Merge branch 'bpf-to-bpf-calls-nfp'

Quentin Monnet says:

====================
This patch series adds support for hardware offload of programs containing
BPF-to-BPF function calls. First, a new callback is added to the kernel
verifier, to collect information after the main part of the verification
has been performed. Then support for BPF-to-BPF calls is incrementally
added to the nfp driver, before offloading programs containing such calls
is eventually allowed by lifting the restriction in the kernel verifier, in
the last patch. Please refer to individual patches for details.

Many thanks to Jiong and Jakub for their precious help and contribution on
the main patches for the JIT-compiler, and everything related to stack
accesses.
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

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

@@ -266,6 +266,38 @@ emit_br_bset(struct nfp_prog *nfp_prog, swreg src, u8 bit, u16 addr, u8 defer)
 	emit_br_bit_relo(nfp_prog, src, bit, addr, defer, true, RELO_BR_REL);
 }
 
+static void
+__emit_br_alu(struct nfp_prog *nfp_prog, u16 areg, u16 breg, u16 imm_hi,
+	      u8 defer, bool dst_lmextn, bool src_lmextn)
+{
+	u64 insn;
+
+	insn = OP_BR_ALU_BASE |
+		FIELD_PREP(OP_BR_ALU_A_SRC, areg) |
+		FIELD_PREP(OP_BR_ALU_B_SRC, breg) |
+		FIELD_PREP(OP_BR_ALU_DEFBR, defer) |
+		FIELD_PREP(OP_BR_ALU_IMM_HI, imm_hi) |
+		FIELD_PREP(OP_BR_ALU_SRC_LMEXTN, src_lmextn) |
+		FIELD_PREP(OP_BR_ALU_DST_LMEXTN, dst_lmextn);
+
+	nfp_prog_push(nfp_prog, insn);
+}
+
+static void emit_rtn(struct nfp_prog *nfp_prog, swreg base, u8 defer)
+{
+	struct nfp_insn_ur_regs reg;
+	int err;
+
+	err = swreg_to_unrestricted(reg_none(), base, reg_imm(0), &reg);
+	if (err) {
+		nfp_prog->error = err;
+		return;
+	}
+
+	__emit_br_alu(nfp_prog, reg.areg, reg.breg, 0, defer, reg.dst_lmextn,
+		      reg.src_lmextn);
+}
+
 static void
 __emit_immed(struct nfp_prog *nfp_prog, u16 areg, u16 breg, u16 imm_hi,
 	     enum immed_width width, bool invert,
@@ -1137,7 +1169,7 @@ mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	     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;
+	s32 off = nfp_prog->stack_frame_depth + meta->insn.off + ptr_off;
 	bool first = true, last;
 	bool needs_inc = false;
 	swreg stack_off_reg;
@@ -1146,7 +1178,8 @@ mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	bool lm3 = true;
 	int ret;
 
-	if (meta->ptr_not_const) {
+	if (meta->ptr_not_const ||
+	    meta->flags & FLAG_INSN_PTR_CALLER_STACK_FRAME) {
 		/* 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.
@@ -1695,7 +1728,7 @@ map_call_stack_common(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	s64 lm_off;
 
 	/* We only have to reload LM0 if the key is not at start of stack */
-	lm_off = nfp_prog->stack_depth;
+	lm_off = nfp_prog->stack_frame_depth;
 	lm_off += meta->arg2.reg.var_off.value + meta->arg2.reg.off;
 	load_lm_ptr = meta->arg2.var_off || lm_off;
 
@@ -1808,10 +1841,10 @@ static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 		swreg stack_depth_reg;
 
 		stack_depth_reg = ur_load_imm_any(nfp_prog,
-						  nfp_prog->stack_depth,
+						  nfp_prog->stack_frame_depth,
 						  stack_imm(nfp_prog));
-		emit_alu(nfp_prog, reg_both(dst),
-			 stack_reg(nfp_prog), ALU_OP_ADD, stack_depth_reg);
+		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);
@@ -3081,7 +3114,93 @@ static int jne_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	return wrp_test_reg(nfp_prog, meta, ALU_OP_XOR, BR_BNE);
 }
 
