Re: [PATCH bpf-next 1/2] bpf, riscv: Add support for signed arena loads
Pu Lehui <[email protected]>
| Newsgroups | org.infradead.lists.linux-riscv,org.kernel.vger.bpf,org.kernel.vger.linux-kernel,org.kernel.vger.linux-kselftest |
|---|---|
| Message-ID | <[email protected]> |
oops need to revert this reviewed-by On 2026/8/18 22:27, Pu Lehui wrote: > > > On 2026/8/17 15:24, Chen Pei wrote: >> Signed loads from arena memory are currently rejected on riscv64, as >> bpf_jit_supports_insn() refuses BPF_MEMSX loads when in_arena is set, >> while x86 and arm64 gained support for them in v6.18. Compilers such >> as GCC-14 are free to generate signed loads into arena memory, which >> breaks loading of otherwise valid BPF programs on riscv64. >> >> Implement BPF_PROBE_MEM32SX support in the RV64 JIT by reusing the >> existing arena handling: the arena base (RV_REG_ARENA) is added to >> the source register and the load is emitted with sign extension >> (lb/lh/lw). Add BPF_PROBE_MEM32SX to the add_exception_handler() >> mode gate so that faulting loads get an exception table entry which >> clears the destination register and resumes execution. >> >> Verified by running the arena LDSX selftests (arena_ldsx_disasm, >> arena_ldsx_exception, arena_ldsx_s8/s16/s32) on riscv64 QEMU, all >> passing. >> >> Signed-off-by: Chen Pei <[email protected]> >> --- >> arch/riscv/net/bpf_jit_comp64.c | 15 +++++++++------ >> 1 file changed, 9 insertions(+), 6 deletions(-) >> >> diff --git a/arch/riscv/net/bpf_jit_comp64.c >> b/arch/riscv/net/bpf_jit_comp64.c >> index f9d5347ba966..5786f7dfc8a7 100644 >> --- a/arch/riscv/net/bpf_jit_comp64.c >> +++ b/arch/riscv/net/bpf_jit_comp64.c >> @@ -777,6 +777,7 @@ static int add_exception_handler(const struct >> bpf_insn *insn, int dst_reg, >> if (BPF_MODE(insn->code) != BPF_PROBE_MEM && >> BPF_MODE(insn->code) != BPF_PROBE_MEMSX && >> BPF_MODE(insn->code) != BPF_PROBE_MEM32 && >> + BPF_MODE(insn->code) != BPF_PROBE_MEM32SX && >> BPF_MODE(insn->code) != BPF_PROBE_ATOMIC) >> return 0; >> @@ -1902,13 +1903,19 @@ int bpf_jit_emit_insn(const struct bpf_insn >> *insn, struct rv_jit_context *ctx, >> case BPF_LDX | BPF_PROBE_MEM32 | BPF_H: >> case BPF_LDX | BPF_PROBE_MEM32 | BPF_W: >> case BPF_LDX | BPF_PROBE_MEM32 | BPF_DW: >> + /* LDX | PROBE_MEM32SX: dst = *(signed size *)(src + RV_REG_ARENA >> + off) */ >> + case BPF_LDX | BPF_PROBE_MEM32SX | BPF_B: >> + case BPF_LDX | BPF_PROBE_MEM32SX | BPF_H: >> + case BPF_LDX | BPF_PROBE_MEM32SX | BPF_W: >> { >> bool sign_ext; >> sign_ext = BPF_MODE(insn->code) == BPF_MEMSX || >> - BPF_MODE(insn->code) == BPF_PROBE_MEMSX; >> + BPF_MODE(insn->code) == BPF_PROBE_MEMSX || >> + BPF_MODE(insn->code) == BPF_PROBE_MEM32SX; >> - if (BPF_MODE(insn->code) == BPF_PROBE_MEM32) { >> + if (BPF_MODE(insn->code) == BPF_PROBE_MEM32 || >> + BPF_MODE(insn->code) == BPF_PROBE_MEM32SX) { >> emit_add(RV_REG_T2, rs, RV_REG_ARENA, ctx); >> rs = RV_REG_T2; >> } >> @@ -2126,10 +2133,6 @@ bool bpf_jit_supports_insn(struct bpf_insn >> *insn, bool in_arena) >> if (insn->imm == BPF_CMPXCHG) >> return rv_ext_enabled(ZACAS); >> break; >> - case BPF_LDX | BPF_MEMSX | BPF_B: >> - case BPF_LDX | BPF_MEMSX | BPF_H: >> - case BPF_LDX | BPF_MEMSX | BPF_W: >> - return false; >> } >> } > > Reviewed-by: Pu Lehui <[email protected]> > Hi Chen Pei, It's happy for the verifier_ldsx, but it not happy for the other test, pls take a look. [2026-08-19 11:33:11] root@(none):/mnt/bpf# ./test_progs -a arena_atomics [2026-08-19 11:33:18] [2026-08-19 11:33:20] [ 34.529770] bpf_testmod: loading out-of-tree module taints kernel. [2026-08-19 11:33:20] [ 34.530186] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel [2026-08-19 11:33:21] [ 35.541256] ------------[ cut here ]------------ [2026-08-19 11:33:21] [ 35.541573] WARNING: arch/riscv/net/bpf_jit_comp64.c:915 at add_exception_handler+0xce/0xf0, CPU#0: test_progs/122 [2026-08-19 11:33:21] [ 35.544546] Modules linked in: bpf_testmod(OE) [2026-08-19 11:33:21] [ 35.545885] CPU: 0 UID: 0 PID: 122 Comm: test_progs Tainted: G OE 7.2.0-next-20260818-00007-gc29447b2149d #8 PREEMPTLAZY [2026-08-19 11:33:21] [ 35.546625] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE [2026-08-19 11:33:21] [ 35.546892] Hardware name: riscv-virtio,qemu (DT) [2026-08-19 11:33:21] [ 35.547240] epc : add_exception_handler+0xce/0xf0 [2026-08-19 11:33:21] [ 35.547538] ra : bpf_jit_emit_insn+0x5a8/0x2d18 [2026-08-19 11:33:21] [ 35.547799] epc : ffffffff8002571e ra : ffffffff8002b3c8 sp : ff20000000eeb700 [2026-08-19 11:33:21] [ 35.548128] gp : ffffffff81db8ed0 tp : ff60000083130d40 t0 : ffffffff8001e650 [2026-08-19 11:33:21] [ 35.548454] t1 : 0000000000000007 t2 : 0000000000000040 s0 : ff20000000eeb710 [2026-08-19 11:33:21] [ 35.548785] s1 : 00000000000000fb a0 : 0000000000000007 a1 : 000000000000000a [2026-08-19 11:33:21] [ 35.549114] a2 : ff600000809549a0 a3 : ffffffff78000790 a4 : ff60000080a8bc24 [2026-08-19 11:33:21] [ 35.549439] a5 : 0000000000000087 a6 : ffffffff78000664 a7 : 0000000000000089 [2026-08-19 11:33:21] [ 35.549765] s2 : ff600000809549a0 s3 : ff2000000017d1e8 s4 : 0000000000000000 [2026-08-19 11:33:21] [ 35.550094] s5 : 0000000000000001 s6 : 0000000000000001 s7 : 0000000000000031 [2026-08-19 11:33:21] [ 35.550419] s8 : ff60000084994800 s9 : 0000000000000000 s10: 0000000000000000 [2026-08-19 11:33:21] [ 35.550737] s11: 000000084290e9f4 t3 : 0000000000000000 t4 : 000000000000000b [2026-08-19 11:33:21] [ 35.551079] t5 : 0000000000000008 t6 : ff600000808fc3a0 ssp : 0000000000000000 [2026-08-19 11:33:21] [ 35.551409] status: 0000000200000120 