1 /*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
5 *
6 * For licencing details, see COPYING.
7 *
8 * Defines low-level handling of mcount calls when the kernel
9 * is compiled with the -pg flag. When using dynamic ftrace, the
10 * mcount call-sites get patched lazily with NOP till they are
11 * enabled. All code mutation routines here take effect atomically.
12 */
13
14 #include <linux/uaccess.h>
15 #include <linux/ftrace.h>
16
17 #include <asm/cacheflush.h>
18 #include <asm/patch.h>
19
20 /* In IA64, each function will be added below two bundles with -pg option */
21 static unsigned char __attribute__((aligned(8)))
22 ftrace_orig_code[MCOUNT_INSN_SIZE] = {
23 0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
24 0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
25 0x05, 0x00, 0xc4, 0x00, /* mov r42=b0 */
26 0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
27 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
28 0x08, 0x00, 0x00, 0x50 /* br.call.sptk.many b0 = _mcount;; */
29 };
30
31 struct ftrace_orig_insn {
32 u64 dummy1, dummy2, dummy3;
33 u64 dummy4:64-41+13;
34 u64 imm20:20;
35 u64 dummy5:3;
36 u64 sign:1;
37 u64 dummy6:4;
38 };
39
40 /* mcount stub will be converted below for nop */
41 static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
42 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
43 0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
44 0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
45 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
46 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
47 0x00, 0x00, 0x04, 0x00
48 };
49
ftrace_nop_replace(void)50 static unsigned char *ftrace_nop_replace(void)
51 {
52 return ftrace_nop_code;
53 }
54
55 /*
56 * mcount stub will be converted below for call
57 * Note: Just the last instruction is changed against nop
58 * */
59 static unsigned char __attribute__((aligned(8)))
60 ftrace_call_code[MCOUNT_INSN_SIZE] = {
61 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
62 0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
63 0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
64 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
65 0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
66 0xf8, 0xff, 0xff, 0xc8
67 };
68
69 struct ftrace_call_insn {
70 u64 dummy1, dummy2;
71 u64 dummy3:48;
72 u64 imm39_l:16;
73 u64 imm39_h:23;
74 u64 dummy4:13;
75 u64 imm20:20;
76 u64 dummy5:3;
77 u64 i:1;
78 u64 dummy6:4;
79 };
80
ftrace_call_replace(unsigned long ip,unsigned long addr)81 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
82 {
83 struct ftrace_call_insn *code = (void *)ftrace_call_code;
84 unsigned long offset = addr - (ip + 0x10);
85
86 code->imm39_l = offset >> 24;
87 code->imm39_h = offset >> 40;
88 code->imm20 = offset >> 4;
89 code->i = offset >> 63;
90 return ftrace_call_code;
91 }
92
93 static int
ftrace_modify_code(unsigned long ip,unsigned char * old_code,unsigned char * new_code,int do_check)94 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
95 unsigned char *new_code, int do_check)
96 {
97 unsigned char replaced[MCOUNT_INSN_SIZE];
98
99 /*
100 * Note:
101 * We are paranoid about modifying text, as if a bug was to happen, it
102 * could cause us to read or write to someplace that could cause harm.
103 * Carefully read and modify the code with probe_kernel_*(), and make
104 * sure what we read is what we expected it to be before modifying it.
105 */
106
107 if (!do_check)
108 goto skip_check;
109
110 /* read the text we want to modify */
111 if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
112 return -EFAULT;
113
114 /* Make sure it is what we expect it to be */
115 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
116 return -EINVAL;
117
118 skip_check:
119 /* replace the text with the new text */
120 if (copy_to_kernel_nofault(((void *)ip), new_code, MCOUNT_INSN_SIZE))
121 return -EPERM;
122 flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
123
124 return 0;
125 }
126
ftrace_make_nop_check(struct dyn_ftrace * rec,unsigned long addr)127 static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
128 {
129 unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
130 unsigned long ip = rec->ip;
131
132 if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
133 return -EFAULT;
134 if (rec->flags & FTRACE_FL_CONVERTED) {
135 struct ftrace_call_insn *call_insn, *tmp_call;
136
137 call_insn = (void *)ftrace_call_code;
138 tmp_call = (void *)replaced;
139 call_insn->imm39_l = tmp_call->imm39_l;
140 call_insn->imm39_h = tmp_call->imm39_h;
141 call_insn->imm20 = tmp_call->imm20;
142 call_insn->i = tmp_call->i;
143 if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
144 return -EINVAL;
145 return 0;
146 } else {
147 struct ftrace_orig_insn *call_insn, *tmp_call;
148
149 call_insn = (void *)ftrace_orig_code;
150 tmp_call = (void *)replaced;
151 call_insn->sign = tmp_call->sign;
152 call_insn->imm20 = tmp_call->imm20;
153 if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
154 return -EINVAL;
155 return 0;
156 }
157 }
158
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)159 int ftrace_make_nop(struct module *mod,
160 struct dyn_ftrace *rec, unsigned long addr)
161 {
162 int ret;
163 char *new;
164
165 ret = ftrace_make_nop_check(rec, addr);
166 if (ret)
167 return ret;
168 new = ftrace_nop_replace();
169 return ftrace_modify_code(rec->ip, NULL, new, 0);
170 }
171
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)172 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
173 {
174 unsigned long ip = rec->ip;
175 unsigned char *old, *new;
176
177 old= ftrace_nop_replace();
178 new = ftrace_call_replace(ip, addr);
179 return ftrace_modify_code(ip, old, new, 1);
180 }
181
182 /* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
ftrace_update_ftrace_func(ftrace_func_t func)183 int ftrace_update_ftrace_func(ftrace_func_t func)
184 {
185 unsigned long ip;
186 unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
187
188 if (func == ftrace_stub)
189 return 0;
190 ip = ((struct fnptr *)func)->ip;
191
192 ia64_patch_imm64(addr + 2, ip);
193
194 flush_icache_range(addr, addr + 16);
195 return 0;
196 }
197