-static int call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+static int
+bpf_to_bpf_call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	u32 ret_tgt, stack_depth, offset_br;
+	swreg tmp_reg;
+
+	stack_depth = round_up(nfp_prog->stack_frame_depth, STACK_FRAME_ALIGN);
+	/* Space for saving the return address is accounted for by the callee,
+	 * so stack_depth can be zero for the main function.
+	 */
+	if (stack_depth) {
+		tmp_reg = ur_load_imm_any(nfp_prog, stack_depth,
+					  stack_imm(nfp_prog));
+		emit_alu(nfp_prog, stack_reg(nfp_prog),
+			 stack_reg(nfp_prog), ALU_OP_ADD, tmp_reg);
+		emit_csr_wr(nfp_prog, stack_reg(nfp_prog),
+			    NFP_CSR_ACT_LM_ADDR0);
+	}
+
+	/* Two cases for jumping to the callee:
+	 *
+	 * - If callee uses and needs to save R6~R9 then:
+	 *     1. Put the start offset of the callee into imm_b(). This will
+	 *        require a fixup step, as we do not necessarily know this
+	 *        address yet.
+	 *     2. Put the return address from the callee to the caller into
+	 *        register ret_reg().
+	 *     3. (After defer slots are consumed) Jump to the subroutine that
+	 *        pushes the registers to the stack.
+	 *   The subroutine acts as a trampoline, and returns to the address in
+	 *   imm_b(), i.e. jumps to the callee.
+	 *
+	 * - If callee does not need to save R6~R9 then just load return
+	 *   address to the caller in ret_reg(), and jump to the callee
+	 *   directly.
+	 *
+	 * Using ret_reg() to pass the return address to the callee is set here
+	 * as a convention. The callee can then push this address onto its
+	 * stack frame in its prologue. The advantages of passing the return
+	 * address through ret_reg(), instead of pushing it to the stack right
+	 * here, are the following:
+	 * - It looks cleaner.
+	 * - If the called function is called multiple time, we get a lower
+	 *   program size.
+	 * - We save two no-op instructions that should be added just before
+	 *   the emit_br() when stack depth is not null otherwise.
+	 * - If we ever find a register to hold the return address during whole
+	 *   execution of the callee, we will not have to push the return
+	 *   address to the stack for leaf functions.
+	 */
+	if (!meta->jmp_dst) {
+		pr_err("BUG: BPF-to-BPF call has no destination recorded\n");
+		return -ELOOP;
+	}
+	if (nfp_prog->subprog[meta->jmp_dst->subprog_idx].needs_reg_push) {
+		ret_tgt = nfp_prog_current_offset(nfp_prog) + 3;
+		emit_br_relo(nfp_prog, BR_UNC, BR_OFF_RELO, 2,
+			     RELO_BR_GO_CALL_PUSH_REGS);
+		offset_br = nfp_prog_current_offset(nfp_prog);
+		wrp_immed_relo(nfp_prog, imm_b(nfp_prog), 0, RELO_IMMED_REL);
+	} else {
+		ret_tgt = nfp_prog_current_offset(nfp_prog) + 2;
+		emit_br(nfp_prog, BR_UNC, meta->n + 1 + meta->insn.imm, 1);
+		offset_br = nfp_prog_current_offset(nfp_prog);
+	}
+	wrp_immed_relo(nfp_prog, ret_reg(nfp_prog), ret_tgt, RELO_IMMED_REL);
+
+	if (!nfp_prog_confirm_current_offset(nfp_prog, ret_tgt))
+		return -EINVAL;
+
+	if (stack_depth) {
+		tmp_reg = ur_load_imm_any(nfp_prog, stack_depth,
+					  stack_imm(nfp_prog));
+		emit_alu(nfp_prog, stack_reg(nfp_prog),
+			 stack_reg(nfp_prog), ALU_OP_SUB, tmp_reg);
+		emit_csr_wr(nfp_prog, stack_reg(nfp_prog),
+			    NFP_CSR_ACT_LM_ADDR0);
+		wrp_nops(nfp_prog, 3);
+	}
+
+	meta->num_insns_after_br = nfp_prog_current_offset(nfp_prog);
+	meta->num_insns_after_br -= offset_br;
+
+	return 0;
+}
+
+static int helper_call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
 	switch (meta->insn.imm) {
 	case BPF_FUNC_xdp_adjust_head:
@@ -3102,6 +3221,19 @@ static int call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	}
 }
 
+static int call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	if (is_mbpf_pseudo_call(meta))
+		return bpf_to_bpf_call(nfp_prog, meta);
+	else
+		return helper_call(nfp_prog, meta);
+}
+
+static bool nfp_is_main_function(struct nfp_insn_meta *meta)
+{
+	return meta->subprog_idx == 0;
+}
+
 static int goto_out(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
 	emit_br_relo(nfp_prog, BR_UNC, BR_OFF_RELO, 0, RELO_BR_GO_OUT);
@@ -3109,6 +3241,39 @@ static int goto_out(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	return 0;
 }
 
+static int
+nfp_subprog_epilogue(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	if (nfp_prog->subprog[meta->subprog_idx].needs_reg_push) {
+		/* Pop R6~R9 to the stack via related subroutine.
+		 * We loaded the return address to the caller into ret_reg().
+		 * This means that the subroutine does not come back here, we
+		 * make it jump back to the subprogram caller directly!
+		 */
+		emit_br_relo(nfp_prog, BR_UNC, BR_OFF_RELO, 1,
+			     RELO_BR_GO_CALL_POP_REGS);
+		/* Pop return address from the stack. */
+		wrp_mov(nfp_prog, ret_reg(nfp_prog), reg_lm(0, 0));
+	} else {
+		/* Pop return address from the stack. */
+		wrp_mov(nfp_prog, ret_reg(nfp_prog), reg_lm(0, 0));
+		/* Jump back to caller if no callee-saved registers were used
+		 * by the subprogram.
+		 */
+		emit_rtn(nfp_prog, ret_reg(nfp_prog), 0);
+	}
+
+	return 0;
+}
+
+static int jmp_exit(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	if (nfp_is_main_function(meta))
+		return goto_out(nfp_prog, meta);
+	else
+		return nfp_subprog_epilogue(nfp_prog, meta);
+}
+
 static const instr_cb_t instr_cb[256] = {
 	[BPF_ALU64 | BPF_MOV | BPF_X] =	mov_reg64,
 	[BPF_ALU64 | BPF_MOV | BPF_K] =	mov_imm64,
@@ -3197,36 +3362,66 @@ static const instr_cb_t instr_cb[256] = {
 	[BPF_JMP | BPF_JSET | BPF_X] =	jset_reg,
 	[BPF_JMP | BPF_JNE | BPF_X] =	jne_reg,
 	[BPF_JMP | BPF_CALL] =		call,
-	[BPF_JMP | BPF_EXIT] =		goto_out,
+	[BPF_JMP | BPF_EXIT] =		jmp_exit,
 };
 
