(&siz))
systemstack(func() {
d := newdefer(siz)
if d._panic != nil {
throw("deferproc: d.panic != nil after newdefer")
}
d.fn = fn
d.pc = callerpc
d.sp = sp
memmove(add(unsafe.Pointer(d), unsafe.Sizeof(*d)), unsafe.Pointer(argp), uintptr(siz))
})
// deferproc returns 0 normally.
// a deferred func that stops a panic
// makes the deferproc return 1.
// the code the compiler generates always
// checks the return value and jumps to the
// end of the function if deferproc returns != 0.
return0()
// No code can go here - the C return register has
// been set and must not be clobbered.
}
// Small malloc size classes >= 16 are the multiples of 16: 16, 32, 48, 64, 80, 96, 112, 128, 144, ...
// Each P holds a pool for defers with small arg sizes.
// Assign defer allocations to pools by rounding to 16, to match malloc size classes.
const (
deferHeaderSize = unsafe.Sizeof(_defer{})
minDeferAlloc = (deferHeaderSize + 15) &^ 15
minDeferArgs = minDeferAlloc - deferHeaderSize
)
// defer size class for arg size sz
//go:nosplit
func deferclass(siz uintptr) uintptr {
if siz <= minDeferArgs {
return 0
}
return (siz - minDeferArgs + 15) / 16
}
// total size of memory block for defer with arg size sz
func totaldefersize(siz uintptr) uintptr {
if siz <= minDeferArgs {
return minDeferAlloc
}
return deferHeaderSize + siz
}
// Ensure that defer arg sizes that map to the same defer size class
// also map to the same malloc size class.
func testdefersizes() {
var m [len(p{}.deferpool)]int32
for i := range m {
m[i] = -1
}
for i := uintptr(0); ; i++ {
defersc := deferclass(i)
if defersc >= uintptr(len(m)) {
break
}
siz := roundupsize(totaldefersize(i))
if m[defersc] < 0 {
m[defersc] = int32(siz)
continue
}
if m[defersc] != int32(siz) {
print("bad defer size class: i=", i, " siz=", siz, " defersc=", defersc, "\n")
throw("bad defer size class")
}
}
}
// The arguments associated with a deferred call are stored
// immediately after the _defer header in memory.
//go:nosplit
func deferArgs(d *_defer) unsafe.Pointer {
return add(unsafe.Pointer(d), unsafe.Sizeof(*d))
}
var deferType *_type // type of _defer struct
func init() {
var x interface{}
x = (*_defer)(nil)
deferType = (*(**ptrtype)(unsafe.Pointer(&x))).elem
}
// Allocate a Defer, usually using per-P pool.
// Each defer must be released with freedefer.
// Note: runs on g0 stack
func newdefer(siz int32) *_defer {
var d *_defer
sc := deferclass(uintptr(siz))
mp := acquirem()
if sc < uintptr(len(p{}.deferpool)) {
pp := mp.p.ptr()
if len(pp.deferpool[sc]) == 0 && sched.deferpool[sc] != nil {
lock(&sched.deferlock)
for len(pp.deferpool[sc]) < cap(pp.deferpool[sc])/2 && sched.deferpool[sc] != nil {
d := sched.deferpool[sc]
sched.deferpool[sc] = d.link
d.link = nil
pp.deferpool[sc] = append(pp.deferpool[sc], d)
}
unlock(&sched.deferlock)
}
if n := len(pp.deferpool[sc]); n > 0 {
d = pp.deferpool[sc][n-1]
pp.deferpool[sc][n-1] = nil
pp.deferpool[sc] = pp.deferpool[sc][:n-1]
}
}
if d == nil {
// Allocate new defer+args.
total := roundupsize(totaldefersize(uintptr(siz)))
d = (*_defer)(mallocgc(total, deferType, true))
}
d.siz = siz
gp := mp.curg
d.link = gp._defer
gp._defer = d
releasem(mp)
return d
}
// Free the given defer.
