[Bug go/30038] When using CGO and C code is calling GO function, not getting call stack of C from core dump. Only getting call stack of GO.

["mariappan.balraj at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30038

--- Comment #17 from mariappan balraj <mariappan.balraj at gmail dot com> ---
Hello GDB experts,

When GO functions calls C function, it switches stack to use system stack.
There are 2 stack Go stack and system stack. Go stack is used for GO functions
and system stack are used for C functions.  When I use gdb to do live
debugging, I am able to see GO stack trace before C function is getting called.
When the C function is called, the stack is switched to system stack. In this
case, GDB is displaying only the C stack. But by using the RBP, I am able to
manually decode the Go stack. Could you please fix it?

//test.go

package main

/*
#include <stdio.h>

void test1(void) {
    printf("Welcome");
}

void test2(void) {
    int val = 2;
    test1();
}

void test3(void) {
    int val = 3;
    test2();
}
*/
import "C"

func test5() {
    C.test3()
}

func test4() {
    test5()
}

func main() {
    test4()
}

Command used to build:

CGO_CFLAGS="-g" go build -compiler gc -gcflags=all="-N -l" test.go


#gdb ./test
(gdb) break main.test5
Breakpoint 1 at 0x464280: file /home/soomohan/mbalraj/test_gdb/test.go, line
22.
(gdb) run
Starting program: /home/soomohan/mbalraj/test_gdb/test 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x15552df4a640 (LWP 1007325)]
[New Thread 0x15552dd49640 (LWP 1007326)]
[New Thread 0x15552db08640 (LWP 1007327)]
[New Thread 0x15552d907640 (LWP 1007328)]
[New Thread 0x15552d6c6640 (LWP 1007329)]

Thread 1 "test" hit Breakpoint 1, main.test5 () at
/home/soomohan/mbalraj/test_gdb/test.go:22
22      func test5() {
(gdb) bt
#0  main.test5 () at /home/soomohan/mbalraj/test_gdb/test.go:22
#1  0x00000000004642d7 in main.test4 () at
/home/soomohan/mbalraj/test_gdb/test.go:27
#2  0x0000000000464317 in main.main () at
/home/soomohan/mbalraj/test_gdb/test.go:31

(gdb) break test1
Breakpoint 2 at 0x46436e: file /home/soomohan/mbalraj/test_gdb/test.go, line 7.
(gdb) c
Continuing.

Thread 1 "test" hit Breakpoint 2, test1 () at
/home/soomohan/mbalraj/test_gdb/test.go:7
7           printf("Welcome");
(gdb) bt
#0  test1 () at /home/soomohan/mbalraj/test_gdb/test.go:7
#1  0x000000000046439d in test2 () at
/home/soomohan/mbalraj/test_gdb/test.go:12
#2  0x00000000004643b8 in test3 () at
/home/soomohan/mbalraj/test_gdb/test.go:17
#3  0x00000000004643d8 in _cgo_b6b18ee597cc_Cfunc_test3 (v=0xc000048f50) at
/tmp/go-build/cgo-gcc-prolog:49
#4  0x000000000045f2e4 in runtime.asmcgocall () at
/home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:848
#5  0x00000000004e3460 in ?? ()
#6  0x0000000000000001 in ?? ()
#7  0x000000c000104100 in ?? ()
#8  0x0a007fffffffdfe8 in ?? ()
#9  0x0000000000000001 in ?? ()
#10 0x0000000000000118 in ?? ()
#11 0x000000c000006340 in ?? ()
#12 0x000000c000048f50 in ?? ()
#13 0x000000000045f20b in runtime.morestack () at
/home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:574
#14 0x0000000000461da5 in runtime.newproc (fn=0x1) at <autogenerated>:1
#15 0x00000000004cc720 in runtime[scavenger] ()
#16 0x0000000000000001 in ?? ()
#17 0x000000000045f025 in runtime.mstart () at
/home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:394
#18 0x000000000045efaf in runtime.rt0_go () at
/home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:358
#19 0x0000000000000001 in ?? ()
#20 0x00007fffffffe168 in ?? ()
#21 0x0000000000000000 in ?? ()

(gdb) frame 3
#3  0x00000000004643d8 in _cgo_b6b18ee597cc_Cfunc_test3 (v=0xc000048f50) at
/tmp/go-build/cgo-gcc-prolog:49
(gdb) info reg
rbp            0x7fffffffdfa0      0x7fffffffdfa0
rip            0x4643d8            0x4643d8 <_cgo_b6b18ee597cc_Cfunc_test3+29>
(gdb) x /4 0x7fffffffdfa0
0x7fffffffdfa0: 0x00048f18      0x000000c0      0x0045f2e4      0x00000000
(gdb) disassemble 0x0045f2e4
Dump of assembler code for function runtime.asmcgocall:
   0x000000000045f280 <+0>:     mov    0x8(%rsp),%rax

(gdb) x /4 0x000000c000048f40 
0xc000048f40:   0x00048f50      0x000000c0      0x00464297      0x00000000

(gdb) disassemble 0x00464297
Dump of assembler code for function main.test5:

(gdb) x /4 0x000000c000048f50 
0xc000048f50:   0x00048f60      0x000000c0      0x004642d7      0x00000000

(gdb) disassemble 0x004642d7
Dump of assembler code for function main.test4:

(gdb) x /4 0x000000c000048f60 
0xc000048f60:   0x00048f70      0x000000c0      0x00464317      0x00000000

(gdb) disassemble 0x00464317
Dump of assembler code for function main.main:

(gdb) x /4 0x000000c000048f70
0xc000048f70:   0x00048fd0      0x000000c0      0x00437073      0x00000000

(gdb) disassemble 0x00437073
Dump of assembler code for function runtime.main:

(gdb) x /4 0x000000c000048fd0
0xc000048fd0:   0x00000000      0x00000000      0x0045f5e1      0x00000000

(gdb) disassemble 0x0045f5e1
Dump of assembler code for function runtime.goexit:

Finally the stack should like as follows:

(dlv) bt
 0  0x000000000046436e in C.test1
    at ./test.go:7
 1  0x000000000046439d in C.test2
    at ./test.go:12
 2  0x00000000004643b8 in C.test3
    at ./test.go:17
 3  0x00000000004643d8 in C._cgo_b6b18ee597cc_Cfunc_test3
    at /tmp/go-build/cgo-gcc-prolog:49
 4  0x000000000045f2e4 in runtime.asmcgocall
    at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:848
 5  0x00000000004643bb in C._cgo_b6b18ee597cc_Cfunc_test3
    at /tmp/go-build/cgo-gcc-prolog:44
 6  0x0000000000404f0a in runtime.cgocall
    at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/cgocall.go:167
 7  0x0000000000464245 in main._Cfunc_test3
    at _cgo_gotypes.go:39
 8  0x0000000000464297 in main.test5
    at ./test.go:23
 9  0x00000000004642d7 in main.test4
    at ./test.go:27
10  0x0000000000464317 in main.main
    at ./test.go:31
11  0x0000000000437073 in runtime.main
    at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/proc.go:250
12  0x000000000045f5e1 in runtime.goexit
    at /home/soomohan/mbalraj/GO/go1.20.2/go/src/runtime/asm_amd64.s:1598

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