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1a59d1b8 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
8b7b80b9 AM |
2 | /* |
3 | * User-space Probes (UProbes) for powerpc | |
4 | * | |
8b7b80b9 AM |
5 | * Copyright IBM Corporation, 2007-2012 |
6 | * | |
7 | * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@in.ibm.com> | |
8 | */ | |
9 | #include <linux/kernel.h> | |
10 | #include <linux/sched.h> | |
11 | #include <linux/ptrace.h> | |
12 | #include <linux/uprobes.h> | |
13 | #include <linux/uaccess.h> | |
14 | #include <linux/kdebug.h> | |
15 | ||
16 | #include <asm/sstep.h> | |
75346251 | 17 | #include <asm/inst.h> |
8b7b80b9 AM |
18 | |
19 | #define UPROBE_TRAP_NR UINT_MAX | |
20 | ||
ab07e807 AM |
21 | /** |
22 | * is_trap_insn - check if the instruction is a trap variant | |
23 | * @insn: instruction to be checked. | |
24 | * Returns true if @insn is a trap variant. | |
25 | */ | |
26 | bool is_trap_insn(uprobe_opcode_t *insn) | |
27 | { | |
28 | return (is_trap(*insn)); | |
29 | } | |
30 | ||
8b7b80b9 AM |
31 | /** |
32 | * arch_uprobe_analyze_insn | |
33 | * @mm: the probed address space. | |
34 | * @arch_uprobe: the probepoint information. | |
35 | * @addr: vaddr to probe. | |
36 | * Return 0 on success or a -ve number on error. | |
37 | */ | |
38 | int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, | |
39 | struct mm_struct *mm, unsigned long addr) | |
40 | { | |
41 | if (addr & 0x03) | |
42 | return -EINVAL; | |
43 | ||
8b7b80b9 AM |
44 | return 0; |
45 | } | |
46 | ||
47 | /* | |
48 | * arch_uprobe_pre_xol - prepare to execute out of line. | |
49 | * @auprobe: the probepoint information. | |
50 | * @regs: reflects the saved user state of current task. | |
51 | */ | |
52 | int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
53 | { | |
54 | struct arch_uprobe_task *autask = ¤t->utask->autask; | |
55 | ||
56 | autask->saved_trap_nr = current->thread.trap_nr; | |
57 | current->thread.trap_nr = UPROBE_TRAP_NR; | |
58 | regs->nip = current->utask->xol_vaddr; | |
65b2c8f0 ON |
59 | |
60 | user_enable_single_step(current); | |
8b7b80b9 AM |
61 | return 0; |
62 | } | |
63 | ||
64 | /** | |
65 | * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs | |
66 | * @regs: Reflects the saved state of the task after it has hit a breakpoint | |
67 | * instruction. | |
68 | * Return the address of the breakpoint instruction. | |
69 | */ | |
70 | unsigned long uprobe_get_swbp_addr(struct pt_regs *regs) | |
71 | { | |
72 | return instruction_pointer(regs); | |
73 | } | |
74 | ||
75 | /* | |
76 | * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc), | |
77 | * then detect the case where a singlestepped instruction jumps back to its | |
78 | * own address. It is assumed that anything like do_page_fault/do_trap/etc | |
79 | * sets thread.trap_nr != UINT_MAX. | |
80 | * | |
81 | * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr, | |
82 | * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to | |
83 | * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol(). | |
84 | */ | |
85 | bool arch_uprobe_xol_was_trapped(struct task_struct *t) | |
86 | { | |
87 | if (t->thread.trap_nr != UPROBE_TRAP_NR) | |
88 | return true; | |
89 | ||
90 | return false; | |
91 | } | |
92 | ||
93 | /* | |
94 | * Called after single-stepping. To avoid the SMP problems that can | |
95 | * occur when we temporarily put back the original opcode to | |
96 | * single-step, we single-stepped a copy of the instruction. | |
97 | * | |
98 | * This function prepares to resume execution after the single-step. | |
