Hello Go Experts,
When panic() is called from Go function, in the below call sequence,
runtime.unwindm() [which is defer function of runtime.cgocallbackg1] is
called. This function is unwinding the system stack. Later, as part of the
function addOneOpenDeferFrame(), systemstack() is called to run a function
in the system stack. This will use the stack which is allocated for C
function calls. This makes stack unwinding impossible in case of panic() is
called. Can someone please help me to fix this issue?
(dlv) bt
0 0x00000000004054e6 in runtime.unwindm
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:326
1 0x0000000000405446 in runtime.cgocallbackg1.func3
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:304
2 0x00000000004340c8 in runtime.deferCallSave
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:796
3 0x0000000000433fa5 in runtime.runOpenDeferFrame
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:769
4 0x0000000000434332 in runtime.gopanic
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:884
5 0x00000000004642a7 in main.Test4
at ./export.go:7
at ./export.go:7
6 0x000000000046431c in _cgoexp_78b81bbf688e_Test4
at _cgo_gotypes.go:61
7 0x000000000040535b in runtime.cgocallbackg1
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:315
8 0x0000000000405079 in runtime.cgocallbackg
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:234
9 0x0000000000461b0f in runtime.cgocallbackg
at <autogenerated>:1
10 0x000000000045f3f4 in runtime.cgocallback
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:998
11 0x00000000004641bd in crosscall2
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgo/asm_amd64.s:30
12 0x0000000000464386 in C.Test4
at /tmp/go-build/_cgo_export.c:33
13 0x0000000000464432 in C.test1
at ./hello.go:9
14 0x000000000046444d in C.test2
at ./hello.go:14
15 0x0000000000464468 in C.test3
15 0x0000000000464468 in C.test3
at ./hello.go:19
16 0x00000000004644a7 in C._cgo_78b81bbf688e_Cfunc_test3
at /tmp/go-build/cgo-gcc-prolog:49
17 0x000000000045f2e4 in runtime.asmcgocall
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:848
18 0x000000000046448a in C._cgo_78b81bbf688e_Cfunc_test3
at /tmp/go-build/cgo-gcc-prolog:44
19 0x0000000000404f0a in runtime.cgocall
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:167
20 0x0000000000464245 in main._Cfunc_test3
at _cgo_gotypes.go:39
21 0x00000000004642d7 in main.main
at ./hello.go:33
22 0x0000000000437073 in runtime.main
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/proc.go:250
23 0x000000000045f5e1 in runtime.goexit
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:1598
254 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) {
304 defer unwindm(&restore)
326 func unwindm(restore *bool) {
327 if *restore {
328 // Restore sp saved by cgocallback during
329 // unwind of g's stack (see comment at top of file).
330 mp := acquirem()
331 sched := &mp.g0.sched
332 sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp +
alignUp(sys.MinFrameSize, sys.StackAlign)))
(dlv)
> runtime.addOneOpenDeferFrame()
/home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:642 (PC:
0x433a45)
Warning: debugging optimized function
637: func addOneOpenDeferFrame(gp *g, pc uintptr, sp unsafe.Pointer) {
638: var prevDefer *_defer
639: if sp == nil {
640: prevDefer = gp._defer
641: pc = prevDefer.framepc
=> 642: sp = unsafe.Pointer(prevDefer.sp)
643: }
644: systemstack(func() {
645: gentraceback(pc, uintptr(sp), 0, gp, 0, nil,
0x7fffffff,
646: func(frame *stkframe, unused
unsafe.Pointer) bool {
647: if prevDefer != nil && prevDefer.sp
== frame.sp {
(dlv) bt
0 0x0000000000433a45 in runtime.addOneOpenDeferFrame
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:642
1 0x0000000000434357 in runtime.gopanic
at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:886
2 0x00000000004642a7 in main.Test4
at ./export.go:7
On Tue, Mar 28, 2023 at 4:14 PM mariappan balraj <mariappan.bal...@gmail.com>
wrote:
> Hello Go Experts,
>
> I am observing system stack corruption when panic() is called from go
> function. When panic is called from Test4(), as part of
> runtime.systemstack_switch(), the RSP and RBP is set in such a way that it
> will corrupt the stack.
