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charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 2025/9/4 18:38, Hengqi Chen wrote: > The ns_bpf_qdisc selftest triggers a kernel panic: > > Unable to handle kernel paging request at virtual address ffffffffa38dbf58 > Current test_progs pgtable: 4K pagesize, 57-bit VAs, pgdp=0x00000001109cc000 > [ffffffffa38dbf58] pgd=000000011fffd801, p4d=000000011fffd401, pud=000000011fffd001, pmd=0000000000000000 > Oops [#1] > Modules linked in: bpf_testmod(OE) xt_conntrack nls_iso8859_1 dm_mod drm drm_panel_orientation_quirks configfs backlight btrfs blake2b_generic xor lzo_compress zlib_deflate raid6_pq efivarfs [last unloaded: bpf_testmod(OE)] > CPU: 1 UID: 0 PID: 23584 Comm: test_progs Tainted: G W OE 6.17.0-rc1-g2465bb83e0b4 #1 NONE > Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE > Hardware name: Unknown Unknown Product/Unknown Product, BIOS 2024.01+dfsg-1ubuntu5.1 01/01/2024 > epc : __qdisc_run+0x82/0x6f0 > ra : __qdisc_run+0x6e/0x6f0 > epc : ffffffff80bd5c7a ra : ffffffff80bd5c66 sp : ff2000000eecb550 > gp : ffffffff82472098 tp : ff60000096895940 t0 : ffffffff8001f180 > t1 : ffffffff801e1664 t2 : 0000000000000000 s0 : ff2000000eecb5d0 > s1 : ff60000093a6a600 a0 : ffffffffa38dbee8 a1 : 0000000000000001 > a2 : ff2000000eecb510 a3 : 0000000000000001 a4 : 0000000000000000 > a5 : 0000000000000010 a6 : 0000000000000000 a7 : 0000000000735049 > s2 : ffffffffa38dbee8 s3 : 0000000000000040 s4 : ff6000008bcda000 > s5 : 0000000000000008 s6 : ff60000093a6a680 s7 : ff60000093a6a6f0 > s8 : ff60000093a6a6ac s9 : ff60000093140000 s10: 0000000000000000 > s11: ff2000000eecb9d0 t3 : 0000000000000000 t4 : 0000000000ff0000 > t5 : 0000000000000000 t6 : ff60000093a6a8b6 > status: 0000000200000120 badaddr: ffffffffa38dbf58 cause: 000000000000000d > [] __qdisc_run+0x82/0x6f0 > [] __dev_queue_xmit+0x4c0/0x1128 > [] neigh_resolve_output+0xd0/0x170 > [] ip6_finish_output2+0x226/0x6c8 > [] ip6_finish_output+0x10c/0x2a0 > [] ip6_output+0x5e/0x178 > [] ip6_xmit+0x29a/0x608 > [] inet6_csk_xmit+0xe6/0x140 > [] __tcp_transmit_skb+0x45c/0xaa8 > [] tcp_connect+0x9ce/0xd10 > [] tcp_v6_connect+0x4ac/0x5e8 > [] __inet_stream_connect+0xd8/0x318 > [] inet_stream_connect+0x3e/0x68 > [] __sys_connect_file+0x50/0x88 > [] __sys_connect+0x96/0xc8 > [] __riscv_sys_connect+0x20/0x30 > [] do_trap_ecall_u+0x256/0x378 > [] handle_exception+0x14a/0x156 > Code: 892a 0363 1205 489c 8bc1 c7e5 2d03 084a 2703 080a (2783) 0709 > ---[ end trace 0000000000000000 ]--- > > The bpf_fifo_dequeue prog returns a skb which is a pointer. > The pointer is treated as a 32bit value and sign extend to > 64bit in epilogue. This behavior is right for most bpf prog > types but wrong for struct ops which requires RISC-V ABI. > > So let's sign extend struct ops return values according to > the function model and RISC-V ABI([0]). > > [0]: https://riscv.org/wp-content/uploads/2024/12/riscv-calling.pdf > > Fixes: 25ad10658dc1 ("riscv, bpf: Adapt bpf trampoline to optimized riscv ftrace framework") > Signed-off-by: Hengqi Chen > --- > arch/riscv/net/bpf_jit_comp64.c | 38 ++++++++++++++++++++++++++++++++- > 1 file changed, 37 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c > index 549c3063c7f1..c7ae4d0a8361 100644 > --- a/arch/riscv/net/bpf_jit_comp64.c > +++ b/arch/riscv/net/bpf_jit_comp64.c > @@ -954,6 +954,35 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of > return ret; > } > > +/* > + * Sign-extend the register if necessary > + */ This helper may be used later, so let's put it higher. > +static int sign_extend(int rd, int rs, u8 size, u8 flags, struct rv_jit_context *ctx) > +{ > + if (!(flags & BTF_FMODEL_SIGNED_ARG) && (size == 1 || size == 2)) emm, this will miss unsigned 1 and 2 byte return values, we should also move them to RV_REG_A0. And also, let we use `sign` but not `flags`, as we may use this helper in other place. That will be: static int sign_extend(u8 rd, u8 rs, u8 sz, bool sign, struct rv_jit_context *ctx) { if (!sign && (sz == 1 || sz == 2)) { if (rd != rs) emit_mv(rd, rs, ctx); return 0; } ... } > + return 0; > + > + switch (size) { > + case 1: > + emit_sextb(rd, rs, ctx); > + break; > + case 2: > + emit_sexth(rd, rs, ctx); > + break; > + case 4: > + emit_sextw(rd, rs, ctx); > + break; > + case 8: let's only move when rd != rs > + emit_mv(rd, rs, ctx); > + break; > + default: > + pr_err("bpf-jit: invalid size %d for sign_extend\n", size); > + return -EINVAL; > + } > + > + return 0; > +} > + > static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > const struct btf_func_model *m, > struct bpf_tramp_links *tlinks, > @@ -1175,8 +1204,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx); > > if (save_ret) { > - emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx); > emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx); > + if (is_struct_ops) { > + ret = sign_extend(RV_REG_A0, regmap[BPF_REG_0], > + m->ret_size, m->ret_flags, ctx); > + if (ret) > + goto out; > + } else { > + emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx); > + } > } > > emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx); _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv