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
19 static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
20 static unsigned long movt_and_call_insn[2];
21
ftrace_nop_replace(void)22 static unsigned char *ftrace_nop_replace(void)
23 {
24 return (char *)&NOP[0];
25 }
26
ftrace_call_replace(unsigned long pc,unsigned long addr)27 static 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
ftrace_modify_code(unsigned long pc,unsigned char * old_code,unsigned char * new_code)51 static 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
ftrace_update_ftrace_func(ftrace_func_t func)82 int 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
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)96 int 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
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)108 int 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 */
ftrace_dyn_arch_init(void)120 int __init ftrace_dyn_arch_init(void)
121 {
122 return 0;
123 }
124