// The defer cannot be used after this call.
func freedefer(d *_defer) {
if d._panic != nil {
freedeferpanic()
}
if d.fn != nil {
freedeferfn()
}
sc := deferclass(uintptr(d.siz))
if sc < uintptr(len(p{}.deferpool)) {
mp := acquirem()
pp := mp.p.ptr()
if len(pp.deferpool[sc]) == cap(pp.deferpool[sc]) {
// Transfer half of local cache to the central cache.
var first, last *_defer
for len(pp.deferpool[sc]) > cap(pp.deferpool[sc])/2 {
n := len(pp.deferpool[sc])
d := pp.deferpool[sc][n-1]
pp.deferpool[sc][n-1] = nil
pp.deferpool[sc] = pp.deferpool[sc][:n-1]
if first == nil {
first = d
} else {
last.link = d
}
last = d
}
lock(&sched.deferlock)
last.link = sched.deferpool[sc]
sched.deferpool[sc] = first
unlock(&sched.deferlock)
}
*d = _defer{}
pp.deferpool[sc] = append(pp.deferpool[sc], d)
releasem(mp)
}
}
// Separate function so that it can split stack.
// Windows otherwise runs out of stack space.
func freedeferpanic() {
// _panic must be cleared before d is unlinked from gp.
throw("freedefer with d._panic != nil")
}
func freedeferfn() {
// fn must be cleared before d is unlinked from gp.
throw("freedefer with d.fn != nil")
}
// Run a deferred function if there is one.
// The compiler inserts a call to this at the end of any
// function which calls defer.
// If there is a deferred function, this will call runtime·jmpdefer,
// which will jump to the deferred function such that it appears
// to have been called by the caller of deferreturn at the point
// just before deferreturn was called. The effect is that deferreturn
// is called again and again until there are no more deferred functions.
// Cannot split the stack because we reuse the caller's frame to
// call the deferred function.
// The single argument isn't actually used - it just has its address
// taken so it can be matched against pending defers.
//go:nosplit
func deferreturn(arg0 uintptr) {
gp := getg()
d := gp._defer
if d == nil {
return
}
sp := getcallersp(unsafe.Pointer(&arg0))
if d.sp != sp {
return
}
// Moving arguments around.
// Do not allow preemption here, because the garbage collector
// won't know the form of the arguments until the jmpdefer can
// flip the PC over to fn.
mp := acquirem()
memmove(unsafe.Pointer(&arg0), deferArgs(d), uintptr(d.siz))
fn := d.fn
d.fn = nil
gp._defer = d.link
// Switch to systemstack merely to save nosplit stack space.
systemstack(func() {
freedefer(d)
})
releasem(mp)
jmpdefer(fn, uintptr(unsafe.Pointer(&arg0)))
}
// Goexit terminates the goroutine that calls it. No other goroutine is affected.
// Goexit runs all deferred calls before terminating the goroutine. Because Goexit
// is not panic, however, any recover calls in those deferred functions will return nil.
//
// Calling Goexit from the main goroutine terminates that goroutine
// without func main returning. Since func main has not returned,
// the program continues execution of other goroutines.
// If all other goroutines exit, the program crashes.
func Goexit() {
// Run all deferred functions for the current goroutine.
// This code is similar to gopanic, see that implementation
// for detailed comments.
gp := getg()
for {
d := gp._defer
if d == nil {
break
}
if d.started {
if d._panic != nil {
d._panic.aborted = true
d._panic = nil
}
d.fn = nil
gp._defer = d.link
freedefer(d)
continue
}
d.started = true
reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
if gp._defer != d {
throw("bad defer entry in Goexit")
}
d._panic = nil
d.fn = nil
gp._defer = d.link
freedefer(d)
// Note: we ignore recovers here because Goexit isn't a panic
}
goexit1()
}
// Call all Error and String methods before freezing the world.
// Used when crashing with panicking.
// This must match types handled by printany.
func preprintpanics(p *_panic) {
for p != nil {
switch v := p.arg.(type) {
case error:
p.arg = v.Error()
case stringer:
p.arg = v.String()
}
p = p.link
}
}
// Print all currently active panics. Used when crashing.
func printpanics(p *_panic) {
if p.link != nil {
printpanics(p.link)
print("\t")
}
print("panic: ")
printany(p.arg)
if p.recovered {
print(" [recovered]")
}
print("\n")
}
// The implementation of the predeclared function panic.
func gopanic(e interface{}) {
gp := getg()
if gp.m.curg != gp {
print("panic: ")
printany(e)
print("\n")
throw("panic on system stack")
}
// m.softfloat is set during software floating point.
// It increments m.locks to avoid preemption.
