1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * User-space Probes (UProbes) for sparc
4  *
5  * Copyright (C) 2013 Oracle Inc.
6  *
7  * Authors:
8  *	Jose E. Marchesi <jose.marchesi@oracle.com>
9  *	Eric Saint Etienne <eric.saint.etienne@oracle.com>
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/highmem.h>
14 #include <linux/uprobes.h>
15 #include <linux/uaccess.h>
16 #include <linux/sched.h> /* For struct task_struct */
17 #include <linux/kdebug.h>
18 
19 #include <asm/cacheflush.h>
20 
21 /* Compute the address of the breakpoint instruction and return it.
22  *
23  * Note that uprobe_get_swbp_addr is defined as a weak symbol in
24  * kernel/events/uprobe.c.
25  */
uprobe_get_swbp_addr(struct pt_regs * regs)26 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
27 {
28 	return instruction_pointer(regs);
29 }
30 
copy_to_page(struct page * page,unsigned long vaddr,const void * src,int len)31 static void copy_to_page(struct page *page, unsigned long vaddr,
32 			 const void *src, int len)
33 {
34 	void *kaddr = kmap_atomic(page);
35 
36 	memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
37 	kunmap_atomic(kaddr);
38 }
39 
40 /* Fill in the xol area with the probed instruction followed by the
41  * single-step trap.  Some fixups in the copied instruction are
42  * performed at this point.
43  *
44  * Note that uprobe_xol_copy is defined as a weak symbol in
45  * kernel/events/uprobe.c.
46  */
arch_uprobe_copy_ixol(struct page * page,unsigned long vaddr,void * src,unsigned long len)47 void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
48 			   void *src, unsigned long len)
49 {
50 	const u32 stp_insn = UPROBE_STP_INSN;
51 	u32 insn = *(u32 *) src;
52 
53 	/* Branches annulling their delay slot must be fixed to not do
54 	 * so.  Clearing the annul bit on these instructions we can be
55 	 * sure the single-step breakpoint in the XOL slot will be
56 	 * executed.
57 	 */
58 
59 	u32 op = (insn >> 30) & 0x3;
60 	u32 op2 = (insn >> 22) & 0x7;
61 
62 	if (op == 0 &&
63 	    (op2 == 1 || op2 == 2 || op2 == 3 || op2 == 5 || op2 == 6) &&
64 	    (insn & ANNUL_BIT) == ANNUL_BIT)
65 		insn &= ~ANNUL_BIT;
66 
67 	copy_to_page(page, vaddr, &insn, len);
68 	copy_to_page(page, vaddr+len, &stp_insn, 4);
69 }
70 
71 
72 /* Instruction analysis/validity.
73  *
74  * This function returns 0 on success or a -ve number on error.
75  */
arch_uprobe_analyze_insn(struct arch_uprobe * auprobe,struct mm_struct * mm,unsigned long addr)76 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
77 			     struct mm_struct *mm, unsigned long addr)
78 {
79 	/* Any unsupported instruction?  Then return -EINVAL  */
80 	return 0;
81 }
82 
83 /* If INSN is a relative control transfer instruction, return the
84  * corrected branch destination value.
85  *
86  * Note that regs->tpc and regs->tnpc still hold the values of the
87  * program counters at the time of the single-step trap due to the
88  * execution of the UPROBE_STP_INSN at utask->xol_vaddr + 4.
89  *
90  */
relbranch_fixup(u32 insn,struct uprobe_task * utask,struct pt_regs * regs)91 static unsigned long relbranch_fixup(u32 insn, struct uprobe_task *utask,
92 				     struct pt_regs *regs)
93 {
94 	/* Branch not taken, no mods necessary.  */
95 	if (regs->tnpc == regs->tpc + 0x4UL)
96 		return utask->autask.saved_tnpc + 0x4UL;
97 
98 	/* The three cases are call, branch w/prediction,
99 	 * and traditional branch.
