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authorIlya Leoshkevich <iii@linux.ibm.com>2023-01-29 22:04:59 +0300
committerAlexei Starovoitov <ast@kernel.org>2023-01-30 06:16:29 +0300
commit63d7b53ab59f0dd8540e672b49836493d1fa0a79 (patch)
tree7cd2072f9a50dbae42724fc6789a53ac52af3bd3 /arch/s390/net
parentdd691e847d28ac5f8b8e3005be44fd0e46722809 (diff)
downloadlinux-63d7b53ab59f0dd8540e672b49836493d1fa0a79.tar.xz
s390/bpf: Implement bpf_jit_supports_kfunc_call()
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> Link: https://lore.kernel.org/r/20230129190501.1624747-7-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/s390/net')
-rw-r--r--arch/s390/net/bpf_jit_comp.c25
1 files changed, 23 insertions, 2 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index b84c7ddb758a..d0846ba818ee 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 @@ out:
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)
{