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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Based on arch/arm64/kernel/ftrace.c
4 *
5 * Copyright (C) 2022 Loongson Technology Corporation Limited
6 */
7
8#include <linux/ftrace.h>
9#include <linux/kprobes.h>
10#include <linux/uaccess.h>
11
12#include <asm/inst.h>
13#include <asm/module.h>
14
15static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate)
16{
17 u32 replaced;
18
19 if (validate) {
20 if (larch_insn_read((void *)pc, &replaced))
21 return -EFAULT;
22
23 if (replaced != old)
24 return -EINVAL;
25 }
26
27 if (larch_insn_patch_text((void *)pc, new))
28 return -EPERM;
29
30 return 0;
31}
32
33#ifdef CONFIG_MODULES
34static bool reachable_by_bl(unsigned long addr, unsigned long pc)
35{
36 long offset = (long)addr - (long)pc;
37
38 return offset >= -SZ_128M && offset < SZ_128M;
39}
40
41static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
42{
43 struct plt_entry *plt = mod->arch.ftrace_trampolines;
44
45 if (addr == FTRACE_ADDR)
46 return &plt[FTRACE_PLT_IDX];
47 if (addr == FTRACE_REGS_ADDR &&
48 IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
49 return &plt[FTRACE_REGS_PLT_IDX];
50
51 return NULL;
52}
53
54/*
55 * Find the address the callsite must branch to in order to reach '*addr'.
56 *
57 * Due to the limited range of 'bl' instruction, modules may be placed too far
58 * away to branch directly and we must use a PLT.
59 *
60 * Returns true when '*addr' contains a reachable target address, or has been
61 * modified to contain a PLT address. Returns false otherwise.
62 */
63static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr)
64{
65 unsigned long pc = rec->ip + LOONGARCH_INSN_SIZE;
66 struct plt_entry *plt;
67
68 /*
69 * If a custom trampoline is unreachable, rely on the ftrace_regs_caller
70 * trampoline which knows how to indirectly reach that trampoline through
71 * ops->direct_call.
72 */
73 if (*addr != FTRACE_ADDR && *addr != FTRACE_REGS_ADDR && !reachable_by_bl(*addr, pc))
74 *addr = FTRACE_REGS_ADDR;
75
76 /*
77 * When the target is within range of the 'bl' instruction, use 'addr'
78 * as-is and branch to that directly.
79 */
80 if (reachable_by_bl(*addr, pc))
81 return true;
82
83 /*
84 * 'mod' is only set at module load time, but if we end up
85 * dealing with an out-of-range condition, we can assume it
86 * is due to a module being loaded far away from the kernel.
87 *
88 * NOTE: __module_text_address() must be called with preemption
89 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
90 * retains its validity throughout the remainder of this code.
91 */
92 if (!mod) {
93 preempt_disable();
94 mod = __module_text_address(pc);
95 preempt_enable();
96 }
97
98 if (WARN_ON(!mod))
99 return false;
100
101 plt = get_ftrace_plt(mod, *addr);
102 if (!plt) {
103 pr_err("ftrace: no module PLT for %ps\n", (void *)*addr);
104 return false;
105 }
106
107 *addr = (unsigned long)plt;
108 return true;
109}
110#else /* !CONFIG_MODULES */
111static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr)
112{
113 return true;
114}
115#endif
116
117#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
118int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
119{
120 u32 old, new;
121 unsigned long pc;
122
123 pc = rec->ip + LOONGARCH_INSN_SIZE;
124
125 if (!ftrace_find_callable_addr(rec, NULL, &addr))
126 return -EINVAL;
127
128 if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
129 return -EINVAL;
130
131 new = larch_insn_gen_bl(pc, addr);
132 old = larch_insn_gen_bl(pc, old_addr);
133
134 return ftrace_modify_code(pc, old, new, true);
135}
136#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
137
138int ftrace_update_ftrace_func(ftrace_func_t func)
139{
140 u32 new;
141 unsigned long pc;
142
143 pc = (unsigned long)&ftrace_call;
144 new = larch_insn_gen_bl(pc, (unsigned long)func);
145
146 return ftrace_modify_code(pc, 0, new, false);
147}
148
149/*
150 * The compiler has inserted 2 NOPs before the regular function prologue.
151 * T series registers are available and safe because of LoongArch's psABI.
152 *
153 * At runtime, we can replace nop with bl to enable ftrace call and replace bl
154 * with nop to disable ftrace call. The bl requires us to save the original RA
155 * value, so it saves RA at t0 here.