100 	 */
101 	if ((insn & 0xc0000000) == 0x40000000 ||
102 	    (insn & 0xc1c00000) == 0x00400000 ||
103 	    (insn & 0xc1c00000) == 0x00800000) {
104 		unsigned long real_pc = (unsigned long) utask->vaddr;
105 		unsigned long ixol_addr = utask->xol_vaddr;
106 
107 		/* The instruction did all the work for us
108 		 * already, just apply the offset to the correct
109 		 * instruction location.
110 		 */
111 		return (real_pc + (regs->tnpc - ixol_addr));
112 	}
113 
114 	/* It is jmpl or some other absolute PC modification instruction,
115 	 * leave NPC as-is.
116 	 */
117 	return regs->tnpc;
118 }
119 
120 /* If INSN is an instruction which writes its PC location
121  * into a destination register, fix that up.
122  */
retpc_fixup(struct pt_regs * regs,u32 insn,unsigned long real_pc)123 static int retpc_fixup(struct pt_regs *regs, u32 insn,
124 		       unsigned long real_pc)
125 {
126 	unsigned long *slot = NULL;
127 	int rc = 0;
128 
129 	/* Simplest case is 'call', which always uses %o7 */
130 	if ((insn & 0xc0000000) == 0x40000000)
131 		slot = &regs->u_regs[UREG_I7];
132 
133 	/* 'jmpl' encodes the register inside of the opcode */
134 	if ((insn & 0xc1f80000) == 0x81c00000) {
135 		unsigned long rd = ((insn >> 25) & 0x1f);
136 
137 		if (rd <= 15) {
138 			slot = &regs->u_regs[rd];
139 		} else {
140 			unsigned long fp = regs->u_regs[UREG_FP];
141 			/* Hard case, it goes onto the stack. */
142 			flushw_all();
143 
144 			rd -= 16;
145 			if (test_thread_64bit_stack(fp)) {
146 				unsigned long __user *uslot =
147 			(unsigned long __user *) (fp + STACK_BIAS) + rd;
148 				rc = __put_user(real_pc, uslot);
149 			} else {
150 				unsigned int __user *uslot = (unsigned int
151 						__user *) fp + rd;
152 				rc = __put_user((u32) real_pc, uslot);
153 			}
154 		}
155 	}
156 	if (slot != NULL)
157 		*slot = real_pc;
158 	return rc;
159 }
160 
161 /* Single-stepping can be avoided for certain instructions: NOPs and
162  * instructions that can be emulated.  This function determines
163  * whether the instruction where the uprobe is installed falls in one
164  * of these cases and emulates it.
165  *
166  * This function returns true if the single-stepping can be skipped,
167  * false otherwise.
168  */
arch_uprobe_skip_sstep(struct arch_uprobe * auprobe,struct pt_regs * regs)169 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
170 {
171 	/* We currently only emulate NOP instructions.
172 	 */
173 
174 	if (auprobe->ixol == (1 << 24)) {
175 		regs->tnpc += 4;
176 		regs->tpc += 4;
177 		return true;
178 	}
179 
180 	return false;
181 }
182 
183 /* Prepare to execute out of line.  At this point
184  * current->utask->xol_vaddr points to an allocated XOL slot properly
185  * initialized with the original instruction and the single-stepping
186  * trap instruction.
187  *
188  * This function returns 0 on success, any other number on error.
189  */
arch_uprobe_pre_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)190 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
191 {
192 	struct uprobe_task *utask = current->utask;
193 	struct arch_uprobe_task *autask = &current->utask->autask;
194 
195 	/* Save the current program counters so they can be restored
196 	 * later.
197 	 */
198 	autask->saved_tpc = regs->tpc;
199 	autask->saved_tnpc = regs->tnpc;
200 
201 	/* Adjust PC and NPC so the first instruction in the XOL slot
202 	 * will be executed by the user task.
203 	 */
204 	instruction_pointer_set(regs, utask->xol_vaddr);
205 
206 	return 0;
207 }
208 
209 /* Prepare to resume execution after the single-step.  Called after
210  * single-stepping. To avoid the SMP problems that can occur when we
211  * temporarily put back the original opcode to single-step, we
212  * single-stepped a copy of the instruction.
