2 * Code for Kernel probes Jump optimization.
4 * Copyright 2017, Anju T, IBM Corp.
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 #include <linux/kprobes.h>
13 #include <linux/jump_label.h>
14 #include <linux/types.h>
15 #include <linux/slab.h>
16 #include <linux/list.h>
17 #include <asm/kprobes.h>
18 #include <asm/ptrace.h>
19 #include <asm/cacheflush.h>
20 #include <asm/code-patching.h>
21 #include <asm/sstep.h>
22 #include <asm/ppc-opcode.h>
24 #define TMPL_CALL_HDLR_IDX \
25 (optprobe_template_call_handler - optprobe_template_entry)
26 #define TMPL_EMULATE_IDX \
27 (optprobe_template_call_emulate - optprobe_template_entry)
28 #define TMPL_RET_IDX \
29 (optprobe_template_ret - optprobe_template_entry)
31 (optprobe_template_op_address - optprobe_template_entry)
32 #define TMPL_INSN_IDX \
33 (optprobe_template_insn - optprobe_template_entry)
34 #define TMPL_END_IDX \
35 (optprobe_template_end - optprobe_template_entry)
37 DEFINE_INSN_CACHE_OPS(ppc_optinsn);
39 static bool insn_page_in_use;
41 static void *__ppc_alloc_insn_page(void)
45 insn_page_in_use = true;
49 static void __ppc_free_insn_page(void *page __maybe_unused)
51 insn_page_in_use = false;
54 struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
55 .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
56 .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
57 /* insn_size initialized later */
58 .alloc = __ppc_alloc_insn_page,
59 .free = __ppc_free_insn_page,
64 * Check if we can optimize this probe. Returns NIP post-emulation if this can
65 * be optimized and 0 otherwise.
67 static unsigned long can_optimize(struct kprobe *p)
70 struct instruction_op op;
71 unsigned long nip = 0;
74 * kprobe placed for kretprobe during boot time
75 * has a 'nop' instruction, which can be emulated.
76 * So further checks can be skipped.
78 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
79 return (unsigned long)p->addr + sizeof(kprobe_opcode_t);
82 * We only support optimizing kernel addresses, but not
85 * FIXME: Optimize kprobes placed in module addresses.
87 if (!is_kernel_addr((unsigned long)p->addr))
90 memset(®s, 0, sizeof(struct pt_regs));
91 regs.nip = (unsigned long)p->addr;
93 regs.msr = MSR_KERNEL;
96 * Kprobe placed in conditional branch instructions are
97 * not optimized, as we can't predict the nip prior with
98 * dummy pt_regs and can not ensure that the return branch
99 * from detour buffer falls in the range of address (i.e 32MB).
100 * A branch back from trampoline is set up in the detour buffer
101 * to the nip returned by the analyse_instr() here.
103 * Ensure that the instruction is not a conditional branch,
104 * and that can be emulated.
106 if (!is_conditional_branch(*p->ainsn.insn) &&
107 analyse_instr(&op, ®s, *p->ainsn.insn))
113 static void optimized_callback(struct optimized_kprobe *op,
114 struct pt_regs *regs)
116 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
119 /* This is possible if op is under delayed unoptimizing */
120 if (kprobe_disabled(&op->kp))
123 local_irq_save(flags);
126 if (kprobe_running()) {
127 kprobes_inc_nmissed_count(&op->kp);
129 __this_cpu_write(current_kprobe, &op->kp);
130 regs->nip = (unsigned long)op->kp.addr;
131 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
132 opt_pre_handler(&op->kp, regs);
133 __this_cpu_write(current_kprobe, NULL);
137 * No need for an explicit __hard_irq_enable() here.
138 * local_irq_restore() will re-enable interrupts,
139 * if they were hard disabled.
141 local_irq_restore(flags);
143 NOKPROBE_SYMBOL(optimized_callback);
145 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
147 if (op->optinsn.insn) {
148 free_ppc_optinsn_slot(op->optinsn.insn, 1);
149 op->optinsn.insn = NULL;
154 * emulate_step() requires insn to be emulated as
155 * second parameter. Load register 'r4' with the
158 void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
160 /* addis r4,0,(insn)@h */
161 patch_instruction(addr, PPC_INST_ADDIS | ___PPC_RT(4) |
162 ((val >> 16) & 0xffff));
165 /* ori r4,r4,(insn)@l */
166 patch_instruction(addr, PPC_INST_ORI | ___PPC_RA(4) |
167 ___PPC_RS(4) | (val & 0xffff));
171 * Generate instructions to load provided immediate 64-bit value
172 * to register 'r3' and patch these instructions at 'addr'.
