[bpf-next,v3,0/2] bpf, arm64: Support Exceptions

Message

Puranjay Mohan Feb. 1, 2024, 12:52 p.m. UTC

Changes in V2->V3:
V2: https://lore.kernel.org/all/[e-mail]/
- Use unwinder from stacktrace.c rather than open coding the unwind logic.
- Fix a bug in the prologue related to BPF_FP (Xu Kuohai)

Changes in V1->V2:
V1: https://lore.kernel.org/all/[e-mail]/
- Remove exceptions from DENYLIST.aarch64 as they are supported now.

The base support for exceptions was merged with [1] and it was enabled for
x86-64.

This patch set enables the support on ARM64, all sefltests are passing:

# ./test_progs -a exceptions
#74/1    exceptions/exception_throw_always_1:OK
#74/2    exceptions/exception_throw_always_2:OK
#74/3    exceptions/exception_throw_unwind_1:OK
#74/4    exceptions/exception_throw_unwind_2:OK
#74/5    exceptions/exception_throw_default:OK
#74/6    exceptions/exception_throw_default_value:OK
#74/7    exceptions/exception_tail_call:OK
#74/8    exceptions/exception_ext:OK
#74/9    exceptions/exception_ext_mod_cb_runtime:OK
#74/10   exceptions/exception_throw_subprog:OK
#74/11   exceptions/exception_assert_nz_gfunc:OK
#74/12   exceptions/exception_assert_zero_gfunc:OK
#74/13   exceptions/exception_assert_neg_gfunc:OK
#74/14   exceptions/exception_assert_pos_gfunc:OK
#74/15   exceptions/exception_assert_negeq_gfunc:OK
#74/16   exceptions/exception_assert_poseq_gfunc:OK
#74/17   exceptions/exception_assert_nz_gfunc_with:OK
#74/18   exceptions/exception_assert_zero_gfunc_with:OK
#74/19   exceptions/exception_assert_neg_gfunc_with:OK
#74/20   exceptions/exception_assert_pos_gfunc_with:OK
#74/21   exceptions/exception_assert_negeq_gfunc_with:OK
#74/22   exceptions/exception_assert_poseq_gfunc_with:OK
#74/23   exceptions/exception_bad_assert_nz_gfunc:OK
#74/24   exceptions/exception_bad_assert_zero_gfunc:OK
#74/25   exceptions/exception_bad_assert_neg_gfunc:OK
#74/26   exceptions/exception_bad_assert_pos_gfunc:OK
#74/27   exceptions/exception_bad_assert_negeq_gfunc:OK
#74/28   exceptions/exception_bad_assert_poseq_gfunc:OK
#74/29   exceptions/exception_bad_assert_nz_gfunc_with:OK
#74/30   exceptions/exception_bad_assert_zero_gfunc_with:OK
#74/31   exceptions/exception_bad_assert_neg_gfunc_with:OK
#74/32   exceptions/exception_bad_assert_pos_gfunc_with:OK
#74/33   exceptions/exception_bad_assert_negeq_gfunc_with:OK
#74/34   exceptions/exception_bad_assert_poseq_gfunc_with:OK
#74/35   exceptions/exception_assert_range:OK
#74/36   exceptions/exception_assert_range_with:OK
#74/37   exceptions/exception_bad_assert_range:OK
#74/38   exceptions/exception_bad_assert_range_with:OK
#74/39   exceptions/non-throwing fentry -> exception_cb:OK
#74/40   exceptions/throwing fentry -> exception_cb:OK
#74/41   exceptions/non-throwing fexit -> exception_cb:OK
#74/42   exceptions/throwing fexit -> exception_cb:OK
#74/43   exceptions/throwing extension (with custom cb) -> exception_cb:OK
#74/44   exceptions/throwing extension -> global func in exception_cb:OK
#74/45   exceptions/exception_ext_mod_cb_runtime:OK
#74/46   exceptions/throwing extension (with custom cb) -> global func in exception_cb:OK
#74/47   exceptions/exception_ext:OK
#74/48   exceptions/non-throwing fentry -> non-throwing subprog:OK
#74/49   exceptions/throwing fentry -> non-throwing subprog:OK
#74/50   exceptions/non-throwing fentry -> throwing subprog:OK
#74/51   exceptions/throwing fentry -> throwing subprog:OK
#74/52   exceptions/non-throwing fexit -> non-throwing subprog:OK
#74/53   exceptions/throwing fexit -> non-throwing subprog:OK
#74/54   exceptions/non-throwing fexit -> throwing subprog:OK
#74/55   exceptions/throwing fexit -> throwing subprog:OK
#74/56   exceptions/non-throwing fmod_ret -> non-throwing subprog:OK
#74/57   exceptions/non-throwing fmod_ret -> non-throwing global subprog:OK
#74/58   exceptions/non-throwing extension -> non-throwing subprog:OK
#74/59   exceptions/non-throwing extension -> throwing subprog:OK
#74/60   exceptions/non-throwing extension -> non-throwing subprog:OK
#74/61   exceptions/non-throwing extension -> throwing global subprog:OK
#74/62   exceptions/throwing extension -> throwing global subprog:OK
#74/63   exceptions/throwing extension -> non-throwing global subprog:OK
#74/64   exceptions/non-throwing extension -> main subprog:OK
#74/65   exceptions/throwing extension -> main subprog:OK
#74/66   exceptions/reject_exception_cb_type_1:OK
#74/67   exceptions/reject_exception_cb_type_2:OK
#74/68   exceptions/reject_exception_cb_type_3:OK
#74/69   exceptions/reject_exception_cb_type_4:OK
#74/70   exceptions/reject_async_callback_throw:OK
#74/71   exceptions/reject_with_lock:OK
#74/72   exceptions/reject_subprog_with_lock:OK
#74/73   exceptions/reject_with_rcu_read_lock:OK
#74/74   exceptions/reject_subprog_with_rcu_read_lock:OK
#74/75   exceptions/reject_with_rbtree_add_throw:OK
#74/76   exceptions/reject_with_reference:OK
#74/77   exceptions/reject_with_cb_reference:OK
#74/78   exceptions/reject_with_cb:OK
#74/79   exceptions/reject_with_subprog_reference:OK
#74/80   exceptions/reject_throwing_exception_cb:OK
#74/81   exceptions/reject_exception_cb_call_global_func:OK
#74/82   exceptions/reject_exception_cb_call_static_func:OK
#74/83   exceptions/reject_multiple_exception_cb:OK
#74/84   exceptions/reject_exception_throw_cb:OK
#74/85   exceptions/reject_exception_throw_cb_diff:OK
#74/86   exceptions/reject_set_exception_cb_bad_ret1:OK
#74/87   exceptions/reject_set_exception_cb_bad_ret2:OK
#74/88   exceptions/check_assert_eq_int_min:OK
#74/89   exceptions/check_assert_eq_int_max:OK
#74/90   exceptions/check_assert_eq_zero:OK
#74/91   exceptions/check_assert_eq_llong_min:OK
#74/92   exceptions/check_assert_eq_llong_max:OK
#74/93   exceptions/check_assert_lt_pos:OK
#74/94   exceptions/check_assert_lt_zero:OK
#74/95   exceptions/check_assert_lt_neg:OK
#74/96   exceptions/check_assert_le_pos:OK
#74/97   exceptions/check_assert_le_zero:OK
#74/98   exceptions/check_assert_le_neg:OK
#74/99   exceptions/check_assert_gt_pos:OK
#74/100  exceptions/check_assert_gt_zero:OK
#74/101  exceptions/check_assert_gt_neg:OK
#74/102  exceptions/check_assert_ge_pos:OK
#74/103  exceptions/check_assert_ge_zero:OK
#74/104  exceptions/check_assert_ge_neg:OK
#74/105  exceptions/check_assert_range_s64:OK
#74/106  exceptions/check_assert_range_u64:OK
#74/107  exceptions/check_assert_single_range_s64:OK
#74/108  exceptions/check_assert_single_range_u64:OK
#74/109  exceptions/check_assert_generic:OK
#74/110  exceptions/check_assert_with_return:OK
#74      exceptions:OK
Summary: 1/110 PASSED, 0 SKIPPED, 0 FAILED

