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Revert "liblink, cmd/ld, runtime: remove stackguard1"

Browse Source 
This reverts commit ab0535ae3f.

I think it will remain useful to distinguish code that must
run on a system stack from code that can run on either stack,
even if that distinction is no
longer based on the implementation language.

That is, I expect to add a //go:systemstack comment that,
in terms of the old implementation, tells the compiler,
to pretend this function was written in C.

Change-Id: I33d2ebb2f99ae12496484c6ec8ed07233d693275
Reviewed-on: https://go-review.googlesource.com/2275
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Russ Cox 2015-01-05 16:29:21 +00:00
parent a1c9e10371
commit e6d3511264
27 changed files with 192 additions and 72 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/link.h
View File

@ -131,6 +131,7 @@ struct LSym
short type;
short version;
uchar dupok;
uchar cfunc;
uchar external;
uchar nosplit;
uchar reachable;

53
src/cmd/ld/lib.c
View File

@ -1564,3 +1564,56 @@ diag(char *fmt, ...)
errorexit();
}
}
void
checkgo(void)
{
LSym *s;
Reloc *r;
int i;
int changed;
if(!debug['C'])
return;
// TODO(rsc,khr): Eventually we want to get to no Go-called C functions at all,
// which would simplify this logic quite a bit.
// Mark every Go-called C function with cfunc=2, recursively.
do {
changed = 0;
for(s = ctxt->textp; s != nil; s = s->next) {
if(s->cfunc == 0 || (s->cfunc == 2 && s->nosplit)) {
for(i=0; i<s->nr; i++) {
r = &s->r[i];
if(r->sym == nil)
continue;
if((r->type == R_CALL || r->type == R_CALLARM) && r->sym->type == STEXT) {
if(r->sym->cfunc == 1) {
changed = 1;
r->sym->cfunc = 2;
}
}
}
}
}
}while(changed);
// Complain about Go-called C functions that can split the stack
// (that can be preempted for garbage collection or trigger a stack copy).
for(s = ctxt->textp; s != nil; s = s->next) {
if(s->cfunc == 0 || (s->cfunc == 2 && s->nosplit)) {
for(i=0; i<s->nr; i++) {
r = &s->r[i];
if(r->sym == nil)
continue;
if((r->type == R_CALL || r->type == R_CALLARM) && r->sym->type == STEXT) {
if(s->cfunc == 0 && r->sym->cfunc == 2 && !r->sym->nosplit)
print("Go %s calls C %s\n", s->name, r->sym->name);
else if(s->cfunc == 2 && s->nosplit && !r->sym->nosplit)
print("Go calls C %s calls %s\n", s->name, r->sym->name);
}
}
}
}
}

1
src/cmd/ld/lib.h
View File

@ -183,6 +183,7 @@ uint16 be16(uchar *b);
uint32 be32(uchar *b);
uint64 be64(uchar *b);
void callgraph(void);
void checkgo(void);
void cflush(void);
void codeblk(int64 addr, int64 size);
vlong cpos(void);

1
src/cmd/ld/pobj.c
View File

@ -172,6 +172,7 @@ main(int argc, char *argv[])
mark(linklookup(ctxt, "runtime.read_tls_fallback", 0));
}
checkgo();
deadcode();
callgraph();
paramspace = "SP"; /* (FP) now (SP) on output */

11
src/liblink/obj5.c
View File

@ -474,7 +474,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
p->as = AMOVW;
p->from.type = D_OREG;
p->from.reg = REGG;
p->from.offset = 3*ctxt->arch->ptrsize; // G.panic
p->from.offset = 4*ctxt->arch->ptrsize; // G.panic
p->to.type = D_REG;
p->to.reg = 1;
@ -783,7 +783,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
p->as = AMOVW;
p->from.type = D_OREG;
p->from.reg = REGG;
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_REG;
p->to.reg = 1;
@ -876,7 +878,10 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
p->as = ABL;
p->scond = C_SCOND_LS;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[noctxt];
if(ctxt->cursym->cfunc)
p->to.sym = linklookup(ctxt, "runtime.morestackc", 0);
else
p->to.sym = ctxt->symmorestack[noctxt];
// BLS start
p = appendp(ctxt, p);