156 *
157 * Details are:
158 *
159 * | Compiled | Disabled | Enabled |
160 * +------------+------------------------+------------------------+
161 * | nop | move t0, ra | move t0, ra |
162 * | nop | nop | bl ftrace_caller |
163 * | func_body | func_body | func_body |
164 *
165 * The RA value will be recovered by ftrace_regs_entry, and restored into RA
166 * before returning to the regular function prologue. When a function is not
167 * being traced, the "move t0, ra" is not harmful.
168 */
169
170int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
171{
172 u32 old, new;
173 unsigned long pc;
174
175 pc = rec->ip;
176 old = larch_insn_gen_nop();
177 new = larch_insn_gen_move(LOONGARCH_GPR_T0, LOONGARCH_GPR_RA);
178
179 return ftrace_modify_code(pc, old, new, true);
180}
181
182int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
183{
184 u32 old, new;
185 unsigned long pc;
186
187 pc = rec->ip + LOONGARCH_INSN_SIZE;
188
189 if (!ftrace_find_callable_addr(rec, NULL, &addr))
190 return -EINVAL;
191
192 old = larch_insn_gen_nop();
193 new = larch_insn_gen_bl(pc, addr);
194
195 return ftrace_modify_code(pc, old, new, true);
196}
197
198int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
199{
200 u32 old, new;
201 unsigned long pc;
202
203 pc = rec->ip + LOONGARCH_INSN_SIZE;
204
205 if (!ftrace_find_callable_addr(rec, NULL, &addr))
206 return -EINVAL;
207
208 new = larch_insn_gen_nop();
209 old = larch_insn_gen_bl(pc, addr);
210
211 return ftrace_modify_code(pc, old, new, true);
212}
213
214void arch_ftrace_update_code(int command)
215{
216 command |= FTRACE_MAY_SLEEP;
217 ftrace_modify_all_code(command);
218}
219
220int __init ftrace_dyn_arch_init(void)
221{
222 return 0;
223}
224
225#ifdef CONFIG_FUNCTION_GRAPH_TRACER
226void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
227{
228 unsigned long old;
229 unsigned long return_hooker = (unsigned long)&return_to_handler;
230
231 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
232 return;
233
234 old = *parent;
235
236 if (!function_graph_enter(old, self_addr, 0, parent))
237 *parent = return_hooker;
238}
239
240#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
241void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
242 struct ftrace_ops *op, struct ftrace_regs *fregs)
243{
244 struct pt_regs *regs = &fregs->regs;
245 unsigned long *parent = (unsigned long *)®s->regs[1];
246
247 prepare_ftrace_return(ip, (unsigned long *)parent);
248}
249#else
250static int ftrace_modify_graph_caller(bool enable)
251{
252 u32 branch, nop;
253 unsigned long pc, func;
254 extern void ftrace_graph_call(void);
255
256 pc = (unsigned long)&ftrace_graph_call;
257 func = (unsigned long)&ftrace_graph_caller;
258
259 nop = larch_insn_gen_nop();
260 branch = larch_insn_gen_b(pc, func);
261
262 if (enable)
263 return ftrace_modify_code(pc, nop, branch, true);
264 else
265 return ftrace_modify_code(pc, branch, nop, true);
266}
267
268int ftrace_enable_ftrace_graph_caller(void)
269{
270 return ftrace_modify_graph_caller(true);
271}
272
273int ftrace_disable_ftrace_graph_caller(void)
274{
275 return ftrace_modify_graph_caller(false);
276}
277#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
278#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
279
280#ifdef CONFIG_KPROBES_ON_FTRACE
281/* Ftrace callback handler for kprobes -- called under preepmt disabled */
282void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
283 struct ftrace_ops *ops, struct ftrace_regs *fregs)
284{
285 int bit;
286 struct pt_regs *regs;
287 struct kprobe *p;
288 struct kprobe_ctlblk *kcb;
289
290 bit = ftrace_test_recursion_trylock(ip, parent_ip);
291 if (bit < 0)
292 return;
293
294 p = get_kprobe((kprobe_opcode_t *)ip);
295 if (unlikely(!p) || kprobe_disabled(p))
296 goto out;
297
298 regs = ftrace_get_regs(fregs);
299 if (!regs)
300 goto out;
301
302 kcb = get_kprobe_ctlblk();
303 if (kprobe_running()) {
304 kprobes_inc_nmissed_count(p);
305 } else {
306 unsigned long orig_ip = instruction_pointer(regs);
307
308 instruction_pointer_set(regs, ip);
309
310 __this_cpu_write(current_kprobe, p);
311 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
312 if (!p->pre_handler || !p->pre_handler(p, regs)) {
313 /*
314 * Emulate singlestep (and also recover regs->csr_era)
315 * as if there is a nop
316 */
317 instruction_pointer_set(regs, (unsigned long)p->addr + MCOUNT_INSN_SIZE);
318 if (unlikely(p->post_handler)) {
319 kcb->kprobe_status = KPROBE_HIT_SSDONE;
320 p->post_handler(p, regs, 0);
321 }
322 instruction_pointer_set(regs, orig_ip);
323 }
324
325 /*
326 * If pre_handler returns !0, it changes regs->csr_era. We have to
327 * skip emulating post_handler.
