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, 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
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