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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Code for replacing ftrace calls with jumps.
4 *
5 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
6 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
7 * Author: Wu Zhangjin <[email protected]>
8 *
9 * Thanks goes to Steven Rostedt for writing the original x86 version.
10 */
11
12#include <linux/uaccess.h>
13#include <linux/init.h>
14#include <linux/ftrace.h>
15#include <linux/syscalls.h>
16
17#include <asm/asm.h>
18#include <asm/asm-offsets.h>
19#include <asm/cacheflush.h>
20#include <asm/syscall.h>
21#include <asm/uasm.h>
22#include <asm/unistd.h>
23
24#include <asm-generic/sections.h>
25
26#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
27#define MCOUNT_OFFSET_INSNS 5
28#else
29#define MCOUNT_OFFSET_INSNS 4
30#endif
31
32#ifdef CONFIG_DYNAMIC_FTRACE
33
34/* Arch override because MIPS doesn't need to run this from stop_machine() */
35void arch_ftrace_update_code(int command)
36{
37 ftrace_modify_all_code(command);
38}
39
40#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
41#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
42#define JUMP_RANGE_MASK ((1UL << 28) - 1)
43
44#define INSN_NOP 0x00000000 /* nop */
45#define INSN_JAL(addr) \
46 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
47
48static unsigned int insn_jal_ftrace_caller __read_mostly;
49static unsigned int insn_la_mcount[2] __read_mostly;
50static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
51
52static inline void ftrace_dyn_arch_init_insns(void)
53{
54 u32 *buf;
55 unsigned int v1;
56
57 /* If we are not in compat space, the number of generated
58 * instructions will exceed the maximum expected limit of 2.
59 * To prevent buffer overflow, we avoid generating them.
60 * insn_la_mcount will not be used later in ftrace_make_call.
61 */
62 if (uasm_in_compat_space_p(MCOUNT_ADDR)) {
63 /* la v1, _mcount */
64 v1 = 3;
65 buf = (u32 *)&insn_la_mcount[0];
66 UASM_i_LA(&buf, v1, MCOUNT_ADDR);
67 } else {
68 pr_warn("ftrace: mcount address beyond 32 bits is not supported (%lX)\n",
69 MCOUNT_ADDR);
70 }
71
72 /* jal (ftrace_caller + 8), jump over the first two instruction */
73 buf = (u32 *)&insn_jal_ftrace_caller;
74 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
75
76#ifdef CONFIG_FUNCTION_GRAPH_TRACER
77 /* j ftrace_graph_caller */
78 buf = (u32 *)&insn_j_ftrace_graph_caller;
79 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
80#endif
81}
82
83static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
84{
85 int faulted;
86
87 /* *(unsigned int *)ip = new_code; */
88 safe_store_code(new_code, ip, faulted);
89
90 if (unlikely(faulted))
91 return -EFAULT;
92
93 flush_icache_range(ip, ip + 8);
94
95 return 0;
96}
97
98#ifndef CONFIG_64BIT
99static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
100 unsigned int new_code2)
101{
102 int faulted;
103
104 safe_store_code(new_code1, ip, faulted);
105 if (unlikely(faulted))
106 return -EFAULT;
107
108 ip += 4;
109 safe_store_code(new_code2, ip, faulted);
110 if (unlikely(faulted))
111 return -EFAULT;
112
113 ip -= 4;
114 flush_icache_range(ip, ip + 8);
115
116 return 0;
117}
118
119static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
120 unsigned int new_code2)
121{
122 int faulted;
123
124 ip += 4;
125 safe_store_code(new_code2, ip, faulted);
126 if (unlikely(faulted))
127 return -EFAULT;
128
129 ip -= 4;
130 safe_store_code(new_code1, ip, faulted);
131 if (unlikely(faulted))
132 return -EFAULT;
133
134 flush_icache_range(ip, ip + 8);
135
136 return 0;
137}
138#endif
139
140/*
141 * The details about the calling site of mcount on MIPS
142 *
143 * 1. For kernel:
144 *
145 * move at, ra
146 * jal _mcount --> nop
147 * sub sp, sp, 8 --> nop (CONFIG_32BIT)
148 *
149 * 2. For modules:
150 *
151 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
152 *
153 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
154 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
155 * move at, ra
156 * move $12, ra_address
157 * jalr v1
158 * sub sp, sp, 8
159 * 1: offset = 5 instructions
160 * 2.2 For the Other situations
161 *
162 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
163 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
164 * move at, ra
165 * jalr v1
166 * nop | move $12, ra_address | sub sp, sp, 8
167 * 1: offset = 4 instructions
168 */
169
170#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
171
172int ftrace_make_nop(struct module *mod,
173 struct dyn_ftrace *rec, unsigned long addr)
174{
175 unsigned int new;
176 unsigned long ip = rec->ip;
177
178 /*
179 * If ip is in kernel space, no long call, otherwise, long call is
180 * needed.
