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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Dynamic function tracer architecture backend.
4 *
5 * Copyright IBM Corp. 2009,2014
6 *
7 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
8 */
9
10#include <linux/hardirq.h>
11#include <linux/uaccess.h>
12#include <linux/ftrace.h>
13#include <linux/kernel.h>
14#include <linux/types.h>
15#include <linux/kmsan-checks.h>
16#include <linux/kprobes.h>
17#include <linux/execmem.h>
18#include <trace/syscall.h>
19#include <asm/asm-offsets.h>
20#include <asm/text-patching.h>
21#include <asm/cacheflush.h>
22#include <asm/ftrace.lds.h>
23#include <asm/nospec-branch.h>
24#include <asm/set_memory.h>
25#include "entry.h"
26#include "ftrace.h"
27
28/*
29 * To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
30 * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
31 * (since gcc 9 / clang 10) is used.
32 * In both cases the original and also the disabled function prologue contains
33 * only a single six byte instruction and looks like this:
34 * > brcl 0,0 # offset 0
35 * To enable ftrace the code gets patched like above and afterwards looks
36 * like this:
37 * > brasl %r0,ftrace_caller # offset 0
38 *
39 * The instruction will be patched by ftrace_make_call / ftrace_make_nop.
40 * The ftrace function gets called with a non-standard C function call ABI
41 * where r0 contains the return address. It is also expected that the called
42 * function only clobbers r0 and r1, but restores r2-r15.
43 * For module code we can't directly jump to ftrace caller, but need a
44 * trampoline (ftrace_plt), which clobbers also r1.
45 */
46
47void *ftrace_func __read_mostly = ftrace_stub;
48struct ftrace_insn {
49 u16 opc;
50 s32 disp;
51} __packed;
52
53static const char *ftrace_shared_hotpatch_trampoline(const char **end)
54{
55 const char *tstart, *tend;
56
57 tstart = ftrace_shared_hotpatch_trampoline_br;
58 tend = ftrace_shared_hotpatch_trampoline_br_end;
59#ifdef CONFIG_EXPOLINE
60 if (!nospec_disable) {
61 tstart = ftrace_shared_hotpatch_trampoline_exrl;
62 tend = ftrace_shared_hotpatch_trampoline_exrl_end;
63 }
64#endif /* CONFIG_EXPOLINE */
65 if (end)
66 *end = tend;
67 return tstart;
68}
69
70bool ftrace_need_init_nop(void)
71{
72 return !MACHINE_HAS_SEQ_INSN;
73}
74
75int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
76{
77 static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline =
78 __ftrace_hotpatch_trampolines_start;
79 static const struct ftrace_insn orig = { .opc = 0xc004, .disp = 0 };
80 static struct ftrace_hotpatch_trampoline *trampoline;
81 struct ftrace_hotpatch_trampoline **next_trampoline;
82 struct ftrace_hotpatch_trampoline *trampolines_end;
83 struct ftrace_hotpatch_trampoline tmp;
84 struct ftrace_insn *insn;
85 struct ftrace_insn old;
86 const char *shared;
87 s32 disp;
88
89 BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) !=
90 SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE);
91
92 next_trampoline = &next_vmlinux_trampoline;
93 trampolines_end = __ftrace_hotpatch_trampolines_end;
94 shared = ftrace_shared_hotpatch_trampoline(NULL);
95#ifdef CONFIG_MODULES
96 if (mod) {
97 next_trampoline = &mod->arch.next_trampoline;
98 trampolines_end = mod->arch.trampolines_end;
99 }
100#endif
101
102 if (WARN_ON_ONCE(*next_trampoline >= trampolines_end))
103 return -ENOMEM;
104 trampoline = (*next_trampoline)++;
105
106 if (copy_from_kernel_nofault(&old, (void *)rec->ip, sizeof(old)))
107 return -EFAULT;
108 /* Check for the compiler-generated fentry nop (brcl 0, .). */
109 if (WARN_ON_ONCE(memcmp(&orig, &old, sizeof(old))))
110 return -EINVAL;
111
112 /* Generate the trampoline. */
113 tmp.brasl_opc = 0xc015; /* brasl %r1, shared */
114 tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2;
115 tmp.interceptor = FTRACE_ADDR;
116 tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn);
117 s390_kernel_write(trampoline, &tmp, sizeof(tmp));
118
119 /* Generate a jump to the trampoline. */
120 disp = ((char *)trampoline - (char *)rec->ip) / 2;
121 insn = (struct ftrace_insn *)rec->ip;
