[PATCH 5/6] powerpc64/bpf: Support exceptions
adubey at linux.ibm.com
adubey at linux.ibm.com
Mon Jan 5 21:52:11 AEDT 2026
From: Abhishek Dubey <adubey at linux.ibm.com>
The modified prologue/epilogue generation code now
enables exception-callback to use the stack frame of
the program marked as exception boundary, where callee
saved registers are stored.
As per ppc64 ABIv2 documentation[1], r14-r31 are callee
saved registers. BPF programs on ppc64 already saves
r26-r31 registers. Saving the remaining set of callee
saved registers(r14-r25) is handled in the next patch.
[1] https://ftp.rtems.org/pub/rtems/people/sebh/ABI64BitOpenPOWERv1.1_16July2015_pub.pdf
Following is exceptions selftest result on ppc64le:
# ./test_progs -t exceptions
#100/1 exceptions/exception_throw_always_1:OK
#100/2 exceptions/exception_throw_always_2:OK
#100/3 exceptions/exception_throw_unwind_1:OK
#100/4 exceptions/exception_throw_unwind_2:OK
#100/5 exceptions/exception_throw_default:OK
#100/6 exceptions/exception_throw_default_value:OK
#100/7 exceptions/exception_tail_call:OK
#100/8 exceptions/exception_ext:OK
#100/9 exceptions/exception_ext_mod_cb_runtime:OK
#100/10 exceptions/exception_throw_subprog:OK
#100/11 exceptions/exception_assert_nz_gfunc:OK
#100/12 exceptions/exception_assert_zero_gfunc:OK
#100/13 exceptions/exception_assert_neg_gfunc:OK
#100/14 exceptions/exception_assert_pos_gfunc:OK
#100/15 exceptions/exception_assert_negeq_gfunc:OK
#100/16 exceptions/exception_assert_poseq_gfunc:OK
#100/17 exceptions/exception_assert_nz_gfunc_with:OK
#100/18 exceptions/exception_assert_zero_gfunc_with:OK
#100/19 exceptions/exception_assert_neg_gfunc_with:OK
#100/20 exceptions/exception_assert_pos_gfunc_with:OK
#100/21 exceptions/exception_assert_negeq_gfunc_with:OK
#100/22 exceptions/exception_assert_poseq_gfunc_with:OK
#100/23 exceptions/exception_bad_assert_nz_gfunc:OK
#100/24 exceptions/exception_bad_assert_zero_gfunc:OK
#100/25 exceptions/exception_bad_assert_neg_gfunc:OK
#100/26 exceptions/exception_bad_assert_pos_gfunc:OK
#100/27 exceptions/exception_bad_assert_negeq_gfunc:OK
#100/28 exceptions/exception_bad_assert_poseq_gfunc:OK
#100/29 exceptions/exception_bad_assert_nz_gfunc_with:OK
#100/30 exceptions/exception_bad_assert_zero_gfunc_with:OK
#100/31 exceptions/exception_bad_assert_neg_gfunc_with:OK
#100/32 exceptions/exception_bad_assert_pos_gfunc_with:OK
#100/33 exceptions/exception_bad_assert_negeq_gfunc_with:OK
#100/34 exceptions/exception_bad_assert_poseq_gfunc_with:OK
#100/35 exceptions/exception_assert_range:OK
#100/36 exceptions/exception_assert_range_with:OK
#100/37 exceptions/exception_bad_assert_range:OK
#100/38 exceptions/exception_bad_assert_range_with:OK
#100/39 exceptions/non-throwing fentry -> exception_cb:OK
#100/40 exceptions/throwing fentry -> exception_cb:OK
#100/41 exceptions/non-throwing fexit -> exception_cb:OK
#100/42 exceptions/throwing fexit -> exception_cb:OK
#100/43 exceptions/throwing extension (with custom cb) -> exception_cb:OK
#100/44 exceptions/throwing extension -> global func in exception_cb:OK
#100/45 exceptions/exception_ext_mod_cb_runtime:OK
#100/46 exceptions/throwing extension (with custom cb) -> global func in exception_cb:OK
#100/47 exceptions/exception_ext:OK
#100/48 exceptions/non-throwing fentry -> non-throwing subprog:OK
#100/49 exceptions/throwing fentry -> non-throwing subprog:OK
#100/50 exceptions/non-throwing fentry -> throwing subprog:OK
#100/51 exceptions/throwing fentry -> throwing subprog:OK
#100/52 exceptions/non-throwing fexit -> non-throwing subprog:OK
#100/53 exceptions/throwing fexit -> non-throwing subprog:OK
#100/54 exceptions/non-throwing fexit -> throwing subprog:OK
#100/55 exceptions/throwing fexit -> throwing subprog:OK
#100/56 exceptions/non-throwing fmod_ret -> non-throwing subprog:OK