 /* --- Assembler logic --- */
+static int
+nfp_fixup_immed_relo(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
+		     struct nfp_insn_meta *jmp_dst, u32 br_idx)
+{
+	if (immed_get_value(nfp_prog->prog[br_idx + 1])) {
+		pr_err("BUG: failed to fix up callee register saving\n");
+		return -EINVAL;
+	}
+
+	immed_set_value(&nfp_prog->prog[br_idx + 1], jmp_dst->off);
+
+	return 0;
+}
+
 static int nfp_fixup_branches(struct nfp_prog *nfp_prog)
 {
 	struct nfp_insn_meta *meta, *jmp_dst;
 	u32 idx, br_idx;
+	int err;
 
 	list_for_each_entry(meta, &nfp_prog->insns, l) {
 		if (meta->skip)
 			continue;
-		if (meta->insn.code == (BPF_JMP | BPF_CALL))
-			continue;
 		if (BPF_CLASS(meta->insn.code) != BPF_JMP)
 			continue;
+		if (meta->insn.code == (BPF_JMP | BPF_EXIT) &&
+		    !nfp_is_main_function(meta))
+			continue;
+		if (is_mbpf_helper_call(meta))
+			continue;
 
 		if (list_is_last(&meta->l, &nfp_prog->insns))
 			br_idx = nfp_prog->last_bpf_off;
 		else
 			br_idx = list_next_entry(meta, l)->off - 1;
 
+		/* For BPF-to-BPF function call, a stack adjustment sequence is
+		 * generated after the return instruction. Therefore, we must
+		 * withdraw the length of this sequence to have br_idx pointing
+		 * to where the "branch" NFP instruction is expected to be.
+		 */
+		if (is_mbpf_pseudo_call(meta))
+			br_idx -= meta->num_insns_after_br;
+
 		if (!nfp_is_br(nfp_prog->prog[br_idx])) {
 			pr_err("Fixup found block not ending in branch %d %02x %016llx!!\n",
 			       br_idx, meta->insn.code, nfp_prog->prog[br_idx]);
 			return -ELOOP;
 		}
+
+		if (meta->insn.code == (BPF_JMP | BPF_EXIT))
+			continue;
+
 		/* Leave special branches for later */
 		if (FIELD_GET(OP_RELO_TYPE, nfp_prog->prog[br_idx]) !=
-		    RELO_BR_REL)
+		    RELO_BR_REL && !is_mbpf_pseudo_call(meta))
 			continue;
 
 		if (!meta->jmp_dst) {
@@ -3241,6 +3436,18 @@ static int nfp_fixup_branches(struct nfp_prog *nfp_prog)
 			return -ELOOP;
 		}
 
+		if (is_mbpf_pseudo_call(meta) &&
+		    nfp_prog->subprog[jmp_dst->subprog_idx].needs_reg_push) {
+			err = nfp_fixup_immed_relo(nfp_prog, meta,
+						   jmp_dst, br_idx);
+			if (err)
+				return err;
+		}
+
+		if (FIELD_GET(OP_RELO_TYPE, nfp_prog->prog[br_idx]) !=
+		    RELO_BR_REL)
+			continue;
+
 		for (idx = meta->off; idx <= br_idx; idx++) {
 			if (!nfp_is_br(nfp_prog->prog[idx]))
 				continue;
@@ -3258,6 +3465,27 @@ static void nfp_intro(struct nfp_prog *nfp_prog)
 		 plen_reg(nfp_prog), ALU_OP_AND, pv_len(nfp_prog));
 }
 
+static void
+nfp_subprog_prologue(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	/* Save return address into the stack. */
+	wrp_mov(nfp_prog, reg_lm(0, 0), ret_reg(nfp_prog));
+}
+
+static void
+nfp_start_subprog(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	unsigned int depth = nfp_prog->subprog[meta->subprog_idx].stack_depth;
+
+	nfp_prog->stack_frame_depth = round_up(depth, 4);
+	nfp_subprog_prologue(nfp_prog, meta);
+}
+
+bool nfp_is_subprog_start(struct nfp_insn_meta *meta)
+{
+	return meta->flags & FLAG_INSN_IS_SUBPROG_START;
+}
+
 static void nfp_outro_tc_da(struct nfp_prog *nfp_prog)
 {
 	/* TC direct-action mode:
@@ -3348,6 +3576,67 @@ static void nfp_outro_xdp(struct nfp_prog *nfp_prog)
 	emit_ld_field(nfp_prog, reg_a(0), 0xc, reg_b(2), SHF_SC_L_SHF, 16);
 }
 
