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-rw-r--r--src/runtime/asm_386.s16
-rw-r--r--src/runtime/asm_amd64.s16
-rw-r--r--src/runtime/asm_amd64p32.s16
-rw-r--r--src/runtime/asm_arm.s18
-rw-r--r--src/runtime/asm_arm64.s17
-rw-r--r--src/runtime/asm_mips64x.s18
-rw-r--r--src/runtime/asm_mipsx.s18
-rw-r--r--src/runtime/asm_ppc64x.s17
-rw-r--r--src/runtime/asm_s390x.s18
-rw-r--r--src/runtime/mgcmark.go7
-rw-r--r--src/runtime/runtime2.go18
-rw-r--r--src/runtime/stack.go12
12 files changed, 41 insertions, 150 deletions
diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index ef82756397..15d9ce9fdf 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -362,18 +362,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-4
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $8-4
MOVL buf+0(FP), BX // gobuf
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVL gobuf_ctxt(BX), DX
- TESTL DX, DX
- JZ nilctxt
- LEAL gobuf_ctxt(BX), AX
- MOVL AX, 0(SP)
- MOVL $0, 4(SP)
- CALL runtime·writebarrierptr_prewrite(SB)
- MOVL buf+0(FP), BX
-
-nilctxt:
MOVL gobuf_g(BX), DX
MOVL 0(DX), CX // make sure g != nil
get_tls(CX)
@@ -536,7 +524,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
MOVL SI, (g_sched+gobuf_g)(SI)
LEAL 4(SP), AX // f's SP
MOVL AX, (g_sched+gobuf_sp)(SI)
- // newstack will fill gobuf.ctxt.
+ MOVL DX, (g_sched+gobuf_ctxt)(SI)
// Call newstack on m->g0's stack.
MOVL m_g0(BX), BP
@@ -544,10 +532,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
MOVL (g_sched+gobuf_sp)(BP), AX
MOVL -4(AX), BX // fault if CALL would, before smashing SP
MOVL AX, SP
- PUSHL DX // ctxt argument
CALL runtime·newstack(SB)
MOVL $0, 0x1003 // crash if newstack returns
- POPL DX // keep balance check happy
RET
TEXT runtime·morestack_noctxt(SB),NOSPLIT,$0-0
diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 7c5e8e9ada..2ac879c31d 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -304,18 +304,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-8
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $16-8
MOVQ buf+0(FP), BX // gobuf
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVQ gobuf_ctxt(BX), AX
- TESTQ AX, AX
- JZ nilctxt
- LEAQ gobuf_ctxt(BX), AX
- MOVQ AX, 0(SP)
- MOVQ $0, 8(SP)
- CALL runtime·writebarrierptr_prewrite(SB)
- MOVQ buf+0(FP), BX
-
-nilctxt:
MOVQ gobuf_g(BX), DX
MOVQ 0(DX), CX // make sure g != nil
get_tls(CX)
@@ -482,16 +470,14 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
LEAQ 8(SP), AX // f's SP
MOVQ AX, (g_sched+gobuf_sp)(SI)
MOVQ BP, (g_sched+gobuf_bp)(SI)
- // newstack will fill gobuf.ctxt.
+ MOVQ DX, (g_sched+gobuf_ctxt)(SI)
// Call newstack on m->g0's stack.
MOVQ m_g0(BX), BX
MOVQ BX, g(CX)
MOVQ (g_sched+gobuf_sp)(BX), SP
- PUSHQ DX // ctxt argument
CALL runtime·newstack(SB)
MOVQ $0, 0x1003 // crash if newstack returns
- POPQ DX // keep balance check happy
RET
// morestack but not preserving ctxt.
diff --git a/src/runtime/asm_amd64p32.s b/src/runtime/asm_amd64p32.s
index c80a563bda..b7fcf2376e 100644
--- a/src/runtime/asm_amd64p32.s
+++ b/src/runtime/asm_amd64p32.s
@@ -198,18 +198,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-4
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $8-4
MOVL buf+0(FP), BX // gobuf
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVL gobuf_ctxt(BX), DX
- TESTL DX, DX
- JZ nilctxt
- LEAL gobuf_ctxt(BX), AX
- MOVL AX, 0(SP)
- MOVL $0, 4(SP)
- CALL runtime·writebarrierptr_prewrite(SB)
- MOVL buf+0(FP), BX
-
-nilctxt:
MOVL gobuf_g(BX), DX
MOVL 0(DX), CX // make sure g != nil
get_tls(CX)
@@ -368,16 +356,14 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
MOVL SI, (g_sched+gobuf_g)(SI)
LEAL 8(SP), AX // f's SP
MOVL AX, (g_sched+gobuf_sp)(SI)
- // newstack will fill gobuf.ctxt.
