[gdb/record] Fix syscall exit recording for arm

[ Submitted earlier [1] with $subject: "[PATCH] [gdb/record] Fix syscall
recording for arm". ]

On arm-linux, I run into:
...
(gdb) continue^M
Continuing.^M
The next instruction is syscall exit_group.  It will make the program exit.  \
  Do you want to stop the program?([y] or n) yes^M
Process record does not support instruction 0xdf00 at address 0xf7e8f984.^M
Process record: failed to record execution log.^M
^M
Program stopped.^M
__libc_do_syscall () at libc-do-syscall.S:46^M
warning: 46     libc-do-syscall.S: No such file or directory^M
(gdb) FAIL: gdb.reverse/sigall-reverse.exp: continue to signal exit
...

The problem is this bit of code here in decode_insn:
...
      ret = thumb2_record_decode_insn_handler (arm_record);

      if (ret != ARM_RECORD_SUCCESS)
       {
         arm_record_unsupported_insn (arm_record);
         ret = -1;
       }
...
where ret == 1 is mapped to -1.

The 1 is returned by arm_linux_syscall_record and is meant to be interpreted
using this categorization:
- res  < 0: Process record: failed to record execution log.
- res == 0: No failure.
- res  > 0: Process record: inferior program stopped.

But the port interprets 1 as ARM_RECORD_FAILURE:
...
enum arm_record_result
{
  ARM_RECORD_SUCCESS = 0,
  ARM_RECORD_FAILURE = 1
};
...

We could fix this confusion this by:
- adding an ARM_RECORD_UNKNOWN = 2, and
- applying translations at the appropriate points, translating:
  - ARM_RECORD_UNKNOWN into 1 and vice versa,
  - ARM_RECORD_FAILURE into -1 and vice versa,
  similar to what we did for aarch64 and loongarch.

But it seems easier to adopt a go-with-the-flow approach, defining
ARM_RECORD_FAILURE as -1, freeing up the 1 for ARM_RECORD_UNKNOWN = 1.

Then the aforementioned FAIL is fixed by simply doing:
...
      if (ret == ARM_RECORD_FAILURE)
       arm_record_unsupported_insn (arm_record);
...

Tested on arm-linux.

Reviewed-By: Guinevere Larsen <guinevere@redhat.com>

[1] https://sourceware.org/pipermail/gdb-patches/2026-February/225372.html

0 files changed, 0 insertions, 0 deletions