badaddr: ffffffff8002571e cause: 0000000000000003 [2026-08-19 11:33:21] [ 35.551882] [<ffffffff8002571e>] add_exception_handler+0xce/0xf0 [2026-08-19 11:33:21] [ 35.552318] [<ffffffff8002b3c8>] bpf_jit_emit_insn+0x5a8/0x2d18 [2026-08-19 11:33:21] [ 35.552602] [<ffffffff80024f1a>] bpf_int_jit_compile+0x9a/0x480 [2026-08-19 11:33:21] [ 35.552888] [<ffffffff801a3d0c>] __bpf_prog_select_runtime+0x10c/0x1d8 [2026-08-19 11:33:21] [ 35.553197] [<ffffffff801d54fa>] bpf_check+0xaca/0x31b8 [2026-08-19 11:33:21] [ 35.553459] [<ffffffff801a8436>] bpf_prog_load+0x546/0xad0 [2026-08-19 11:33:21] [ 35.553720] [<ffffffff801af850>] __sys_bpf+0x1948/0x2c38 [2026-08-19 11:33:21] [ 35.553974] [<ffffffff801b0b6a>] __riscv_sys_bpf+0x2a/0x40 [2026-08-19 11:33:21] [ 35.554238] [<ffffffff80a91872>] do_trap_ecall_u+0x1ea/0x398 [2026-08-19 11:33:21] [ 35.554528] [<ffffffff80aa088c>] handle_exception+0x16c/0x178 [2026-08-19 11:33:21] [ 35.555320] ---[ end trace 0000000000000000 ]--- [2026-08-19 11:33:21] serial_test_arena_atomics:PASS:arena atomics skeleton open 0 nsec [2026-08-19 11:33:21] libbpf: prog 'add': BPF program load failed: -ENOTSUPP [2026-08-19 11:33:21] libbpf: prog 'add': -- BEGIN PROG LOAD LOG -- [2026-08-19 11:33:21] processed 37 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 0 [2026-08-19 11:33:21] -- END PROG LOAD LOG -- [2026-08-19 11:33:21] libbpf: prog 'add': failed to load: -ENOTSUPP [2026-08-19 11:33:21] libbpf: failed to load object 'arena_atomics' [2026-08-19 11:33:21] libbpf: failed to load BPF skeleton 'arena_atomics': -ENOTSUPP [2026-08-19 11:33:21] serial_test_arena_atomics:FAIL:arena atomics skeleton load unexpected error: -524 (errno 524) [2026-08-19 11:33:21] #1 arena_atomics:FAIL [2026-08-19 11:33:21] [2026-08-19 11:33:21] All error logs: [2026-08-19 11:33:21] serial_test_arena_atomics:PASS:arena atomics skeleton open 0 nsec [2026-08-19 11:33:21] libbpf: prog 'add': BPF program load failed: -ENOTSUPP [2026-08-19 11:33:21] libbpf: prog 'add': -- BEGIN PROG LOAD LOG -- [2026-08-19 11:33:21] processed 37 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 0 [2026-08-19 11:33:21] -- END PROG LOAD LOG -- [2026-08-19 11:33:21] libbpf: prog 'add': failed to load: -ENOTSUPP [2026-08-19 11:33:21] libbpf: failed to load object 'arena_atomics' [2026-08-19 11:33:21] libbpf: failed to load BPF skeleton 'arena_atomics': -ENOTSUPP [2026-08-19 11:33:21] serial_test_arena_atomics:FAIL:arena atomics skeleton load unexpected error: -524 (errno 524) [2026-08-19 11:33:21] #1 arena_atomics:FAIL [2026-08-19 11:33:21] Summary: 0/0 PASSED, 0 SKIPPED, 1/0 FAILED [2026-08-19 11:33:21] root@(none):/mnt/bpf# _______________________________________________ linux-riscv mailing list [email protected] http://lists.infradead.org/mailman/listinfo/linux-riscv