--- /dev/null
+/*
+ * 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)
+ .globl sk_load_word_positive
+sk_load_word_positive:
+ is_offset_in_header(4, word)
+ /* Offset within header boundaries */
+ PTR_ADDU t1, $r_skb_data, offset
+ lw $r_A, 0(t1)
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+ wsbh t0, $r_A
+ rotr $r_A, t0, 16
+#endif
+ jr $r_ra
+ move $r_ret, zero
+ END(sk_load_word)
+
+LEAF(sk_load_half)
+ is_offset_negative(half)
+ .globl sk_load_half_positive
+sk_load_half_positive:
+ is_offset_in_header(2, half)
+ /* Offset within header boundaries */
+ PTR_ADDU t1, $r_skb_data, offset
+ lh $r_A, 0(t1)
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+ wsbh t0, $r_A
+ seh $r_A, t0
+#endif
+ jr $r_ra
+ move $r_ret, zero
+ END(sk_load_half)
+
+LEAF(sk_load_byte)
+ is_offset_negative(byte)
+ .globl sk_load_byte_positive
+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
+ wsbh t0, $r_s0
+ jr $r_ra
+ rotr $r_A, t0, 16
+#endif
+ jr $r_ra
+ move $r_A, $r_s0
+
+ END(bpf_slow_path_word)
+
+NESTED(bpf_slow_path_half, (6 * SZREG), $r_sp)
+ bpf_slow_path_common(2)
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+ jr $r_ra
+ wsbh $r_A, $r_s0
+#endif
+ jr $r_ra
+ move $r_A, $r_s0
+
+ 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
projects / linux-drm-fsl-dcu.git / blobdiff