>
> Rbp = 0x00007ffdb188bd20===> This should be less than 0x7ffdb188bc50. But
> it is set to the value which is already used for CGO calls. So it is making
> the system stack to corrupt. When the core file is generated, it makes it
> unable to debug from the core file using dlv. Can someone please help on
> this issue?
>
> RBP 0x7ffdb188bc50 RA 0x45f3f4 runtime.cgocallback
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s 1003
> RBP 0x7ffdb188bca0 RA 0x4641bd crosscall2
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgo/asm_amd64.s 32
> RBP 0x7ffdb188bcd0 RA 0x464386 C.Test4 /tmp/go-build/_cgo_export.c 35
> RBP 0x7ffdb188bce0 RA 0x464432 C.test1
> /home/soomohan/mbalraj/test/hello.go 10
> RBP 0x7ffdb188bd00 RA 0x46444d C.test2
> /home/soomohan/mbalraj/test/hello.go 15
> RBP 0x7ffdb188bd20 RA 0x464468 C.test3
> /home/soomohan/mbalraj/test/hello.go 20
> RBP 0x7ffdb188bd50 RA 0x4644a7 C._cgo_78b81bbf688e_Cfunc_test3
> /tmp/go-build/cgo-gcc-prolog 51
>
> go version
> go version go1.20.2 linux/amd64
>
> //hello.go
> package main
>
> /*
> #include <stdio.h>
>
> extern void Test4(void);
>
> void test1(void) {
> Test4();
> }
>
> void test2(void) {
> int val = 2;
> test1();
> }
>
> void test3(void) {
> int val = 3;
> test2();
> }
>
> void test4(void) {
> printf("Test4()");
> }
> */
> import "C"
>
> func Test5() {
> C.test4()
> }
>
> func main() {
> C.test3()
> }
>
> //export.go
> package main
>
> import "C"
>
> //export Test4
> func Test4() {
> panic("Panic inside Test4")
> //Test5()
> }
>
> I have written the following script test.start to debug this issue further
> in DLV.
> def command_goroutine_start_line(args):
> regs = registers().Regs
> rip = 0
> for reg in regs:
> if reg.Name == "Rbp":
> rbp = int(reg.Value, 16)
> elif reg.Name == "Rip":
> rip = int(reg.Value, 16)
>
> da = disassemble(StartPC=rip, EndPC=rip+1).Disassemble
> print("RBP 0x%x RIP 0x%x %s %s %s" % (rbp, rip,
> da[0].Loc.Function.Name_, da[0].Loc.File, da[0].Loc.Line))
>
> while True:
> mem = examine_memory(rbp, 8).Mem
> val = 0
> for i in range(len(mem)):
> val <<= 8
> val += mem[len(mem) - i - 1]
> prbp = val
>
> mem = examine_memory(rbp + 8, 8).Mem
> val = 0
> for i in range(len(mem)):
> val <<= 8
> val += mem[len(mem) - i - 1]
> ra = val
>
> da = disassemble(StartPC=ra, EndPC=ra+1).Disassemble
> print("RBP 0x%x RA 0x%x %s %s %s" % (prbp, ra,
> da[0].Loc.Function.Name_, da[0].Loc.File, da[0].Loc.Line))
> if prbp == 0:
> break
> rbp = prbp
>
> def main():
> dlv_command("config alias goroutine_start_line gsl")
>
> (dlv)bt
> RBP 0x0 RA 0x45f5e1 runtime.goexit
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s 1599
>
> 0 0x0000000000433b04 in runtime.addOneOpenDeferFrame.func1
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:646
> 1 0x000000000045f0c0 in runtime.systemstack_switch
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:463
> 2 0x0000000000433a89 in runtime.addOneOpenDeferFrame
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:644
> 3 0x0000000000434357 in runtime.gopanic
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:886
> 4 0x00000000004642a7 in main.Test4
> at ./export.go:7
> 5 0x000000000046431c in _cgoexp_78b81bbf688e_Test4
> at _cgo_gotypes.go:61
> 6 0x000000000040535b in runtime.cgocallbackg1
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:315
> 7 0x0000000000405079 in runtime.cgocallbackg
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:234
> 8 0x0000000000461b0f in runtime.cgocallbackg
> at <autogenerated>:1
> 9 0x000000000045f3f4 in runtime.cgocallback
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:998
> 10 0x0000000000000001 in ???