// We moved the memory loads out, so there shouldn't be
// any reason for it to panic anymore.
if gp.m.softfloat != 0 {
gp.m.locks--
gp.m.softfloat = 0
throw("panic during softfloat")
}
if gp.m.mallocing != 0 {
print("panic: ")
printany(e)
print("\n")
throw("panic during malloc")
}
if gp.m.preemptoff != "" {
print("panic: ")
printany(e)
print("\n")
print("preempt off reason: ")
print(gp.m.preemptoff)
print("\n")
throw("panic during preemptoff")
}
if gp.m.locks != 0 {
print("panic: ")
printany(e)
print("\n")
throw("panic holding locks")
}
var p _panic
p.arg = e
p.link = gp._panic
gp._panic = (*_panic)(noescape(unsafe.Pointer(&p)))
for {
d := gp._defer
if d == nil {
break
}
// If defer was started by earlier panic or Goexit (and, since we're back here, that triggered a new panic),
// take defer off list. The earlier panic or Goexit will not continue running.
if d.started {
if d._panic != nil {
d._panic.aborted = true
}
d._panic = nil
d.fn = nil
gp._defer = d.link
freedefer(d)
continue
}
// Mark defer as started, but keep on list, so that traceback
// can find and update the defer's argument frame if stack growth
// or a garbage collection happens before reflectcall starts executing d.fn.
d.started = true
// Record the panic that is running the defer.
// If there is a new panic during the deferred call, that panic
// will find d in the list and will mark d._panic (this panic) aborted.
d._panic = (*_panic)(noescape(unsafe.Pointer(&p)))
p.argp = unsafe.Pointer(getargp(0))
reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
p.argp = nil
// reflectcall did not panic. Remove d.
if gp._defer != d {
throw("bad defer entry in panic")
}
d._panic = nil
d.fn = nil
gp._defer = d.link
// trigger shrinkage to test stack copy. See stack_test.go:TestStackPanic
//GC()
pc := d.pc
sp := unsafe.Pointer(d.sp) // must be pointer so it gets adjusted during stack copy
freedefer(d)
if p.recovered {
gp._panic = p.link
// Aborted panics are marked but remain on the g.panic list.
// Remove them from the list.
for gp._panic != nil && gp._panic.aborted {
gp._panic = gp._panic.link
}
if gp._panic == nil { // must be done with signal
gp.sig = 0
}
// Pass information about recovering frame to recovery.
gp.sigcode0 = uintptr(sp)
gp.sigcode1 = pc
mcall(recovery)
throw("recovery failed") // mcall should not return
}
}
// ran out of deferred calls - old-school panic now
// Because it is unsafe to call arbitrary user code after freezing
// the world, we call preprintpanics to invoke all necessary Error
// and String methods to prepare the panic strings before startpanic.
preprintpanics(gp._panic)
startpanic()
printpanics(gp._panic)
dopanic(0) // should not return
*(*int)(nil) = 0 // not reached
}
// getargp returns the location where the caller
// writes outgoing function call arguments.
//go:nosplit
func getargp(x int) uintptr {
// x is an argument mainly so that we can return its address.
// However, we need to make the function complex enough
// that it won't be inlined. We always pass x = 0, so this code
// does nothing other than keep the compiler from thinking
// the function is simple enough to inline.
if x > 0 {
return getcallersp(unsafe.Pointer(&x)) * 0
}
return uintptr(noescape(unsafe.Pointer(&x)))
}
// The implementation of the predeclared function recover.
// Cannot split the stack because it needs to reliably
// find the stack segment of its caller.
//
// TODO(rsc): Once we commit to CopyStackAlways,
// this doesn't need to be nosplit.
//go:nosplit
func gorecover(argp uintptr) interface{} {
// Must be in a function running as part of a deferred call during the panic.
// Must be called from the topmost function of the call
// (the function used in the defer statement).
// p.argp is the argument pointer of that topmost deferred function call.
// Compare against argp reported by caller.
