arch/mips/net/bpf_jit_asm.S - kernel/bruno - Git at Google

 /*
  * 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/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 defined(__mips_isa_rev) && (__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
 	.set	reorder
 	lh	$r_A, 0(t1)
 	.set	noreorder
 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 # if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
 	wsbh	t0, $r_A
 	seh	$r_A, t0
 # else
 	sll	t0, $r_A, 24
 	andi	t1, $r_A, 0xff00
 	sra	t0, t0, 16
 	srl	t1, t1, 8
 	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
 	lb	$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
  *
  */
 #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 */				\
 	move		a2, $r_sp;				\
 	jalr		t0;					\
 	/* Reset our destination slot (DS but it's ok) */	\
 	 INT_S		zero, (4 * SZREG)($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 defined(__mips_isa_rev) && (__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 defined(__mips_isa_rev) && (__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
	/*
	* 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/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 defined(__mips_isa_rev) && (__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
	.set reorder
	lh $r_A, 0(t1)
	.set noreorder
	#ifdef CONFIG_CPU_LITTLE_ENDIAN
	# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
	wsbh t0, $r_A
	seh $r_A, t0
	# else
	sll t0, $r_A, 24
	andi t1, $r_A, 0xff00
	sra t0, t0, 16
	srl t1, t1, 8
	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
	lb $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
	*
	*/
	#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 */ \
	move a2, $r_sp; \
	jalr t0; \
	/* Reset our destination slot (DS but it's ok) */ \
	INT_S zero, (4 * SZREG)($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 defined(__mips_isa_rev) && (__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 defined(__mips_isa_rev) && (__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