1/*
2 * Copyright (C) 2008 Imagination Technologies Ltd.
3 * Licensed under the GPL
4 *
5 * Dynamic ftrace support.
6 */
7
8#include <linux/ftrace.h>
9#include <linux/io.h>
10#include <linux/uaccess.h>
11
12#include <asm/cacheflush.h>
13
14#define D04_MOVT_TEMPLATE	0x02200005
15#define D04_CALL_TEMPLATE	0xAC200005
16#define D1RTP_MOVT_TEMPLATE	0x03200005
17#define D1RTP_CALL_TEMPLATE	0xAC200006
18
19static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
20static unsigned long movt_and_call_insn[2];
21
22static unsigned char *ftrace_nop_replace(void)
23{
24	return (char *)&NOP[0];
25}
26
27static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
28{
29	unsigned long hi16, low16;
30
31	hi16 = (addr & 0xffff0000) >> 13;
32	low16 = (addr & 0x0000ffff) << 3;
33
34	/*
35	 * The compiler makes the call to mcount_wrapper()
36	 * (Meta's wrapper around mcount()) through the register
37	 * D0.4. So whenever we're patching one of those compiler-generated
38	 * calls we also need to go through D0.4. Otherwise use D1RtP.
39	 */
40	if (pc == (unsigned long)&ftrace_call) {
41		writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
42		writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
43	} else {
44		writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
45		writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
46	}
47
48	return (unsigned char *)&movt_and_call_insn[0];
49}
50
51static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
52			      unsigned char *new_code)
53{
54	unsigned char replaced[MCOUNT_INSN_SIZE];
55
56	/*
57	 * Note: Due to modules and __init, code can
58	 *  disappear and change, we need to protect against faulting
59	 *  as well as code changing.
60	 *
61	 * No real locking needed, this code is run through
62	 * kstop_machine.
63	 */
64
65	/* read the text we want to modify */
66	if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE))
67		return -EFAULT;
68
69	/* Make sure it is what we expect it to be */
70	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
71		return -EINVAL;
72
73	/* replace the text with the new text */
74	if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE))
75		return -EPERM;
76
77	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
78
79	return 0;
80}
81
82int ftrace_update_ftrace_func(ftrace_func_t func)
83{
84	int ret;
85	unsigned long pc;
86	unsigned char old[MCOUNT_INSN_SIZE], *new;
87
88	pc = (unsigned long)&ftrace_call;
89	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
90	new = ftrace_call_replace(pc, (unsigned long)func);
91	ret = ftrace_modify_code(pc, old, new);
92
93	return ret;
94}
95
96int ftrace_make_nop(struct module *mod,
97		    struct dyn_ftrace *rec, unsigned long addr)
98{
99	unsigned char *new, *old;
100	unsigned long ip = rec->ip;
101
102	old = ftrace_call_replace(ip, addr);
103	new = ftrace_nop_replace();
104
105	return ftrace_modify_code(ip, old, new);
106}
107
108int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
109{
110	unsigned char *new, *old;
111	unsigned long ip = rec->ip;
112
113	old = ftrace_nop_replace();
114	new = ftrace_call_replace(ip, addr);
115
116	return ftrace_modify_code(ip, old, new);
117}
118
119/* run from kstop_machine */
120int __init ftrace_dyn_arch_init(void)
121{
122	return 0;
123}
124