181 */
182 new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
183#ifdef CONFIG_64BIT
184 return ftrace_modify_code(ip, new);
185#else
186 /*
187 * On 32 bit MIPS platforms, gcc adds a stack adjust
188 * instruction in the delay slot after the branch to
189 * mcount and expects mcount to restore the sp on return.
190 * This is based on a legacy API and does nothing but
191 * waste instructions so it's being removed at runtime.
192 */
193 return ftrace_modify_code_2(ip, new, INSN_NOP);
194#endif
195}
196
197int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
198{
199 unsigned int new;
200 unsigned long ip = rec->ip;
201
202 /* When the code to patch does not belong to the kernel code
203 * space, we must use insn_la_mcount. However, if MCOUNT_ADDR
204 * is not in compat space, insn_la_mcount is not usable.
205 */
206 if (!core_kernel_text(ip) && !uasm_in_compat_space_p(MCOUNT_ADDR))
207 return -EFAULT;
208
209 new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
210
211#ifdef CONFIG_64BIT
212 return ftrace_modify_code(ip, new);
213#else
214 return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
215 INSN_NOP : insn_la_mcount[1]);
216#endif
217}
218
219#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
220
221int ftrace_update_ftrace_func(ftrace_func_t func)
222{
223 unsigned int new;
224
225 new = INSN_JAL((unsigned long)func);
226
227 return ftrace_modify_code(FTRACE_CALL_IP, new);
228}
229
230int __init ftrace_dyn_arch_init(void)
231{
232 /* Encode the instructions when booting */
233 ftrace_dyn_arch_init_insns();
234
235 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
236 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
237
238 return 0;
239}
240#endif /* CONFIG_DYNAMIC_FTRACE */
241
242#ifdef CONFIG_FUNCTION_GRAPH_TRACER
243
244#ifdef CONFIG_DYNAMIC_FTRACE
245
246extern void ftrace_graph_call(void);
247#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
248
249int ftrace_enable_ftrace_graph_caller(void)
250{
251 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
252 insn_j_ftrace_graph_caller);
253}
254
255int ftrace_disable_ftrace_graph_caller(void)
256{
257 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
258}
259
260#endif /* CONFIG_DYNAMIC_FTRACE */
261
262#ifndef KBUILD_MCOUNT_RA_ADDRESS
263
264#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
265#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
266#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
267
268static unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
269 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
270{
271 unsigned long sp, ip, tmp;
272 unsigned int code;
273 int faulted;
274
275 /*
276 * For module, move the ip from the return address after the
277 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
278 * kernel, move after the instruction "move ra, at"(offset is 16)
279 */
280 ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
281
282 /*
283 * search the text until finding the non-store instruction or "s{d,w}
284 * ra, offset(sp)" instruction
285 */
286 do {
287 /* get the code at "ip": code = *(unsigned int *)ip; */
288 safe_load_code(code, ip, faulted);
289
290 if (unlikely(faulted))
291 return 0;
292 /*
293 * If we hit the non-store instruction before finding where the
294 * ra is stored, then this is a leaf function and it does not
295 * store the ra on the stack
296 */
297 if ((code & S_R_SP) != S_R_SP)
298 return parent_ra_addr;
299
300 /* Move to the next instruction */
301 ip -= 4;
302 } while ((code & S_RA_SP) != S_RA_SP);
303
304 sp = fp + (code & OFFSET_MASK);
305
306 /* tmp = *(unsigned long *)sp; */
307 safe_load_stack(tmp, sp, faulted);
308 if (unlikely(faulted))
309 return 0;
310
311 if (tmp == old_parent_ra)
312 return sp;
313 return 0;
314}
315
316#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
317
318/*
319 * Hook the return address and push it in the stack of return addrs
320 * in current thread info.