+static bool nfp_prog_needs_callee_reg_save(struct nfp_prog *nfp_prog)
+{
+	unsigned int idx;
+
+	for (idx = 1; idx < nfp_prog->subprog_cnt; idx++)
+		if (nfp_prog->subprog[idx].needs_reg_push)
+			return true;
+
+	return false;
+}
+
+static void nfp_push_callee_registers(struct nfp_prog *nfp_prog)
+{
+	u8 reg;
+
+	/* Subroutine: Save all callee saved registers (R6 ~ R9).
+	 * imm_b() holds the return address.
+	 */
+	nfp_prog->tgt_call_push_regs = nfp_prog_current_offset(nfp_prog);
+	for (reg = BPF_REG_6; reg <= BPF_REG_9; reg++) {
+		u8 adj = (reg - BPF_REG_0) * 2;
+		u8 idx = (reg - BPF_REG_6) * 2;
+
+		/* The first slot in the stack frame is used to push the return
+		 * address in bpf_to_bpf_call(), start just after.
+		 */
+		wrp_mov(nfp_prog, reg_lm(0, 1 + idx), reg_b(adj));
+
+		if (reg == BPF_REG_8)
+			/* Prepare to jump back, last 3 insns use defer slots */
+			emit_rtn(nfp_prog, imm_b(nfp_prog), 3);
+
+		wrp_mov(nfp_prog, reg_lm(0, 1 + idx + 1), reg_b(adj + 1));
+	}
+}
+
+static void nfp_pop_callee_registers(struct nfp_prog *nfp_prog)
+{
+	u8 reg;
+
+	/* Subroutine: Restore all callee saved registers (R6 ~ R9).
+	 * ret_reg() holds the return address.
+	 */
+	nfp_prog->tgt_call_pop_regs = nfp_prog_current_offset(nfp_prog);
+	for (reg = BPF_REG_6; reg <= BPF_REG_9; reg++) {
+		u8 adj = (reg - BPF_REG_0) * 2;
+		u8 idx = (reg - BPF_REG_6) * 2;
+
+		/* The first slot in the stack frame holds the return address,
+		 * start popping just after that.
+		 */
+		wrp_mov(nfp_prog, reg_both(adj), reg_lm(0, 1 + idx));
+
+		if (reg == BPF_REG_8)
+			/* Prepare to jump back, last 3 insns use defer slots */
+			emit_rtn(nfp_prog, ret_reg(nfp_prog), 3);
+
+		wrp_mov(nfp_prog, reg_both(adj + 1), reg_lm(0, 1 + idx + 1));
+	}
+}
+
 static void nfp_outro(struct nfp_prog *nfp_prog)
 {
 	switch (nfp_prog->type) {
@@ -3360,13 +3649,23 @@ static void nfp_outro(struct nfp_prog *nfp_prog)
 	default:
 		WARN_ON(1);
 	}
+
+	if (!nfp_prog_needs_callee_reg_save(nfp_prog))
+		return;
+
+	nfp_push_callee_registers(nfp_prog);
+	nfp_pop_callee_registers(nfp_prog);
 }
 
 static int nfp_translate(struct nfp_prog *nfp_prog)
 {
 	struct nfp_insn_meta *meta;
+	unsigned int depth;
 	int err;
 
+	depth = nfp_prog->subprog[0].stack_depth;
+	nfp_prog->stack_frame_depth = round_up(depth, 4);
+
 	nfp_intro(nfp_prog);
 	if (nfp_prog->error)
 		return nfp_prog->error;
@@ -3376,6 +3675,12 @@ static int nfp_translate(struct nfp_prog *nfp_prog)
 
 		meta->off = nfp_prog_current_offset(nfp_prog);
 
+		if (nfp_is_subprog_start(meta)) {
+			nfp_start_subprog(nfp_prog, meta);
+			if (nfp_prog->error)
+				return nfp_prog->error;
+		}
+
 		if (meta->skip) {
 			nfp_prog->n_translated++;
 			continue;
@@ -4018,20 +4323,35 @@ void nfp_bpf_jit_prepare(struct nfp_prog *nfp_prog, unsigned int cnt)
 
 	/* Another pass to record jump information. */
 	list_for_each_entry(meta, &nfp_prog->insns, l) {
+		struct nfp_insn_meta *dst_meta;
 		u64 code = meta->insn.code;
+		unsigned int dst_idx;
+		bool pseudo_call;
+
+		if (BPF_CLASS(code) != BPF_JMP)
+			continue;
+		if (BPF_OP(code) == BPF_EXIT)
+			continue;
+		if (is_mbpf_helper_call(meta))
+			continue;
 
-		if (BPF_CLASS(code) == BPF_JMP && BPF_OP(code) != BPF_EXIT &&
-		    BPF_OP(code) != BPF_CALL) {
-			struct nfp_insn_meta *dst_meta;
-			unsigned short dst_indx;
+		/* If opcode is BPF_CALL at this point, this can only be a
+		 * BPF-to-BPF call (a.k.a pseudo call).
+		 */
+		pseudo_call = BPF_OP(code) == BPF_CALL;
 
-			dst_indx = meta->n + 1 + meta->insn.off;
-			dst_meta = nfp_bpf_goto_meta(nfp_prog, meta, dst_indx,
-						     cnt);
+		if (pseudo_call)
+			dst_idx = meta->n + 1 + meta->insn.imm;
+		else
+			dst_idx = meta->n + 1 + meta->insn.off;
 
-			meta->jmp_dst = dst_meta;
-			dst_meta->flags |= FLAG_INSN_IS_JUMP_DST;
-		}
+		dst_meta = nfp_bpf_goto_meta(nfp_prog, meta, dst_idx, cnt);
+
+		if (pseudo_call)
+			dst_meta->flags |= FLAG_INSN_IS_SUBPROG_START;
+
+		dst_meta->flags |= FLAG_INSN_IS_JUMP_DST;
+		meta->jmp_dst = dst_meta;
 	}
 }
 
