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proc: fix arm64 crosscall2 SP restore for cgo stacktraces #4399

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proc: fix arm64 crosscall2 SP restore for cgo stacktraces #4399

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1071039
proc: fix arm64 crosscall2 SP restore for cgo stacktraces
derekparker Jul 23, 2026
f54d9fb
proc: compute crosscall2 caller SP on riscv64, loong64, ppc64le
derekparker Jul 23, 2026
fddd94e
proc: enable TestCgoStacktrace on windows/arm64
derekparker Jul 27, 2026
2460f79
proc: restore TestCgoStacktrace skip on windows/arm64
derekparker Jul 27, 2026
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3 changes: 1 addition & 2 deletions Documentation/backend_test_health.md
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Original file line number Diff line number Diff line change
Expand Up @@ -25,8 +25,7 @@ Tests skipped by each supported backend:
* 1 broken
* linux/loong64 skipped = 1
* 1 not working on linux/loong64
* linux/ppc64le skipped = 3
* 1 broken - cgo stacktraces
* linux/ppc64le skipped = 2
* 2 not working on linux/ppc64le when -gcflags=-N -l is passed
* linux/ppc64le/native skipped = 1
* 1 broken in linux ppc64le
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13 changes: 6 additions & 7 deletions pkg/proc/arm64_arch.go
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Expand Up @@ -238,15 +238,18 @@ func arm64SwitchStack(it *stackIterator, callFrameRegs *op.DwarfRegisters) bool
return true

case "crosscall2":
// The offsets get from runtime/cgo/asm_arm64.s:10
// The offsets get from runtime/cgo/asm_arm64.s
bpoff := uint64(14)
lroff := uint64(15)
if producer := it.bi.Producer(); producer != "" && goversion.ProducerAfterOrEqual(producer, 1, 19) {
// In Go 1.19 (specifically eee6f9f82) the order registers are saved was changed.
bpoff = 22
lroff = 23
}
newsp, _ := readUintRaw(it.mem, it.regs.SP()+8*24, int64(it.bi.Arch.PtrSize()))
// crosscall2 does SUB $(8*24), RSP but does not spill SP. The caller's SP is
// therefore current SP + 8*24, not a value loaded from that address (which is
// the caller's stack contents).
newsp := it.regs.SP() + 8*24
newbp, _ := readUintRaw(it.mem, it.regs.SP()+8*bpoff, int64(it.bi.Arch.PtrSize()))
newlr, _ := readUintRaw(it.mem, it.regs.SP()+8*lroff, int64(it.bi.Arch.PtrSize()))
if it.regs.Reg(it.regs.BPRegNum) != nil {
Expand All @@ -256,11 +259,7 @@ func arm64SwitchStack(it *stackIterator, callFrameRegs *op.DwarfRegisters) bool
it.regs.AddReg(it.regs.BPRegNum, reg)
}
it.regs.Reg(it.regs.LRRegNum).Uint64Val = newlr
if linux {
it.regs.Reg(it.regs.SPRegNum).Uint64Val = newbp
} else {
it.regs.Reg(it.regs.SPRegNum).Uint64Val = newsp
}
it.regs.Reg(it.regs.SPRegNum).Uint64Val = newsp
it.pc = newlr
return true
case "runtime.mstart":
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6 changes: 4 additions & 2 deletions pkg/proc/loong64_arch.go
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Expand Up @@ -202,8 +202,10 @@ func loong64SwitchStack(it *stackIterator, callFrameRegs *op.DwarfRegisters) boo
return true