328 */
329 __this_cpu_write(current_kprobe, NULL);
330 }
331out:
332 ftrace_test_recursion_unlock(bit);
333}
334NOKPROBE_SYMBOL(kprobe_ftrace_handler);
335
336int arch_prepare_kprobe_ftrace(struct kprobe *p)
337{
338 p->ainsn.insn = NULL;
339 return 0;
340}
341#endif /* CONFIG_KPROBES_ON_FTRACE */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Based on arch/arm64/kernel/ftrace.c
4 *
5 * Copyright (C) 2022 Loongson Technology Corporation Limited
6 */
7
8#include <linux/ftrace.h>
9#include <linux/uaccess.h>
10
11#include <asm/inst.h>
12#include <asm/module.h>
13
14static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate)
15{
16 u32 replaced;
17
18 if (validate) {
19 if (larch_insn_read((void *)pc, &replaced))
20 return -EFAULT;
21
22 if (replaced != old)
23 return -EINVAL;
24 }
25
26 if (larch_insn_patch_text((void *)pc, new))
27 return -EPERM;
28
29 return 0;
30}
31
32#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
33
34#ifdef CONFIG_MODULES
35static inline int __get_mod(struct module **mod, unsigned long addr)
36{
37 preempt_disable();
38 *mod = __module_text_address(addr);
39 preempt_enable();
40
41 if (WARN_ON(!(*mod)))
42 return -EINVAL;
43
44 return 0;
45}
46
47static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
48{
49 struct plt_entry *plt = mod->arch.ftrace_trampolines;
50
51 if (addr == FTRACE_ADDR)
52 return &plt[FTRACE_PLT_IDX];
53 if (addr == FTRACE_REGS_ADDR &&
54 IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
55 return &plt[FTRACE_REGS_PLT_IDX];
56
57 return NULL;
58}
59
60static unsigned long get_plt_addr(struct module *mod, unsigned long addr)
61{
62 struct plt_entry *plt;
63
64 plt = get_ftrace_plt(mod, addr);
65 if (!plt) {
66 pr_err("ftrace: no module PLT for %ps\n", (void *)addr);
67 return -EINVAL;
68 }
69
70 return (unsigned long)plt;
71}
72#endif
73
74int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
75{
76 u32 old, new;
77 unsigned long pc;
78 long offset __maybe_unused;
79
80 pc = rec->ip + LOONGARCH_INSN_SIZE;
81
82#ifdef CONFIG_MODULES
83 offset = (long)pc - (long)addr;
84
85 if (offset < -SZ_128M || offset >= SZ_128M) {
86 int ret;
87 struct module *mod;
88
89 ret = __get_mod(&mod, pc);
90 if (ret)
91 return ret;
92
93 addr = get_plt_addr(mod, addr);
94
95 old_addr = get_plt_addr(mod, old_addr);
96 }
97#endif
98
99 new = larch_insn_gen_bl(pc, addr);
100 old = larch_insn_gen_bl(pc, old_addr);
101
102 return ftrace_modify_code(pc, old, new, true);
103}
104
105#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
106
107int ftrace_update_ftrace_func(ftrace_func_t func)
108{
109 u32 new;
110 unsigned long pc;
111
112 pc = (unsigned long)&ftrace_call;
113 new = larch_insn_gen_bl(pc, (unsigned long)func);
114
115 return ftrace_modify_code(pc, 0, new, false);
116}
117
118/*
119 * The compiler has inserted 2 NOPs before the regular function prologue.
