1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 2013 Linaro Limited 4 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> 5 * Copyright (C) 2017 Andes Technology Corporation 6 */ 7 8 #include <linux/ftrace.h> 9 #include <linux/uaccess.h> 10 #include <asm/cacheflush.h> 11 12 #ifdef CONFIG_DYNAMIC_FTRACE 13 static int ftrace_check_current_call(unsigned long hook_pos, 14 unsigned int *expected) 15 { 16 unsigned int replaced[2]; 17 unsigned int nops[2] = {NOP4, NOP4}; 18 19 /* we expect nops at the hook position */ 20 if (!expected) 21 expected = nops; 22 23 /* 24 * Read the text we want to modify; 25 * return must be -EFAULT on read error 26 */ 27 if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE)) 28 return -EFAULT; 29 30 /* 31 * Make sure it is what we expect it to be; 32 * return must be -EINVAL on failed comparison 33 */ 34 if (memcmp(expected, replaced, sizeof(replaced))) { 35 pr_err("%p: expected (%08x %08x) but get (%08x %08x)", 36 (void *)hook_pos, expected[0], expected[1], replaced[0], 37 replaced[1]); 38 return -EINVAL; 39 } 40 41 return 0; 42 } 43 44 static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, 45 bool enable) 46 { 47 unsigned int call[2]; 48 unsigned int nops[2] = {NOP4, NOP4}; 49 int ret = 0; 50 51 make_call(hook_pos, target, call); 52 53 /* replace the auipc-jalr pair at once */ 54 ret = probe_kernel_write((void *)hook_pos, enable ? call : nops, 55 MCOUNT_INSN_SIZE); 56 /* return must be -EPERM on write error */ 57 if (ret) 58 return -EPERM; 59 60 smp_mb(); 61 flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE); 62 63 return 0; 64 } 65 66 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 67 { 68 int ret = ftrace_check_current_call(rec->ip, NULL); 69 70 if (ret) 71 return ret; 72 73 return __ftrace_modify_call(rec->ip, addr, true); 74 } 75 76 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, 77 unsigned long addr) 78 { 79 unsigned int call[2]; 80 int ret; 81 82 make_call(rec->ip, addr, call); 83 ret = ftrace_check_current_call(rec->ip, call); 84 85 if (ret) 86 return ret; 87 88 return __ftrace_modify_call(rec->ip, addr, false); 89 } 90 91 int ftrace_update_ftrace_func(ftrace_func_t func) 92 { 93 int ret = __ftrace_modify_call((unsigned long)&ftrace_call, 94 (unsigned long)func, true); 95 if (!ret) { 96 ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call, 97 (unsigned long)func, true); 98 } 99 100 return ret; 101 } 102 103 int __init ftrace_dyn_arch_init(void) 104 { 105 return 0; 106 } 107 #endif 108 109 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 110 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, 111 unsigned long addr) 112 { 113 unsigned int call[2]; 114 int ret; 115 116 make_call(rec->ip, old_addr, call); 117 ret = ftrace_check_current_call(rec->ip, call); 118 119 if (ret) 120 return ret; 121 122 return __ftrace_modify_call(rec->ip, addr, true); 123 } 124 #endif 125 126 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 127 /* 128 * Most of this function is copied from arm64. 129 */ 130 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 131 unsigned long frame_pointer) 132 { 133 unsigned long return_hooker = (unsigned long)&return_to_handler; 134 unsigned long old; 135 int err; 136 137 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 138 return; 139 140 /* 141 * We don't suffer access faults, so no extra fault-recovery assembly 142 * is needed here. 143 */ 144 old = *parent; 145 146 if (function_graph_enter(old, self_addr, frame_pointer, parent)) 147 *parent = return_hooker; 148 } 149 150 #ifdef CONFIG_DYNAMIC_FTRACE 151 extern void ftrace_graph_call(void); 152 int ftrace_enable_ftrace_graph_caller(void) 153 { 154 unsigned int call[2]; 155 static int init_graph = 1; 156 int ret; 157 158 make_call(&ftrace_graph_call, &ftrace_stub, call); 159 160 /* 161 * When enabling graph tracer for the first time, ftrace_graph_call 162 * should contains a call to ftrace_stub. Once it has been disabled, 163 * the 8-bytes at the position becomes NOPs. 164 */ 165 if (init_graph) { 166 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 167 call); 168 init_graph = 0; 169 } else { 170 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 171 NULL); 172 } 173 174 if (ret) 175 return ret; 176 177 return __ftrace_modify_call((unsigned long)&ftrace_graph_call, 178 (unsigned long)&prepare_ftrace_return, true); 179 } 180 181 int ftrace_disable_ftrace_graph_caller(void) 182 { 183 unsigned int call[2]; 184 int ret; 185 186 make_call(&ftrace_graph_call, &prepare_ftrace_return, call); 187 188 /* 189 * This is to make sure that ftrace_enable_ftrace_graph_caller 190 * did the right thing. 191 */ 192 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 193 call); 194 195 if (ret) 196 return ret; 197 198 return __ftrace_modify_call((unsigned long)&ftrace_graph_call, 199 (unsigned long)&prepare_ftrace_return, false); 200 } 201 #endif /* CONFIG_DYNAMIC_FTRACE */ 202 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 203