> at ?:-1
> 11 0x0000000000464386 in C.Test4
> at /tmp/go-build/_cgo_export.c:33
> 12 0x0000000000464432 in C.test1
> at ./hello.go:9
> 13 0x000000000046444d in C.test2
> at ./hello.go:14
> 14 0x0000000000464468 in C.test3
> at ./hello.go:19
> 15 0x00000000004644a7 in C._cgo_78b81bbf688e_Cfunc_test3
> 15 0x00000000004644a7 in C._cgo_78b81bbf688e_Cfunc_test3
> at /tmp/go-build/cgo-gcc-prolog:49
> 16 0x000000000045f2e4 in runtime.asmcgocall
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:848
> 17 0x000000000046448a in C._cgo_78b81bbf688e_Cfunc_test3
> at /tmp/go-build/cgo-gcc-prolog:44
> 18 0x0000000000404f0a in runtime.cgocall
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:167
> 19 0x0000000000464245 in main._Cfunc_test3
> at _cgo_gotypes.go:39
> 20 0x00000000004642d7 in main.main
> at ./hello.go:33
> 21 0x0000000000437073 in runtime.main
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/proc.go:250
> 22 0x000000000045f5e1 in runtime.goexit
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:1598
>
> (dlv)source test.star
> (dlv)gsl
> (dlv) gsl
> RBP 0xc000048c68 RIP 0x433b04 runtime.addOneOpenDeferFrame.func1
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go 646
> RBP 0xc000048d28 RA 0x434357 runtime.gopanic
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go 905
> RBP 0xc000048d48 RA 0x4642a7 main.Test4
> /home/soomohan/mbalraj/test/export.go 7
> RBP 0xc000048d58 RA 0x46431c _cgoexp_78b81bbf688e_Test4 _cgo_gotypes.go 62
> RBP 0xc000048e18 RA 0x40535b runtime.cgocallbackg1
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go 323
> RBP 0xc000048ea8 RA 0x405079 runtime.cgocallbackg
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go 240
> RBP 0xc000048ed0 RA 0x461b0f runtime.cgocallbackg <autogenerated> 1
> RBP 0x7ffdb188bc50 RA 0x45f3f4 runtime.cgocallback
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s 1003
> RBP 0x7ffdb188bca0 RA 0x4641bd crosscall2
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgo/asm_amd64.s 32
> RBP 0x7ffdb188bcd0 RA 0x464386 C.Test4 /tmp/go-build/_cgo_export.c 35
> RBP 0x7ffdb188bce0 RA 0x464432 C.test1
> /home/soomohan/mbalraj/test/hello.go 10
> RBP 0x7ffdb188bd00 RA 0x46444d C.test2
> /home/soomohan/mbalraj/test/hello.go 15
> RBP 0x7ffdb188bd20 RA 0x464468 C.test3
> /home/soomohan/mbalraj/test/hello.go 20
> RBP 0x7ffdb188bd50 RA 0x4644a7 C._cgo_78b81bbf688e_Cfunc_test3
> /tmp/go-build/cgo-gcc-prolog 51
> RBP 0xc000048f38 RA 0x45f2e4 runtime.asmcgocall
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s 852
> RBP 0xc000048f60 RA 0x464245 main._Cfunc_test3 _cgo_gotypes.go 40
> RBP 0xc000048f70 RA 0x4642d7 main.main
> /home/soomohan/mbalraj/test/hello.go 33
> RBP 0xc000048fd0 RA 0x437073 runtime.main
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/proc.go 260
> RBP 0x0 RA 0x45f5e1 runtime.goexit
> /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s 1599
>
> (dlv)si
>
> (dlv)bt
> 0 0x000000000045587f in runtime.gentraceback
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/traceback.go:32
> 1 0x000000000045f0c0 in runtime.systemstack_switch
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:463
> 2 0x0000000000433a89 in runtime.addOneOpenDeferFrame
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:644
> 3 0x0000000000434357 in runtime.gopanic
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:886
> 4 0x00000000004642a7 in main.Test4
> at ./export.go:7
> 5 0x000000000046431c in _cgoexp_78b81bbf688e_Test4
> at _cgo_gotypes.go:61
> 6 0x000000000040535b in runtime.cgocallbackg1
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:315
> 7 0x0000000000405079 in runtime.cgocallbackg
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:234
> 8 0x0000000000461b0f in runtime.cgocallbackg
> at <autogenerated>:1
> 9 0x000000000045f3f4 in runtime.cgocallback
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:998
> 10 0x0000000000000001 in ???