// If they match, the caller is the one who can recover.
gp := getg()
p := gp._panic
if p != nil && !p.recovered && argp == uintptr(p.argp) {
p.recovered = true
return p.arg
}
return nil
}
//go:nosplit
func startpanic() {
systemstack(startpanic_m)
}
//go:nosplit
func dopanic(unused int) {
pc := getcallerpc(unsafe.Pointer(&unused))
sp := getcallersp(unsafe.Pointer(&unused))
gp := getg()
systemstack(func() {
dopanic_m(gp, pc, sp) // should never return
})
*(*int)(nil) = 0
}
//go:nosplit
func throw(s string) {
print("fatal error: ", s, "\n")
gp := getg()
if gp.m.throwing == 0 {
gp.m.throwing = 1
}
startpanic()
dopanic(0)
*(*int)(nil) = 0 // not reached
}
//uint32 runtime·panicking;
var paniclk mutex
// Unwind the stack after a deferred function calls recover
// after a panic. Then arrange to continue running as though
// the caller of the deferred function returned normally.
func recovery(gp *g) {
// Info about defer passed in G struct.
sp := gp.sigcode0
pc := gp.sigcode1
// d's arguments need to be in the stack.
if sp != 0 && (sp < gp.stack.lo || gp.stack.hi < sp) {
print("recover: ", hex(sp), " not in [", hex(gp.stack.lo), ", ", hex(gp.stack.hi), "]\n")
throw("bad recovery")
}
// Make the deferproc for this d return again,
// this time returning 1. The calling function will
// jump to the standard return epilogue.
gcUnwindBarriers(gp, sp)
gp.sched.sp = sp
gp.sched.pc = pc
gp.sched.lr = 0
gp.sched.ret = 1
gogo(&gp.sched)
}
func startpanic_m() {
_g_ := getg()
if mheap_.cachealloc.size == 0 { // very early
print("runtime: panic before malloc heap initialized\n")
_g_.m.mallocing = 1 // tell rest of panic not to try to malloc
} else if _g_.m.mcache == nil { // can happen if called from signal handler or throw
_g_.m.mcache = allocmcache()
}
switch _g_.m.dying {
case 0:
_g_.m.dying = 1
_g_.writebuf = nil
atomic.Xadd(&panicking, 1)
lock(&paniclk)
if debug.schedtrace > 0 || debug.scheddetail > 0 {
schedtrace(true)
}
freezetheworld()
return
case 1:
// Something failed while panicing, probably the print of the
// argument to panic(). Just print a stack trace and exit.
_g_.m.dying = 2
print("panic during panic\n")
dopanic(0)
exit(3)
fallthrough
case 2:
// This is a genuine bug in the runtime, we couldn't even
// print the stack trace successfully.
_g_.m.dying = 3
print("stack trace unavailable\n")
exit(4)
fallthrough
default:
// Can't even print! Just exit.
exit(5)
}
}
var didothers bool
var deadlock mutex
func dopanic_m(gp *g, pc, sp uintptr) {
if gp.sig != 0 {
signame := signame(gp.sig)
if signame != "" {
print("[signal ", signame)
} else {
print("[signal ", hex(gp.sig))
}
print(" code=", hex(gp.sigcode0), " addr=", hex(gp.sigcode1), " pc=", hex(gp.sigpc), "]\n")
}
level, all, docrash := gotraceback()
_g_ := getg()
if level > 0 {
if gp != gp.m.curg {
all = true
}
if gp != gp.m.g0 {
print("\n")
goroutineheader(gp)
traceback(pc, sp, 0, gp)
} else if level >= 2 || _g_.m.throwing > 0 {
print("\nruntime stack:\n")
traceback(pc, sp, 0, gp)
}
if !didothers && all {
didothers = true
tracebackothers(gp)
}
}
unlock(&paniclk)
if atomic.Xadd(&panicking, -1) != 0 {
// Some other m is panicking too.
// Let it print what it needs to print.
// Wait forever without chewing up cpu.
// It will exit when it's done.
lock(&deadlock)
lock(&deadlock)
}
if docrash {
crash()
}
exit(2)
}
//go:nosplit
func canpanic(gp *g) bool {
// Note that g is m->gsignal, different from gp.
// Note also that g->m can change at preemption, so m can go stale
// if this function ever makes a function call.
_g_ := getg()
_m_ := _g_.m
// Is it okay for gp to panic instead of crashing the program?
// Yes, as long as it is running Go code, not runtime code,
// and not stuck in a system call.
if gp == nil || gp != _m_.curg {
return false
}
if _m_.locks-_m_.softfloat != 0 || _m_.mallocing != 0 || _m_.throwing != 0 || _m_.preemptoff != "" || _m_.dying != 0 {
return false
}
status := readgstatus(gp)
if status&^_Gscan != _Grunning || gp.syscallsp != 0 {
return false
}
if GOOS == "windows" && _m_.libcallsp != 0 {
return false
}
return true
}