[PATCH v2 0/6] powerpc64/bpf: Support tailcalls with subprogs & BPF exceptions

adubey
2026-01-14T11:45:56Z

From: Abhishek Dubey <adubey@linux.ibm.com>

This patch series enables support for two BPF JIT features
on powerpc64. The first three patches target support for
tail calls with subprogram combinations. The first patch
supports realignment of tail_call_cnt offset in stack frame.
Implementation details are provided in the commit messages.

The last three patches add support for BPF exceptions. An
architecture-specific stack walker is implemented to assist
with stack walk during exceptions.

All selftests related to tailcalls and exceptions are passing:

# ./test_progs -t tailcalls
#442/1 tailcalls/tailcall_1:OK
#442/2 tailcalls/tailcall_2:OK
#442/3 tailcalls/tailcall_3:OK
#442/4 tailcalls/tailcall_4:OK
#442/5 tailcalls/tailcall_5:OK
#442/6 tailcalls/tailcall_6:OK
#442/7 tailcalls/tailcall_bpf2bpf_1:OK
#442/8 tailcalls/tailcall_bpf2bpf_2:OK
#442/9 tailcalls/tailcall_bpf2bpf_3:OK
#442/10 tailcalls/tailcall_bpf2bpf_4:OK
#442/11 tailcalls/tailcall_bpf2bpf_5:OK
#442/12 tailcalls/tailcall_bpf2bpf_6:OK
#442/13 tailcalls/tailcall_bpf2bpf_fentry:OK
#442/14 tailcalls/tailcall_bpf2bpf_fexit:OK
#442/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:OK
#442/16 tailcalls/tailcall_bpf2bpf_fentry_entry:OK
#442/17 tailcalls/tailcall_poke:OK
#442/18 tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
#442/19 tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
#442/20 tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
#442/21 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
#442/22 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
#442/23 tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
#442/24 tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
#442/25 tailcalls/tailcall_freplace:OK
#442/26 tailcalls/tailcall_bpf2bpf_freplace:OK
#442/27 tailcalls/tailcall_failure:OK
#442/28 tailcalls/reject_tail_call_spin_lock:OK
#442/29 tailcalls/reject_tail_call_rcu_lock:OK
#442/30 tailcalls/reject_tail_call_preempt_lock:OK
#442/31 tailcalls/reject_tail_call_ref:OK
#442 tailcalls:OK
Summary: 1/31 PASSED, 0 SKIPPED, 0 FAILED

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

[v1]: https://lore.kernel.org/all/20260105105212.136645-1-adubey@linux.ibm.com/

Changes v1->v2:
Move tail_call_cnt to offset 0 in stack frame
Remove trampoline NVR remapping-patch3/6[v1]

Abhishek Dubey (6):
powerpc64/bpf: Move tail_call_cnt to bottom of stack frame
powerpc64/bpf: Support tailcalls with subprogs
powerpc64/bpf: Tailcall handling with trampolines
powerpc64/bpf: Add arch_bpf_stack_walk() for BPF JIT
powerpc64/bpf: Support exceptions
powerpc64/bpf: Additional NVR handling for bpf_throw

arch/powerpc/net/bpf_jit.h | 18 ++-
arch/powerpc/net/bpf_jit_comp.c | 98 ++++++++----
arch/powerpc/net/bpf_jit_comp64.c | 240 ++++++++++++++++++++++++------
3 files changed, 280 insertions(+), 76 deletions(-)

--
2.48.1