122 s390_kernel_write(&insn->disp, &disp, sizeof(disp));
123
124 return 0;
125}
126
127static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
128{
129 struct ftrace_hotpatch_trampoline *trampoline;
130 struct ftrace_insn insn;
131 s64 disp;
132 u16 opc;
133
134 if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn)))
135 return ERR_PTR(-EFAULT);
136 disp = (s64)insn.disp * 2;
137 trampoline = (void *)(rec->ip + disp);
138 if (get_kernel_nofault(opc, &trampoline->brasl_opc))
139 return ERR_PTR(-EFAULT);
140 if (opc != 0xc015)
141 return ERR_PTR(-EINVAL);
142 return trampoline;
143}
144
145static inline struct ftrace_insn
146ftrace_generate_branch_insn(unsigned long ip, unsigned long target)
147{
148 /* brasl r0,target or brcl 0,0 */
149 return (struct ftrace_insn){ .opc = target ? 0xc005 : 0xc004,
150 .disp = target ? (target - ip) / 2 : 0 };
151}
152
153static int ftrace_patch_branch_insn(unsigned long ip, unsigned long old_target,
154 unsigned long target)
155{
156 struct ftrace_insn orig = ftrace_generate_branch_insn(ip, old_target);
157 struct ftrace_insn new = ftrace_generate_branch_insn(ip, target);
158 struct ftrace_insn old;
159
160 if (!IS_ALIGNED(ip, 8))
161 return -EINVAL;
162 if (copy_from_kernel_nofault(&old, (void *)ip, sizeof(old)))
163 return -EFAULT;
164 /* Verify that the to be replaced code matches what we expect. */
165 if (memcmp(&orig, &old, sizeof(old)))
166 return -EINVAL;
167 s390_kernel_write((void *)ip, &new, sizeof(new));
168 return 0;
169}
170
171static int ftrace_modify_trampoline_call(struct dyn_ftrace *rec,
172 unsigned long old_addr,
173 unsigned long addr)
174{
175 struct ftrace_hotpatch_trampoline *trampoline;
176 u64 old;
177
178 trampoline = ftrace_get_trampoline(rec);
179 if (IS_ERR(trampoline))
180 return PTR_ERR(trampoline);
181 if (get_kernel_nofault(old, &trampoline->interceptor))
182 return -EFAULT;
183 if (old != old_addr)
184 return -EINVAL;
185 s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
186 return 0;
187}
188
189int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
190 unsigned long addr)
191{
192 if (MACHINE_HAS_SEQ_INSN)
193 return ftrace_patch_branch_insn(rec->ip, old_addr, addr);
194 else
195 return ftrace_modify_trampoline_call(rec, old_addr, addr);
196}
197
198static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
199{
200 u16 old;
201 u8 op;
202
203 if (get_kernel_nofault(old, addr))
204 return -EFAULT;
205 if (old != expected)
206 return -EINVAL;
207 /* set mask field to all ones or zeroes */
208 op = enable ? 0xf4 : 0x04;
209 s390_kernel_write((char *)addr + 1, &op, sizeof(op));
210 return 0;
211}
212
213int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
214 unsigned long addr)
215{
216 /* Expect brcl 0xf,... for the !MACHINE_HAS_SEQ_INSN case */
217 if (MACHINE_HAS_SEQ_INSN)
218 return ftrace_patch_branch_insn(rec->ip, addr, 0);
219 else
220 return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
221}
222
223static int ftrace_make_trampoline_call(struct dyn_ftrace *rec, unsigned long addr)
224{
225 struct ftrace_hotpatch_trampoline *trampoline;
226
227 trampoline = ftrace_get_trampoline(rec);
228 if (IS_ERR(trampoline))
229 return PTR_ERR(trampoline);
230 s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
231 /* Expect brcl 0x0,... */
232 return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
233}
234
235int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
236{
237 if (MACHINE_HAS_SEQ_INSN)
238 return ftrace_patch_branch_insn(rec->ip, 0, addr);
239 else
240 return ftrace_make_trampoline_call(rec, addr);
241}
242
243int ftrace_update_ftrace_func(ftrace_func_t func)
244{
245 ftrace_func = func;
246 return 0;
247}
248
249void arch_ftrace_update_code(int command)
250{
251 ftrace_modify_all_code(command);
252}
253
254void ftrace_arch_code_modify_post_process(void)
255{
256 /*
257 * Flush any pre-fetched instructions on all
258 * CPUs to make the new code visible.
259 */
260 text_poke_sync_lock();
261}
262
263#ifdef CONFIG_FUNCTION_GRAPH_TRACER
264/*
265 * Hook the return address and push it in the stack of return addresses
266 * in current thread info.