#100/57 exceptions/non-throwing fmod_ret -> non-throwing global subprog:OK
#100/58 exceptions/non-throwing extension -> non-throwing subprog:OK
#100/59 exceptions/non-throwing extension -> throwing subprog:OK
#100/60 exceptions/non-throwing extension -> non-throwing subprog:OK
#100/61 exceptions/non-throwing extension -> throwing global subprog:OK
#100/62 exceptions/throwing extension -> throwing global subprog:OK
#100/63 exceptions/throwing extension -> non-throwing global subprog:OK
#100/64 exceptions/non-throwing extension -> main subprog:OK
#100/65 exceptions/throwing extension -> main subprog:OK
#100/66 exceptions/reject_exception_cb_type_1:OK
#100/67 exceptions/reject_exception_cb_type_2:OK
#100/68 exceptions/reject_exception_cb_type_3:OK
#100/69 exceptions/reject_exception_cb_type_4:OK
#100/70 exceptions/reject_async_callback_throw:OK
#100/71 exceptions/reject_with_lock:OK
#100/72 exceptions/reject_subprog_with_lock:OK
#100/73 exceptions/reject_with_rcu_read_lock:OK
#100/74 exceptions/reject_subprog_with_rcu_read_lock:OK
#100/75 exceptions/reject_with_rbtree_add_throw:OK
#100/76 exceptions/reject_with_reference:OK
#100/77 exceptions/reject_with_cb_reference:OK
#100/78 exceptions/reject_with_cb:OK
#100/79 exceptions/reject_with_subprog_reference:OK
#100/80 exceptions/reject_throwing_exception_cb:OK
#100/81 exceptions/reject_exception_cb_call_global_func:OK
#100/82 exceptions/reject_exception_cb_call_static_func:OK
#100/83 exceptions/reject_multiple_exception_cb:OK
#100/84 exceptions/reject_exception_throw_cb:OK
#100/85 exceptions/reject_exception_throw_cb_diff:OK
#100/86 exceptions/reject_set_exception_cb_bad_ret1:OK
#100/87 exceptions/reject_set_exception_cb_bad_ret2:OK
#100/88 exceptions/check_assert_eq_int_min:OK
#100/89 exceptions/check_assert_eq_int_max:OK
#100/90 exceptions/check_assert_eq_zero:OK
#100/91 exceptions/check_assert_eq_llong_min:OK
#100/92 exceptions/check_assert_eq_llong_max:OK
#100/93 exceptions/check_assert_lt_pos:OK
#100/94 exceptions/check_assert_lt_zero:OK
#100/95 exceptions/check_assert_lt_neg:OK
#100/96 exceptions/check_assert_le_pos:OK
#100/97 exceptions/check_assert_le_zero:OK
#100/98 exceptions/check_assert_le_neg:OK
#100/99 exceptions/check_assert_gt_pos:OK
#100/100 exceptions/check_assert_gt_zero:OK
#100/101 exceptions/check_assert_gt_neg:OK
#100/102 exceptions/check_assert_ge_pos:OK
#100/103 exceptions/check_assert_ge_zero:OK
#100/104 exceptions/check_assert_ge_neg:OK
#100/105 exceptions/check_assert_range_s64:OK
#100/106 exceptions/check_assert_range_u64:OK
#100/107 exceptions/check_assert_single_range_s64:OK
#100/108 exceptions/check_assert_single_range_u64:OK
#100/109 exceptions/check_assert_generic:OK
#100/110 exceptions/check_assert_with_return:OK
#100 exceptions:OK
Summary: 1/110 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Abhishek Dubey <adubey at linux.ibm.com>
---
arch/powerpc/net/bpf_jit.h | 2 ++
arch/powerpc/net/bpf_jit_comp.c | 7 ++++
arch/powerpc/net/bpf_jit_comp64.c | 53 +++++++++++++++++++++----------
3 files changed, 45 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 98e8b1f9c2f9..b9316780a501 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -177,6 +177,8 @@ struct codegen_context {
u64 arena_vm_start;
u64 user_vm_start;
bool is_subprog;
+ bool exception_boundary;
+ bool exception_cb;
};
#define bpf_to_ppc(r) (ctx->b2p[r])
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index b09d294084d4..3c030a7d8e73 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -207,6 +207,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
cgctx.arena_vm_start = bpf_arena_get_kern_vm_start(fp->aux->arena);
cgctx.user_vm_start = bpf_arena_get_user_vm_start(fp->aux->arena);
cgctx.is_subprog = bpf_is_subprog(fp);
+ cgctx.exception_boundary = fp->aux->exception_boundary;
