[Bug 2041396] [NEW] gdb 12.1 generates SIGILL on armhf

[Zixing Liu]

Public bug reported:

GDB 12.1 had a regression where it will break program execution when the
program contains mixed ARM code and THUMB code.

Considering the following C program:

```
__attribute__((target("arm"), noinline))
int thumb_func() {
  return 42;
}

__attribute__((target("thumb")))
int main() { return thumb_func(); }
```

If you build it using `gcc repro.c -ggdb3 -Og -o repro` and run the GDB
using the following commands:

```
b 3
r
c
```

(you can save it to a file and run GDB using `gdb -x script ./repro`)

You will notice GDB broke the program and threw SIGILL.
If you run the program without GDB, the program exits normally.

This bug has been fixed in GDB 13, but the fix was never backported to
GDB 12. You can find the upstream bug in the remote bug watch.

** Affects: gdb
     Importance: Unknown
         Status: Unknown

** Affects: gdb (Ubuntu)
     Importance: Undecided
         Status: New

** Bug watch added: Sourceware.org Bugzilla #29272
   https://sourceware.org/bugzilla/show_bug.cgi?id=29272

** Also affects: gdb (Debian) via
   https://sourceware.org/bugzilla/show_bug.cgi?id=29272
   Importance: Unknown
       Status: Unknown

** Package changed: gdb (Debian) => gdb

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https://bugs.launchpad.net/bugs/2041396

Title:
  gdb 12.1 generates SIGILL on armhf

Status in gdb:
  Unknown
Status in gdb package in Ubuntu:
  New

Bug description:
  GDB 12.1 had a regression where it will break program execution when
  the program contains mixed ARM code and THUMB code.

  Considering the following C program:

  ```
  __attribute__((target("arm"), noinline))
  int thumb_func() {
    return 42;
  }

  __attribute__((target("thumb")))
  int main() { return thumb_func(); }
  ```

  If you build it using `gcc repro.c -ggdb3 -Og -o repro` and run the
  GDB using the following commands:

  ```
  b 3
  r
  c
  ```

  (you can save it to a file and run GDB using `gdb -x script ./repro`)

  You will notice GDB broke the program and threw SIGILL.
  If you run the program without GDB, the program exits normally.

  This bug has been fixed in GDB 13, but the fix was never backported to
  GDB 12. You can find the upstream bug in the remote bug watch.

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