MIPS: eBPF: Initial eBPF support for MIPS32 architecture.

Currently MIPS32 supports a JIT for classic BPF only, not extended BPF.
This patch adds JIT support for extended BPF on MIPS32, so code is
actually JIT'ed instead of being only interpreted. Instructions with
64-bit operands are not supported at this point.
We can delete classic BPF because the kernel will translate classic BPF
programs into extended BPF and JIT them, eliminating the need for
classic BPF.
Signed-off-by: Hassan Naveed <hnaveed@wavecomp.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: kafai@fb.com
Cc: songliubraving@fb.com
Cc: yhs@fb.com
Cc: netdev@vger.kernel.org
Cc: bpf@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: open list:MIPS <linux-mips@linux-mips.org>
Cc: open list <linux-kernel@vger.kernel.org>

arch/mips/Kconfig

@@ -44,8 +44,7 @@ config MIPS
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
-	select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
-	select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
+	select HAVE_EBPF_JIT if (!CPU_MICROMIPS)
 	select HAVE_CONTEXT_TRACKING
 	select HAVE_COPY_THREAD_TLS
 	select HAVE_C_RECORDMCOUNT

arch/mips/net/Makefile

 # MIPS networking code
 
-obj-$(CONFIG_MIPS_CBPF_JIT) += bpf_jit.o bpf_jit_asm.o
 obj-$(CONFIG_MIPS_EBPF_JIT) += ebpf_jit.o