+ cgctx.exception_cb = fp->aux->exception_cb;
/* Scouting faux-generate pass 0 */
if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
@@ -436,6 +438,11 @@ void bpf_jit_free(struct bpf_prog *fp)
bpf_prog_unlock_free(fp);
}
+bool bpf_jit_supports_exceptions(void)
+{
+ return IS_ENABLED(CONFIG_PPC64);
+}
+
bool bpf_jit_supports_subprog_tailcalls(void)
{
return IS_ENABLED(CONFIG_PPC64);
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 0f3af67914d6..5ec8e3654098 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -85,7 +85,9 @@ static inline bool bpf_has_stack_frame(struct codegen_context *ctx)
* - the bpf program uses its stack area
* The latter condition is deduced from the usage of BPF_REG_FP
*/
- return ctx->seen & SEEN_FUNC || bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP));
+ return ctx->seen & SEEN_FUNC ||
+ bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)) ||
+ ctx->exception_cb;
}
/*
@@ -180,23 +182,32 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
EMIT(PPC_RAW_STDU(_R1, _R1, -(BPF_PPC_STACKFRAME + ctx->stack_size)));
}
- /*
- * Back up non-volatile regs -- BPF registers 6-10
- * If we haven't created our own stack frame, we save these
- * in the protected zone below the previous stack frame
- */
- for (i = BPF_REG_6; i <= BPF_REG_10; i++)
- if (bpf_is_seen_register(ctx, bpf_to_ppc(i)))
- EMIT(PPC_RAW_STD(bpf_to_ppc(i), _R1, bpf_jit_stack_offsetof(ctx, bpf_to_ppc(i))));
+ if (!ctx->exception_cb) {
+ /*
+ * Back up non-volatile regs -- BPF registers 6-10
+ * If we haven't created our own stack frame, we save these
+ * in the protected zone below the previous stack frame
+ */
+ for (i = BPF_REG_6; i <= BPF_REG_10; i++)
+ if (ctx->exception_boundary || bpf_is_seen_register(ctx, bpf_to_ppc(i)))
+ EMIT(PPC_RAW_STD(bpf_to_ppc(i), _R1,
+ bpf_jit_stack_offsetof(ctx, bpf_to_ppc(i))));
- if (ctx->arena_vm_start)
- EMIT(PPC_RAW_STD(bpf_to_ppc(ARENA_VM_START), _R1,
+ if (ctx->exception_boundary || ctx->arena_vm_start)
+ EMIT(PPC_RAW_STD(bpf_to_ppc(ARENA_VM_START), _R1,
bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ARENA_VM_START))));
- /* Setup frame pointer to point to the bpf stack area */
- if (bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)))
- EMIT(PPC_RAW_ADDI(bpf_to_ppc(BPF_REG_FP), _R1,
+ /* Setup frame pointer to point to the bpf stack area */
+ if (bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)))
+ EMIT(PPC_RAW_ADDI(bpf_to_ppc(BPF_REG_FP), _R1,
STACK_FRAME_MIN_SIZE + ctx->stack_size));
+ } else {
+ /*
+ * Exception callback receives Frame Pointer of main
+ * program as third arg
+ */
+ EMIT(PPC_RAW_MR(_R1, _R5));
+ }
if (ctx->arena_vm_start)
PPC_LI64(bpf_to_ppc(ARENA_VM_START), ctx->arena_vm_start);
@@ -208,17 +219,25 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx
/* Restore NVRs */
for (i = BPF_REG_6; i <= BPF_REG_10; i++)
- if (bpf_is_seen_register(ctx, bpf_to_ppc(i)))
+ if (ctx->exception_cb || bpf_is_seen_register(ctx, bpf_to_ppc(i)))
EMIT(PPC_RAW_LD(bpf_to_ppc(i), _R1, bpf_jit_stack_offsetof(ctx, bpf_to_ppc(i))));
- if (ctx->arena_vm_start)
+ if (ctx->exception_cb || ctx->arena_vm_start)
EMIT(PPC_RAW_LD(bpf_to_ppc(ARENA_VM_START), _R1,
bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ARENA_VM_START))));
+ if (ctx->exception_cb) {
+ /*
+ * LR value from boundary-frame is received as second parameter
+ * in exception callback.
+ */
+ EMIT(PPC_RAW_MTLR(_R4));
+ }
+
/* Tear down our stack frame */
if (bpf_has_stack_frame(ctx)) {
EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME + ctx->stack_size));
- if (ctx->seen & SEEN_FUNC) {
+ if (ctx->seen & SEEN_FUNC || ctx->exception_cb) {
EMIT(PPC_RAW_LD(_R0, _R1, PPC_LR_STKOFF));
EMIT(PPC_RAW_MTLR(_R0));
}
--
2.48.1
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