From: Ilya Leoshkevich <iii@linux.ibm.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH bpf-next v2 31/31] s390/bpf: Implement bpf_jit_supports_kfunc_call()
Date: Sat, 28 Jan 2023 01:06:50 +0100 [thread overview]
Message-ID: <20230128000650.1516334-32-iii@linux.ibm.com> (raw)
In-Reply-To: <20230128000650.1516334-1-iii@linux.ibm.com>
Implement calling kernel functions from eBPF. In general, the eBPF ABI
is fairly close to that of s390x, with one important difference: on
s390x callers should sign-extend signed arguments. Handle that by using
information returned by bpf_jit_find_kfunc_model().
Here is an example of how sign extensions works. Suppose we need to
call the following function from BPF:
; long noinline bpf_kfunc_call_test4(signed char a, short b, int c,
long d)
0000000000936a78 <bpf_kfunc_call_test4>:
936a78: c0 04 00 00 00 00 jgnop bpf_kfunc_call_test4
; return (long)a + (long)b + (long)c + d;
936a7e: b9 08 00 45 agr %r4,%r5
936a82: b9 08 00 43 agr %r4,%r3
936a86: b9 08 00 24 agr %r2,%r4
936a8a: c0 f4 00 1e 3b 27 jg <__s390_indirect_jump_r14>
As per the s390x ABI, bpf_kfunc_call_test4() has the right to assume
that a, b and c are sign-extended by the caller, which results in using
64-bit additions (agr) without any additional conversions. Without sign
extension we would have the following on the JITed code side:
; tmp = bpf_kfunc_call_test4(-3, -30, -200, -1000);
; 5: b4 10 00 00 ff ff ff fd w1 = -3
0x3ff7fdcdad4: llilf %r2,0xfffffffd
; 6: b4 20 00 00 ff ff ff e2 w2 = -30
0x3ff7fdcdada: llilf %r3,0xffffffe2
; 7: b4 30 00 00 ff ff ff 38 w3 = -200
0x3ff7fdcdae0: llilf %r4,0xffffff38
; 8: b7 40 00 00 ff ff fc 18 r4 = -1000
0x3ff7fdcdae6: lgfi %r5,-1000
0x3ff7fdcdaec: mvc 64(4,%r15),160(%r15)
0x3ff7fdcdaf2: lgrl %r1,bpf_kfunc_call_test4@GOT
0x3ff7fdcdaf8: brasl %r14,__s390_indirect_jump_r1
This first 3 llilfs are 32-bit loads, that need to be sign-extended
to 64 bits.
Note: at the moment bpf_jit_find_kfunc_model() does not seem to play
nicely with XDP metadata functions: add_kfunc_call() adds an "abstract"
bpf_*() version to kfunc_btf_tab, but then fixup_kfunc_call() puts the
concrete version into insn->imm, which bpf_jit_find_kfunc_model() cannot
find. But this seems to be a common code problem.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/net/bpf_jit_comp.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index e035dd24b430..3001d96a2b23 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1401,9 +1401,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
*/
case BPF_JMP | BPF_CALL:
{
- u64 func;
+ const struct btf_func_model *m;
bool func_addr_fixed;
- int ret;
+ int j, ret;
+ u64 func;
ret = bpf_jit_get_func_addr(fp, insn, extra_pass,
&func, &func_addr_fixed);
@@ -1425,6 +1426,21 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
/* mvc STK_OFF_TCCNT(4,%r15),N(%r15) */
_EMIT6(0xd203f000 | STK_OFF_TCCNT,
0xf000 | (STK_OFF_TCCNT + STK_OFF + stack_depth));
+
+ /* Sign-extend the kfunc arguments. */
+ if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
+ m = bpf_jit_find_kfunc_model(fp, insn);
+ if (!m)
+ 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]))
+ return -1;
+ }
+ }
+
/* lgrl %w1,func */
EMIT6_PCREL_RILB(0xc4080000, REG_W1, _EMIT_CONST_U64(func));
/* %r1() */
@@ -1980,6 +1996,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
return fp;
}
+bool bpf_jit_supports_kfunc_call(void)
+{
+ return true;
+}
+
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr)
{
--
2.39.1
next prev parent reply other threads:[~2023-01-28 0:08 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-28 0:06 [PATCH bpf-next v2 00/31] Support bpf trampoline for s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 01/31] bpf: Use ARG_CONST_SIZE_OR_ZERO for 3rd argument of bpf_tcp_raw_gen_syncookie_ipv{4,6}() Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 02/31] bpf: Change BPF_MAX_TRAMP_LINKS to enum Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 03/31] selftests/bpf: Query BPF_MAX_TRAMP_LINKS using BTF Ilya Leoshkevich
2023-01-28 20:49 ` Alexei Starovoitov
2023-01-29 1:50 ` Alexei Starovoitov
2023-01-28 0:06 ` [PATCH bpf-next v2 04/31] selftests/bpf: Fix liburandom_read.so linker error Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 05/31] selftests/bpf: Fix symlink creation error Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 06/31] selftests/bpf: Fix kfree_skb on s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 07/31] selftests/bpf: Set errno when urand_spawn() fails Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 08/31] selftests/bpf: Fix decap_sanity_ns cleanup Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 09/31] selftests/bpf: Fix verify_pkcs7_sig on s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 10/31] selftests/bpf: Fix xdp_do_redirect " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 11/31] selftests/bpf: Fix cgrp_local_storage " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 12/31] selftests/bpf: Check stack_mprotect() return value Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 13/31] selftests/bpf: Increase SIZEOF_BPF_LOCAL_STORAGE_ELEM on s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 14/31] selftests/bpf: Add a sign-extension test for kfuncs Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 15/31] selftests/bpf: Fix test_lsm on s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 16/31] selftests/bpf: Fix test_xdp_adjust_tail_grow2 " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 17/31] selftests/bpf: Fix vmlinux test " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 18/31] selftests/bpf: Fix sk_assign " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 19/31] selftests/bpf: Fix xdp_synproxy/tc " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 20/31] selftests/bpf: Fix profiler " Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 21/31] libbpf: Simplify barrier_var() Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 22/31] libbpf: Fix unbounded memory access in bpf_usdt_arg() Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 23/31] libbpf: Fix BPF_PROBE_READ{_STR}_INTO() on s390x Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 24/31] bpf: iterators: Split iterators.lskel.h into little- and big- endian versions Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 25/31] bpf: btf: Add BTF_FMODEL_SIGNED_ARG flag Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 26/31] s390/bpf: Fix a typo in a comment Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 27/31] s390/bpf: Add expoline to tail calls Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 28/31] s390/bpf: Implement bpf_arch_text_poke() Ilya Leoshkevich
2023-01-28 0:06 ` [PATCH bpf-next v2 29/31] s390/bpf: Implement arch_prepare_bpf_trampoline() Ilya Leoshkevich
2023-01-28 8:37 ` kernel test robot
2023-01-28 0:06 ` [PATCH bpf-next v2 30/31] s390/bpf: Implement bpf_jit_supports_subprog_tailcalls() Ilya Leoshkevich
2023-01-28 0:06 ` Ilya Leoshkevich [this message]
2023-01-28 20:50 ` [PATCH bpf-next v2 00/31] Support bpf trampoline for s390x patchwork-bot+netdevbpf
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