arch/mips/net/bpf_jit_asm.S

-/*
- * bpf_jib_asm.S: Packet/header access helper functions for MIPS/MIPS64 BPF
- * compiler.
- *
- * Copyright (C) 2015 Imagination Technologies Ltd.
- * Author: Markos Chandras <markos.chandras@imgtec.com>
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the
- * Free Software Foundation; version 2 of the License.
- */
-
-#include <asm/asm.h>
-#include <asm/isa-rev.h>
-#include <asm/regdef.h>
-#include "bpf_jit.h"
-
-/* ABI
- *
- * r_skb_hl	skb header length
- * r_skb_data	skb data
- * r_off(a1)	offset register
- * r_A		BPF register A
- * r_X		PF register X
- * r_skb(a0)	*skb
- * r_M		*scratch memory
- * r_skb_le	skb length
- * r_s0		Scratch register 0
- * r_s1		Scratch register 1
- *
- * On entry:
- * a0: *skb
- * a1: offset (imm or imm + X)
- *
- * All non-BPF-ABI registers are free for use. On return, we only
- * care about r_ret. The BPF-ABI registers are assumed to remain
- * unmodified during the entire filter operation.
- */
-
-#define skb	a0
-#define offset	a1
-#define SKF_LL_OFF  (-0x200000) /* Can't include linux/filter.h in assembly */
-
-	/* We know better :) so prevent assembler reordering etc */
-	.set 	noreorder
-
-#define is_offset_negative(TYPE)				\
-	/* If offset is negative we have more work to do */	\
-	slti	t0, offset, 0;					\
-	bgtz	t0, bpf_slow_path_##TYPE##_neg;			\
-	/* Be careful what follows in DS. */
-
-#define is_offset_in_header(SIZE, TYPE)				\
-	/* Reading from header? */				\
-	addiu	$r_s0, $r_skb_hl, -SIZE;			\
-	slt	t0, $r_s0, offset;				\
-	bgtz	t0, bpf_slow_path_##TYPE;			\
-
-LEAF(sk_load_word)
-	is_offset_negative(word)
-FEXPORT(sk_load_word_positive)
-	is_offset_in_header(4, word)
-	/* Offset within header boundaries */
-	PTR_ADDU t1, $r_skb_data, offset
-	.set	reorder
-	lw	$r_A, 0(t1)
-	.set	noreorder
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-# if MIPS_ISA_REV >= 2
-	wsbh	t0, $r_A
-	rotr	$r_A, t0, 16
-# else
-	sll	t0, $r_A, 24
-	srl	t1, $r_A, 24
-	srl	t2, $r_A, 8
-	or	t0, t0, t1
-	andi	t2, t2, 0xff00
-	andi	t1, $r_A, 0xff00
-	or	t0, t0, t2
-	sll	t1, t1, 8
-	or	$r_A, t0, t1
-# endif
-#endif
-	jr	$r_ra
-	 move	$r_ret, zero
-	END(sk_load_word)
-
-LEAF(sk_load_half)
-	is_offset_negative(half)
-FEXPORT(sk_load_half_positive)
-	is_offset_in_header(2, half)
-	/* Offset within header boundaries */
-	PTR_ADDU t1, $r_skb_data, offset
-	lhu	$r_A, 0(t1)
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-# if MIPS_ISA_REV >= 2
-	wsbh	$r_A, $r_A
-# else
-	sll	t0, $r_A, 8
-	srl	t1, $r_A, 8
-	andi	t0, t0, 0xff00
-	or	$r_A, t0, t1
-# endif
-#endif
-	jr	$r_ra
-	 move	$r_ret, zero
-	END(sk_load_half)
-
-LEAF(sk_load_byte)
-	is_offset_negative(byte)
-FEXPORT(sk_load_byte_positive)
-	is_offset_in_header(1, byte)
-	/* Offset within header boundaries */
-	PTR_ADDU t1, $r_skb_data, offset
-	lbu	$r_A, 0(t1)
-	jr	$r_ra
-	 move	$r_ret, zero
-	END(sk_load_byte)
-
-/*
- * call skb_copy_bits:
- * (prototype in linux/skbuff.h)
- *
- * int skb_copy_bits(sk_buff *skb, int offset, void *to, int len)
- *
- * o32 mandates we leave 4 spaces for argument registers in case
- * the callee needs to use them. Even though we don't care about
- * the argument registers ourselves, we need to allocate that space
- * to remain ABI compliant since the callee may want to use that space.
- * We also allocate 2 more spaces for $r_ra and our return register (*to).
- *
- * n64 is a bit different. The *caller* will allocate the space to preserve
- * the arguments. So in 64-bit kernels, we allocate the 4-arg space for no
- * good reason but it does not matter that much really.
- *
- * (void *to) is returned in r_s0
- *
- */
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-#define DS_OFFSET(SIZE) (4 * SZREG)
-#else
-#define DS_OFFSET(SIZE) ((4 * SZREG) + (4 - SIZE))
-#endif
-#define bpf_slow_path_common(SIZE)				\
-	/* Quick check. Are we within reasonable boundaries? */ \
-	LONG_ADDIU	$r_s1, $r_skb_len, -SIZE;		\
-	sltu		$r_s0, offset, $r_s1;			\
-	beqz		$r_s0, fault;				\
-	/* Load 4th argument in DS */				\
-	 LONG_ADDIU	a3, zero, SIZE;				\
-	PTR_ADDIU	$r_sp, $r_sp, -(6 * SZREG);		\
-	PTR_LA		t0, skb_copy_bits;			\
-	PTR_S		$r_ra, (5 * SZREG)($r_sp);		\
-	/* Assign low slot to a2 */				\
-	PTR_ADDIU	a2, $r_sp, DS_OFFSET(SIZE);		\
-	jalr		t0;					\
-	/* Reset our destination slot (DS but it's ok) */	\
-	 INT_S		zero, (4 * SZREG)($r_sp);		\
-	/*							\
-	 * skb_copy_bits returns 0 on success and -EFAULT	\
-	 * on error. Our data live in a2. Do not bother with	\
-	 * our data if an error has been returned.		\
-	 */							\
-	/* Restore our frame */					\
-	PTR_L		$r_ra, (5 * SZREG)($r_sp);		\
-	INT_L		$r_s0, (4 * SZREG)($r_sp);		\
-	bltz		v0, fault;				\
-	 PTR_ADDIU	$r_sp, $r_sp, 6 * SZREG;		\
-	move		$r_ret, zero;				\
-
-NESTED(bpf_slow_path_word, (6 * SZREG), $r_sp)
-	bpf_slow_path_common(4)
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-# if MIPS_ISA_REV >= 2
-	wsbh	t0, $r_s0
-	jr	$r_ra
-	 rotr	$r_A, t0, 16
-# else
-	sll	t0, $r_s0, 24
-	srl	t1, $r_s0, 24
-	srl	t2, $r_s0, 8
-	or	t0, t0, t1
-	andi	t2, t2, 0xff00
-	andi	t1, $r_s0, 0xff00
-	or	t0, t0, t2
-	sll	t1, t1, 8
-	jr	$r_ra
-	 or	$r_A, t0, t1
-# endif
-#else
-	jr	$r_ra
-	 move	$r_A, $r_s0
-#endif
-
-	END(bpf_slow_path_word)
-
-NESTED(bpf_slow_path_half, (6 * SZREG), $r_sp)
-	bpf_slow_path_common(2)
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-# if MIPS_ISA_REV >= 2
-	jr	$r_ra
-	 wsbh	$r_A, $r_s0
-# else
-	sll	t0, $r_s0, 8
-	andi	t1, $r_s0, 0xff00
-	andi	t0, t0, 0xff00
-	srl	t1, t1, 8
-	jr	$r_ra
-	 or	$r_A, t0, t1
-# endif
-#else
-	jr	$r_ra
-	 move	$r_A, $r_s0
-#endif
-
-	END(bpf_slow_path_half)
-
-NESTED(bpf_slow_path_byte, (6 * SZREG), $r_sp)
-	bpf_slow_path_common(1)
-	jr	$r_ra
-	 move	$r_A, $r_s0
-
-	END(bpf_slow_path_byte)
-
-/*
- * Negative entry points
- */
-	.macro bpf_is_end_of_data
-	li	t0, SKF_LL_OFF
-	/* Reading link layer data? */
-	slt	t1, offset, t0
-	bgtz	t1, fault
-	/* Be careful what follows in DS. */
-	.endm
-/*
- * call skb_copy_bits:
- * (prototype in linux/filter.h)
- *
- * void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb,
- *                                            int k, unsigned int size)
- *
- * see above (bpf_slow_path_common) for ABI restrictions
- */
-#define bpf_negative_common(SIZE)					\
-	PTR_ADDIU	$r_sp, $r_sp, -(6 * SZREG);			\
-	PTR_LA		t0, bpf_internal_load_pointer_neg_helper;	\
-	PTR_S		$r_ra, (5 * SZREG)($r_sp);			\
-	jalr		t0;						\
-	 li		a2, SIZE;					\
-	PTR_L		$r_ra, (5 * SZREG)($r_sp);			\
-	/* Check return pointer */					\
-	beqz		v0, fault;					\
-	 PTR_ADDIU	$r_sp, $r_sp, 6 * SZREG;			\
-	/* Preserve our pointer */					\
-	move		$r_s0, v0;					\
-	/* Set return value */						\
-	move		$r_ret, zero;					\
-
-bpf_slow_path_word_neg:
-	bpf_is_end_of_data
-NESTED(sk_load_word_negative, (6 * SZREG), $r_sp)
-	bpf_negative_common(4)
-	jr	$r_ra
-	 lw	$r_A, 0($r_s0)
-	END(sk_load_word_negative)
-
-bpf_slow_path_half_neg:
-	bpf_is_end_of_data
-NESTED(sk_load_half_negative, (6 * SZREG), $r_sp)
-	bpf_negative_common(2)
-	jr	$r_ra
-	 lhu	$r_A, 0($r_s0)
-	END(sk_load_half_negative)
-
-bpf_slow_path_byte_neg:
-	bpf_is_end_of_data
-NESTED(sk_load_byte_negative, (6 * SZREG), $r_sp)
-	bpf_negative_common(1)
-	jr	$r_ra
-	 lbu	$r_A, 0($r_s0)
-	END(sk_load_byte_negative)
-
-fault:
-	jr	$r_ra
-	 addiu $r_ret, zero, 1

