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8b7b80b9 AM |
1 | /* |
2 | * User-space Probes (UProbes) for powerpc | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
18 | * Copyright IBM Corporation, 2007-2012 | |
19 | * | |
20 | * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com> | |
21 | */ | |
22 | #include <linux/kernel.h> | |
23 | #include <linux/sched.h> | |
24 | #include <linux/ptrace.h> | |
25 | #include <linux/uprobes.h> | |
26 | #include <linux/uaccess.h> | |
27 | #include <linux/kdebug.h> | |
28 | ||
29 | #include <asm/sstep.h> | |
30 | ||
31 | #define UPROBE_TRAP_NR UINT_MAX | |
32 | ||
ab07e807 AM |
33 | /** |
34 | * is_trap_insn - check if the instruction is a trap variant | |
35 | * @insn: instruction to be checked. | |
36 | * Returns true if @insn is a trap variant. | |
37 | */ | |
38 | bool is_trap_insn(uprobe_opcode_t *insn) | |
39 | { | |
40 | return (is_trap(*insn)); | |
41 | } | |
42 | ||
8b7b80b9 AM |
43 | /** |
44 | * arch_uprobe_analyze_insn | |
45 | * @mm: the probed address space. | |
46 | * @arch_uprobe: the probepoint information. | |
47 | * @addr: vaddr to probe. | |
48 | * Return 0 on success or a -ve number on error. | |
49 | */ | |
50 | int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, | |
51 | struct mm_struct *mm, unsigned long addr) | |
52 | { | |
53 | if (addr & 0x03) | |
54 | return -EINVAL; | |
55 | ||
8b7b80b9 AM |
56 | return 0; |
57 | } | |
58 | ||
59 | /* | |
60 | * arch_uprobe_pre_xol - prepare to execute out of line. | |
61 | * @auprobe: the probepoint information. | |
62 | * @regs: reflects the saved user state of current task. | |
63 | */ | |
64 | int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
65 | { | |
66 | struct arch_uprobe_task *autask = ¤t->utask->autask; | |
67 | ||
68 | autask->saved_trap_nr = current->thread.trap_nr; | |
69 | current->thread.trap_nr = UPROBE_TRAP_NR; | |
70 | regs->nip = current->utask->xol_vaddr; | |
65b2c8f0 ON |
71 | |
72 | user_enable_single_step(current); | |
8b7b80b9 AM |
73 | return 0; |
74 | } | |
75 | ||
76 | /** | |
77 | * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs | |
78 | * @regs: Reflects the saved state of the task after it has hit a breakpoint | |
79 | * instruction. | |
80 | * Return the address of the breakpoint instruction. | |
81 | */ | |
82 | unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) | |
83 | { | |
84 | return instruction_pointer(regs); | |
85 | } | |
86 | ||
87 | /* | |
88 | * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), | |
89 | * then detect the case where a singlestepped instruction jumps back to its | |
90 | * own address. It is assumed that anything like do_page_fault/do_trap/etc | |
91 | * sets thread.trap_nr != UINT_MAX. | |
92 | * | |
93 | * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, | |
94 | * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to | |
95 | * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). | |
96 | */ | |
97 | bool arch_uprobe_xol_was_trapped(struct task_struct *t) | |
98 | { | |
99 | if (t->thread.trap_nr != UPROBE_TRAP_NR) | |
100 | return true; | |
101 | ||
102 | return false; | |
103 | } | |
104 | ||
105 | /* | |
106 | * Called after single-stepping. To avoid the SMP problems that can | |
107 | * occur when we temporarily put back the original opcode to | |
108 | * single-step, we single-stepped a copy of the instruction. | |
109 | * | |
110 | * This function prepares to resume execution after the single-step. | |
111 | */ | |
112 | int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
113 | { | |
114 | struct uprobe_task *utask = current->utask; | |
115 | ||
116 | WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); | |
117 | ||
118 | current->thread.trap_nr = utask->autask.saved_trap_nr; | |
119 | ||
120 | /* | |
121 | * On powerpc, except for loads and stores, most instructions | |
122 | * including ones that alter code flow (branches, calls, returns) | |
123 | * are emulated in the kernel. We get here only if the emulation | |
124 | * support doesn't exist and have to fix-up the next instruction | |
125 | * to be executed. | |
126 | */ | |
127 | regs->nip = utask->vaddr + MAX_UINSN_BYTES; | |
65b2c8f0 ON |
128 | |
129 | user_disable_single_step(current); | |
8b7b80b9 AM |
130 | return 0; |
131 | } | |
132 | ||
133 | /* callback routine for handling exceptions. */ | |
134 | int arch_uprobe_exception_notify(struct notifier_block *self, | |
135 | unsigned long val, void *data) | |
136 | { | |
137 | struct die_args *args = data; | |
138 | struct pt_regs *regs = args->regs; | |
139 | ||
140 | /* regs == NULL is a kernel bug */ | |
141 | if (WARN_ON(!regs)) | |
142 | return NOTIFY_DONE; | |
143 | ||
144 | /* We are only interested in userspace traps */ | |
145 | if (!user_mode(regs)) | |
146 | return NOTIFY_DONE; | |
147 | ||
148 | switch (val) { | |
149 | case DIE_BPT: | |
150 | if (uprobe_pre_sstep_notifier(regs)) | |
151 | return NOTIFY_STOP; | |
152 | break; | |
153 | case DIE_SSTEP: | |
154 | if (uprobe_post_sstep_notifier(regs)) | |
155 | return NOTIFY_STOP; | |
156 | default: | |
157 | break; | |
158 | } | |
159 | return NOTIFY_DONE; | |
160 | } | |
161 | ||
162 | /* | |
163 | * This function gets called when XOL instruction either gets trapped or | |
164 | * the thread has a fatal signal, so reset the instruction pointer to its | |
165 | * probed address. | |
166 | */ | |
167 | void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
168 | { | |
169 | struct uprobe_task *utask = current->utask; | |
170 | ||
171 | current->thread.trap_nr = utask->autask.saved_trap_nr; | |
172 | instruction_pointer_set(regs, utask->vaddr); | |
65b2c8f0 ON |
173 | |
174 | user_disable_single_step(current); | |
8b7b80b9 AM |
175 | } |
176 | ||
177 | /* | |
178 | * See if the instruction can be emulated. | |
179 | * Returns true if instruction was emulated, false otherwise. | |
180 | */ | |
181 | bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
182 | { | |
183 | int ret; | |
184 | ||
185 | /* | |
186 | * emulate_step() returns 1 if the insn was successfully emulated. | |
187 | * For all other cases, we need to single-step in hardware. | |
188 | */ | |
3d78e945 | 189 | ret = emulate_step(regs, auprobe->insn); |
8b7b80b9 AM |
190 | if (ret > 0) |
191 | return true; | |
192 | ||
193 | return false; | |
194 | } | |
f15706b7 AA |
195 | |
196 | unsigned long | |
197 | arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) | |
198 | { | |
199 | unsigned long orig_ret_vaddr; | |
200 | ||
201 | orig_ret_vaddr = regs->link; | |
202 | ||
203 | /* Replace the return addr with trampoline addr */ | |
204 | regs->link = trampoline_vaddr; | |
205 | ||
206 | return orig_ret_vaddr; | |
207 | } |