19
src/liblink/obj6.c
View File

@ -452,7 +452,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
p = appendp(ctxt, p);
p->as = AMOVQ;
p->from.type = D_INDIR+D_CX;
p->from.offset = 3*ctxt->arch->ptrsize; // G.panic
p->from.offset = 4*ctxt->arch->ptrsize; // G.panic
p->to.type = D_BX;
if(ctxt->headtype == Hnacl) {
p->as = AMOVL;
@ -689,7 +689,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p->as = cmp;
p->from.type = D_SP;
indir_cx(ctxt, &p->to);
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else if(framesize <= StackBig) {
// large stack: SP-framesize <= stackguard-StackSmall
// LEAQ -xxx(SP), AX
@ -704,7 +706,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p->as = cmp;
p->from.type = D_AX;
indir_cx(ctxt, &p->to);
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else {
// Such a large stack we need to protect against wraparound.
// If SP is close to zero:
@ -724,7 +728,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p = appendp(ctxt, p);
p->as = mov;
indir_cx(ctxt, &p->from);
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_SI;
p = appendp(ctxt, p);
@ -765,7 +771,10 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int32 textarg, int noctxt, Prog
p = appendp(ctxt, p);
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[noctxt];
if(ctxt->cursym->cfunc)
p->to.sym = linklookup(ctxt, "runtime.morestackc", 0);
else
p->to.sym = ctxt->symmorestack[noctxt];
p = appendp(ctxt, p);
p->as = AJMP;

19
src/liblink/obj8.c
View File

@ -335,7 +335,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
p = appendp(ctxt, p);
p->as = AMOVL;
p->from.type = D_INDIR+D_CX;
p->from.offset = 3*ctxt->arch->ptrsize; // G.panic
p->from.offset = 4*ctxt->arch->ptrsize; // G.panic
p->to.type = D_BX;
p = appendp(ctxt, p);
@ -538,7 +538,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt, Prog **jmpok)
p->as = ACMPL;
p->from.type = D_SP;
p->to.type = D_INDIR+D_CX;
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else if(framesize <= StackBig) {
// large stack: SP-framesize <= stackguard-StackSmall
// LEAL -(framesize-StackSmall)(SP), AX
@ -553,7 +555,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt, Prog **jmpok)
p->as = ACMPL;
p->from.type = D_AX;
p->to.type = D_INDIR+D_CX;
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->to.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->to.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
} else {
// Such a large stack we need to protect against wraparound
// if SP is close to zero.
@ -573,7 +577,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt, Prog **jmpok)
p->as = AMOVL;
p->from.type = D_INDIR+D_CX;
p->from.offset = 0;
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_SI;
p = appendp(ctxt, p);
@ -616,7 +622,10 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt, Prog **jmpok)
p = appendp(ctxt, p);
p->as = ACALL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[noctxt];
if(ctxt->cursym->cfunc)
p->to.sym = linklookup(ctxt, "runtime.morestackc", 0);
else
p->to.sym = ctxt->symmorestack[noctxt];
p = appendp(ctxt, p);
p->as = AJMP;