arch/mips/net/ebpf_jit.c

@@ -126,15 +126,21 @@ static enum reg_val_type get_reg_val_type(const struct jit_ctx *ctx,
 }
 
 /* Simply emit the instruction if the JIT memory space has been allocated */
-#define emit_instr(ctx, func, ...)			\
+#define emit_instr_long(ctx, func64, func32, ...)		\
 do {								\
 	if ((ctx)->target != NULL) {				\
 		u32 *p = &(ctx)->target[ctx->idx];		\
-		uasm_i_##func(&p, ##__VA_ARGS__);	\
+		if (IS_ENABLED(CONFIG_64BIT))			\
+			uasm_i_##func64(&p, ##__VA_ARGS__);	\
+		else						\
+			uasm_i_##func32(&p, ##__VA_ARGS__);	\
 	}							\
 	(ctx)->idx++;						\
 } while (0)
 
+#define emit_instr(ctx, func, ...)				\
+	emit_instr_long(ctx, func, func, ##__VA_ARGS__)
+
 static unsigned int j_target(struct jit_ctx *ctx, int target_idx)
 {
 	unsigned long target_va, base_va;
@@ -274,17 +280,17 @@ static int gen_int_prologue(struct jit_ctx *ctx)
 		 * If RA we are doing a function call and may need
 		 * extra 8-byte tmp area.
 		 */
-		stack_adjust += 16;
+		stack_adjust += 2 * sizeof(long);
 	if (ctx->flags & EBPF_SAVE_S0)
-		stack_adjust += 8;
+		stack_adjust += sizeof(long);
 	if (ctx->flags & EBPF_SAVE_S1)
-		stack_adjust += 8;
+		stack_adjust += sizeof(long);
 	if (ctx->flags & EBPF_SAVE_S2)
-		stack_adjust += 8;
+		stack_adjust += sizeof(long);
 	if (ctx->flags & EBPF_SAVE_S3)
-		stack_adjust += 8;
+		stack_adjust += sizeof(long);
 	if (ctx->flags & EBPF_SAVE_S4)
-		stack_adjust += 8;
+		stack_adjust += sizeof(long);
 
