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 got (%08x %08x)\n", 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; 135 136 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 137 return; 138 139 /* 140 * We don't suffer access faults, so no extra fault-recovery assembly 141 * is needed here. 142 */ 143 old = *parent; 144 145 if (!function_graph_enter(old, self_addr, frame_pointer, parent)) 146 *parent = return_hooker; 147 } 148 149 #ifdef CONFIG_DYNAMIC_FTRACE 150 extern void ftrace_graph_call(void); 151 int ftrace_enable_ftrace_graph_caller(void) 152 { 153 unsigned int call[2]; 154 static int init_graph = 1; 155 int ret; 156 157 make_call(&ftrace_graph_call, &ftrace_stub, call); 158 159 /* 160 * When enabling graph tracer for the first time, ftrace_graph_call 161 * should contains a call to ftrace_stub. Once it has been disabled, 162 * the 8-bytes at the position becomes NOPs. 163 */ 164 if (init_graph) { 165 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 166 call); 167 init_graph = 0; 168 } else { 169 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 170 NULL); 171 } 172 173 if (ret) 174 return ret; 175 176 return __ftrace_modify_call((unsigned long)&ftrace_graph_call, 177 (unsigned long)&prepare_ftrace_return, true); 178 } 179 180 int ftrace_disable_ftrace_graph_caller(void) 181 { 182 unsigned int call[2]; 183 int ret; 184 185 make_call(&ftrace_graph_call, &prepare_ftrace_return, call); 186 187 /* 188 * This is to make sure that ftrace_enable_ftrace_graph_caller 189 * did the right thing. 190 */ 191 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call, 192 call); 193 194 if (ret) 195 return ret; 196 197 return __ftrace_modify_call((unsigned long)&ftrace_graph_call, 198 (unsigned long)&prepare_ftrace_return, false); 199 } 200 #endif /* CONFIG_DYNAMIC_FTRACE */ 201 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 202