1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * User-space Probes (UProbes) for powerpc |
4 | * |
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> |
17 | #include <asm/inst.h> |
18 | |
19 | #define UPROBE_TRAP_NR UINT_MAX |
20 | |
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 | |
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 | |
44 | if (cpu_has_feature(CPU_FTR_ARCH_31) && |
45 | ppc_inst_prefixed(ppc_inst_read(auprobe->insn)) && |
46 | (addr & 0x3f) == 60) { |
47 | pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n" ); |
48 | return -EINVAL; |
49 | } |
50 | |
51 | if (!can_single_step(ppc_inst_val(ppc_inst_read(auprobe->insn)))) { |
52 | pr_info_ratelimited("Cannot register a uprobe on instructions that can't be single stepped\n" ); |
53 | return -ENOTSUPP; |
54 | } |
55 | |
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_set_return_ip(regs, current->utask->xol_vaddr); |
71 | |
72 | user_enable_single_step(current); |
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_set_return_ip(regs, (unsigned long)ppc_inst_next((void *)utask->vaddr, auprobe->insn)); |
128 | |
129 | user_disable_single_step(current); |
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 | break; |
157 | default: |
158 | break; |
159 | } |
160 | return NOTIFY_DONE; |
161 | } |
162 | |
163 | /* |
164 | * This function gets called when XOL instruction either gets trapped or |
165 | * the thread has a fatal signal, so reset the instruction pointer to its |
166 | * probed address. |
167 | */ |
168 | void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) |
169 | { |
170 | struct uprobe_task *utask = current->utask; |
171 | |
172 | current->thread.trap_nr = utask->autask.saved_trap_nr; |
173 | instruction_pointer_set(regs, val: utask->vaddr); |
174 | |
175 | user_disable_single_step(current); |
176 | } |
177 | |
178 | /* |
179 | * See if the instruction can be emulated. |
180 | * Returns true if instruction was emulated, false otherwise. |
181 | */ |
182 | bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) |
183 | { |
184 | int ret; |
185 | |
186 | /* |
187 | * emulate_step() returns 1 if the insn was successfully emulated. |
188 | * For all other cases, we need to single-step in hardware. |
189 | */ |
190 | ret = emulate_step(regs, ppc_inst_read(auprobe->insn)); |
191 | if (ret > 0) |
192 | return true; |
193 | |
194 | return false; |
195 | } |
196 | |
197 | unsigned long |
198 | arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) |
199 | { |
200 | unsigned long orig_ret_vaddr; |
201 | |
202 | orig_ret_vaddr = regs->link; |
203 | |
204 | /* Replace the return addr with trampoline addr */ |
205 | regs->link = trampoline_vaddr; |
206 | |
207 | return orig_ret_vaddr; |
208 | } |
209 | |
210 | bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, |
211 | struct pt_regs *regs) |
212 | { |
213 | if (ctx == RP_CHECK_CHAIN_CALL) |
214 | return regs->gpr[1] <= ret->stack; |
215 | else |
216 | return regs->gpr[1] < ret->stack; |
217 | } |
218 | |