From b14157eeed4eff2b293e0ca7738f6a3dbfff51cc Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Mon, 23 Oct 2017 11:58:13 -0700 Subject: [PATCH] nfp: bpf: support stack accesses via non-constant pointers If stack pointer has a different value on different paths but the alignment to words (4B) remains the same, we can set a new LMEM access pointer to the calculated value and access whichever word it's pointing to. Signed-off-by: Jakub Kicinski Reviewed-by: Quentin Monnet Signed-off-by: David S. Miller --- drivers/net/ethernet/netronome/nfp/bpf/jit.c | 41 +++++++++++++++++++---- drivers/net/ethernet/netronome/nfp/bpf/main.h | 2 ++ drivers/net/ethernet/netronome/nfp/bpf/verifier.c | 12 +++++-- 3 files changed, 45 insertions(+), 10 deletions(-) diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c index 5105b92..d84f00b 100644 --- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c +++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c @@ -832,8 +832,8 @@ wrp_lmem_store(struct nfp_prog *nfp_prog, u8 src, u8 src_byte, s32 off, static int mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, - unsigned int size, unsigned int ptr_off, u8 gpr, bool clr_gpr, - lmem_step step) + unsigned int size, unsigned int ptr_off, u8 gpr, u8 ptr_gpr, + bool clr_gpr, lmem_step step) { s32 off = nfp_prog->stack_depth + meta->insn.off + ptr_off; bool first = true, last; @@ -844,7 +844,19 @@ mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, bool lm3 = true; int ret; - if (off + size <= 64) { + if (meta->ptr_not_const) { + /* Use of the last encountered ptr_off is OK, they all have + * the same alignment. Depend on low bits of value being + * discarded when written to LMaddr register. + */ + stack_off_reg = ur_load_imm_any(nfp_prog, meta->insn.off, + stack_imm(nfp_prog)); + + emit_alu(nfp_prog, imm_b(nfp_prog), + reg_a(ptr_gpr), ALU_OP_ADD, stack_off_reg); + + needs_inc = true; + } else if (off + size <= 64) { /* We can reach bottom 64B with LMaddr0 */ lm3 = false; } else if (round_down(off, 32) == round_down(off + size - 1, 32)) { @@ -1096,9 +1108,22 @@ static void wrp_end32(struct nfp_prog *nfp_prog, swreg reg_in, u8 gpr_out) static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta) { const struct bpf_insn *insn = &meta->insn; + u8 dst = insn->dst_reg * 2; + u8 src = insn->src_reg * 2; + + if (insn->src_reg == BPF_REG_10) { + swreg stack_depth_reg; - wrp_reg_mov(nfp_prog, insn->dst_reg * 2, insn->src_reg * 2); - wrp_reg_mov(nfp_prog, insn->dst_reg * 2 + 1, insn->src_reg * 2 + 1); + stack_depth_reg = ur_load_imm_any(nfp_prog, + nfp_prog->stack_depth, + stack_imm(nfp_prog)); + emit_alu(nfp_prog, reg_both(dst), + stack_reg(nfp_prog), ALU_OP_ADD, stack_depth_reg); + wrp_immed(nfp_prog, reg_both(dst + 1), 0); + } else { + wrp_reg_mov(nfp_prog, dst, src); + wrp_reg_mov(nfp_prog, dst + 1, src + 1); + } return 0; } @@ -1413,7 +1438,8 @@ mem_ldx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, unsigned int size, unsigned int ptr_off) { return mem_op_stack(nfp_prog, meta, size, ptr_off, - meta->insn.dst_reg * 2, true, wrp_lmem_load); + meta->insn.dst_reg * 2, meta->insn.src_reg * 2, + true, wrp_lmem_load); } static int mem_ldx_skb(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, @@ -1585,7 +1611,8 @@ mem_stx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, unsigned int size, unsigned int ptr_off) { return mem_op_stack(nfp_prog, meta, size, ptr_off, - meta->insn.src_reg * 2, false, wrp_lmem_store); + meta->insn.src_reg * 2, meta->insn.dst_reg * 2, + false, wrp_lmem_store); } static int diff --git a/drivers/net/ethernet/netronome/nfp/bpf/main.h b/drivers/net/ethernet/netronome/nfp/bpf/main.h index d4f144a..86edc06 100644 --- a/drivers/net/ethernet/netronome/nfp/bpf/main.h +++ b/drivers/net/ethernet/netronome/nfp/bpf/main.h @@ -101,6 +101,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *); * struct nfp_insn_meta - BPF instruction wrapper * @insn: BPF instruction * @ptr: pointer type for memory operations + * @ptr_not_const: pointer is not always constant * @off: index of first generated machine instruction (in nfp_prog.prog) * @n: eBPF instruction number * @skip: skip this instruction (optimized out) @@ -110,6 +111,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *); struct nfp_insn_meta { struct bpf_insn insn; struct bpf_reg_state ptr; + bool ptr_not_const; unsigned int off; unsigned short n; bool skip; diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c index 633db3e..3d3dcac 100644 --- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c +++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c @@ -112,7 +112,8 @@ nfp_bpf_check_exit(struct nfp_prog *nfp_prog, } static int -nfp_bpf_check_stack_access(struct nfp_insn_meta *meta, +nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog, + struct nfp_insn_meta *meta, const struct bpf_reg_state *reg) { s32 old_off, new_off; @@ -128,7 +129,12 @@ nfp_bpf_check_stack_access(struct nfp_insn_meta *meta, old_off = meta->ptr.off + meta->ptr.var_off.value; new_off = reg->off + reg->var_off.value; - if (old_off == new_off) + meta->ptr_not_const |= old_off != new_off; + + if (!meta->ptr_not_const) + return 0; + + if (old_off % 4 == new_off % 4) return 0; pr_info("stack access changed location was:%d is:%d\n", @@ -151,7 +157,7 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, } if (reg->type == PTR_TO_STACK) { - err = nfp_bpf_check_stack_access(meta, reg); + err = nfp_bpf_check_stack_access(nfp_prog, meta, reg); if (err) return err; } -- 2.7.4