> at ?:-1
> 11 0x0000000000464386 in C.Test4
> at /tmp/go-build/_cgo_export.c:33
> 12 0x0000000000464432 in C.test1
> at ./hello.go:9
> 13 0x000000000046444d in C.test2
> at ./hello.go:14
> 14 0x0000000000464468 in C.test3
> at ./hello.go:19
> 15 0x0000000000433b4b in runtime.addOneOpenDeferFrame.func1
> 15 0x0000000000433b4b in runtime.addOneOpenDeferFrame.func1
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/panic.go:645
> 16 0x000000000045f129 in runtime.systemstack
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:496
> 17 0x0000000000461da5 in runtime.newproc
> at <autogenerated>:1
> 18 0x00000000004cc720 in ???
> at ?:-1
> 19 0x000000000046431c in _cgoexp_78b81bbf688e_Test4
> at _cgo_gotypes.go:61
> 20 0x000000000040535b in runtime.cgocallbackg1
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:315
> 21 0x0000000000405079 in runtime.cgocallbackg
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:234
> 22 0x0000000000461b0f in runtime.cgocallbackg
> at <autogenerated>:1
> 23 0x000000000045f3f4 in runtime.cgocallback
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:998
> 24 0x000000000045f0c0 in runtime.systemstack_switch
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:463
> 25 0x0000000000404f0a in runtime.cgocall
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:167
> 26 0x0000000000464245 in main._Cfunc_test3
> at _cgo_gotypes.go:39
> 27 0x00000000004642d7 in main.main
> at ./hello.go:33
> 28 0x0000000000437073 in runtime.main
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/proc.go:250
> 29 0x000000000045f5e1 in runtime.goexit
> at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:1598
>
> (dlv) regs
> (dlv) regs
> Rip = 0x000000000045587f
> Rsp = 0x00007ffdb188ba08
> Rax = 0x000000000040535b
> Rbx = 0x000000c000048d68
> Rcx = 0x0000000000000000
> Rdx = 0x0000000000433b60
> Rsi = 0x0000000000000000
> Rdi = 0x000000c0000061a0
> Rbp = 0x00007ffdb188bd20
> R8 = 0x0000000000000000
> R9 = 0x000000007fffffff
> R10 = 0x00007ffdb188bd80
> R11 = 0x0000000000000000
> R12 = 0x00007ffdb188ba88
> R13 = 0x000000c000048c18
> R14 = 0x00000000004cc720
> R15 = 0x0000000000000000
> Rflags = 0x0000000000000246 [PF ZF IF IOPL=0]
> Es = 0x0000000000000000
> Cs = 0x0000000000000033
> Ss = 0x000000000000002b
> Ds = 0x0000000000000000
> Fs = 0x0000000000000000
> Gs = 0x0000000000000000
> Fs_base = 0x000015128ba66740
> Gs_base = 0x0000000000000000
>
> Best Regards
> Mariappan
>
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