11
src/liblink/obj9.c
View File

@ -492,7 +492,7 @@ addstacksplit(Link *ctxt, LSym *cursym)
q->as = AMOVD;
q->from.type = D_OREG;
q->from.reg = REGG;
q->from.offset = 3*ctxt->arch->ptrsize; // G.panic
q->from.offset = 4*ctxt->arch->ptrsize; // G.panic
q->to.type = D_REG;
q->to.reg = 3;
@ -724,7 +724,9 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
p->as = AMOVD;
p->from.type = D_OREG;
p->from.reg = REGG;
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard
p->from.offset = 2*ctxt->arch->ptrsize; // G.stackguard0
if(ctxt->cursym->cfunc)
p->from.offset = 3*ctxt->arch->ptrsize; // G.stackguard1
p->to.type = D_REG;
p->to.reg = 3;
@ -832,7 +834,10 @@ stacksplit(Link *ctxt, Prog *p, int32 framesize, int noctxt)
p = appendp(ctxt, p);
p->as = ABL;
p->to.type = D_BRANCH;
p->to.sym = ctxt->symmorestack[noctxt];
if(ctxt->cursym->cfunc)
p->to.sym = linklookup(ctxt, "runtime.morestackc", 0);
else
p->to.sym = ctxt->symmorestack[noctxt];
// BR start
p = appendp(ctxt, p);

7
src/liblink/objfile.c
View File

@ -332,6 +332,8 @@ writesym(Link *ctxt, Biobuf *b, LSym *s)
Bprint(ctxt->bso, "t=%d ", s->type);
if(s->dupok)
Bprint(ctxt->bso, "dupok ");
if(s->cfunc)
Bprint(ctxt->bso, "cfunc ");
if(s->nosplit)
Bprint(ctxt->bso, "nosplit ");
Bprint(ctxt->bso, "size=%lld value=%lld", (vlong)s->size, (vlong)s->value);
@ -397,7 +399,7 @@ writesym(Link *ctxt, Biobuf *b, LSym *s)
wrint(b, s->args);
wrint(b, s->locals);
wrint(b, s->nosplit);
wrint(b, s->leaf);
wrint(b, s->leaf | s->cfunc<<1);
n = 0;
for(a = s->autom; a != nil; a = a->link)
n++;
@ -641,6 +643,7 @@ overwrite:
s->nosplit = rdint(f);
v = rdint(f);
s->leaf = v&1;
s->cfunc = v&2;
n = rdint(f);
for(i=0; i<n; i++) {
a = emallocz(sizeof *a);
@ -696,6 +699,8 @@ overwrite:
Bprint(ctxt->bso, "t=%d ", s->type);
if(s->dupok)
Bprint(ctxt->bso, "dupok ");
if(s->cfunc)
Bprint(ctxt->bso, "cfunc ");
if(s->nosplit)
Bprint(ctxt->bso, "nosplit ");
Bprint(ctxt->bso, "size=%lld value=%lld", (vlong)s->size, (vlong)s->value);

6
src/runtime/asm_386.s
View File

@ -20,7 +20,8 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$0
// _cgo_init may update stackguard.
MOVL $runtime·g0(SB), BP
LEAL (-64*1024+104)(SP), BX
MOVL BX, g_stackguard(BP)
MOVL BX, g_stackguard0(BP)
MOVL BX, g_stackguard1(BP)
MOVL BX, (g_stack+stack_lo)(BP)
MOVL SP, (g_stack+stack_hi)(BP)
@ -50,7 +51,8 @@ nocpuinfo:
MOVL $runtime·g0(SB), CX
MOVL (g_stack+stack_lo)(CX), AX
ADDL $const__StackGuard, AX
MOVL AX, g_stackguard(CX)
MOVL AX, g_stackguard0(CX)
MOVL AX, g_stackguard1(CX)
// skip runtime·ldt0setup(SB) and tls test after _cgo_init for non-windows
CMPL runtime·iswindows(SB), $0