174 void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
176 /* lis r3,(op)@highest */
177 patch_instruction(addr, PPC_INST_ADDIS | ___PPC_RT(3) |
178 ((val >> 48) & 0xffff));
181 /* ori r3,r3,(op)@higher */
182 patch_instruction(addr, PPC_INST_ORI | ___PPC_RA(3) |
183 ___PPC_RS(3) | ((val >> 32) & 0xffff));
186 /* rldicr r3,r3,32,31 */
187 patch_instruction(addr, PPC_INST_RLDICR | ___PPC_RA(3) |
188 ___PPC_RS(3) | __PPC_SH64(32) | __PPC_ME64(31));
191 /* oris r3,r3,(op)@h */
192 patch_instruction(addr, PPC_INST_ORIS | ___PPC_RA(3) |
193 ___PPC_RS(3) | ((val >> 16) & 0xffff));
196 /* ori r3,r3,(op)@l */
197 patch_instruction(addr, PPC_INST_ORI | ___PPC_RA(3) |
198 ___PPC_RS(3) | (val & 0xffff));
201 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
203 kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step;
204 kprobe_opcode_t *op_callback_addr, *emulate_step_addr;
206 unsigned long nip, size;
209 kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
211 nip = can_optimize(p);
215 /* Allocate instruction slot for detour buffer */
216 buff = get_ppc_optinsn_slot();
221 * OPTPROBE uses 'b' instruction to branch to optinsn.insn.
223 * The target address has to be relatively nearby, to permit use
224 * of branch instruction in powerpc, because the address is specified
225 * in an immediate field in the instruction opcode itself, ie 24 bits
226 * in the opcode specify the address. Therefore the address should
227 * be within 32MB on either side of the current instruction.
229 b_offset = (unsigned long)buff - (unsigned long)p->addr;
230 if (!is_offset_in_branch_range(b_offset))
233 /* Check if the return address is also within 32MB range */
234 b_offset = (unsigned long)(buff + TMPL_RET_IDX) -
236 if (!is_offset_in_branch_range(b_offset))
240 /* We can optimize this via patch_instruction_window later */
241 size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);
242 pr_devel("Copying template to %p, size %lu\n", buff, size);
243 for (i = 0; i < size; i++) {
244 rc = patch_instruction(buff + i, *(optprobe_template_entry + i));
250 * Fixup the template with instructions to:
251 * 1. load the address of the actual probepoint
253 patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX);
256 * 2. branch to optimized_callback() and emulate_step()
258 op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");
259 emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step");
260 if (!op_callback_addr || !emulate_step_addr) {
261 WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
265 branch_op_callback = create_branch((unsigned int *)buff + TMPL_CALL_HDLR_IDX,
266 (unsigned long)op_callback_addr,
269 branch_emulate_step = create_branch((unsigned int *)buff + TMPL_EMULATE_IDX,
270 (unsigned long)emulate_step_addr,
273 if (!branch_op_callback || !branch_emulate_step)
276 patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback);
277 patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step);
280 * 3. load instruction to be emulated into relevant register, and
282 patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX);
285 * 4. branch back from trampoline
287 patch_branch(buff + TMPL_RET_IDX, (unsigned long)nip, 0);
289 flush_icache_range((unsigned long)buff,
290 (unsigned long)(&buff[TMPL_END_IDX]));
292 op->optinsn.insn = buff;
297 free_ppc_optinsn_slot(buff, 0);
302 int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
304 return optinsn->insn != NULL;
308 * On powerpc, Optprobes always replaces one instruction (4 bytes
309 * aligned and 4 bytes long). It is impossible to encounter another
310 * kprobe in this address range. So always return 0.
312 int arch_check_optimized_kprobe(struct optimized_kprobe *op)
317 void arch_optimize_kprobes(struct list_head *oplist)
319 struct optimized_kprobe *op;
320 struct optimized_kprobe *tmp;
322 list_for_each_entry_safe(op, tmp, oplist, list) {
324 * Backup instructions which will be replaced
327 memcpy(op->optinsn.copied_insn, op->kp.addr,
329 patch_instruction(op->kp.addr,
330 create_branch((unsigned int *)op->kp.addr,
331 (unsigned long)op->optinsn.insn, 0));
332 list_del_init(&op->list);
336 void arch_unoptimize_kprobe(struct optimized_kprobe *op)
338 arch_arm_kprobe(&op->kp);
341 void arch_unoptimize_kprobes(struct list_head *oplist,
342 struct list_head *done_list)
344 struct optimized_kprobe *op;
345 struct optimized_kprobe *tmp;
347 list_for_each_entry_safe(op, tmp, oplist, list) {
348 arch_unoptimize_kprobe(op);
349 list_move(&op->list, done_list);
353 int arch_within_optimized_kprobe(struct optimized_kprobe *op,
356 return ((unsigned long)op->kp.addr <= addr &&
357 (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);