+ MOVL DX, (g_sched+gobuf_ctxt)(SI)
// Call newstack on m->g0's stack.
MOVL m_g0(BX), BX
MOVL BX, g(CX)
MOVL (g_sched+gobuf_sp)(BX), SP
- PUSHQ DX // ctxt argument
CALL runtime·newstack(SB)
MOVL $0, 0x1003 // crash if newstack returns
- POPQ DX // keep balance check happy
RET
// morestack trampolines
diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index 47fa565c52..caa96cc4b3 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -227,19 +227,6 @@ TEXT runtime·gosave(SB),NOSPLIT,$-4-4
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB),NOSPLIT,$8-4
MOVW buf+0(FP), R1
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVW gobuf_ctxt(R1), R0
- CMP $0, R0
- B.EQ nilctxt
- MOVW $gobuf_ctxt(R1), R0
- MOVW R0, 4(R13)
- MOVW $0, R0
- MOVW R0, 8(R13)
- BL runtime·writebarrierptr_prewrite(SB)
- MOVW buf+0(FP), R1
-
-nilctxt:
MOVW gobuf_g(R1), R0
BL setg<>(SB)
@@ -412,7 +399,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
MOVW R13, (g_sched+gobuf_sp)(g)
MOVW LR, (g_sched+gobuf_pc)(g)
MOVW R3, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVW R7, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's caller.
@@ -426,8 +413,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
BL setg<>(SB)
MOVW (g_sched+gobuf_sp)(g), R13
MOVW $0, R0
- MOVW.W R0, -8(R13) // create a call frame on g0
- MOVW R7, 4(R13) // ctxt argument
+ MOVW.W R0, -4(R13) // create a call frame on g0 (saved LR)
BL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index e4b2c37038..b2aff1aab7 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -122,18 +122,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $24-8
MOVD buf+0(FP), R5
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVD gobuf_ctxt(R5), R0
- CMP $0, R0
- BEQ nilctxt
- MOVD $gobuf_ctxt(R5), R0
- MOVD R0, 8(RSP)
- MOVD ZR, 16(RSP)
- BL runtime·writebarrierptr_prewrite(SB)
- MOVD buf+0(FP), R5
-
-nilctxt:
MOVD gobuf_g(R5), g
BL runtime·save_g(SB)
@@ -289,7 +277,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
MOVD R0, (g_sched+gobuf_sp)(g)
MOVD LR, (g_sched+gobuf_pc)(g)
MOVD R3, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVD R26, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's callers.
@@ -303,8 +291,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
BL runtime·save_g(SB)
MOVD (g_sched+gobuf_sp)(g), R0
MOVD R0, RSP
- MOVD.W $0, -16(RSP) // create a call frame on g0
- MOVD R26, 8(RSP) // ctxt argument
+ MOVD.W $0, -16(RSP) // create a call frame on g0 (saved LR; keep 16-aligned)
BL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_mips64x.s b/src/runtime/asm_mips64x.s
index 4902d04640..3510853804 100644
--- a/src/runtime/asm_mips64x.s
+++ b/src/runtime/asm_mips64x.s
@@ -108,17 +108,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $16-8
MOVV buf+0(FP), R3
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVV gobuf_ctxt(R3), R1
- BEQ R1, nilctxt
- MOVV $gobuf_ctxt(R3), R1
- MOVV R1, 8(R29)
- MOVV R0, 16(R29)
- JAL runtime·writebarrierptr_prewrite(SB)
- MOVV buf+0(FP), R3
-
-nilctxt:
MOVV gobuf_g(R3), g // make sure g is not nil
JAL runtime·save_g(SB)
@@ -260,7 +249,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
MOVV R29, (g_sched+gobuf_sp)(g)
MOVV R31, (g_sched+gobuf_pc)(g)
MOVV R3, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVV REGCTXT, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's caller.