6
src/runtime/asm_amd64.s
View File

@ -20,7 +20,8 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$0
// _cgo_init may update stackguard.
MOVQ $runtime·g0(SB), DI
LEAQ (-64*1024+104)(SP), BX
MOVQ BX, g_stackguard(DI)
MOVQ BX, g_stackguard0(DI)
MOVQ BX, g_stackguard1(DI)
MOVQ BX, (g_stack+stack_lo)(DI)
MOVQ SP, (g_stack+stack_hi)(DI)
@ -48,7 +49,8 @@ nocpuinfo:
MOVQ $runtime·g0(SB), CX
MOVQ (g_stack+stack_lo)(CX), AX
ADDQ $const__StackGuard, AX
MOVQ AX, g_stackguard(CX)
MOVQ AX, g_stackguard0(CX)
MOVQ AX, g_stackguard1(CX)
CMPL runtime·iswindows(SB), $0
JEQ ok

3
src/runtime/asm_amd64p32.s
View File

@ -22,7 +22,8 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$0
// create istack out of the given (operating system) stack.
MOVL $runtime·g0(SB), DI
LEAL (-64*1024+104)(SP), BX
MOVL BX, g_stackguard(DI)
MOVL BX, g_stackguard0(DI)
MOVL BX, g_stackguard1(DI)
MOVL BX, (g_stack+stack_lo)(DI)
MOVL SP, (g_stack+stack_hi)(DI)

6
src/runtime/asm_arm.s
View File

@ -32,7 +32,8 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$-4
// create istack out of the OS stack
MOVW $(-8192+104)(R13), R0
MOVW R0, g_stackguard(g)
MOVW R0, g_stackguard0(g)
MOVW R0, g_stackguard1(g)
MOVW R0, (g_stack+stack_lo)(g)
MOVW R13, (g_stack+stack_hi)(g)
@ -55,7 +56,8 @@ nocgo:
// update stackguard after _cgo_init
MOVW (g_stack+stack_lo)(g), R0
ADD $const__StackGuard, R0
MOVW R0, g_stackguard(g)
MOVW R0, g_stackguard0(g)
MOVW R0, g_stackguard1(g)
BL runtime·checkgoarm(SB)
BL runtime·check(SB)

3
src/runtime/asm_ppc64x.s
View File

@ -22,7 +22,8 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$0
MOVD $runtime·g0(SB), g
MOVD $(-64*1024), R31
ADD R31, R1, R3
MOVD R3, g_stackguard(g)
MOVD R3, g_stackguard0(g)
MOVD R3, g_stackguard1(g)
MOVD R3, (g_stack+stack_lo)(g)
MOVD R1, (g_stack+stack_hi)(g)

2
src/runtime/lock_futex.go
View File

@ -114,7 +114,7 @@ func unlock(l *mutex) {
throw("runtime·unlock: lock count")
}
if gp.m.locks == 0 && gp.preempt { // restore the preemption request in case we've cleared it in newstack
gp.stackguard = stackPreempt
gp.stackguard0 = stackPreempt
}
}

2
src/runtime/lock_sema.go
View File

@ -115,7 +115,7 @@ func unlock(l *mutex) {
throw("runtime·unlock: lock count")
}
if gp.m.locks == 0 && gp.preempt { // restore the preemption request in case we've cleared it in newstack
gp.stackguard = stackPreempt
gp.stackguard0 = stackPreempt
}
}

6
src/runtime/malloc.go
View File

@ -64,7 +64,7 @@ func mallocgc(size uintptr, typ *_type, flags uint32) unsafe.Pointer {
}
mp.mallocing = 1
if mp.curg != nil {
mp.curg.stackguard = ^uintptr(0xfff) | 0xbad
mp.curg.stackguard0 = ^uintptr(0xfff) | 0xbad
}
}
@ -127,7 +127,7 @@ func mallocgc(size uintptr, typ *_type, flags uint32) unsafe.Pointer {
}
mp.mallocing = 0
if mp.curg != nil {
mp.curg.stackguard = mp.curg.stack.lo + _StackGuard
mp.curg.stackguard0 = mp.curg.stack.lo + _StackGuard
}
// Note: one releasem for the acquirem just above.
// The other for the acquirem at start of malloc.
@ -319,7 +319,7 @@ marked:
}
mp.mallocing = 0
if mp.curg != nil {
mp.curg.stackguard = mp.curg.stack.lo + _StackGuard
mp.curg.stackguard0 = mp.curg.stack.lo + _StackGuard
}
// Note: one releasem for the acquirem just above.
// The other for the acquirem at start of malloc.

