[Bug gdb/33481] GDB crashes upon target remote :1234 for ppc64le guest vm

[vishalc at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=33481

--- Comment #14 from Vishal Chourasia <vishalc at linux dot ibm.com> ---
So far...

GDB crashes with a segmentation fault when attempting to connect to a remote
target (e.g., `target remote :1234`) while debugging the Linux kernel
(`vmlinux`) ARCH=powerpc

## Root Cause

The Linux kernel binary (`vmlinux`) contains a `.interp` section that exists
but is completely empty (size = 0). This causes a chain of failures:

1. `bfd_get_section_by_name()` successfully finds the `.interp` section
(returns non-NULL)
2. `bfd_section_size(interp_sect)` returns **0**
3. An empty `gdb::byte_vector buf(0)` is created
4. `bfd_get_section_contents()` returns **true** (reading 0 bytes always
succeeds)
5. The empty byte vector is returned from `find_program_interpreter()`
6. Calling code at line 2313 attempts to use `interp_name_holder->data()` as a
C string
7. Since the buffer is empty, this results in a **NULL or invalid pointer**
8. `solib_bfd_open()` crashes when trying to open a file with a NULL/empty path

- `vmlinux` is a **statically-linked kernel binary**, not a userspace program
- The empty `.interp` section is likely a linker artifact

Verification:
```bash
(i) ❯ llvm-readelf -S vmlinux | grep -E '(\.interp)|Name'
  [Nr] Name              Type            Address          Off    Size   ES Flg
Lk Inf Al
  [46] .interp           PROGBITS        c0000000033d06f4 33e06f4 000000 00   A
 0   0  1
```


## The Bug in GDB Code

In `gdb/solib-svr4.c` around line 605:

```c
interp_sect = bfd_get_section_by_name (current_program_space->exec_bfd (),
                                       ".interp");
if (interp_sect != NULL)
{
    int sect_size = bfd_section_size (interp_sect);  // Returns 0

    gdb::byte_vector buf (sect_size);  // Creates empty buffer
    bool res
        = bfd_get_section_contents (current_program_space->exec_bfd (),
                                    interp_sect, buf.data (), 0, sect_size);
    if (res)  // Returns TRUE for 0-byte read
        return buf;  // Returns EMPTY buffer - BUG!
}
```

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