213  *
214  * This function returns 0 on success, any other number on error.
215  */
arch_uprobe_post_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)216 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
217 {
218 	struct uprobe_task *utask = current->utask;
219 	struct arch_uprobe_task *autask = &utask->autask;
220 	u32 insn = auprobe->ixol;
221 	int rc = 0;
222 
223 	if (utask->state == UTASK_SSTEP_ACK) {
224 		regs->tnpc = relbranch_fixup(insn, utask, regs);
225 		regs->tpc = autask->saved_tnpc;
226 		rc =  retpc_fixup(regs, insn, (unsigned long) utask->vaddr);
227 	} else {
228 		regs->tnpc = utask->vaddr+4;
229 		regs->tpc = autask->saved_tnpc+4;
230 	}
231 	return rc;
232 }
233 
234 /* Handler for uprobe traps.  This is called from the traps table and
235  * triggers the proper die notification.
236  */
uprobe_trap(struct pt_regs * regs,unsigned long trap_level)237 asmlinkage void uprobe_trap(struct pt_regs *regs,
238 			    unsigned long trap_level)
239 {
240 	BUG_ON(trap_level != 0x173 && trap_level != 0x174);
241 
242 	/* We are only interested in user-mode code.  Uprobe traps
243 	 * shall not be present in kernel code.
244 	 */
245 	if (!user_mode(regs)) {
246 		local_irq_enable();
247 		bad_trap(regs, trap_level);
248 		return;
249 	}
250 
251 	/* trap_level == 0x173 --> ta 0x73
252 	 * trap_level == 0x174 --> ta 0x74
253 	 */
254 	if (notify_die((trap_level == 0x173) ? DIE_BPT : DIE_SSTEP,
255 				(trap_level == 0x173) ? "bpt" : "sstep",
256 				regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
257 		bad_trap(regs, trap_level);
258 }
259 
260 /* Callback routine for handling die notifications.
261 */
arch_uprobe_exception_notify(struct notifier_block * self,unsigned long val,void * data)262 int arch_uprobe_exception_notify(struct notifier_block *self,
263 				 unsigned long val, void *data)
264 {
265 	int ret = NOTIFY_DONE;
266 	struct die_args *args = (struct die_args *)data;
267 
268 	/* We are only interested in userspace traps */
269 	if (args->regs && !user_mode(args->regs))
270 		return NOTIFY_DONE;
271 
272 	switch (val) {
273 	case DIE_BPT:
274 		if (uprobe_pre_sstep_notifier(args->regs))
275 			ret = NOTIFY_STOP;
276 		break;
277 
278 	case DIE_SSTEP:
279 		if (uprobe_post_sstep_notifier(args->regs))
280 			ret = NOTIFY_STOP;
281 
282 	default:
283 		break;
284 	}
285 
286 	return ret;
287 }
288 
289 /* This function gets called when a XOL instruction either gets
290  * trapped or the thread has a fatal signal, so reset the instruction
291  * pointer to its probed address.
292  */
arch_uprobe_abort_xol(struct arch_uprobe * auprobe,struct pt_regs * regs)293 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
294 {
295 	struct uprobe_task *utask = current->utask;
296 
297 	instruction_pointer_set(regs, utask->vaddr);
298 }
299 
300 /* If xol insn itself traps and generates a signal(Say,
301  * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
302  * instruction jumps back to its own address.
303  */
arch_uprobe_xol_was_trapped(struct task_struct * t)304 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
305 {
306 	return false;
307 }
308 
309 unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,struct pt_regs * regs)310 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
311 				  struct pt_regs *regs)
312 {
313 	unsigned long orig_ret_vaddr = regs->u_regs[UREG_I7];
314 
315 	regs->u_regs[UREG_I7] = trampoline_vaddr-8;
316 
317 	return orig_ret_vaddr + 8;
318 }
319