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 static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 83 { 84 /* NMI safe access to clock monotonic */ 85 return ktime_get_mono_fast_ns(); 86 } 87 88 static const struct bpf_func_proto bpf_ktime_get_ns_proto = { 89 .func = bpf_ktime_get_ns, 90 .gpl_only = true, 91 .ret_type = RET_INTEGER, 92 }; 93 94 /* 95 * limited trace_printk() 96 * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed 97 */ 98 static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5) 99 { 100 char *fmt = (char *) (long) r1; 101 int mod[3] = {}; 102 int fmt_cnt = 0; 103 int i; 104 105 /* 106 * bpf_check()->check_func_arg()->check_stack_boundary() 107 * guarantees that fmt points to bpf program stack, 108 * fmt_size bytes of it were initialized and fmt_size > 0 109 */ 110 if (fmt[--fmt_size] != 0) 111 return -EINVAL; 112 113 /* check format string for allowed specifiers */ 114 for (i = 0; i < fmt_size; i++) { 115 if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) 116 return -EINVAL; 117 118 if (fmt[i] != '%') 119 continue; 120 121 if (fmt_cnt >= 3) 122 return -EINVAL; 123 124 /* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */ 125 i++; 126 if (fmt[i] == 'l') { 127 mod[fmt_cnt]++; 128 i++; 129 } else if (fmt[i] == 'p') { 130 mod[fmt_cnt]++; 131 i++; 132 if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0) 133 return -EINVAL; 134 fmt_cnt++; 135 continue; 136 } 137 138 if (fmt[i] == 'l') { 139 mod[fmt_cnt]++; 140 i++; 141 } 142 143 if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x') 144 return -EINVAL; 145 fmt_cnt++; 146 } 147 148 return __trace_printk(1/* fake ip will not be printed */, fmt, 149 mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3, 150 mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4, 151 mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5); 152 } 153 154 static const struct bpf_func_proto bpf_trace_printk_proto = { 155 .func = bpf_trace_printk, 156 .gpl_only = true, 157 .ret_type = RET_INTEGER, 158 .arg1_type = ARG_PTR_TO_STACK, 159 .arg2_type = ARG_CONST_STACK_SIZE, 160 }; 161 162 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id) 163 { 164 switch (func_id) { 165 case BPF_FUNC_map_lookup_elem: 166 return &bpf_map_lookup_elem_proto; 167 case BPF_FUNC_map_update_elem: 168 return &bpf_map_update_elem_proto; 169 case BPF_FUNC_map_delete_elem: 170 return &bpf_map_delete_elem_proto; 171 case BPF_FUNC_probe_read: 172 return &bpf_probe_read_proto; 173 case BPF_FUNC_ktime_get_ns: 174 return &bpf_ktime_get_ns_proto; 175 176 case BPF_FUNC_trace_printk: 177 /* 178 * this program might be calling bpf_trace_printk, 179 * so allocate per-cpu printk buffers 180 */ 181 trace_printk_init_buffers(); 182 183 return &bpf_trace_printk_proto; 184 default: 185 return NULL; 186 } 187 } 188 189 /* bpf+kprobe programs can access fields of 'struct pt_regs' */ 190 static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type) 191 { 192 /* check bounds */ 193 if (off < 0 || off >= sizeof(struct pt_regs)) 194 return false; 195 196 /* only read is allowed */ 197 if (type != BPF_READ) 198 return false; 199 200 /* disallow misaligned access */ 201 if (off % size != 0) 202 return false; 203 204 return true; 205 } 206 207 static struct bpf_verifier_ops kprobe_prog_ops = { 208 .get_func_proto = kprobe_prog_func_proto, 209 .is_valid_access = kprobe_prog_is_valid_access, 210 }; 211 212 static struct bpf_prog_type_list kprobe_tl = { 213 .ops = &kprobe_prog_ops, 214 .type = BPF_PROG_TYPE_KPROBE, 215 }; 216 217 static int __init register_kprobe_prog_ops(void) 218 { 219 bpf_register_prog_type(&kprobe_tl); 220 return 0; 221 } 222 late_initcall(register_kprobe_prog_ops); 223