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s390/bpf: Support internal-only MOV instruction to resolve per-CPU addrs

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The verifier emits BPF_MOV64_PERCPU_REG to turn the address of a per-cpu
variable into the address of the copy of this cpu. s390 keeps the per-cpu
offset of the cpu in the lowcore. Add it to the register with one insn, the
way the JIT reads cpu_nr and current_task for the helpers that it inlines.

With bpf_jit_supports_percpu_insn() the verifier inlines the lookup in
per-cpu array and per-cpu hash maps, and resolves the address of a value in
a per-cpu array. Patch 7 needs the insn for may_goto.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261031215543.682284-6-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2026-10-31 21:55:39 +00:00
parent 5eced83779
commit 85b6a11252
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1 changed files with 16 additions and 0 deletions
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16
arch/s390/net/bpf_jit_comp.c
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@ -1005,6 +1005,17 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
(jit->prg - patch_brc) >> 1;
break;
}
if (insn_is_mov_percpu_addr(insn)) {
const u64 *percpu_offset = &get_lowcore()->percpu_offset;
if (dst_reg != src_reg)
/* lgr %dst,%src */
EMIT4(0xb9040000, dst_reg, src_reg);
/* ag %dst,percpu_offset */
EMIT6_DISP_LH(0xe3000000, 0x0008, dst_reg, REG_0, REG_0,
(unsigned long)percpu_offset);
break;
}
switch (insn->off) {
case 0: /* DST = SRC */
/* lgr %dst,%src */
@ -3114,6 +3125,11 @@ bool bpf_jit_supports_timed_may_goto(void)
return true;
}
bool bpf_jit_supports_percpu_insn(void)
{
return true;
}
bool bpf_jit_inlines_helper_call(s32 imm)
{
switch (imm) {