@@ -4054,6 +4374,7 @@ void *nfp_bpf_relo_for_vnic(struct nfp_prog *nfp_prog, struct nfp_bpf_vnic *bv)
 	for (i = 0; i < nfp_prog->prog_len; i++) {
 		enum nfp_relo_type special;
 		u32 val;
+		u16 off;
 
 		special = FIELD_GET(OP_RELO_TYPE, prog[i]);
 		switch (special) {
@@ -4070,6 +4391,24 @@ void *nfp_bpf_relo_for_vnic(struct nfp_prog *nfp_prog, struct nfp_bpf_vnic *bv)
 			br_set_offset(&prog[i],
 				      nfp_prog->tgt_abort + bv->start_off);
 			break;
+		case RELO_BR_GO_CALL_PUSH_REGS:
+			if (!nfp_prog->tgt_call_push_regs) {
+				pr_err("BUG: failed to detect subprogram registers needs\n");
+				err = -EINVAL;
+				goto err_free_prog;
+			}
+			off = nfp_prog->tgt_call_push_regs + bv->start_off;
+			br_set_offset(&prog[i], off);
+			break;
+		case RELO_BR_GO_CALL_POP_REGS:
+			if (!nfp_prog->tgt_call_pop_regs) {
+				pr_err("BUG: failed to detect subprogram registers needs\n");
+				err = -EINVAL;
+				goto err_free_prog;
+			}
+			off = nfp_prog->tgt_call_pop_regs + bv->start_off;
+			br_set_offset(&prog[i], off);
+			break;
 		case RELO_BR_NEXT_PKT:
 			br_set_offset(&prog[i], bv->tgt_done);
 			break;

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

@@ -61,6 +61,8 @@ enum nfp_relo_type {
 	/* internal jumps to parts of the outro */
 	RELO_BR_GO_OUT,
 	RELO_BR_GO_ABORT,
+	RELO_BR_GO_CALL_PUSH_REGS,
+	RELO_BR_GO_CALL_POP_REGS,
 	/* external jumps to fixed addresses */
 	RELO_BR_NEXT_PKT,
 	RELO_BR_HELPER,
@@ -104,6 +106,7 @@ enum pkt_vec {
 #define imma_a(np)	reg_a(STATIC_REG_IMMA)
 #define imma_b(np)	reg_b(STATIC_REG_IMMA)
 #define imm_both(np)	reg_both(STATIC_REG_IMM)
+#define ret_reg(np)	imm_a(np)
 
 #define NFP_BPF_ABI_FLAGS	reg_imm(0)
 #define   NFP_BPF_ABI_FLAG_MARK	1
@@ -262,7 +265,9 @@ struct nfp_bpf_reg_state {
 	bool var_off;
 };
 
-#define FLAG_INSN_IS_JUMP_DST	BIT(0)
+#define FLAG_INSN_IS_JUMP_DST			BIT(0)
+#define FLAG_INSN_IS_SUBPROG_START		BIT(1)
+#define FLAG_INSN_PTR_CALLER_STACK_FRAME	BIT(2)
 
 /**
  * struct nfp_insn_meta - BPF instruction wrapper
@@ -279,6 +284,7 @@ struct nfp_bpf_reg_state {
  * @xadd_maybe_16bit: 16bit immediate is possible
  * @jmp_dst: destination info for jump instructions
  * @jump_neg_op: jump instruction has inverted immediate, use ADD instead of SUB
+ * @num_insns_after_br: number of insns following a branch jump, used for fixup
  * @func_id: function id for call instructions
  * @arg1: arg1 for call instructions
  * @arg2: arg2 for call instructions
@@ -289,6 +295,7 @@ struct nfp_bpf_reg_state {
  * @off: index of first generated machine instruction (in nfp_prog.prog)
  * @n: eBPF instruction number
  * @flags: eBPF instruction extra optimization flags
+ * @subprog_idx: index of subprogram to which the instruction belongs
  * @skip: skip this instruction (optimized out)
  * @double_cb: callback for second part of the instruction
  * @l: link on nfp_prog->insns list
@@ -314,6 +321,7 @@ struct nfp_insn_meta {
 		struct {
 			struct nfp_insn_meta *jmp_dst;
 			bool jump_neg_op;
+			u32 num_insns_after_br; /* only for BPF-to-BPF calls */
 		};
 		/* function calls */
 		struct {
@@ -335,6 +343,7 @@ struct nfp_insn_meta {
 	unsigned int off;
 	unsigned short n;
 	unsigned short flags;
+	unsigned short subprog_idx;
 	bool skip;
 	instr_cb_t double_cb;
 
@@ -423,6 +432,34 @@ static inline bool is_mbpf_div(const struct nfp_insn_meta *meta)
 	return is_mbpf_alu(meta) && mbpf_op(meta) == BPF_DIV;
 }
 