@@ -273,9 +262,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
JAL runtime·save_g(SB)
MOVV (g_sched+gobuf_sp)(g), R29
// Create a stack frame on g0 to call newstack.
- MOVV R0, -16(R29) // Zero saved LR in frame
- ADDV $-16, R29
- MOVV REGCTXT, 8(R29) // ctxt argument
+ MOVV R0, -8(R29) // Zero saved LR in frame
+ ADDV $-8, R29
JAL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_mipsx.s b/src/runtime/asm_mipsx.s
index 82e01b0bac..334f259186 100644
--- a/src/runtime/asm_mipsx.s
+++ b/src/runtime/asm_mipsx.s
@@ -109,17 +109,6 @@ TEXT runtime·gosave(SB),NOSPLIT,$-4-4
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB),NOSPLIT,$8-4
MOVW buf+0(FP), R3
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVW gobuf_ctxt(R3), R1
- BEQ R1, nilctxt
- MOVW $gobuf_ctxt(R3), R1
- MOVW R1, 4(R29)
- MOVW R0, 8(R29)
- JAL runtime·writebarrierptr_prewrite(SB)
- MOVW buf+0(FP), R3
-
-nilctxt:
MOVW gobuf_g(R3), g // make sure g is not nil
JAL runtime·save_g(SB)
@@ -261,7 +250,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
MOVW R29, (g_sched+gobuf_sp)(g)
MOVW R31, (g_sched+gobuf_pc)(g)
MOVW R3, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVW REGCTXT, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's caller.
@@ -274,9 +263,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
JAL runtime·save_g(SB)
MOVW (g_sched+gobuf_sp)(g), R29
// Create a stack frame on g0 to call newstack.
- MOVW R0, -8(R29) // Zero saved LR in frame
- ADDU $-8, R29
- MOVW REGCTXT, 4(R29) // ctxt argument
+ MOVW R0, -4(R29) // Zero saved LR in frame
+ ADDU $-4, R29
JAL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 40ad1010a9..2f2a4a7b04 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -133,18 +133,6 @@ TEXT runtime·gosave(SB), NOSPLIT|NOFRAME, $0-8
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $16-8
MOVD buf+0(FP), R5
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVD gobuf_ctxt(R5), R3
- CMP R0, R3
- BEQ nilctxt
- MOVD $gobuf_ctxt(R5), R3
- MOVD R3, FIXED_FRAME+0(R1)
- MOVD R0, FIXED_FRAME+8(R1)
- BL runtime·writebarrierptr_prewrite(SB)
- MOVD buf+0(FP), R5
-
-nilctxt:
MOVD gobuf_g(R5), g // make sure g is not nil
BL runtime·save_g(SB)
@@ -317,7 +305,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
MOVD LR, R8
MOVD R8, (g_sched+gobuf_pc)(g)
MOVD R5, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVD R11, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's caller.
@@ -329,8 +317,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
MOVD m_g0(R7), g
BL runtime·save_g(SB)
MOVD (g_sched+gobuf_sp)(g), R1
- MOVDU R0, -(FIXED_FRAME+8)(R1) // create a call frame on g0
- MOVD R11, FIXED_FRAME+0(R1) // ctxt argument
+ MOVDU R0, -(FIXED_FRAME+0)(R1) // create a call frame on g0
BL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 241be17842..524b866b21 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -116,17 +116,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
// restore state from Gobuf; longjmp
TEXT runtime·gogo(SB), NOSPLIT, $16-8
MOVD buf+0(FP), R5
-
- // If ctxt is not nil, invoke deletion barrier before overwriting.
- MOVD gobuf_ctxt(R5), R1
- CMPBEQ R1, $0, nilctxt
- MOVD $gobuf_ctxt(R5), R1
- MOVD R1, 8(R15)
- MOVD R0, 16(R15)
- BL runtime·writebarrierptr_prewrite(SB)
- MOVD buf+0(FP), R5
-
-nilctxt:
MOVD gobuf_g(R5), g // make sure g is not nil
BL runtime·save_g(SB)
@@ -272,7 +261,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
MOVD LR, R8
MOVD R8, (g_sched+gobuf_pc)(g)
MOVD R5, (g_sched+gobuf_lr)(g)
- // newstack will fill gobuf.ctxt.