120 * T series registers are available and safe because of LoongArch's psABI.
121 *
122 * At runtime, we can replace nop with bl to enable ftrace call and replace bl
123 * with nop to disable ftrace call. The bl requires us to save the original RA
124 * value, so it saves RA at t0 here.
125 *
126 * Details are:
127 *
128 * | Compiled | Disabled | Enabled |
129 * +------------+------------------------+------------------------+
130 * | nop | move t0, ra | move t0, ra |
131 * | nop | nop | bl ftrace_caller |
132 * | func_body | func_body | func_body |
133 *
134 * The RA value will be recovered by ftrace_regs_entry, and restored into RA
135 * before returning to the regular function prologue. When a function is not
136 * being traced, the "move t0, ra" is not harmful.
137 */
138
139int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
140{
141 u32 old, new;
142 unsigned long pc;
143
144 pc = rec->ip;
145 old = larch_insn_gen_nop();
146 new = larch_insn_gen_move(LOONGARCH_GPR_T0, LOONGARCH_GPR_RA);
147
148 return ftrace_modify_code(pc, old, new, true);
149}
150
151int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
152{
153 u32 old, new;
154 unsigned long pc;
155 long offset __maybe_unused;
156
157 pc = rec->ip + LOONGARCH_INSN_SIZE;
158
159#ifdef CONFIG_MODULES
160 offset = (long)pc - (long)addr;
161
162 if (offset < -SZ_128M || offset >= SZ_128M) {
163 int ret;
164 struct module *mod;
165
166 ret = __get_mod(&mod, pc);
167 if (ret)
168 return ret;
169
170 addr = get_plt_addr(mod, addr);
171 }
172#endif
173
174 old = larch_insn_gen_nop();
175 new = larch_insn_gen_bl(pc, addr);
176
177 return ftrace_modify_code(pc, old, new, true);
178}
179
180int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
181{
182 u32 old, new;
183 unsigned long pc;
184 long offset __maybe_unused;
185
186 pc = rec->ip + LOONGARCH_INSN_SIZE;
187
188#ifdef CONFIG_MODULES
189 offset = (long)pc - (long)addr;
190
191 if (offset < -SZ_128M || offset >= SZ_128M) {
192 int ret;
193 struct module *mod;
194
195 ret = __get_mod(&mod, pc);
196 if (ret)
197 return ret;
198
199 addr = get_plt_addr(mod, addr);
200 }
201#endif
202
203 new = larch_insn_gen_nop();
204 old = larch_insn_gen_bl(pc, addr);
205
206 return ftrace_modify_code(pc, old, new, true);
207}
208
209void arch_ftrace_update_code(int command)
210{
211 command |= FTRACE_MAY_SLEEP;
212 ftrace_modify_all_code(command);
213}
214
215int __init ftrace_dyn_arch_init(void)
216{
217 return 0;
218}
219
220#ifdef CONFIG_FUNCTION_GRAPH_TRACER
221void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
222{
223 unsigned long old;
224 unsigned long return_hooker = (unsigned long)&return_to_handler;
225
226 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
227 return;
228
229 old = *parent;
230
231 if (!function_graph_enter(old, self_addr, 0, parent))
232 *parent = return_hooker;
233}
234
235#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
236void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
237 struct ftrace_ops *op, struct ftrace_regs *fregs)
238{
239 struct pt_regs *regs = &fregs->regs;
240 unsigned long *parent = (unsigned long *)®s->regs[1];
241
242 prepare_ftrace_return(ip, (unsigned long *)parent);
243}
244#else
245static int ftrace_modify_graph_caller(bool enable)
246{
247 u32 branch, nop;
248 unsigned long pc, func;
249 extern void ftrace_graph_call(void);
250
251 pc = (unsigned long)&ftrace_graph_call;
252 func = (unsigned long)&ftrace_graph_caller;
253
254 nop = larch_insn_gen_nop();
255 branch = larch_insn_gen_b(pc, func);
256
257 if (enable)
258 return ftrace_modify_code(pc, nop, branch, true);
259 else
260 return ftrace_modify_code(pc, branch, nop, true);
261}
262
263int ftrace_enable_ftrace_graph_caller(void)
264{
265 return ftrace_modify_graph_caller(true);
266}
267
268int ftrace_disable_ftrace_graph_caller(void)
269{
270 return ftrace_modify_graph_caller(false);
271}
272#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
273#endif /* CONFIG_FUNCTION_GRAPH_TRACER */