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
 13static 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
 44static 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
 66int 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
 76int 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
 91int 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
103int __init ftrace_dyn_arch_init(void)
104{
105	return 0;
106}
107#endif
108
109#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
110int 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 */
130void 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	struct ftrace_graph_ent trace;
136	int err;
137
138	if (unlikely(atomic_read(&current->tracing_graph_pause)))
139		return;
140
141	/*
142	 * We don't suffer access faults, so no extra fault-recovery assembly
143	 * is needed here.
144	 */
145	old = *parent;
146
147	trace.func = self_addr;
148	trace.depth = current->curr_ret_stack + 1;
149
150	if (!ftrace_graph_entry(&trace))
151		return;
152
153	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
154				       frame_pointer, parent);
155	if (err == -EBUSY)
156		return;
157	*parent = return_hooker;
158}
159
160#ifdef CONFIG_DYNAMIC_FTRACE
161extern void ftrace_graph_call(void);
162int ftrace_enable_ftrace_graph_caller(void)
163{
164	unsigned int call[2];
165	static int init_graph = 1;
166	int ret;
167
168	make_call(&ftrace_graph_call, &ftrace_stub, call);
169
170	/*
171	 * When enabling graph tracer for the first time, ftrace_graph_call
172	 * should contains a call to ftrace_stub.  Once it has been disabled,
173	 * the 8-bytes at the position becomes NOPs.
174	 */
175	if (init_graph) {
176		ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
177						call);
178		init_graph = 0;
179	} else {
180		ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
181						NULL);
182	}
183
184	if (ret)
185		return ret;
186
187	return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
188				    (unsigned long)&prepare_ftrace_return, true);
189}
190
191int ftrace_disable_ftrace_graph_caller(void)
192{
193	unsigned int call[2];
194	int ret;
195
196	make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
197
198	/*
199	 * This is to make sure that ftrace_enable_ftrace_graph_caller
200	 * did the right thing.
201	 */
202	ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
203					call);
204
205	if (ret)
206		return ret;
207
208	return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
209				    (unsigned long)&prepare_ftrace_return, false);
210}
211#endif /* CONFIG_DYNAMIC_FTRACE */
212#endif /* CONFIG_FUNCTION_GRAPH_TRACER */