49
src/runtime/proc1.go
View File

@ -179,6 +179,9 @@ func mcommoninit(mp *m) {
sched.mcount++
checkmcount()
mpreinit(mp)
if mp.gsignal != nil {
mp.gsignal.stackguard1 = mp.gsignal.stack.lo + _StackGuard
}
// Add to allm so garbage collector doesn't free g->m
// when it is just in a register or thread-local storage.
@ -210,7 +213,7 @@ func ready(gp *g) {
}
_g_.m.locks--
if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
}
}
@ -460,7 +463,7 @@ func stopg(gp *g) bool {
if !gp.gcworkdone {
gp.preemptscan = true
gp.preempt = true
gp.stackguard = stackPreempt
gp.stackguard0 = stackPreempt
}
// Unclaim.
@ -542,7 +545,7 @@ func mquiesce(gpmaster *g) {
gp.gcworkdone = true // scan is a noop
break
}
if status == _Grunning && gp.stackguard == uintptr(stackPreempt) && notetsleep(&sched.stopnote, 100*1000) { // nanosecond arg
if status == _Grunning && gp.stackguard0 == uintptr(stackPreempt) && notetsleep(&sched.stopnote, 100*1000) { // nanosecond arg
noteclear(&sched.stopnote)
} else {
stopscanstart(gp)
@ -701,7 +704,7 @@ func starttheworld() {
}
_g_.m.locks--
if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
}
}
@ -722,7 +725,8 @@ func mstart() {
}
// Initialize stack guards so that we can start calling
// both Go and C functions with stack growth prologues.
_g_.stackguard = _g_.stack.lo + _StackGuard
_g_.stackguard0 = _g_.stack.lo + _StackGuard
_g_.stackguard1 = _g_.stackguard0
mstart1()
}
@ -802,7 +806,7 @@ func allocm(_p_ *p) *m {
}
_g_.m.locks--
if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
}
return mp
@ -879,7 +883,7 @@ func needm(x byte) {
_g_ := getg()
_g_.stack.hi = uintptr(noescape(unsafe.Pointer(&x))) + 1024
_g_.stack.lo = uintptr(noescape(unsafe.Pointer(&x))) - 32*1024
_g_.stackguard = _g_.stack.lo + _StackGuard
_g_.stackguard0 = _g_.stack.lo + _StackGuard
// Initialize this thread to use the m.
asminit()
@ -1217,7 +1221,7 @@ func execute(gp *g) {
casgstatus(gp, _Grunnable, _Grunning)
gp.waitsince = 0
gp.preempt = false
gp.stackguard = gp.stack.lo + _StackGuard
gp.stackguard0 = gp.stack.lo + _StackGuard
_g_.m.p.schedtick++
_g_.m.curg = gp
gp.m = _g_.m
@ -1613,7 +1617,7 @@ func reentersyscall(pc, sp uintptr) {
// (See details in comment above.)
// Catch calls that might, by replacing the stack guard with something that
// will trip any stack check and leaving a flag to tell newstack to die.
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
_g_.throwsplit = true
// Leave SP around for GC and traceback.
@ -1644,7 +1648,7 @@ func reentersyscall(pc, sp uintptr) {
// Goroutines must not split stacks in Gsyscall status (it would corrupt g->sched).
// We set _StackGuard to StackPreempt so that first split stack check calls morestack.
// Morestack detects this case and throws.
