1
2
3
4#include <linux/sched.h>
5#include <linux/mm.h>
6#include <linux/ptrace.h>
7#include <asm/desc.h>
8#include <asm/mmu_context.h>
9
10unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs)
11{
12 unsigned long addr, seg;
13
14 addr = regs->ip;
15 seg = regs->cs & 0xffff;
16 if (v8086_mode(regs)) {
17 addr = (addr & 0xffff) + (seg << 4);
18 return addr;
19 }
20
21#ifdef CONFIG_MODIFY_LDT_SYSCALL
22
23
24
25
26
27
28 if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) {
29 struct desc_struct *desc;
30 unsigned long base;
31
32 seg >>= 3;
33
34 mutex_lock(&child->mm->context.lock);
35 if (unlikely(!child->mm->context.ldt ||
36 seg >= child->mm->context.ldt->size))
37 addr = -1L;
38 else {
39 desc = &child->mm->context.ldt->entries[seg];
40 base = get_desc_base(desc);
41
42
43 if (!desc->d)
44 addr &= 0xffff;
45 addr += base;
46 }
47 mutex_unlock(&child->mm->context.lock);
48 }
49#endif
50
51 return addr;
52}
53
54static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
55{
56 int i, copied;
57 unsigned char opcode[15];
58 unsigned long addr = convert_ip_to_linear(child, regs);
59
60 copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
61 for (i = 0; i < copied; i++) {
62 switch (opcode[i]) {
63
64 case 0x9d: case 0xcf:
65 return 1;
66
67
68
69
70 case 0x66: case 0x67:
71 continue;
72
73 case 0x26: case 0x2e:
74 case 0x36: case 0x3e:
75 case 0x64: case 0x65:
76 case 0xf0: case 0xf2: case 0xf3:
77 continue;
78
79#ifdef CONFIG_X86_64
80 case 0x40 ... 0x4f:
81 if (!user_64bit_mode(regs))
82
83 return 0;
84
85 continue;
86#endif
87
88
89
90
91
92
93
94
95
96
97 case 0x9c:
98 default:
99 return 0;
100 }
101 }
102 return 0;
103}
104
105
106
107
108static int enable_single_step(struct task_struct *child)
109{
110 struct pt_regs *regs = task_pt_regs(child);
111 unsigned long oflags;
112
113
114
115
116
117
118
119
120
121
122
123 if (unlikely(test_tsk_thread_flag(child, TIF_SINGLESTEP)))
124 regs->flags |= X86_EFLAGS_TF;
125
126
127
128
129
130
131 set_tsk_thread_flag(child, TIF_SINGLESTEP);
132
133 oflags = regs->flags;
134
135
136 regs->flags |= X86_EFLAGS_TF;
137
138
139
140
141
142
143
144
145
146
147 if (is_setting_trap_flag(child, regs)) {
148 clear_tsk_thread_flag(child, TIF_FORCED_TF);
149 return 0;
150 }
151
152
153
154
155
156 if (oflags & X86_EFLAGS_TF)
157 return test_tsk_thread_flag(child, TIF_FORCED_TF);
158
159 set_tsk_thread_flag(child, TIF_FORCED_TF);
160
161 return 1;
162}
163
164void set_task_blockstep(struct task_struct *task, bool on)
165{
166 unsigned long debugctl;
167
168
169
170
171
172
173
174
175
176
177
178 local_irq_disable();
179 debugctl = get_debugctlmsr();
180 if (on) {
181 debugctl |= DEBUGCTLMSR_BTF;
182 set_tsk_thread_flag(task, TIF_BLOCKSTEP);
183 } else {
184 debugctl &= ~DEBUGCTLMSR_BTF;
185 clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
186 }
187 if (task == current)
188 update_debugctlmsr(debugctl);
189 local_irq_enable();
190}
191
192
193
194
195static void enable_step(struct task_struct *child, bool block)
196{
197
198
199
200
201
202
203
204 if (enable_single_step(child) && block)
205 set_task_blockstep(child, true);
206 else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
207 set_task_blockstep(child, false);
208}
209
210void user_enable_single_step(struct task_struct *child)
211{
212 enable_step(child, 0);
213}
214
215void user_enable_block_step(struct task_struct *child)
216{
217 enable_step(child, 1);
218}
219
220void user_disable_single_step(struct task_struct *child)
221{
222
223
224
225 if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
226 set_task_blockstep(child, false);
227
228
229 clear_tsk_thread_flag(child, TIF_SINGLESTEP);
230
231
232 if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))
233 task_pt_regs(child)->flags &= ~X86_EFLAGS_TF;
234}
235