267 */
268unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
269 unsigned long ip)
270{
271 if (unlikely(ftrace_graph_is_dead()))
272 goto out;
273 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
274 goto out;
275 ip -= MCOUNT_INSN_SIZE;
276 if (!function_graph_enter(ra, ip, 0, (void *) sp))
277 ra = (unsigned long) return_to_handler;
278out:
279 return ra;
280}
281NOKPROBE_SYMBOL(prepare_ftrace_return);
282
283/*
284 * Patch the kernel code at ftrace_graph_caller location. The instruction
285 * there is branch relative on condition. To enable the ftrace graph code
286 * block, we simply patch the mask field of the instruction to zero and
287 * turn the instruction into a nop.
288 * To disable the ftrace graph code the mask field will be patched to
289 * all ones, which turns the instruction into an unconditional branch.
290 */
291int ftrace_enable_ftrace_graph_caller(void)
292{
293 /* Expect brc 0xf,... */
294 return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
295}
296
297int ftrace_disable_ftrace_graph_caller(void)
298{
299 /* Expect brc 0x0,... */
300 return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
301}
302
303#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
304
305#ifdef CONFIG_KPROBES_ON_FTRACE
306void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
307 struct ftrace_ops *ops, struct ftrace_regs *fregs)
308{
309 struct kprobe_ctlblk *kcb;
310 struct pt_regs *regs;
311 struct kprobe *p;
312 int bit;
313
314 if (unlikely(kprobe_ftrace_disabled))
315 return;
316
317 bit = ftrace_test_recursion_trylock(ip, parent_ip);
318 if (bit < 0)
319 return;
320
321 kmsan_unpoison_memory(fregs, ftrace_regs_size());
322 regs = ftrace_get_regs(fregs);
323 p = get_kprobe((kprobe_opcode_t *)ip);
324 if (!regs || unlikely(!p) || kprobe_disabled(p))
325 goto out;
326
327 if (kprobe_running()) {
328 kprobes_inc_nmissed_count(p);
329 goto out;
330 }
331
332 __this_cpu_write(current_kprobe, p);
333
334 kcb = get_kprobe_ctlblk();
335 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
336
337 instruction_pointer_set(regs, ip);
338
339 if (!p->pre_handler || !p->pre_handler(p, regs)) {
340
341 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
342
343 if (unlikely(p->post_handler)) {
344 kcb->kprobe_status = KPROBE_HIT_SSDONE;
345 p->post_handler(p, regs, 0);
346 }
347 }
348 __this_cpu_write(current_kprobe, NULL);
349out:
350 ftrace_test_recursion_unlock(bit);
351}
352NOKPROBE_SYMBOL(kprobe_ftrace_handler);
353
354int arch_prepare_kprobe_ftrace(struct kprobe *p)
355{
356 p->ainsn.insn = NULL;
357 return 0;
358}
359#endif
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Dynamic function tracer architecture backend.
4 *
5 * Copyright IBM Corp. 2009,2014
6 *
7 * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
8 * Martin Schwidefsky <schwidefsky@de.ibm.com>
9 */
10
11#include <linux/moduleloader.h>
12#include <linux/hardirq.h>
13#include <linux/uaccess.h>
14#include <linux/ftrace.h>
15#include <linux/kernel.h>
16#include <linux/types.h>
17#include <linux/kprobes.h>
18#include <trace/syscall.h>
19#include <asm/asm-offsets.h>
20#include <asm/cacheflush.h>
21#include <asm/set_memory.h>
22#include "entry.h"
23
24/*
25 * To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
26 * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
27 * (since gcc 9 / clang 10) is used.
28 * In both cases the original and also the disabled function prologue contains
29 * only a single six byte instruction and looks like this:
30 * > brcl 0,0 # offset 0
31 * To enable ftrace the code gets patched like above and afterwards looks
32 * like this:
33 * > brasl %r0,ftrace_caller # offset 0
34 *
35 * The instruction will be patched by ftrace_make_call / ftrace_make_nop.
36 * The ftrace function gets called with a non-standard C function call ABI
37 * where r0 contains the return address. It is also expected that the called
38 * function only clobbers r0 and r1, but restores r2-r15.
39 * For module code we can't directly jump to ftrace caller, but need a
40 * trampoline (ftrace_plt), which clobbers also r1.