+static inline bool is_mbpf_helper_call(const struct nfp_insn_meta *meta)
+{
+	struct bpf_insn insn = meta->insn;
+
+	return insn.code == (BPF_JMP | BPF_CALL) &&
+		insn.src_reg != BPF_PSEUDO_CALL;
+}
+
+static inline bool is_mbpf_pseudo_call(const struct nfp_insn_meta *meta)
+{
+	struct bpf_insn insn = meta->insn;
+
+	return insn.code == (BPF_JMP | BPF_CALL) &&
+		insn.src_reg == BPF_PSEUDO_CALL;
+}
+
+#define STACK_FRAME_ALIGN 64
+
+/**
+ * struct nfp_bpf_subprog_info - nfp BPF sub-program (a.k.a. function) info
+ * @stack_depth:	maximum stack depth used by this sub-program
+ * @needs_reg_push:	whether sub-program uses callee-saved registers
+ */
+struct nfp_bpf_subprog_info {
+	u16 stack_depth;
+	u8 needs_reg_push : 1;
+};
+
 /**
  * struct nfp_prog - nfp BPF program
  * @bpf: backpointer to the bpf app priv structure
@@ -434,12 +471,16 @@ static inline bool is_mbpf_div(const struct nfp_insn_meta *meta)
  * @last_bpf_off: address of the last instruction translated from BPF
  * @tgt_out: jump target for normal exit
  * @tgt_abort: jump target for abort (e.g. access outside of packet buffer)
+ * @tgt_call_push_regs: jump target for subroutine for saving R6~R9 to stack
+ * @tgt_call_pop_regs: jump target for subroutine used for restoring R6~R9
  * @n_translated: number of successfully translated instructions (for errors)
  * @error: error code if something went wrong
- * @stack_depth: max stack depth from the verifier
+ * @stack_frame_depth: max stack depth for current frame
  * @adjust_head_location: if program has single adjust head call - the insn no.
  * @map_records_cnt: the number of map pointers recorded for this prog
+ * @subprog_cnt: number of sub-programs, including main function
  * @map_records: the map record pointers from bpf->maps_neutral
+ * @subprog: pointer to an array of objects holding info about sub-programs
  * @insns: list of BPF instruction wrappers (struct nfp_insn_meta)
  */
 struct nfp_prog {
@@ -456,15 +497,19 @@ struct nfp_prog {
 	unsigned int last_bpf_off;
 	unsigned int tgt_out;
 	unsigned int tgt_abort;
+	unsigned int tgt_call_push_regs;
+	unsigned int tgt_call_pop_regs;
 
 	unsigned int n_translated;
 	int error;
 
-	unsigned int stack_depth;
+	unsigned int stack_frame_depth;
 	unsigned int adjust_head_location;
 
 	unsigned int map_records_cnt;
+	unsigned int subprog_cnt;
 	struct nfp_bpf_neutral_map **map_records;
+	struct nfp_bpf_subprog_info *subprog;
 
 	struct list_head insns;
 };
@@ -481,6 +526,7 @@ struct nfp_bpf_vnic {
 	unsigned int tgt_done;
 };
 
+bool nfp_is_subprog_start(struct nfp_insn_meta *meta);
 void nfp_bpf_jit_prepare(struct nfp_prog *nfp_prog, unsigned int cnt);
 int nfp_bpf_jit(struct nfp_prog *prog);
 bool nfp_bpf_supported_opcode(u8 code);

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

@@ -208,6 +208,8 @@ static void nfp_prog_free(struct nfp_prog *nfp_prog)
 {
 	struct nfp_insn_meta *meta, *tmp;
 
+	kfree(nfp_prog->subprog);
+
 	list_for_each_entry_safe(meta, tmp, &nfp_prog->insns, l) {
 		list_del(&meta->l);
 		kfree(meta);
@@ -250,18 +252,9 @@ nfp_bpf_verifier_prep(struct nfp_app *app, struct nfp_net *nn,
 static int nfp_bpf_translate(struct nfp_net *nn, struct bpf_prog *prog)
 {
 	struct nfp_prog *nfp_prog = prog->aux->offload->dev_priv;
-	unsigned int stack_size;
 	unsigned int max_instr;
 	int err;
 
-	stack_size = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
-	if (prog->aux->stack_depth > stack_size) {
-		nn_info(nn, "stack too large: program %dB > FW stack %dB\n",
-			prog->aux->stack_depth, stack_size);
-		return -EOPNOTSUPP;
-	}
-	nfp_prog->stack_depth = round_up(prog->aux->stack_depth, 4);
-
 	max_instr = nn_readw(nn, NFP_NET_CFG_BPF_MAX_LEN);
 	nfp_prog->__prog_alloc_len = max_instr * sizeof(u64);
 

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

@@ -34,10 +34,12 @@
 #include <linux/bpf.h>
 #include <linux/bpf_verifier.h>
 #include <linux/kernel.h>
+#include <linux/netdevice.h>
 #include <linux/pkt_cls.h>
 
 #include "../nfp_app.h"
 #include "../nfp_main.h"
+#include "../nfp_net.h"
 #include "fw.h"
 #include "main.h"
 
@@ -155,8 +157,9 @@ nfp_bpf_map_call_ok(const char *fname, struct bpf_verifier_env *env,
 }
 
 static int
-nfp_bpf_check_call(struct nfp_prog *nfp_prog, struct bpf_verifier_env *env,
-		   struct nfp_insn_meta *meta)
+nfp_bpf_check_helper_call(struct nfp_prog *nfp_prog,
+			  struct bpf_verifier_env *env,
+			  struct nfp_insn_meta *meta)
 {
 	const struct bpf_reg_state *reg1 = cur_regs(env) + BPF_REG_1;
 	const struct bpf_reg_state *reg2 = cur_regs(env) + BPF_REG_2;
@@ -333,6 +336,9 @@ nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
 {
 	s32 old_off, new_off;
 
