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Commit b14157ee authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

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: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2df03a50

drivers/net/ethernet/netronome/nfp/bpf/jit.c

+34 −7
Original line number Diff line number Diff line
@@ -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;



	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);

	if (insn->src_reg == BPF_REG_10) {

		swreg stack_depth_reg;



		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

drivers/net/ethernet/netronome/nfp/bpf/main.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

drivers/net/ethernet/netronome/nfp/bpf/verifier.c

+9 −3
Original line number Diff line number Diff line
@@ -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;

	}