ftrace.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Code for replacing ftrace calls with jumps.
  4 *
  5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  6 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
  7 * Author: Wu Zhangjin <wuzhangjin@gmail.com>
  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 */