+	if (reg->frameno != env->cur_state->curframe)
+		meta->flags |= FLAG_INSN_PTR_CALLER_STACK_FRAME;
+
 	if (!tnum_is_const(reg->var_off)) {
 		pr_vlog(env, "variable ptr stack access\n");
 		return -EINVAL;
@@ -620,8 +626,8 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 		return -EINVAL;
 	}
 
-	if (meta->insn.code == (BPF_JMP | BPF_CALL))
-		return nfp_bpf_check_call(nfp_prog, env, meta);
+	if (is_mbpf_helper_call(meta))
+		return nfp_bpf_check_helper_call(nfp_prog, env, meta);
 	if (meta->insn.code == (BPF_JMP | BPF_EXIT))
 		return nfp_bpf_check_exit(nfp_prog, env);
 
@@ -640,6 +646,131 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 	return 0;
 }
 
+static int
+nfp_assign_subprog_idx_and_regs(struct bpf_verifier_env *env,
+				struct nfp_prog *nfp_prog)
+{
+	struct nfp_insn_meta *meta;
+	int index = 0;
+
+	list_for_each_entry(meta, &nfp_prog->insns, l) {
+		if (nfp_is_subprog_start(meta))
+			index++;
+		meta->subprog_idx = index;
+
+		if (meta->insn.dst_reg >= BPF_REG_6 &&
+		    meta->insn.dst_reg <= BPF_REG_9)
+			nfp_prog->subprog[index].needs_reg_push = 1;
+	}
+
+	if (index + 1 != nfp_prog->subprog_cnt) {
+		pr_vlog(env, "BUG: number of processed BPF functions is not consistent (processed %d, expected %d)\n",
+			index + 1, nfp_prog->subprog_cnt);
+		return -EFAULT;
+	}
+
+	return 0;
+}
+
+static unsigned int
+nfp_bpf_get_stack_usage(struct nfp_prog *nfp_prog, unsigned int cnt)
+{
+	struct nfp_insn_meta *meta = nfp_prog_first_meta(nfp_prog);
+	unsigned int max_depth = 0, depth = 0, frame = 0;
+	struct nfp_insn_meta *ret_insn[MAX_CALL_FRAMES];
+	unsigned short frame_depths[MAX_CALL_FRAMES];
+	unsigned short ret_prog[MAX_CALL_FRAMES];
+	unsigned short idx = meta->subprog_idx;
+
+	/* Inspired from check_max_stack_depth() from kernel verifier.
+	 * Starting from main subprogram, walk all instructions and recursively
+	 * walk all callees that given subprogram can call. Since recursion is
+	 * prevented by the kernel verifier, this algorithm only needs a local
+	 * stack of MAX_CALL_FRAMES to remember callsites.
+	 */
+process_subprog:
+	frame_depths[frame] = nfp_prog->subprog[idx].stack_depth;
+	frame_depths[frame] = round_up(frame_depths[frame], STACK_FRAME_ALIGN);
+	depth += frame_depths[frame];
+	max_depth = max(max_depth, depth);
+
+continue_subprog:
+	for (; meta != nfp_prog_last_meta(nfp_prog) && meta->subprog_idx == idx;
+	     meta = nfp_meta_next(meta)) {
+		if (!is_mbpf_pseudo_call(meta))
+			continue;
+
+		/* We found a call to a subprogram. Remember instruction to
+		 * return to and subprog id.
+		 */
+		ret_insn[frame] = nfp_meta_next(meta);
+		ret_prog[frame] = idx;
+
+		/* Find the callee and start processing it. */
+		meta = nfp_bpf_goto_meta(nfp_prog, meta,
+					 meta->n + 1 + meta->insn.imm, cnt);
+		idx = meta->subprog_idx;
+		frame++;
+		goto process_subprog;
+	}
+	/* End of for() loop means the last instruction of the subprog was
+	 * reached. If we popped all stack frames, return; otherwise, go on
+	 * processing remaining instructions from the caller.
+	 */
+	if (frame == 0)
+		return max_depth;
+
+	depth -= frame_depths[frame];
+	frame--;
+	meta = ret_insn[frame];
+	idx = ret_prog[frame];
+	goto continue_subprog;
+}
+
+static int nfp_bpf_finalize(struct bpf_verifier_env *env)
+{
+	unsigned int stack_size, stack_needed;
+	struct bpf_subprog_info *info;
+	struct nfp_prog *nfp_prog;
+	struct nfp_net *nn;
+	int i;
+
+	nfp_prog = env->prog->aux->offload->dev_priv;
+	nfp_prog->subprog_cnt = env->subprog_cnt;
+	nfp_prog->subprog = kcalloc(nfp_prog->subprog_cnt,
+				    sizeof(nfp_prog->subprog[0]), GFP_KERNEL);
+	if (!nfp_prog->subprog)
+		return -ENOMEM;
+
+	nfp_assign_subprog_idx_and_regs(env, nfp_prog);
+
+	info = env->subprog_info;
+	for (i = 0; i < nfp_prog->subprog_cnt; i++) {
+		nfp_prog->subprog[i].stack_depth = info[i].stack_depth;
+
+		if (i == 0)
+			continue;
+
+		/* Account for size of return address. */
+		nfp_prog->subprog[i].stack_depth += REG_WIDTH;
+		/* Account for size of saved registers, if necessary. */
+		if (nfp_prog->subprog[i].needs_reg_push)
+			nfp_prog->subprog[i].stack_depth += BPF_REG_SIZE * 4;
+	}
+
+	nn = netdev_priv(env->prog->aux->offload->netdev);
+	stack_size = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
+	stack_needed = nfp_bpf_get_stack_usage(nfp_prog, env->prog->len);
+	if (stack_needed > stack_size) {
+		pr_vlog(env, "stack too large: program %dB > FW stack %dB\n",
+			stack_needed, stack_size);
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
 const struct bpf_prog_offload_ops nfp_bpf_analyzer_ops = {
-	.insn_hook = nfp_verify_insn,
+	.insn_hook	= nfp_verify_insn,
+	.finalize	= nfp_bpf_finalize,
 };

