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 */
is_trap_insn(uprobe_opcode_t * insn)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 */
arch_uprobe_analyze_insn(struct arch_uprobe * auprobe,struct mm_struct * mm,unsigned long addr)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(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 return 0;
52 }
53
54 /*
55 * arch_uprobe_pre_xol - prepare to execute out of line.
56 * @auprobe: the probepoint information.
57 * @regs: reflects the saved user state of current task.
58 */
arch_uprobe_pre_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)59 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
60 {
61 struct arch_uprobe_task *autask = ¤t->utask->autask;
62
63 autask->saved_trap_nr = current->thread.trap_nr;
64 current->thread.trap_nr = UPROBE_TRAP_NR;
65 regs->nip = current->utask->xol_vaddr;
66
67 user_enable_single_step(current);
68 return 0;
69 }
70
71 /**
72 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
73 * @regs: Reflects the saved state of the task after it has hit a breakpoint
74 * instruction.
75 * Return the address of the breakpoint instruction.
76 */
uprobe_get_swbp_addr(struct pt_regs * regs)77 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
78 {
79 return instruction_pointer(regs);
80 }
81
82 /*
83 * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc),
84 * then detect the case where a singlestepped instruction jumps back to its
85 * own address. It is assumed that anything like do_page_fault/do_trap/etc
86 * sets thread.trap_nr != UINT_MAX.
87 *
88 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
89 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
90 * UPROBE_TRAP_NR == UINT_MAX set by arch_uprobe_pre_xol().
91 */
arch_uprobe_xol_was_trapped(struct task_struct * t)92 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
93 {
94 if (t->thread.trap_nr != UPROBE_TRAP_NR)
95 return true;
96
97 return false;
98 }
99
100 /*
101 * Called after single-stepping. To avoid the SMP problems that can
102 * occur when we temporarily put back the original opcode to
103 * single-step, we single-stepped a copy of the instruction.
104 *
105 * This function prepares to resume execution after the single-step.
106 */
arch_uprobe_post_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)107 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
108 {
109 struct uprobe_task *utask = current->utask;
110
111 WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
112
113 current->thread.trap_nr = utask->autask.saved_trap_nr;
114
115 /*
116 * On powerpc, except for loads and stores, most instructions
117 * including ones that alter code flow (branches, calls, returns)
118 * are emulated in the kernel. We get here only if the emulation
119 * support doesn't exist and have to fix-up the next instruction
120 * to be executed.
121 */
122 regs->nip = (unsigned long)ppc_inst_next((void *)utask->vaddr, &auprobe->insn);
123
124 user_disable_single_step(current);
125 return 0;
126 }
127
128 /* callback routine for handling exceptions. */
arch_uprobe_exception_notify(struct notifier_block * self,unsigned long val,void * data)129 int arch_uprobe_exception_notify(struct notifier_block *self,
130 unsigned long val, void *data)
131 {
132 struct die_args *args = data;
133 struct pt_regs *regs = args->regs;
134
135 /* regs == NULL is a kernel bug */
136 if (WARN_ON(!regs))
137 return NOTIFY_DONE;
138
139 /* We are only interested in userspace traps */
140 if (!user_mode(regs))
141 return NOTIFY_DONE;
142
143 switch (val) {
144 case DIE_BPT:
145 if (uprobe_pre_sstep_notifier(regs))
146 return NOTIFY_STOP;
147 break;
148 case DIE_SSTEP:
149 if (uprobe_post_sstep_notifier(regs))
150 return NOTIFY_STOP;
151 break;
152 default:
153 break;
154 }
155 return NOTIFY_DONE;
156 }
157
158 /*
159 * This function gets called when XOL instruction either gets trapped or
160 * the thread has a fatal signal, so reset the instruction pointer to its
161 * probed address.
162 */
arch_uprobe_abort_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)163 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
164 {
165 struct uprobe_task *utask = current->utask;
166
167 current->thread.trap_nr = utask->autask.saved_trap_nr;
168 instruction_pointer_set(regs, utask->vaddr);
169
170 user_disable_single_step(current);
171 }
172
173 /*
174 * See if the instruction can be emulated.
175 * Returns true if instruction was emulated, false otherwise.
176 */
arch_uprobe_skip_sstep(struct arch_uprobe * auprobe,struct pt_regs * regs)177 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
178 {
179 int ret;
180
181 /*
182 * emulate_step() returns 1 if the insn was successfully emulated.
183 * For all other cases, we need to single-step in hardware.
184 */
185 ret = emulate_step(regs, ppc_inst_read(&auprobe->insn));
186 if (ret > 0)
187 return true;
188
189 return false;
190 }
191
192 unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,struct pt_regs * regs)193 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
194 {
195 unsigned long orig_ret_vaddr;
196
197 orig_ret_vaddr = regs->link;
198
199 /* Replace the return addr with trampoline addr */
200 regs->link = trampoline_vaddr;
201
202 return orig_ret_vaddr;
203 }
204
arch_uretprobe_is_alive(struct return_instance * ret,enum rp_check ctx,struct pt_regs * regs)205 bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
206 struct pt_regs *regs)
207 {
208 if (ctx == RP_CHECK_CHAIN_CALL)
209 return regs->gpr[1] <= ret->stack;
210 else
211 return regs->gpr[1] < ret->stack;
212 }
213