+ MOVD R12, (g_sched+gobuf_ctxt)(g)
// Called from f.
// Set m->morebuf to f's caller.
@@ -285,9 +274,8 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
BL runtime·save_g(SB)
MOVD (g_sched+gobuf_sp)(g), R15
// Create a stack frame on g0 to call newstack.
- MOVD $0, -16(R15) // Zero saved LR in frame
- SUB $16, R15
- MOVD R12, 8(R15) // ctxt argument
+ MOVD $0, -8(R15) // Zero saved LR in frame
+ SUB $8, R15
BL runtime·newstack(SB)
// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index ed256efc80..ce697e5809 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -770,6 +770,13 @@ func scanstack(gp *g, gcw *gcWork) {
shrinkstack(gp)
}
+ // Scan the saved context register. This is effectively a live
+ // register that gets moved back and forth between the
+ // register and sched.ctxt without a write barrier.
+ if gp.sched.ctxt != nil {
+ scanblock(uintptr(unsafe.Pointer(&gp.sched.ctxt)), sys.PtrSize, &oneptrmask[0], gcw)
+ }
+
// Scan the stack.
var cache pcvalueCache
scanframe := func(frame *stkframe, unused unsafe.Pointer) bool {
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index ca796169fe..a79faba8ce 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -254,17 +254,19 @@ type gobuf struct {
// The offsets of sp, pc, and g are known to (hard-coded in) libmach.
//
// ctxt is unusual with respect to GC: it may be a
- // heap-allocated funcval so write require a write barrier,
- // but gobuf needs to be cleared from assembly. We take
- // advantage of the fact that the only path that uses a
- // non-nil ctxt is morestack. As a result, gogo is the only
- // place where it may not already be nil, so gogo uses an
- // explicit write barrier. Everywhere else that resets the
- // gobuf asserts that ctxt is already nil.
+ // heap-allocated funcval, so GC needs to track it, but it
+ // needs to be set and cleared from assembly, where it's
+ // difficult to have write barriers. However, ctxt is really a
+ // saved, live register, and we only ever exchange it between
+ // the real register and the gobuf. Hence, we treat it as a
+ // root during stack scanning, which means assembly that saves
+ // and restores it doesn't need write barriers. It's still
+ // typed as a pointer so that any other writes from Go get
+ // write barriers.
sp uintptr
pc uintptr
g guintptr
- ctxt unsafe.Pointer // this has to be a pointer so that gc scans it
+ ctxt unsafe.Pointer
ret sys.Uintreg
lr uintptr
bp uintptr // for GOEXPERIMENT=framepointer
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 4e60e80863..89458b7ff6 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -913,9 +913,12 @@ func round2(x int32) int32 {
// g->atomicstatus will be Grunning or Gscanrunning upon entry.
// If the GC is trying to stop this g then it will set preemptscan to true.
//
-// ctxt is the value of the context register on morestack. newstack
-// will write it to g.sched.ctxt.
-func newstack(ctxt unsafe.Pointer) {
+// This must be nowritebarrierrec because it can be called as part of
+// stack growth from other nowritebarrierrec functions, but the
+// compiler doesn't check this.
+//
+//go:nowritebarrierrec
+func newstack() {
thisg := getg()
// TODO: double check all gp. shouldn't be getg().
if thisg.m.morebuf.g.ptr().stackguard0 == stackFork {
@@ -929,9 +932,6 @@ func newstack(ctxt unsafe.Pointer) {
}
gp := thisg.m.curg
- // Write ctxt to gp.sched. We do this here instead of in
- // morestack so it has the necessary write barrier.
- gp.sched.ctxt = ctxt
if thisg.m.curg.throwsplit {
// Update syscallsp, syscallpc in case traceback uses them.
generated by cgit v1.3-5-g9baa (git 2.53.0) at 2026-04-17 14:59:21 +0000