case "crosscall2":
// The offsets get from runtime/cgo/asm_loong64.s:25
newsp, _ := readUintRaw(it.mem, it.regs.SP()+8*23, int64(it.bi.Arch.PtrSize()))
// The offsets get from runtime/cgo/asm_loong64.s
// crosscall2 does ADDV $(-23*8), R3 but does not spill SP. The caller's SP is
// therefore current SP + 23*8, not a value loaded from that address.
newsp := it.regs.SP() + 8*23
newbp, _ := readUintRaw(it.mem, it.regs.SP()+8*4, int64(it.bi.Arch.PtrSize()))
newlr, _ := readUintRaw(it.mem, it.regs.SP()+8*22, int64(it.bi.Arch.PtrSize()))
if it.regs.Reg(it.regs.BPRegNum) != nil {
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18 changes: 13 additions & 5 deletions pkg/proc/ppc64le_arch.go
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Expand Up @@ -129,14 +129,22 @@ func ppc64leSwitchStack(it *stackIterator, callFrameRegs *op.DwarfRegisters) boo
it.atend = true
return true
case "crosscall2":
//The offsets get from runtime/cgo/asm_ppc64x.s:10
newsp, _ := readUintRaw(it.mem, it.regs.SP()+8*24, int64(it.bi.Arch.PtrSize()))
newbp, _ := readUintRaw(it.mem, it.regs.SP()+8*14, int64(it.bi.Arch.PtrSize()))
newlr, _ := readUintRaw(it.mem, it.regs.SP()+16, int64(it.bi.Arch.PtrSize()))
// Frame size from STACK_AND_SAVE_HOST_TO_GO_ABI(32) in
// runtime/cgo/abi_ppc64x.h: extra(32) + FIXED_FRAME(32) +
// SAVE_GPR(18*8) + SAVE_FPR(18*8) + SAVE_VR(12*16).
const frameSize = 32 + 32 + 18*8 + 18*8 + 12*16
newsp := it.regs.SP() + frameSize
// R31 (frame pointer) is the last GPR saved by SAVE_GPR at
// extra+FIXED_FRAME+8*17.
bpoff := uint64(32 + 32 + 8*17)
newbp, _ := readUintRaw(it.mem, it.regs.SP()+bpoff, int64(it.bi.Arch.PtrSize()))
// LR is saved into the caller's frame at 16(SP) before the stack
// allocation (host ELFv2 ABI).
newlr, _ := readUintRaw(it.mem, newsp+16, int64(it.bi.Arch.PtrSize()))
if it.regs.Reg(it.regs.BPRegNum) != nil {
it.regs.Reg(it.regs.BPRegNum).Uint64Val = newbp
} else {
reg, _ := it.readRegisterAt(it.regs.BPRegNum, it.regs.SP()+8*14)
reg, _ := it.readRegisterAt(it.regs.BPRegNum, it.regs.SP()+bpoff)
it.regs.AddReg(it.regs.BPRegNum, reg)
}
it.regs.Reg(it.regs.LRRegNum).Uint64Val = newlr
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4 changes: 3 additions & 1 deletion pkg/proc/proc_test.go
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Expand Up @@ -3127,8 +3127,10 @@ func TestCgoStacktrace(t *testing.T) {
}
}
skipOn(t, "broken - cgo stacktraces", "386")
// C frames on windows/arm64 use PE .pdata/.xdata (clang), not DWARF
// .debug_frame; Delve does not unwind via .pdata yet. Unrelated to the
// arm64 crosscall2 SP restore.
skipOn(t, "broken - cgo stacktraces", "windows", "arm64")
skipOn(t, "broken - cgo stacktraces", "linux", "ppc64le")
protest.MustHaveCgo(t)

// Tests that:
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4 changes: 3 additions & 1 deletion pkg/proc/riscv64_arch.go
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Expand Up @@ -226,7 +226,9 @@ func riscv64SwitchStack(it *stackIterator, callFrameRegs *op.DwarfRegisters) boo

case "crosscall2":
// The offsets get from runtime/cgo/asm_riscv64.s
newsp, _ := readUintRaw(it.mem, it.regs.SP()+8*29, int64(it.bi.Arch.PtrSize()))
// crosscall2 does ADD $(-8*29), X2 but does not spill SP. The caller's SP is
// therefore current SP + 8*29, not a value loaded from that address.
newsp := it.regs.SP() + 8*29
newbp, _ := readUintRaw(it.mem, it.regs.SP()+8*4, int64(it.bi.Arch.PtrSize()))
newlr, _ := readUintRaw(it.mem, it.regs.SP()+8*16, int64(it.bi.Arch.PtrSize()))
if it.regs.Reg(it.regs.BPRegNum) != nil {
Expand Down