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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/x86/net/bpf_jit.S
Initial import
Diffstat (limited to 'arch/x86/net/bpf_jit.S')
-rw-r--r--arch/x86/net/bpf_jit.S159
1 files changed, 159 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit.S b/arch/x86/net/bpf_jit.S
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+++ b/arch/x86/net/bpf_jit.S
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+/* bpf_jit.S : BPF JIT helper functions
+ *
+ * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.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 <linux/linkage.h>
+#include <asm/dwarf2.h>
+
+/*
+ * Calling convention :
+ * rbx : skb pointer (callee saved)
+ * esi : offset of byte(s) to fetch in skb (can be scratched)
+ * r10 : copy of skb->data
+ * r9d : hlen = skb->len - skb->data_len
+ */
+#define SKBDATA %r10
+#define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */
+#define MAX_BPF_STACK (512 /* from filter.h */ + \
+ 32 /* space for rbx,r13,r14,r15 */ + \
+ 8 /* space for skb_copy_bits */)
+
+sk_load_word:
+ .globl sk_load_word
+
+ test %esi,%esi
+ js bpf_slow_path_word_neg
+
+sk_load_word_positive_offset:
+ .globl sk_load_word_positive_offset
+
+ mov %r9d,%eax # hlen
+ sub %esi,%eax # hlen - offset
+ cmp $3,%eax
+ jle bpf_slow_path_word
+ mov (SKBDATA,%rsi),%eax
+ bswap %eax /* ntohl() */
+ ret
+
+sk_load_half:
+ .globl sk_load_half
+
+ test %esi,%esi
+ js bpf_slow_path_half_neg
+
+sk_load_half_positive_offset:
+ .globl sk_load_half_positive_offset
+
+ mov %r9d,%eax
+ sub %esi,%eax # hlen - offset
+ cmp $1,%eax
+ jle bpf_slow_path_half
+ movzwl (SKBDATA,%rsi),%eax
+ rol $8,%ax # ntohs()
+ ret
+
+sk_load_byte:
+ .globl sk_load_byte
+
+ test %esi,%esi
+ js bpf_slow_path_byte_neg
+
+sk_load_byte_positive_offset:
+ .globl sk_load_byte_positive_offset
+
+ cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte */
+ jle bpf_slow_path_byte
+ movzbl (SKBDATA,%rsi),%eax
+ ret
+
+/* rsi contains offset and can be scratched */
+#define bpf_slow_path_common(LEN) \
+ mov %rbx, %rdi; /* arg1 == skb */ \
+ push %r9; \
+ push SKBDATA; \
+/* rsi already has offset */ \
+ mov $LEN,%ecx; /* len */ \
+ lea - MAX_BPF_STACK + 32(%rbp),%rdx; \
+ call skb_copy_bits; \
+ test %eax,%eax; \
+ pop SKBDATA; \
+ pop %r9;
+
+
+bpf_slow_path_word:
+ bpf_slow_path_common(4)
+ js bpf_error
+ mov - MAX_BPF_STACK + 32(%rbp),%eax
+ bswap %eax
+ ret
+
+bpf_slow_path_half:
+ bpf_slow_path_common(2)
+ js bpf_error
+ mov - MAX_BPF_STACK + 32(%rbp),%ax
+ rol $8,%ax
+ movzwl %ax,%eax
+ ret
+
+bpf_slow_path_byte:
+ bpf_slow_path_common(1)
+ js bpf_error
+ movzbl - MAX_BPF_STACK + 32(%rbp),%eax
+ ret
+
+#define sk_negative_common(SIZE) \
+ mov %rbx, %rdi; /* arg1 == skb */ \
+ push %r9; \
+ push SKBDATA; \
+/* rsi already has offset */ \
+ mov $SIZE,%edx; /* size */ \
+ call bpf_internal_load_pointer_neg_helper; \
+ test %rax,%rax; \
+ pop SKBDATA; \
+ pop %r9; \
+ jz bpf_error
+
+bpf_slow_path_word_neg:
+ cmp SKF_MAX_NEG_OFF, %esi /* test range */
+ jl bpf_error /* offset lower -> error */
+sk_load_word_negative_offset:
+ .globl sk_load_word_negative_offset
+ sk_negative_common(4)
+ mov (%rax), %eax
+ bswap %eax
+ ret
+
+bpf_slow_path_half_neg:
+ cmp SKF_MAX_NEG_OFF, %esi
+ jl bpf_error
+sk_load_half_negative_offset:
+ .globl sk_load_half_negative_offset
+ sk_negative_common(2)
+ mov (%rax),%ax
+ rol $8,%ax
+ movzwl %ax,%eax
+ ret
+
+bpf_slow_path_byte_neg:
+ cmp SKF_MAX_NEG_OFF, %esi
+ jl bpf_error
+sk_load_byte_negative_offset:
+ .globl sk_load_byte_negative_offset
+ sk_negative_common(1)
+ movzbl (%rax), %eax
+ ret
+
+bpf_error:
+# force a return 0 from jit handler
+ xor %eax,%eax
+ mov - MAX_BPF_STACK(%rbp),%rbx
+ mov - MAX_BPF_STACK + 8(%rbp),%r13
+ mov - MAX_BPF_STACK + 16(%rbp),%r14
+ mov - MAX_BPF_STACK + 24(%rbp),%r15
+ leaveq
+ ret