1 /* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com 2 * 3 * This program is free software; you can redistribute it and/or 4 * modify it under the terms of version 2 of the GNU General Public 5 * License as published by the Free Software Foundation. 6 */ 7 #include <linux/kernel.h> 8 #include <linux/types.h> 9 #include <linux/slab.h> 10 #include <linux/bpf.h> 11 #include <linux/filter.h> 12 #include <linux/uaccess.h> 13 #include <linux/ctype.h> 14 #include "trace.h" 15 16 static DEFINE_PER_CPU(int, bpf_prog_active); 17 18 /** 19 * trace_call_bpf - invoke BPF program 20 * @prog: BPF program 21 * @ctx: opaque context pointer 22 * 23 * kprobe handlers execute BPF programs via this helper. 24 * Can be used from static tracepoints in the future. 25 * 26 * Return: BPF programs always return an integer which is interpreted by 27 * kprobe handler as: 28 * 0 - return from kprobe (event is filtered out) 29 * 1 - store kprobe event into ring buffer 30 * Other values are reserved and currently alias to 1 31 */ 32 unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx) 33 { 34 unsigned int ret; 35 36 if (in_nmi()) /* not supported yet */ 37 return 1; 38 39 preempt_disable(); 40 41 if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) { 42 /* 43 * since some bpf program is already running on this cpu, 44 * don't call into another bpf program (same or different) 45 * and don't send kprobe event into ring-buffer, 46 * so return zero here 47 */ 48 ret = 0; 49 goto out; 50 } 51 52 rcu_read_lock(); 53 ret = BPF_PROG_RUN(prog, ctx); 54 rcu_read_unlock(); 55 56 out: 57 __this_cpu_dec(bpf_prog_active); 58 preempt_enable(); 59 60 return ret; 61 } 62 EXPORT_SYMBOL_GPL(trace_call_bpf); 63 64 static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 65 { 66 void *dst = (void *) (long) r1; 67 int size = (int) r2; 68 void *unsafe_ptr = (void *) (long) r3; 69 70 return probe_kernel_read(dst, unsafe_ptr, size); 71 } 72 73 static const struct bpf_func_proto bpf_probe_read_proto = { 74 .func = bpf_probe_read, 75 .gpl_only = true, 76 .ret_type = RET_INTEGER, 77 .arg1_type = ARG_PTR_TO_STACK, 78 .arg2_type = ARG_CONST_STACK_SIZE, 79 .arg3_type = ARG_ANYTHING, 80 }; 81 82 /* 83 * limited trace_printk() 84 * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed 85 */ 86 static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5) 87 { 88 char *fmt = (char *) (long) r1; 89 int mod[3] = {}; 90 int fmt_cnt = 0; 91 int i; 92 93 /* 94 * bpf_check()->check_func_arg()->check_stack_boundary() 95 * guarantees that fmt points to bpf program stack, 96 * fmt_size bytes of it were initialized and fmt_size > 0 97 */ 98 if (fmt[--fmt_size] != 0) 99 return -EINVAL; 100 101 /* check format string for allowed specifiers */ 102 for (i = 0; i < fmt_size; i++) { 103 if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) 104 return -EINVAL; 105 106 if (fmt[i] != '%') 107 continue; 108 109 if (fmt_cnt >= 3) 110 return -EINVAL; 111 112 /* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */ 113 i++; 114 if (fmt[i] == 'l') { 115 mod[fmt_cnt]++; 116 i++; 117 } else if (fmt[i] == 'p') { 118 mod[fmt_cnt]++; 119 i++; 120 if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0) 121 return -EINVAL; 122 fmt_cnt++; 123 continue; 124 } 125 126 if (fmt[i] == 'l') { 127 mod[fmt_cnt]++; 128 i++; 129 } 130 131 if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x') 132 return -EINVAL; 133 fmt_cnt++; 134 } 135 136 return __trace_printk(1/* fake ip will not be printed */, fmt, 137 mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3, 138 mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4, 139 mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5); 140 } 141 142 static const struct bpf_func_proto bpf_trace_printk_proto = { 143 .func = bpf_trace_printk, 144 .gpl_only = true, 145 .ret_type = RET_INTEGER, 146 .arg1_type = ARG_PTR_TO_STACK, 147 .arg2_type = ARG_CONST_STACK_SIZE, 148 }; 149 150 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id) 151 { 152 switch (func_id) { 153 case BPF_FUNC_map_lookup_elem: 154 return &bpf_map_lookup_elem_proto; 155 case BPF_FUNC_map_update_elem: 156 return &bpf_map_update_elem_proto; 157 case BPF_FUNC_map_delete_elem: 158 return &bpf_map_delete_elem_proto; 159 case BPF_FUNC_probe_read: 160 return &bpf_probe_read_proto; 161 case BPF_FUNC_ktime_get_ns: 162 return &bpf_ktime_get_ns_proto; 163 case BPF_FUNC_tail_call: 164 return &bpf_tail_call_proto; 165 166 case BPF_FUNC_trace_printk: 167 /* 168 * this program might be calling bpf_trace_printk, 169 * so allocate per-cpu printk buffers 170 */ 171 trace_printk_init_buffers(); 172 173 return &bpf_trace_printk_proto; 174 default: 175 return NULL; 176 } 177 } 178 179 /* bpf+kprobe programs can access fields of 'struct pt_regs' */ 180 static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type) 181 { 182 /* check bounds */ 183 if (off < 0 || off >= sizeof(struct pt_regs)) 184 return false; 185 186 /* only read is allowed */ 187 if (type != BPF_READ) 188 return false; 189 190 /* disallow misaligned access */ 191 if (off % size != 0) 192 return false; 193 194 return true; 195 } 196 197 static struct bpf_verifier_ops kprobe_prog_ops = { 198 .get_func_proto = kprobe_prog_func_proto, 199 .is_valid_access = kprobe_prog_is_valid_access, 200 }; 201 202 static struct bpf_prog_type_list kprobe_tl = { 203 .ops = &kprobe_prog_ops, 204 .type = BPF_PROG_TYPE_KPROBE, 205 }; 206 207 static int __init register_kprobe_prog_ops(void) 208 { 209 bpf_register_prog_type(&kprobe_tl); 210 return 0; 211 } 212 late_initcall(register_kprobe_prog_ops); 213