99 | */ | |
100 | int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
101 | { | |
102 | struct uprobe_task *utask = current->utask; | |
103 | ||
104 | WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); | |
105 | ||
106 | current->thread.trap_nr = utask->autask.saved_trap_nr; | |
107 | ||
108 | /* | |
109 | * On powerpc, except for loads and stores, most instructions | |
110 | * including ones that alter code flow (branches, calls, returns) | |
111 | * are emulated in the kernel. We get here only if the emulation | |
112 | * support doesn't exist and have to fix-up the next instruction | |
113 | * to be executed. | |
114 | */ | |
622cf6f4 | 115 | regs->nip = utask->vaddr + ppc_inst_len(ppc_inst_read(&auprobe->insn)); |
65b2c8f0 ON |
116 | |
117 | user_disable_single_step(current); | |
8b7b80b9 AM |
118 | return 0; |
119 | } | |
120 | ||
121 | /* callback routine for handling exceptions. */ | |
122 | int arch_uprobe_exception_notify(struct notifier_block *self, | |
123 | unsigned long val, void *data) | |
124 | { | |
125 | struct die_args *args = data; | |
126 | struct pt_regs *regs = args->regs; | |
127 | ||
128 | /* regs == NULL is a kernel bug */ | |
129 | if (WARN_ON(!regs)) | |
130 | return NOTIFY_DONE; | |
131 | ||
132 | /* We are only interested in userspace traps */ | |
133 | if (!user_mode(regs)) | |
134 | return NOTIFY_DONE; | |
135 | ||
136 | switch (val) { | |
137 | case DIE_BPT: | |
138 | if (uprobe_pre_sstep_notifier(regs)) | |
139 | return NOTIFY_STOP; | |
140 | break; | |
141 | case DIE_SSTEP: | |
142 | if (uprobe_post_sstep_notifier(regs)) | |
143 | return NOTIFY_STOP; | |
144 | default: | |
145 | break; | |
146 | } | |
147 | return NOTIFY_DONE; | |
148 | } | |
149 | ||
150 | /* | |
151 | * This function gets called when XOL instruction either gets trapped or | |
152 | * the thread has a fatal signal, so reset the instruction pointer to its | |
153 | * probed address. | |
154 | */ | |
155 | void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
156 | { | |
157 | struct uprobe_task *utask = current->utask; | |
158 | ||
159 | current->thread.trap_nr = utask->autask.saved_trap_nr; | |
160 | instruction_pointer_set(regs, utask->vaddr); | |
65b2c8f0 ON |
161 | |
162 | user_disable_single_step(current); | |
8b7b80b9 AM |
163 | } |
164 | ||
165 | /* | |
166 | * See if the instruction can be emulated. | |
167 | * Returns true if instruction was emulated, false otherwise. | |
168 | */ | |
169 | bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) | |
170 | { | |
171 | int ret; | |
172 | ||
173 | /* | |
174 | * emulate_step() returns 1 if the insn was successfully emulated. | |
175 | * For all other cases, we need to single-step in hardware. | |
176 | */ | |
f8faaffa | 177 | ret = emulate_step(regs, ppc_inst_read(&auprobe->insn)); |
8b7b80b9 AM |
178 | if (ret > 0) |
179 | return true; | |
180 | ||
181 | return false; | |
182 | } | |
f15706b7 AA |
183 | |
184 | unsigned long | |
185 | arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) | |
186 | { | |
187 | unsigned long orig_ret_vaddr; | |
188 | ||
189 | orig_ret_vaddr = regs->link; | |
190 | ||
191 | /* Replace the return addr with trampoline addr */ | |
192 | regs->link = trampoline_vaddr; | |
193 | ||
194 | return orig_ret_vaddr; | |
195 | } | |
2dea1d9c NR |
196 | |
197 | bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, | |
198 | struct pt_regs *regs) | |
199 | { | |
200 | if (ctx == RP_CHECK_CHAIN_CALL) | |
201 | return regs->gpr[1] <= ret->stack; | |
202 | else | |
203 | return regs->gpr[1] < ret->stack; | |
204 | } |