41 */
42
43void *ftrace_func __read_mostly = ftrace_stub;
44unsigned long ftrace_plt;
45
46int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
47 unsigned long addr)
48{
49 return 0;
50}
51
52int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
53 unsigned long addr)
54{
55 struct ftrace_insn orig, new, old;
56
57 if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
58 return -EFAULT;
59 /* Replace ftrace call with a nop. */
60 ftrace_generate_call_insn(&orig, rec->ip);
61 ftrace_generate_nop_insn(&new);
62
63 /* Verify that the to be replaced code matches what we expect. */
64 if (memcmp(&orig, &old, sizeof(old)))
65 return -EINVAL;
66 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
67 return 0;
68}
69
70int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
71{
72 struct ftrace_insn orig, new, old;
73
74 if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
75 return -EFAULT;
76 /* Replace nop with an ftrace call. */
77 ftrace_generate_nop_insn(&orig);
78 ftrace_generate_call_insn(&new, rec->ip);
79
80 /* Verify that the to be replaced code matches what we expect. */
81 if (memcmp(&orig, &old, sizeof(old)))
82 return -EINVAL;
83 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
84 return 0;
85}
86
87int ftrace_update_ftrace_func(ftrace_func_t func)
88{
89 ftrace_func = func;
90 return 0;
91}
92
93int __init ftrace_dyn_arch_init(void)
94{
95 return 0;
96}
97
98#ifdef CONFIG_MODULES
99
100static int __init ftrace_plt_init(void)
101{
102 unsigned int *ip;
103
104 ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
105 if (!ftrace_plt)
106 panic("cannot allocate ftrace plt\n");
107 ip = (unsigned int *) ftrace_plt;
108 ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
109 ip[1] = 0x100a0004;
110 ip[2] = 0x07f10000;
111 ip[3] = FTRACE_ADDR >> 32;
112 ip[4] = FTRACE_ADDR & 0xffffffff;
113 set_memory_ro(ftrace_plt, 1);
114 return 0;
115}
116device_initcall(ftrace_plt_init);
117
118#endif /* CONFIG_MODULES */
119
120#ifdef CONFIG_FUNCTION_GRAPH_TRACER
121/*
122 * Hook the return address and push it in the stack of return addresses
123 * in current thread info.
124 */
125unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
126 unsigned long ip)
127{
128 if (unlikely(ftrace_graph_is_dead()))
129 goto out;
130 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
131 goto out;
132 ip -= MCOUNT_INSN_SIZE;
133 if (!function_graph_enter(ra, ip, 0, (void *) sp))
134 ra = (unsigned long) return_to_handler;
135out:
136 return ra;
137}
138NOKPROBE_SYMBOL(prepare_ftrace_return);
139
140/*
141 * Patch the kernel code at ftrace_graph_caller location. The instruction
142 * there is branch relative on condition. To enable the ftrace graph code
143 * block, we simply patch the mask field of the instruction to zero and
144 * turn the instruction into a nop.
145 * To disable the ftrace graph code the mask field will be patched to
146 * all ones, which turns the instruction into an unconditional branch.
147 */
148int ftrace_enable_ftrace_graph_caller(void)
149{
150 u8 op = 0x04; /* set mask field to zero */
151
152 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
153 return 0;
154}
155
156int ftrace_disable_ftrace_graph_caller(void)
157{
158 u8 op = 0xf4; /* set mask field to all ones */
159
160 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
161 return 0;
162}
163
164#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
165
166#ifdef CONFIG_KPROBES_ON_FTRACE
167void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
168 struct ftrace_ops *ops, struct ftrace_regs *fregs)
169{
170 struct kprobe_ctlblk *kcb;
171 struct pt_regs *regs;
172 struct kprobe *p;
173 int bit;
174
175 bit = ftrace_test_recursion_trylock(ip, parent_ip);
176 if (bit < 0)
177 return;
178
179 regs = ftrace_get_regs(fregs);
180 preempt_disable_notrace();
181 p = get_kprobe((kprobe_opcode_t *)ip);
182 if (unlikely(!p) || kprobe_disabled(p))
183 goto out;
184
185 if (kprobe_running()) {
186 kprobes_inc_nmissed_count(p);
187 goto out;
188 }
189
190 __this_cpu_write(current_kprobe, p);
191
192 kcb = get_kprobe_ctlblk();
193 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
194
195 instruction_pointer_set(regs, ip);
196
197 if (!p->pre_handler || !p->pre_handler(p, regs)) {
198
199 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
200
201 if (unlikely(p->post_handler)) {
202 kcb->kprobe_status = KPROBE_HIT_SSDONE;
203 p->post_handler(p, regs, 0);
204 }
205 }
206 __this_cpu_write(current_kprobe, NULL);
207out:
208 preempt_enable_notrace();
209 ftrace_test_recursion_unlock(bit);
210}
211NOKPROBE_SYMBOL(kprobe_ftrace_handler);
212
213int arch_prepare_kprobe_ftrace(struct kprobe *p)
214{
215 p->ainsn.insn = NULL;
216 return 0;
217}
218#endif