1 /* Emulation of eBPF helpers. 2 Copyright (C) 2020 Free Software Foundation, Inc. 3 4 This file is part of GDB, the GNU debugger. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19 /* BPF programs rely on the existence of several helper functions, 20 which are provided by the kernel. This simulator provides an 21 implementation of the helpers, which can be customized by the 22 user. */ 23 24 #define WANT_CPU_BPFBF 25 #define WANT_CPU bpfbf 26 27 #include "sim-main.h" 28 #include "cgen-mem.h" 29 #include "cgen-ops.h" 30 #include "cpu.h" 31 32 /* bpf_trace_printk is a printk-like facility for debugging. 33 34 In the kernel, it appends a line to the Linux's tracing debugging 35 interface. 36 37 In this simulator, it uses the simulator's tracing interface 38 instead. 39 40 The format tags recognized by this helper are: 41 %d, %i, %u, %x, %ld, %li, %lu, %lx, %lld, %lli, %llu, %llx, 42 %p, %s 43 44 A maximum of three tags are supported. 45 46 This helper returns the number of bytes written, or a negative 47 value in case of failure. */ 48 49 int 50 bpf_trace_printk (SIM_CPU *current_cpu) 51 { 52 va_list ap; 53 SIM_DESC sd = CPU_STATE (current_cpu); 54 55 DI fmt_address; 56 uint32_t size, tags_processed; 57 size_t i, bytes_written = 0; 58 59 /* The first argument is the format string, which is passed as a 60 pointer in %r1. */ 61 fmt_address = GET_H_GPR (1); 62 63 /* The second argument is the length of the format string, as an 64 unsigned 32-bit number in %r2. */ 65 size = GET_H_GPR (2); 66 67 /* Read the format string from the memory pointed by %r2, printing 68 out the stuff as we go. There is a maximum of three format tags 69 supported, which are read from %r3, %r4 and %r5 respectively. */ 70 for (i = 0, tags_processed = 0; i < size;) 71 { 72 QI c = GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu), 73 fmt_address + i); 74 75 switch (c) 76 { 77 case '%': 78 /* Check we are not exceeding the limit of three format 79 tags. */ 80 if (tags_processed > 2) 81 return -1; /* XXX look for kernel error code. */ 82 83 /* Depending on the kind of tag, extract the value from the 84 proper argument. */ 85 if (i++ >= size) 86 return -1; /* XXX look for kernel error code. */ 87 88 UDI value = GET_H_GPR (3 + tags_processed); 89 90 switch ((GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu), 91 fmt_address + i))) 92 { 93 case 'd': 94 trace_printf (sd, current_cpu, "%d", value); 95 break; 96 case 'i': 97 trace_printf (sd, current_cpu, "%i", value); 98 break; 99 case 'u': 100 trace_printf (sd, current_cpu, "%u", value); 101 break; 102 case 'x': 103 trace_printf (sd, current_cpu, "%x", value); 104 break; 105 case 'l': 106 { 107 if (i++ >= size) 108 return -1; 109 switch (GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu), 110 fmt_address + i)) 111 { 112 case 'd': 113 trace_printf (sd, current_cpu, "%ld", value); 114 break; 115 case 'i': 116 trace_printf (sd, current_cpu, "%li", value); 117 break; 118 case 'u': 119 trace_printf (sd, current_cpu, "%lu", value); 120 break; 121 case 'x': 122 trace_printf (sd, current_cpu, "%lx", value); 123 break; 124 case 'l': 125 { 126 if (i++ >= size) 127 return -1; 128 switch (GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu), 129 fmt_address + i)) { 130 case 'd': 131 trace_printf (sd, current_cpu, "%lld", value); 132 break; 133 case 'i': 134 trace_printf (sd, current_cpu, "%lli", value); 135 break; 136 case 'u': 137 trace_printf (sd, current_cpu, "%llu", value); 138 break; 139 case 'x': 140 trace_printf (sd, current_cpu, "%llx", value); 141 break; 142 default: 143 assert (0); 144 break; 145 } 146 break; 147 } 148 default: 149 assert (0); 150 break; 151 } 152 break; 153 } 154 default: 155 /* XXX completeme */ 156 assert (0); 157 break; 158 } 159 160 tags_processed++; 161 i++; 162 break; 163 case '\0': 164 i = size; 165 break; 166 default: 167 trace_printf (sd, current_cpu, "%c", c); 168 bytes_written++; 169 i++; 170 break; 171 } 172 } 173 174 return bytes_written; 175 } 176