From 555469cc9be4a7f52c0ad07a4a237d63e8c5c5f4 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Tue, 2 Jul 2024 01:40:25 +0200 Subject: s390/bpf: Support address space cast instruction The new address cast instruction translates arena offsets to userspace addresses. NULL pointers must not be translated. The common code sets up the mappings in such a way that it's enough to replace the higher 32 bits to achieve the desired result. s390x has just an instruction for this: INSERT IMMEDIATE. Implement the sequence using 3 instruction: LOAD AND TEST, BRANCH RELATIVE ON CONDITION and INSERT IMMEDIATE. Signed-off-by: Ilya Leoshkevich Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20240701234304.14336-8-iii@linux.ibm.com --- arch/s390/net/bpf_jit_comp.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'arch/s390/net') diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 4b62b5162dfb..39c1d9aa7f1e 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -54,6 +54,7 @@ struct bpf_jit { int prologue_plt_ret; /* Return address for prologue hotpatch PLT */ int prologue_plt; /* Start of prologue hotpatch PLT */ int kern_arena; /* Pool offset of kernel arena address */ + u64 user_arena; /* User arena address */ }; #define SEEN_MEM BIT(0) /* use mem[] for temporary storage */ @@ -863,6 +864,22 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, } break; case BPF_ALU64 | BPF_MOV | BPF_X: + if (insn_is_cast_user(insn)) { + int patch_brc; + + /* ltgr %dst,%src */ + EMIT4(0xb9020000, dst_reg, src_reg); + /* brc 8,0f */ + patch_brc = jit->prg; + EMIT4_PCREL_RIC(0xa7040000, 8, 0); + /* iihf %dst,user_arena>>32 */ + EMIT6_IMM(0xc0080000, dst_reg, jit->user_arena >> 32); + /* 0: */ + if (jit->prg_buf) + *(u16 *)(jit->prg_buf + patch_brc + 2) = + (jit->prg - patch_brc) >> 1; + break; + } switch (insn->off) { case 0: /* DST = SRC */ /* lgr %dst,%src */ @@ -2076,6 +2093,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp, kern_arena = bpf_arena_get_kern_vm_start(fp->aux->arena); if (kern_arena) jit->kern_arena = _EMIT_CONST_U64(kern_arena); + jit->user_arena = bpf_arena_get_user_vm_start(fp->aux->arena); bpf_jit_prologue(jit, fp, stack_depth); if (bpf_set_addr(jit, 0) < 0) -- cgit v1.2.3