 	BUILD_BUG_ON(MAX_BPF_STACK & 7);
 	locals_size = (ctx->flags & EBPF_SEEN_FP) ? MAX_BPF_STACK : 0;
@@ -298,41 +304,49 @@ static int gen_int_prologue(struct jit_ctx *ctx)
 	 * On tail call we skip this instruction, and the TCC is
 	 * passed in $v1 from the caller.
 	 */
-	emit_instr(ctx, daddiu, MIPS_R_V1, MIPS_R_ZERO, MAX_TAIL_CALL_CNT);
+	emit_instr(ctx, addiu, MIPS_R_V1, MIPS_R_ZERO, MAX_TAIL_CALL_CNT);
 	if (stack_adjust)
-		emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, -stack_adjust);
+		emit_instr_long(ctx, daddiu, addiu,
+					MIPS_R_SP, MIPS_R_SP, -stack_adjust);
 	else
 		return 0;
 
-	store_offset = stack_adjust - 8;
+	store_offset = stack_adjust - sizeof(long);
 
 	if (ctx->flags & EBPF_SAVE_RA) {
-		emit_instr(ctx, sd, MIPS_R_RA, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_RA, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S0) {
-		emit_instr(ctx, sd, MIPS_R_S0, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_S0, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S1) {
-		emit_instr(ctx, sd, MIPS_R_S1, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_S1, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S2) {
-		emit_instr(ctx, sd, MIPS_R_S2, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_S2, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S3) {
-		emit_instr(ctx, sd, MIPS_R_S3, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_S3, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S4) {
-		emit_instr(ctx, sd, MIPS_R_S4, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, sd, sw,
+					MIPS_R_S4, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 
 	if ((ctx->flags & EBPF_SEEN_TC) && !(ctx->flags & EBPF_TCC_IN_V1))
-		emit_instr(ctx, daddu, MIPS_R_S4, MIPS_R_V1, MIPS_R_ZERO);
+		emit_instr_long(ctx, daddu, addu,
+					MIPS_R_S4, MIPS_R_V1, MIPS_R_ZERO);
 
 	return 0;
 }
@@ -341,7 +355,7 @@ static int build_int_epilogue(struct jit_ctx *ctx, int dest_reg)
 {
 	const struct bpf_prog *prog = ctx->skf;
 	int stack_adjust = ctx->stack_size;
-	int store_offset = stack_adjust - 8;
+	int store_offset = stack_adjust - sizeof(long);
 	enum reg_val_type td;
 	int r0 = MIPS_R_V0;
 
@@ -353,33 +367,40 @@ static int build_int_epilogue(struct jit_ctx *ctx, int dest_reg)
 	}
 
 	if (ctx->flags & EBPF_SAVE_RA) {
-		emit_instr(ctx, ld, MIPS_R_RA, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+					MIPS_R_RA, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S0) {
-		emit_instr(ctx, ld, MIPS_R_S0, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+					MIPS_R_S0, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S1) {
-		emit_instr(ctx, ld, MIPS_R_S1, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+					MIPS_R_S1, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S2) {
-		emit_instr(ctx, ld, MIPS_R_S2, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+				MIPS_R_S2, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S3) {
-		emit_instr(ctx, ld, MIPS_R_S3, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+					MIPS_R_S3, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	if (ctx->flags & EBPF_SAVE_S4) {
-		emit_instr(ctx, ld, MIPS_R_S4, store_offset, MIPS_R_SP);
-		store_offset -= 8;
+		emit_instr_long(ctx, ld, lw,
+					MIPS_R_S4, store_offset, MIPS_R_SP);
+		store_offset -= sizeof(long);
 	}
 	emit_instr(ctx, jr, dest_reg);
 
 	if (stack_adjust)
-		emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, stack_adjust);
+		emit_instr_long(ctx, daddiu, addiu,
+					MIPS_R_SP, MIPS_R_SP, stack_adjust);
 	else
 		emit_instr(ctx, nop);
 
@@ -646,6 +667,10 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 	s64 t64s;
 	int bpf_op = BPF_OP(insn->code);
 
+	if (IS_ENABLED(CONFIG_32BIT) && ((BPF_CLASS(insn->code) == BPF_ALU64)
+						|| (bpf_op == BPF_DW)))
+		return -EINVAL;
+
 	switch (insn->code) {
 	case BPF_ALU64 | BPF_ADD | BPF_K: /* ALU64_IMM */
 	case BPF_ALU64 | BPF_SUB | BPF_K: /* ALU64_IMM */
@@ -1283,7 +1308,7 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 
 	case BPF_JMP | BPF_CALL:
 		ctx->flags |= EBPF_SAVE_RA;
-		t64s = (s64)insn->imm + (s64)__bpf_call_base;
+		t64s = (s64)insn->imm + (long)__bpf_call_base;
 		emit_const_to_reg(ctx, MIPS_R_T9, (u64)t64s);
 		emit_instr(ctx, jalr, MIPS_R_RA, MIPS_R_T9);
 		/* delay slot */