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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 <linux/memory.h>
11#include <asm/cacheflush.h>
12#include <asm/patch.h>
13
14#ifdef CONFIG_DYNAMIC_FTRACE
15void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
16{
17 mutex_lock(&text_mutex);
18}
19
20void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
21{
22 mutex_unlock(&text_mutex);
23}
24
25static int ftrace_check_current_call(unsigned long hook_pos,
26 unsigned int *expected)
27{
28 unsigned int replaced[2];
29 unsigned int nops[2] = {NOP4, NOP4};
30
31 /* we expect nops at the hook position */
32 if (!expected)
33 expected = nops;
34
35 /*
36 * Read the text we want to modify;
37 * return must be -EFAULT on read error
38 */
39 if (copy_from_kernel_nofault(replaced, (void *)hook_pos,
40 MCOUNT_INSN_SIZE))
41 return -EFAULT;
42
43 /*
44 * Make sure it is what we expect it to be;
45 * return must be -EINVAL on failed comparison
46 */
47 if (memcmp(expected, replaced, sizeof(replaced))) {
48 pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
49 (void *)hook_pos, expected[0], expected[1], replaced[0],
50 replaced[1]);
51 return -EINVAL;
52 }
53
54 return 0;
55}
56
57static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
58 bool enable)
59{
60 unsigned int call[2];
61 unsigned int nops[2] = {NOP4, NOP4};
62
63 make_call(hook_pos, target, call);
64
65 /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
66 if (patch_text_nosync
67 ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
68 return -EPERM;
69
70 return 0;
71}
72
73/*
74 * Put 5 instructions with 16 bytes at the front of function within
75 * patchable function entry nops' area.
76 *
77 * 0: REG_S ra, -SZREG(sp)
78 * 1: auipc ra, 0x?
79 * 2: jalr -?(ra)
80 * 3: REG_L ra, -SZREG(sp)
81 *
82 * So the opcodes is:
83 * 0: 0xfe113c23 (sd)/0xfe112e23 (sw)
84 * 1: 0x???????? -> auipc
85 * 2: 0x???????? -> jalr
86 * 3: 0xff813083 (ld)/0xffc12083 (lw)
87 */
88#if __riscv_xlen == 64
89#define INSN0 0xfe113c23
90#define INSN3 0xff813083
91#elif __riscv_xlen == 32
92#define INSN0 0xfe112e23
93#define INSN3 0xffc12083
94#endif
95
96#define FUNC_ENTRY_SIZE 16
97#define FUNC_ENTRY_JMP 4
98
99int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
100{
101 unsigned int call[4] = {INSN0, 0, 0, INSN3};
102 unsigned long target = addr;
103 unsigned long caller = rec->ip + FUNC_ENTRY_JMP;
104
105 call[1] = to_auipc_insn((unsigned int)(target - caller));
106 call[2] = to_jalr_insn((unsigned int)(target - caller));
107
108 if (patch_text_nosync((void *)rec->ip, call, FUNC_ENTRY_SIZE))
109 return -EPERM;
110
111 return 0;
112}
113
114int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
115 unsigned long addr)
116{
117 unsigned int nops[4] = {NOP4, NOP4, NOP4, NOP4};
118
119 if (patch_text_nosync((void *)rec->ip, nops, FUNC_ENTRY_SIZE))
120 return -EPERM;
121
122 return 0;
123}
124
125
126/*
127 * This is called early on, and isn't wrapped by
128 * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
129 * text_mutex, which triggers a lockdep failure. SMP isn't running so we could
130 * just directly poke the text, but it's simpler to just take the lock
131 * ourselves.
132 */
133int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
134{
135 int out;
136
137 ftrace_arch_code_modify_prepare();
138 out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
139 ftrace_arch_code_modify_post_process();
140
141 return out;
142}
143
144int ftrace_update_ftrace_func(ftrace_func_t func)
145{
146 int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
147 (unsigned long)func, true);
148 if (!ret) {
149 ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
150 (unsigned long)func, true);
151 }
152
153 return ret;
154}
155#endif
156
157#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
158int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
159 unsigned long addr)
160{
161 unsigned int call[2];
162 unsigned long caller = rec->ip + FUNC_ENTRY_JMP;
163 int ret;
164
165 make_call(caller, old_addr, call);
166 ret = ftrace_check_current_call(caller, call);
167
168 if (ret)
169 return ret;
170
171 return __ftrace_modify_call(caller, addr, true);
172}
173#endif
174
175#ifdef CONFIG_FUNCTION_GRAPH_TRACER
176/*
177 * Most of this function is copied from arm64.
178 */
179void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
180 unsigned long frame_pointer)
181{
182 unsigned long return_hooker = (unsigned long)&return_to_handler;
183 unsigned long old;
184
185 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
186 return;
187
188 /*
189 * We don't suffer access faults, so no extra fault-recovery assembly
190 * is needed here.
191 */
192 old = *parent;
193
194 if (!function_graph_enter(old, self_addr, frame_pointer, parent))
195 *parent = return_hooker;
196}
197
198#ifdef CONFIG_DYNAMIC_FTRACE
199extern void ftrace_graph_call(void);
200extern void ftrace_graph_regs_call(void);
201int ftrace_enable_ftrace_graph_caller(void)
202{
203 int ret;
204
205 ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
206 (unsigned long)&prepare_ftrace_return, true);
207 if (ret)
208 return ret;
209
210 return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
211 (unsigned long)&prepare_ftrace_return, true);
212}
213
214int ftrace_disable_ftrace_graph_caller(void)
215{
216 int ret;
217
218 ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
219 (unsigned long)&prepare_ftrace_return, false);
220 if (ret)
221 return ret;
222
223 return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
224 (unsigned long)&prepare_ftrace_return, false);
225}
226#endif /* CONFIG_DYNAMIC_FTRACE */
227#endif /* CONFIG_FUNCTION_GRAPH_TRACER */