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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 <jakub.kicinski@netronome.com> Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -832,8 +832,8 @@ wrp_lmem_store(struct nfp_prog *nfp_prog, u8 src, u8 src_byte, s32 off,
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static int
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mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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unsigned int size, unsigned int ptr_off, u8 gpr, bool clr_gpr,
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lmem_step step)
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unsigned int size, unsigned int ptr_off, u8 gpr, u8 ptr_gpr,
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bool clr_gpr, lmem_step step)
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{
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s32 off = nfp_prog->stack_depth + meta->insn.off + ptr_off;
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bool first = true, last;
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@ -844,7 +844,19 @@ mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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bool lm3 = true;
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int ret;
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if (off + size <= 64) {
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if (meta->ptr_not_const) {
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/* Use of the last encountered ptr_off is OK, they all have
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* the same alignment. Depend on low bits of value being
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* discarded when written to LMaddr register.
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*/
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stack_off_reg = ur_load_imm_any(nfp_prog, meta->insn.off,
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stack_imm(nfp_prog));
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emit_alu(nfp_prog, imm_b(nfp_prog),
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reg_a(ptr_gpr), ALU_OP_ADD, stack_off_reg);
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needs_inc = true;
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} else if (off + size <= 64) {
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/* We can reach bottom 64B with LMaddr0 */
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lm3 = false;
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} else if (round_down(off, 32) == round_down(off + size - 1, 32)) {
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@ -1096,9 +1108,22 @@ static void wrp_end32(struct nfp_prog *nfp_prog, swreg reg_in, u8 gpr_out)
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static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
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{
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const struct bpf_insn *insn = &meta->insn;
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u8 dst = insn->dst_reg * 2;
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u8 src = insn->src_reg * 2;
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wrp_reg_mov(nfp_prog, insn->dst_reg * 2, insn->src_reg * 2);
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wrp_reg_mov(nfp_prog, insn->dst_reg * 2 + 1, insn->src_reg * 2 + 1);
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if (insn->src_reg == BPF_REG_10) {
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swreg stack_depth_reg;
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stack_depth_reg = ur_load_imm_any(nfp_prog,
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nfp_prog->stack_depth,
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stack_imm(nfp_prog));
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emit_alu(nfp_prog, reg_both(dst),
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stack_reg(nfp_prog), ALU_OP_ADD, stack_depth_reg);
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wrp_immed(nfp_prog, reg_both(dst + 1), 0);
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} else {
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wrp_reg_mov(nfp_prog, dst, src);
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wrp_reg_mov(nfp_prog, dst + 1, src + 1);
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}
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return 0;
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}
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@ -1413,7 +1438,8 @@ mem_ldx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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unsigned int size, unsigned int ptr_off)
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{
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return mem_op_stack(nfp_prog, meta, size, ptr_off,
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meta->insn.dst_reg * 2, true, wrp_lmem_load);
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meta->insn.dst_reg * 2, meta->insn.src_reg * 2,
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true, wrp_lmem_load);
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}
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static int mem_ldx_skb(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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@ -1585,7 +1611,8 @@ mem_stx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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unsigned int size, unsigned int ptr_off)
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{
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return mem_op_stack(nfp_prog, meta, size, ptr_off,
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meta->insn.src_reg * 2, false, wrp_lmem_store);
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meta->insn.src_reg * 2, meta->insn.dst_reg * 2,
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false, wrp_lmem_store);
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}
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static int
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@ -101,6 +101,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *);
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* struct nfp_insn_meta - BPF instruction wrapper
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* @insn: BPF instruction
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* @ptr: pointer type for memory operations
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* @ptr_not_const: pointer is not always constant
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* @off: index of first generated machine instruction (in nfp_prog.prog)
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* @n: eBPF instruction number
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* @skip: skip this instruction (optimized out)
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@ -110,6 +111,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *);
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struct nfp_insn_meta {
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struct bpf_insn insn;
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struct bpf_reg_state ptr;
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bool ptr_not_const;
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unsigned int off;
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unsigned short n;
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bool skip;
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@ -112,7 +112,8 @@ nfp_bpf_check_exit(struct nfp_prog *nfp_prog,
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}
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static int
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nfp_bpf_check_stack_access(struct nfp_insn_meta *meta,
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nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
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struct nfp_insn_meta *meta,
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const struct bpf_reg_state *reg)
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{
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s32 old_off, new_off;
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@ -128,7 +129,12 @@ nfp_bpf_check_stack_access(struct nfp_insn_meta *meta,
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old_off = meta->ptr.off + meta->ptr.var_off.value;
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new_off = reg->off + reg->var_off.value;
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if (old_off == new_off)
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meta->ptr_not_const |= old_off != new_off;
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if (!meta->ptr_not_const)
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return 0;
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if (old_off % 4 == new_off % 4)
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return 0;
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pr_info("stack access changed location was:%d is:%d\n",
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@ -151,7 +157,7 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
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}
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if (reg->type == PTR_TO_STACK) {
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err = nfp_bpf_check_stack_access(meta, reg);
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err = nfp_bpf_check_stack_access(nfp_prog, meta, reg);
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if (err)
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return err;
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}
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