[1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?h=for-next&id=ec6f1b4db95b7eedb3fe85f4f14e08fa0e9281c3

Puranjay Mohan (2):
  arm64: stacktrace: Implement arch_bpf_stack_walk() for the BPF JIT
  bpf, arm64: support exceptions

 arch/arm64/kernel/stacktrace.c               | 26 ++++++
 arch/arm64/net/bpf_jit_comp.c                | 87 +++++++++++++++-----
 tools/testing/selftests/bpf/DENYLIST.aarch64 |  1 -
 3 files changed, 94 insertions(+), 20 deletions(-)

Comments

Kumar Kartikeya Dwivedi Feb. 20, 2024, 10:12 p.m. UTC | #1

On Thu, 1 Feb 2024 at 13:52, Puranjay Mohan <[e-mail]> wrote:
>
> Changes in V2->V3:
> V2: https://lore.kernel.org/all/[e-mail]/
> - Use unwinder from stacktrace.c rather than open coding the unwind logic.
> - Fix a bug in the prologue related to BPF_FP (Xu Kuohai)
>
> Changes in V1->V2:
> V1: https://lore.kernel.org/all/[e-mail]/
> - Remove exceptions from DENYLIST.aarch64 as they are supported now.
>
> The base support for exceptions was merged with [1] and it was enabled for
> x86-64.
>
> This patch set enables the support on ARM64, all sefltests are passing:
>
> # ./test_progs -a exceptions
> #74/1    exceptions/exception_throw_always_1:OK
> [...]

I think this looks ok, would be nice if it received acks from arm64 experts.

If you have cycles to spare, please also look into
https://lore.kernel.org/bpf/[e-mail]
and let me know how architecture independent the cleanup code right
now in the x86 JIT should be made so that we can do the
same for arm64 as well later. That would be required to complete the
support for cleanups.

I guess we just need bpf_frame_spilled_caller_reg_off to be arch
specific and lift the rest out into the BPF core.
I will make that change in v2 in any case.

Just a note but based on our off-list discussion for supporting this
stuff on riscv as well (where a lot of registers would have to be
saved on entry),
the hidden subprog trampoline could be a way to avoid that. They can
be pushed by this subprog before entry into bpf_throw, and since the
BPF program does not touch the extra callee-saved registers, they
should be what the kernel had originally upon entry into the BPF
program itself. The same could be done on arm64 and x86, but the
returns would be diminishing. It would be nice to quantify how much
this saves in terms of costs of pushing extra registers, before doing
this.