Commit | Line | Data |
---|---|---|
fa1e03ea RM |
1 | /* |
2 | * x86 single-step support code, common to 32-bit and 64-bit. | |
3 | */ | |
4 | #include <linux/sched.h> | |
5 | #include <linux/mm.h> | |
6 | #include <linux/ptrace.h> | |
7 | ||
8 | #define LDT_SEGMENT 4 | |
9 | ||
10 | unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs) | |
11 | { | |
12 | unsigned long addr, seg; | |
13 | ||
14 | addr = regs->rip; | |
15 | seg = regs->cs & 0xffff; | |
16 | ||
17 | /* | |
18 | * We'll assume that the code segments in the GDT | |
19 | * are all zero-based. That is largely true: the | |
20 | * TLS segments are used for data, and the PNPBIOS | |
21 | * and APM bios ones we just ignore here. | |
22 | */ | |
23 | if (seg & LDT_SEGMENT) { | |
24 | u32 *desc; | |
25 | unsigned long base; | |
26 | ||
27 | seg &= ~7UL; | |
28 | ||
29 | mutex_lock(&child->mm->context.lock); | |
30 | if (unlikely((seg >> 3) >= child->mm->context.size)) | |
31 | addr = -1L; /* bogus selector, access would fault */ | |
32 | else { | |
33 | desc = child->mm->context.ldt + seg; | |
34 | base = ((desc[0] >> 16) | | |
35 | ((desc[1] & 0xff) << 16) | | |
36 | (desc[1] & 0xff000000)); | |
37 | ||
38 | /* 16-bit code segment? */ | |
39 | if (!((desc[1] >> 22) & 1)) | |
40 | addr &= 0xffff; | |
41 | addr += base; | |
42 | } | |
43 | mutex_unlock(&child->mm->context.lock); | |
44 | } | |
45 | ||
46 | return addr; | |
47 | } | |
48 | ||
49 | static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs) | |
50 | { | |
51 | int i, copied; | |
52 | unsigned char opcode[15]; | |
53 | unsigned long addr = convert_rip_to_linear(child, regs); | |
54 | ||
55 | copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0); | |
56 | for (i = 0; i < copied; i++) { | |
57 | switch (opcode[i]) { | |
58 | /* popf and iret */ | |
59 | case 0x9d: case 0xcf: | |
60 | return 1; | |
61 | ||
62 | /* CHECKME: 64 65 */ | |
63 | ||
64 | /* opcode and address size prefixes */ | |
65 | case 0x66: case 0x67: | |
66 | continue; | |
67 | /* irrelevant prefixes (segment overrides and repeats) */ | |
68 | case 0x26: case 0x2e: | |
69 | case 0x36: case 0x3e: | |
70 | case 0x64: case 0x65: | |
71 | case 0xf2: case 0xf3: | |
72 | continue; | |
73 | ||
74 | case 0x40 ... 0x4f: | |
75 | if (regs->cs != __USER_CS) | |
76 | /* 32-bit mode: register increment */ | |
77 | return 0; | |
78 | /* 64-bit mode: REX prefix */ | |
79 | continue; | |
80 | ||
81 | /* CHECKME: f2, f3 */ | |
82 | ||
83 | /* | |
84 | * pushf: NOTE! We should probably not let | |
85 | * the user see the TF bit being set. But | |
86 | * it's more pain than it's worth to avoid | |
87 | * it, and a debugger could emulate this | |
88 | * all in user space if it _really_ cares. | |
89 | */ | |
90 | case 0x9c: | |
91 | default: | |
92 | return 0; | |
93 | } | |
94 | } | |
95 | return 0; | |
96 | } | |
97 | ||
98 | void user_enable_single_step(struct task_struct *child) | |
99 | { | |
100 | struct pt_regs *regs = task_pt_regs(child); | |
101 | ||
102 | /* | |
103 | * Always set TIF_SINGLESTEP - this guarantees that | |
104 | * we single-step system calls etc.. This will also | |
105 | * cause us to set TF when returning to user mode. | |
106 | */ | |
107 | set_tsk_thread_flag(child, TIF_SINGLESTEP); | |
108 | ||
109 | /* | |
110 | * If TF was already set, don't do anything else | |
111 | */ | |
112 | if (regs->eflags & X86_EFLAGS_TF) | |
113 | return; | |
114 | ||
115 | /* Set TF on the kernel stack.. */ | |
116 | regs->eflags |= X86_EFLAGS_TF; | |
117 | ||
118 | /* | |
119 | * ..but if TF is changed by the instruction we will trace, | |
120 | * don't mark it as being "us" that set it, so that we | |
121 | * won't clear it by hand later. | |
122 | */ | |
123 | if (is_setting_trap_flag(child, regs)) | |
124 | return; | |
125 | ||
126 | child->ptrace |= PT_DTRACE; | |
127 | } | |
128 | ||
129 | void user_disable_single_step(struct task_struct *child) | |
130 | { | |
131 | /* Always clear TIF_SINGLESTEP... */ | |
132 | clear_tsk_thread_flag(child, TIF_SINGLESTEP); | |
133 | ||
134 | /* But touch TF only if it was set by us.. */ | |
135 | if (child->ptrace & PT_DTRACE) { | |
136 | struct pt_regs *regs = task_pt_regs(child); | |
137 | regs->eflags &= ~X86_EFLAGS_TF; | |
138 | child->ptrace &= ~PT_DTRACE; | |
139 | } | |
140 | } |