[Bug 1908063] [NEW] gdb-multiarch 8.1.1-0ubuntu1 regression: assertion failure or internal error when connecting to QEMU aarch64 gdbstub

[Peter Maydell]

Public bug reported:

This bug is a regression introduced in 8.1.1-0ubuntu1 for Bionic -- the
previous 8.1-0ubuntu3.2 gdb works fine with QEMU's gdbstub.

Reproduce:
Get the sources for QEMU 5.2.0, and build the aarch64-linux-user target. (It looks like Bionic's QEMU is old enough that it doesn't provoke this gdb error.)

Run
 qemu-aarch64 -g 1234 path/to/some/aarch64/binary

In another terminal, start gdb-multiarch. At the (gdb) prompt, type
"target remote :1234". GDB will dump core:

(gdb) target remote :1234
Remote debugging using :1234
Recursive internal problem.
Aborted (core dumped)

You can see a variant of this also in the QEMU test suite with "make -C
your-qemu-build-dir check-tcg", where the error message includes an
assertion failure:

[...]

timeout 60  /home/petmay01/linaro/qemu-from-laptop/qemu/tests/guest-debug/run-test.py --gdb /usr/bin/gdb-multiarch --qemu /home/petmay01/linaro/qemu-from-laptop/qemu/build/aarch64-linux/qemu-aarch64 --qargs "" --bin sha1 --test /home/petmay01/linaro/qemu-from-laptop/qemu/tests/tcg/multiarch/gdbstub/sha1.py >  run-gdbstub-sha1.out
/build/gdb-veKdC1/gdb-8.1.1/gdb/regcache.c:122: internal-error: void* init_regcache_descr(gdbarch*): Assertion `MAX_REGISTER_SIZE >= descr->sizeof_register[i]' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.

This is a bug, please report it.  For instructions, see:
<http://www.gnu.org/software/gdb/bugs/>.

Aborted (core dumped)
/home/petmay01/linaro/qemu-from-laptop/qemu/tests/tcg/multiarch/Makefile.target:51: recipe for target 'run-gdbstub-sha1' failed

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

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

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https://bugs.launchpad.net/bugs/1908063

Title:
  gdb-multiarch 8.1.1-0ubuntu1 regression: assertion failure or internal
  error when connecting to QEMU aarch64 gdbstub

Status in gdb package in Ubuntu:
  New
Status in gdb source package in Bionic:
  New

Bug description:
  This bug is a regression introduced in 8.1.1-0ubuntu1 for Bionic --
  the previous 8.1-0ubuntu3.2 gdb works fine with QEMU's gdbstub.

  Reproduce:
  Get the sources for QEMU 5.2.0, and build the aarch64-linux-user target. (It looks like Bionic's QEMU is old enough that it doesn't provoke this gdb error.)

  Run
   qemu-aarch64 -g 1234 path/to/some/aarch64/binary

  In another terminal, start gdb-multiarch. At the (gdb) prompt, type
  "target remote :1234". GDB will dump core:

  (gdb) target remote :1234
  Remote debugging using :1234
  Recursive internal problem.
  Aborted (core dumped)

  You can see a variant of this also in the QEMU test suite with "make
  -C your-qemu-build-dir check-tcg", where the error message includes an
  assertion failure:

  [...]

  timeout 60  /home/petmay01/linaro/qemu-from-laptop/qemu/tests/guest-debug/run-test.py --gdb /usr/bin/gdb-multiarch --qemu /home/petmay01/linaro/qemu-from-laptop/qemu/build/aarch64-linux/qemu-aarch64 --qargs "" --bin sha1 --test /home/petmay01/linaro/qemu-from-laptop/qemu/tests/tcg/multiarch/gdbstub/sha1.py >  run-gdbstub-sha1.out
  /build/gdb-veKdC1/gdb-8.1.1/gdb/regcache.c:122: internal-error: void* init_regcache_descr(gdbarch*): Assertion `MAX_REGISTER_SIZE >= descr->sizeof_register[i]' failed.
  A problem internal to GDB has been detected,
  further debugging may prove unreliable.

  This is a bug, please report it.  For instructions, see:
  <http://www.gnu.org/software/gdb/bugs/>.

  Aborted (core dumped)
  /home/petmay01/linaro/qemu-from-laptop/qemu/tests/tcg/multiarch/Makefile.target:51: recipe for target 'run-gdbstub-sha1' failed

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