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
_g_.m.locks--
}
@ -1682,7 +1686,7 @@ func entersyscallblock(dummy int32) {
_g_.m.locks++ // see comment in entersyscall
_g_.throwsplit = true
_g_.stackguard = stackPreempt // see comment in entersyscall
_g_.stackguard0 = stackPreempt // see comment in entersyscall
// Leave SP around for GC and traceback.
pc := getcallerpc(unsafe.Pointer(&dummy))
@ -1748,10 +1752,10 @@ func exitsyscall(dummy int32) {
_g_.m.locks--
if _g_.preempt {
// restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
} else {
// otherwise restore the real _StackGuard, we've spoiled it in entersyscall/entersyscallblock
_g_.stackguard = _g_.stack.lo + _StackGuard
_g_.stackguard0 = _g_.stack.lo + _StackGuard
}
_g_.throwsplit = false
return
@ -1869,7 +1873,7 @@ func beforefork() {
// Code between fork and exec must not allocate memory nor even try to grow stack.
// Here we spoil g->_StackGuard to reliably detect any attempts to grow stack.
// runtime_AfterFork will undo this in parent process, but not in child.
gp.stackguard = stackFork
gp.stackguard0 = stackFork
}
// Called from syscall package before fork.
@ -1883,7 +1887,7 @@ func afterfork() {
gp := getg().m.curg
// See the comment in beforefork.
gp.stackguard = gp.stack.lo + _StackGuard
gp.stackguard0 = gp.stack.lo + _StackGuard
hz := sched.profilehz
if hz != 0 {
@ -1907,7 +1911,8 @@ func malg(stacksize int32) *g {
systemstack(func() {
newg.stack = stackalloc(uint32(stacksize))
})
newg.stackguard = newg.stack.lo + _StackGuard
newg.stackguard0 = newg.stack.lo + _StackGuard
newg.stackguard1 = ^uintptr(0)
}
return newg
}
@ -2003,7 +2008,7 @@ func newproc1(fn *funcval, argp *uint8, narg int32, nret int32, callerpc uintptr
}
_g_.m.locks--
if _g_.m.locks == 0 && _g_.preempt { // restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
}
return newg
}
@ -2022,7 +2027,7 @@ func gfput(_p_ *p, gp *g) {
stackfree(gp.stack)
gp.stack.lo = 0
gp.stack.hi = 0
gp.stackguard = 0
gp.stackguard0 = 0
}
gp.schedlink = _p_.gfree
@ -2068,7 +2073,7 @@ retry:
systemstack(func() {
gp.stack = stackalloc(_FixedStack)
})
gp.stackguard = gp.stack.lo + _StackGuard
gp.stackguard0 = gp.stack.lo + _StackGuard
} else {
if raceenabled {
racemalloc(unsafe.Pointer(gp.stack.lo), gp.stack.hi-gp.stack.lo)
@ -2773,10 +2778,10 @@ func preemptone(_p_ *p) bool {
gp.preempt = true
// Every call in a go routine checks for stack overflow by
// comparing the current stack pointer to gp->stackguard.
// Setting gp->stackguard to StackPreempt folds
// comparing the current stack pointer to gp->stackguard0.
// Setting gp->stackguard0 to StackPreempt folds
// preemption into the normal stack overflow check.
gp.stackguard = stackPreempt
gp.stackguard0 = stackPreempt
return true
}