drivers/net/ethernet/netronome/nfp/nfp_asm.h

@@ -82,6 +82,15 @@
 #define OP_BR_BIT_ADDR_LO	OP_BR_ADDR_LO
 #define OP_BR_BIT_ADDR_HI	OP_BR_ADDR_HI
 
+#define OP_BR_ALU_BASE		0x0e800000000ULL
+#define OP_BR_ALU_BASE_MASK	0x0ff80000000ULL
+#define OP_BR_ALU_A_SRC		0x000000003ffULL
+#define OP_BR_ALU_B_SRC		0x000000ffc00ULL
+#define OP_BR_ALU_DEFBR		0x00000300000ULL
+#define OP_BR_ALU_IMM_HI	0x0007fc00000ULL
+#define OP_BR_ALU_SRC_LMEXTN	0x40000000000ULL
+#define OP_BR_ALU_DST_LMEXTN	0x80000000000ULL
+
 static inline bool nfp_is_br(u64 insn)
 {
 	return (insn & OP_BR_BASE_MASK) == OP_BR_BASE ||

drivers/net/netdevsim/bpf.c

@@ -86,8 +86,14 @@ nsim_bpf_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn)
 	return 0;
 }
 
+static int nsim_bpf_finalize(struct bpf_verifier_env *env)
+{
+	return 0;
+}
+
 static const struct bpf_prog_offload_ops nsim_bpf_analyzer_ops = {
-	.insn_hook = nsim_bpf_verify_insn,
+	.insn_hook	= nsim_bpf_verify_insn,
+	.finalize	= nsim_bpf_finalize,
 };
 
 static bool nsim_xdp_offload_active(struct netdevsim *ns)

include/linux/bpf.h

@@ -263,6 +263,7 @@ struct bpf_verifier_ops {
 struct bpf_prog_offload_ops {
 	int (*insn_hook)(struct bpf_verifier_env *env,
 			 int insn_idx, int prev_insn_idx);
+	int (*finalize)(struct bpf_verifier_env *env);
 };
 
 struct bpf_prog_offload {

include/linux/bpf_verifier.h

@@ -245,5 +245,6 @@ static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
 				 int insn_idx, int prev_insn_idx);
+int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
 
 #endif /* _LINUX_BPF_VERIFIER_H */

kernel/bpf/offload.c

@@ -172,6 +172,24 @@ int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
 	return ret;
 }
 
+int bpf_prog_offload_finalize(struct bpf_verifier_env *env)
+{
+	struct bpf_prog_offload *offload;
+	int ret = -ENODEV;
+
+	down_read(&bpf_devs_lock);
+	offload = env->prog->aux->offload;
+	if (offload) {
+		if (offload->dev_ops->finalize)
+			ret = offload->dev_ops->finalize(env);
+		else
+			ret = 0;
+	}
+	up_read(&bpf_devs_lock);
+
+	return ret;
+}
+
 static void __bpf_prog_offload_destroy(struct bpf_prog *prog)
 {
 	struct bpf_prog_offload *offload = prog->aux->offload;

kernel/bpf/verifier.c

@@ -1009,10 +1009,6 @@ static int check_subprogs(struct bpf_verifier_env *env)
 			verbose(env, "function calls to other bpf functions are allowed for root only\n");
 			return -EPERM;
 		}
-		if (bpf_prog_is_dev_bound(env->prog->aux)) {
-			verbose(env, "function calls in offloaded programs are not supported yet\n");
-			return -EINVAL;
-		}
 		ret = add_subprog(env, i + insn[i].imm + 1);
 		if (ret < 0)
 			return ret;
@@ -5968,10 +5964,10 @@ static int fixup_call_args(struct bpf_verifier_env *env)
 	struct bpf_insn *insn = prog->insnsi;
 	int i, depth;
 #endif
-	int err;
+	int err = 0;
 
-	err = 0;
-	if (env->prog->jit_requested) {
+	if (env->prog->jit_requested &&
+	    !bpf_prog_is_dev_bound(env->prog->aux)) {
 		err = jit_subprogs(env);
 		if (err == 0)
 			return 0;
@@ -6309,6 +6305,9 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
 		env->cur_state = NULL;
 	}
 
+	if (ret == 0 && bpf_prog_is_dev_bound(env->prog->aux))
+		ret = bpf_prog_offload_finalize(env);
+
 skip_full_check:
 	while (!pop_stack(env, NULL, NULL));
 	free_states(env);