321 */
322void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
323 unsigned long fp)
324{
325 unsigned long old_parent_ra;
326 unsigned long return_hooker = (unsigned long)
327 &return_to_handler;
328 int faulted, insns;
329
330 if (unlikely(ftrace_graph_is_dead()))
331 return;
332
333 if (unlikely(atomic_read(&current->tracing_graph_pause)))
334 return;
335
336 /*
337 * "parent_ra_addr" is the stack address where the return address of
338 * the caller of _mcount is saved.
339 *
340 * If gcc < 4.5, a leaf function does not save the return address
341 * in the stack address, so we "emulate" one in _mcount's stack space,
342 * and hijack it directly.
343 * For a non-leaf function, it does save the return address to its own
344 * stack space, so we can not hijack it directly, but need to find the
345 * real stack address, which is done by ftrace_get_parent_addr().
346 *
347 * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
348 * non-leaf function, the location of the return address will be saved
349 * to $12 for us.
350 * For a leaf function, it just puts a zero into $12, so we handle
351 * it in ftrace_graph_caller() of mcount.S.
352 */
353
354 /* old_parent_ra = *parent_ra_addr; */
355 safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
356 if (unlikely(faulted))
357 goto out;
358#ifndef KBUILD_MCOUNT_RA_ADDRESS
359 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
360 old_parent_ra, (unsigned long)parent_ra_addr, fp);
361 /*
362 * If fails when getting the stack address of the non-leaf function's
363 * ra, stop function graph tracer and return
364 */
365 if (parent_ra_addr == NULL)
366 goto out;
367#endif
368 /* *parent_ra_addr = return_hooker; */
369 safe_store_stack(return_hooker, parent_ra_addr, faulted);
370 if (unlikely(faulted))
371 goto out;
372
373 /*
374 * Get the recorded ip of the current mcount calling site in the
375 * __mcount_loc section, which will be used to filter the function
376 * entries configured through the tracing/set_graph_function interface.
377 */
378
379 insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
380 self_ra -= (MCOUNT_INSN_SIZE * insns);
381
382 if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
383 *parent_ra_addr = old_parent_ra;
384 return;
385out:
386 ftrace_graph_stop();
387 WARN_ON(1);
388}
389#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
390
391#ifdef CONFIG_FTRACE_SYSCALLS
392
393#ifdef CONFIG_32BIT
394unsigned long __init arch_syscall_addr(int nr)
395{
396 return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
397}
398#endif
399
400#ifdef CONFIG_64BIT
401
402unsigned long __init arch_syscall_addr(int nr)
403{
404#ifdef CONFIG_MIPS32_N32
405 if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
406 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
407#endif
408 if (nr >= __NR_64_Linux && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
409 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
410#ifdef CONFIG_MIPS32_O32
411 if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
412 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
413#endif
414
415 return (unsigned long) &sys_ni_syscall;
416}
417#endif
418
419#endif /* CONFIG_FTRACE_SYSCALLS */