[Bug go/29357] New: gdb for golang prints wrong frame info at the ret instruction

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

https://sourceware.org/bugzilla/show_bug.cgi?id=29357

            Bug ID: 29357
           Summary: gdb for golang prints wrong frame info at the ret
                    instruction
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: go
          Assignee: unassigned at sourceware dot org
          Reporter: greyschwinger at gmail dot com
  Target Milestone: ---

Prepare a hello world golang program:

```
$ cat -n ./main.go 
     1  package main
     2  
     3  import "fmt"
     4  
     5  func main() {
     6          fmt.Println("hello world")
     7  }
```

Compile the code using go1.18.3 linux/amd64:

```
$ go build .
```

Disassemble the main function:

```
$ gdb -ex "disas/mr 'main.main'" -ex q ./go_hello_world

5       func main() {
   0x000000000047dfe0 <+0>:     49 3b 66 10     cmp    0x10(%r14),%rsp
   0x000000000047dfe4 <+4>:     76 56   jbe    0x47e03c <main.main+92>
   0x000000000047dfe6 <+6>:     48 83 ec 40     sub    $0x40,%rsp
   0x000000000047dfea <+10>:    48 89 6c 24 38  mov    %rbp,0x38(%rsp)
   0x000000000047dfef <+15>:    48 8d 6c 24 38  lea    0x38(%rsp),%rbp
   0x000000000047e03c <+92>:    0f 1f 40 00     nopl   0x0(%rax)
   0x000000000047e040 <+96>:    e8 5b a9 fd ff  call   0x4589a0
<runtime.morestack_noctxt>
   0x000000000047e045 <+101>:   eb 99   jmp    0x47dfe0 <main.main>

6               fmt.Println("hello world")
   0x000000000047dff4 <+20>:    44 0f 11 7c 24 28       movups
%xmm15,0x28(%rsp)
   0x000000000047dffa <+26>:    48 8d 15 5f 7e 00 00    lea   
0x7e5f(%rip),%rdx        # 0x485e60
   0x000000000047e001 <+33>:    48 89 54 24 28  mov    %rdx,0x28(%rsp)
   0x000000000047e006 <+38>:    48 8d 15 7b 4b 03 00    lea   
0x34b7b(%rip),%rdx        # 0x4b2b88
   0x000000000047e00d <+45>:    48 89 54 24 30  mov    %rdx,0x30(%rsp)

7       }
   0x000000000047e032 <+82>:    48 8b 6c 24 38  mov    0x38(%rsp),%rbp
   0x000000000047e037 <+87>:    48 83 c4 40     add    $0x40,%rsp
   0x000000000047e03b <+91>:    c3      ret

End of assembler dump.
```

Then I'll add a breakpoint at the ret instruction, <+91>

```
$ gdb ./go_hello_world 

(gdb) b *0x000000000047e03b
Breakpoint 1 at 0x47e03b: file
/home/gray/src/proving_grounds/go_hello_world/main.go, line 7.
(gdb) r

Thread 1 "go_hello_world" hit Breakpoint 1, 0x000000000047e03b in main.main ()
at /home/gray/src/proving_grounds/go_hello_world/main.go:7
7       }
```

Then let's check the frame info and register:

```
(gdb) i f
Stack level 0, frame at 0xc00011cf78:
 rip = 0x47e03b in main.main
(/home/gray/src/proving_grounds/go_hello_world/main.go:7); saved rip = 0x4324d2
 source language unknown.
 Arglist at 0xc00011cf70, args: 
 Locals at 0xc00011cf70, Previous frame's sp is 0xc00011cf80
 Saved registers:
  rip at 0xc00011cf78

(gdb) p/x $rsp
$1 = 0xc00011cf78
```

However the "frame at 0xc00011cf78" is incorrect. As far as I know, "the frame
at" shows the CFA of the current stack frame, and at the ret instruction, the
CFA should be $rsp+8.

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