2
src/runtime/runtime1.go
View File

@ -386,7 +386,7 @@ func releasem(mp *m) {
mp.locks--
if mp.locks == 0 && _g_.preempt {
// restore the preemption request in case we've cleared it in newstack
_g_.stackguard = stackPreempt
_g_.stackguard0 = stackPreempt
}
}

12
src/runtime/runtime2.go
View File

@ -154,10 +154,14 @@ type stack struct {
type g struct {
// Stack parameters.
// stack describes the actual stack memory: [stack.lo, stack.hi).
// stackguard is the stack pointer compared in the Go stack growth prologue.
// stackguard0 is the stack pointer compared in the Go stack growth prologue.
// It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption.
stack stack // offset known to runtime/cgo
stackguard uintptr // offset known to liblink
// stackguard1 is the stack pointer compared in the C stack growth prologue.
// It is stack.lo+StackGuard on g0 and gsignal stacks.
// It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash).
stack stack // offset known to runtime/cgo
stackguard0 uintptr // offset known to liblink
stackguard1 uintptr // offset known to liblink
_panic *_panic // innermost panic - offset known to liblink
_defer *_defer // innermost defer
@ -171,7 +175,7 @@ type g struct {
waitreason string // if status==gwaiting
schedlink *g
issystem bool // do not output in stack dump, ignore in deadlock detector
preempt bool // preemption signal, duplicates stackguard = stackpreempt
preempt bool // preemption signal, duplicates stackguard0 = stackpreempt
paniconfault bool // panic (instead of crash) on unexpected fault address
preemptscan bool // preempted g does scan for gc
gcworkdone bool // debug: cleared at begining of gc work phase cycle, set by gcphasework, tested at end of cycle

21
src/runtime/stack1.go
View File

@ -26,13 +26,13 @@ const (
poisonStack = uintptrMask & 0x6868686868686868
// Goroutine preemption request.
// Stored into g->stackguard to cause split stack check failure.
// Stored into g->stackguard0 to cause split stack check failure.
// Must be greater than any real sp.
// 0xfffffade in hex.
stackPreempt = uintptrMask & -1314
// Thread is forking.
// Stored into g->stackguard to cause split stack check failure.
// Stored into g->stackguard0 to cause split stack check failure.
// Must be greater than any real sp.
stackFork = uintptrMask & -1234
)
@ -566,7 +566,7 @@ func copystack(gp *g, newsize uintptr) {
// Swap out old stack for new one
gp.stack = new
gp.stackguard = new.lo + _StackGuard // NOTE: might clobber a preempt request
gp.stackguard0 = new.lo + _StackGuard // NOTE: might clobber a preempt request
gp.sched.sp = new.hi - used
// free old stack
@ -611,7 +611,7 @@ func round2(x int32) int32 {
func newstack() {
thisg := getg()
// TODO: double check all gp. shouldn't be getg().
if thisg.m.morebuf.g.stackguard == stackFork {
if thisg.m.morebuf.g.stackguard0 == stackFork {
throw("stack growth after fork")
}
if thisg.m.morebuf.g != thisg.m.curg {
@ -674,7 +674,7 @@ func newstack() {
writebarrierptr_nostore((*uintptr)(unsafe.Pointer(&gp.sched.ctxt)), uintptr(gp.sched.ctxt))
}
if gp.stackguard == stackPreempt {
if gp.stackguard0 == stackPreempt {
if gp == thisg.m.g0 {
throw("runtime: preempt g0")
}
@ -689,7 +689,7 @@ func newstack() {
gcphasework(gp)
casfrom_Gscanstatus(gp, _Gscanwaiting, _Gwaiting)
casgstatus(gp, _Gwaiting, _Grunning)
gp.stackguard = gp.stack.lo + _StackGuard
gp.stackguard0 = gp.stack.lo + _StackGuard
gp.preempt = false
gp.preemptscan = false // Tells the GC premption was successful.
gogo(&gp.sched) // never return
@ -700,7 +700,7 @@ func newstack() {
if thisg.m.locks != 0 || thisg.m.mallocing != 0 || thisg.m.gcing != 0 || thisg.m.p.status != _Prunning {
// Let the goroutine keep running for now.
// gp->preempt is set, so it will be preempted next time.
gp.stackguard = gp.stack.lo + _StackGuard
gp.stackguard0 = gp.stack.lo + _StackGuard
casgstatus(gp, _Gwaiting, _Grunning)
gogo(&gp.sched) // never return
}
@ -804,3 +804,10 @@ func shrinkfinish() {
s = t
}
}
//go:nosplit
func morestackc() {
systemstack(func() {
throw("attempt to execute C code on Go stack")
})
}

