From: Ilya Leoshkevich Date: Fri, 13 Mar 2026 17:46:25 +0000 (+0100) Subject: s390/bpf: Zero-extend bpf prog return values and kfunc arguments X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=202e42e4aa890172366354b233c42c73107a3f59;p=thirdparty%2Flinux.git s390/bpf: Zero-extend bpf prog return values and kfunc arguments s390x ABI requires callers to zero-extend unsigned arguments and sign-extend signed arguments, and callees to zero-extend unsigned return values and sign-extend signed return values. s390 BPF JIT currently implements only sign extension. Fix this omission and implement zero extension too. Fixes: 528eb2cb87bc ("s390/bpf: Implement arch_prepare_bpf_trampoline()") Reported-by: Hari Bathini Closes: https://lore.kernel.org/bpf/20260312080113.843408-1-hbathini@linux.ibm.com/ Signed-off-by: Ilya Leoshkevich Tested-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260313174807.581826-1-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov --- diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 1f9a6b728beb3..d08d159b63193 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -830,25 +830,34 @@ static int bpf_jit_probe_post(struct bpf_jit *jit, struct bpf_prog *fp, } /* - * Sign-extend the register if necessary + * Sign- or zero-extend the register if necessary */ -static int sign_extend(struct bpf_jit *jit, int r, u8 size, u8 flags) +static int sign_zero_extend(struct bpf_jit *jit, int r, u8 size, u8 flags) { - if (!(flags & BTF_FMODEL_SIGNED_ARG)) - return 0; - switch (size) { case 1: - /* lgbr %r,%r */ - EMIT4(0xb9060000, r, r); + if (flags & BTF_FMODEL_SIGNED_ARG) + /* lgbr %r,%r */ + EMIT4(0xb9060000, r, r); + else + /* llgcr %r,%r */ + EMIT4(0xb9840000, r, r); return 0; case 2: - /* lghr %r,%r */ - EMIT4(0xb9070000, r, r); + if (flags & BTF_FMODEL_SIGNED_ARG) + /* lghr %r,%r */ + EMIT4(0xb9070000, r, r); + else + /* llghr %r,%r */ + EMIT4(0xb9850000, r, r); return 0; case 4: - /* lgfr %r,%r */ - EMIT4(0xb9140000, r, r); + if (flags & BTF_FMODEL_SIGNED_ARG) + /* lgfr %r,%r */ + EMIT4(0xb9140000, r, r); + else + /* llgfr %r,%r */ + EMIT4(0xb9160000, r, r); return 0; case 8: return 0; @@ -1798,9 +1807,9 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, return -1; for (j = 0; j < m->nr_args; j++) { - if (sign_extend(jit, BPF_REG_1 + j, - m->arg_size[j], - m->arg_flags[j])) + if (sign_zero_extend(jit, BPF_REG_1 + j, + m->arg_size[j], + m->arg_flags[j])) return -1; } } @@ -2566,7 +2575,7 @@ static int invoke_bpf_prog(struct bpf_tramp_jit *tjit, EMIT6_PCREL_RILB_PTR(0xc0050000, REG_14, p->bpf_func); /* stg %r2,retval_off(%r15) */ if (save_ret) { - if (sign_extend(jit, REG_2, m->ret_size, m->ret_flags)) + if (sign_zero_extend(jit, REG_2, m->ret_size, m->ret_flags)) return -1; EMIT6_DISP_LH(0xe3000000, 0x0024, REG_2, REG_0, REG_15, tjit->retval_off);