2
src/runtime/stack2.go
View File

@ -97,7 +97,7 @@ const (
)
// Goroutine preemption request.
// Stored into g->stackguard to cause split stack check failure.
// Stored into g->stackguard0 to cause split stack check failure.
// Must be greater than any real sp.
// 0xfffffade in hex.
const (

3
src/runtime/sys_plan9_386.s
View File

@ -148,7 +148,8 @@ TEXT runtime·tstart_plan9(SB),NOSPLIT,$0
MOVL AX, (g_stack+stack_hi)(DX)
SUBL $(64*1024), AX // stack size
MOVL AX, (g_stack+stack_lo)(DX)
MOVL AX, g_stackguard(DX)
MOVL AX, g_stackguard0(DX)
MOVL AX, g_stackguard1(DX)
// Initialize procid from TOS struct.
MOVL _tos(SB), AX

3
src/runtime/sys_plan9_amd64.s
View File

@ -145,7 +145,8 @@ TEXT runtime·tstart_plan9(SB),NOSPLIT,$0
MOVQ AX, (g_stack+stack_hi)(DX)
SUBQ $(64*1024), AX // stack size
MOVQ AX, (g_stack+stack_lo)(DX)
MOVQ AX, g_stackguard(DX)
MOVQ AX, g_stackguard0(DX)
MOVQ AX, g_stackguard1(DX)
// Initialize procid from TOS struct.
MOVQ _tos(SB), AX

3
src/runtime/sys_solaris_amd64.s
View File

@ -134,7 +134,8 @@ TEXT runtime·tstart_sysvicall(SB),NOSPLIT,$0
SUBQ $(0x100000), AX // stack size
MOVQ AX, (g_stack+stack_lo)(DX)
ADDQ $const__StackGuard, AX
MOVQ AX, g_stackguard(DX)
MOVQ AX, g_stackguard0(DX)
MOVQ AX, g_stackguard1(DX)
// Someday the convention will be D is always cleared.
CLD

6
src/runtime/sys_windows_386.s
View File

@ -209,7 +209,8 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
LEAL -8192(SP), CX
MOVL CX, (g_stack+stack_lo)(SP)
ADDL $const__StackGuard, CX
MOVL CX, g_stackguard(SP)
MOVL CX, g_stackguard0(SP)
MOVL CX, g_stackguard1(SP)
MOVL DX, (g_stack+stack_hi)(SP)
PUSHL 16(BP) // arg for handler
@ -314,7 +315,8 @@ TEXT runtime·tstart(SB),NOSPLIT,$0
SUBL $(64*1024), AX // stack size
MOVL AX, (g_stack+stack_lo)(DX)
ADDL $const__StackGuard, AX
MOVL AX, g_stackguard(DX)
MOVL AX, g_stackguard0(DX)
MOVL AX, g_stackguard1(DX)
// Set up tls.
LEAL m_tls(CX), SI

6
src/runtime/sys_windows_amd64.s
View File

@ -246,7 +246,8 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
LEAQ -8192(SP), CX
MOVQ CX, (g_stack+stack_lo)(SP)
ADDQ $const__StackGuard, CX
MOVQ CX, g_stackguard(SP)
MOVQ CX, g_stackguard0(SP)
MOVQ CX, g_stackguard1(SP)
MOVQ DX, (g_stack+stack_hi)(SP)
PUSHQ 32(BP) // arg for handler
@ -355,7 +356,8 @@ TEXT runtime·tstart_stdcall(SB),NOSPLIT,$0
SUBQ $(64*1024), AX // stack size
MOVQ AX, (g_stack+stack_lo)(DX)
ADDQ $const__StackGuard, AX
MOVQ AX, g_stackguard(DX)
MOVQ AX, g_stackguard0(DX)
MOVQ AX, g_stackguard1(DX)
// Set up tls.
LEAQ m_tls(CX), SI