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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/moduleloader.h>
11#include <linux/hardirq.h>
12#include <linux/uaccess.h>
13#include <linux/ftrace.h>
14#include <linux/kernel.h>
15#include <linux/types.h>
16#include <linux/kprobes.h>
17#include <trace/syscall.h>
18#include <asm/asm-offsets.h>
19#include <asm/text-patching.h>
20#include <asm/cacheflush.h>
21#include <asm/ftrace.lds.h>
22#include <asm/nospec-branch.h>
23#include <asm/set_memory.h>
24#include "entry.h"
25#include "ftrace.h"
26
27/*
28 * To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
29 * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
30 * (since gcc 9 / clang 10) is used.
31 * In both cases the original and also the disabled function prologue contains
32 * only a single six byte instruction and looks like this:
33 * > brcl 0,0 # offset 0
34 * To enable ftrace the code gets patched like above and afterwards looks
35 * like this:
36 * > brasl %r0,ftrace_caller # offset 0
37 *
38 * The instruction will be patched by ftrace_make_call / ftrace_make_nop.
39 * The ftrace function gets called with a non-standard C function call ABI
40 * where r0 contains the return address. It is also expected that the called
41 * function only clobbers r0 and r1, but restores r2-r15.
42 * For module code we can't directly jump to ftrace caller, but need a
43 * trampoline (ftrace_plt), which clobbers also r1.
44 */
45
46void *ftrace_func __read_mostly = ftrace_stub;
47struct ftrace_insn {
48 u16 opc;
49 s32 disp;
50} __packed;
51
52asm(
53 " .align 16\n"
54 "ftrace_shared_hotpatch_trampoline_br:\n"
55 " lmg %r0,%r1,2(%r1)\n"
56 " br %r1\n"
57 "ftrace_shared_hotpatch_trampoline_br_end:\n"
58);
59
60#ifdef CONFIG_EXPOLINE
61asm(
62 " .align 16\n"
63 "ftrace_shared_hotpatch_trampoline_exrl:\n"
64 " lmg %r0,%r1,2(%r1)\n"
65 " exrl %r0,0f\n"
66 " j .\n"
67 "0: br %r1\n"
68 "ftrace_shared_hotpatch_trampoline_exrl_end:\n"
69);
70#endif /* CONFIG_EXPOLINE */
71
72#ifdef CONFIG_MODULES
73static char *ftrace_plt;
74#endif /* CONFIG_MODULES */
75
76static const char *ftrace_shared_hotpatch_trampoline(const char **end)
77{
78 const char *tstart, *tend;
79
80 tstart = ftrace_shared_hotpatch_trampoline_br;
81 tend = ftrace_shared_hotpatch_trampoline_br_end;
82#ifdef CONFIG_EXPOLINE
83 if (!nospec_disable) {
84 tstart = ftrace_shared_hotpatch_trampoline_exrl;
85 tend = ftrace_shared_hotpatch_trampoline_exrl_end;
86 }
87#endif /* CONFIG_EXPOLINE */
88 if (end)
89 *end = tend;
90 return tstart;
91}
92
93bool ftrace_need_init_nop(void)
94{
95 return true;
96}
97
98int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
99{
100 static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline =
101 __ftrace_hotpatch_trampolines_start;
102 static const char orig[6] = { 0xc0, 0x04, 0x00, 0x00, 0x00, 0x00 };
103 static struct ftrace_hotpatch_trampoline *trampoline;
104 struct ftrace_hotpatch_trampoline **next_trampoline;
105 struct ftrace_hotpatch_trampoline *trampolines_end;
106 struct ftrace_hotpatch_trampoline tmp;
107 struct ftrace_insn *insn;
108 const char *shared;
109 s32 disp;
110
111 BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) !=
112 SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE);
113
114 next_trampoline = &next_vmlinux_trampoline;
115 trampolines_end = __ftrace_hotpatch_trampolines_end;
116 shared = ftrace_shared_hotpatch_trampoline(NULL);
117#ifdef CONFIG_MODULES
118 if (mod) {
119 next_trampoline = &mod->arch.next_trampoline;
120 trampolines_end = mod->arch.trampolines_end;
121 shared = ftrace_plt;
122 }
123#endif
124
125 if (WARN_ON_ONCE(*next_trampoline >= trampolines_end))
126 return -ENOMEM;
127 trampoline = (*next_trampoline)++;
128
129 /* Check for the compiler-generated fentry nop (brcl 0, .). */
130 if (WARN_ON_ONCE(memcmp((const void *)rec->ip, &orig, sizeof(orig))))
131 return -EINVAL;
132
133 /* Generate the trampoline. */
134 tmp.brasl_opc = 0xc015; /* brasl %r1, shared */
135 tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2;
136 tmp.interceptor = FTRACE_ADDR;
137 tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn);
138 s390_kernel_write(trampoline, &tmp, sizeof(tmp));
139
140 /* Generate a jump to the trampoline. */
141 disp = ((char *)trampoline - (char *)rec->ip) / 2;
142 insn = (struct ftrace_insn *)rec->ip;
143 s390_kernel_write(&insn->disp, &disp, sizeof(disp));
144
145 return 0;
146}
147
148static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
149{
150 struct ftrace_hotpatch_trampoline *trampoline;
151 struct ftrace_insn insn;
152 s64 disp;
153 u16 opc;
154
155 if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn)))
156 return ERR_PTR(-EFAULT);
157 disp = (s64)insn.disp * 2;
158 trampoline = (void *)(rec->ip + disp);
159 if (get_kernel_nofault(opc, &trampoline->brasl_opc))
160 return ERR_PTR(-EFAULT);
161 if (opc != 0xc015)
162 return ERR_PTR(-EINVAL);
163 return trampoline;
164}
165
166int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
167 unsigned long addr)
168{
169 struct ftrace_hotpatch_trampoline *trampoline;
170 u64 old;
171
172 trampoline = ftrace_get_trampoline(rec);
173 if (IS_ERR(trampoline))
174 return PTR_ERR(trampoline);
175 if (get_kernel_nofault(old, &trampoline->interceptor))
176 return -EFAULT;
177 if (old != old_addr)
178 return -EINVAL;
179 s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
180 return 0;
181}
182
183static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
184{
185 u16 old;
186 u8 op;
187
188 if (get_kernel_nofault(old, addr))
189 return -EFAULT;
190 if (old != expected)
191 return -EINVAL;
192 /* set mask field to all ones or zeroes */
193 op = enable ? 0xf4 : 0x04;
194 s390_kernel_write((char *)addr + 1, &op, sizeof(op));
195 return 0;
196}
197
198int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
199 unsigned long addr)
200{
201 /* Expect brcl 0xf,... */
202 return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
203}
204
205int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
206{
207 struct ftrace_hotpatch_trampoline *trampoline;
208
209 trampoline = ftrace_get_trampoline(rec);
210 if (IS_ERR(trampoline))
211 return PTR_ERR(trampoline);
212 s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
213 /* Expect brcl 0x0,... */
214 return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
215}
216
217int ftrace_update_ftrace_func(ftrace_func_t func)
218{
219 ftrace_func = func;
220 return 0;
221}
222
223void arch_ftrace_update_code(int command)
224{
225 ftrace_modify_all_code(command);
226}
227
228void ftrace_arch_code_modify_post_process(void)
229{
230 /*
231 * Flush any pre-fetched instructions on all
232 * CPUs to make the new code visible.
233 */
234 text_poke_sync_lock();
235}
236
237#ifdef CONFIG_MODULES
238
239static int __init ftrace_plt_init(void)
240{
241 const char *start, *end;
242
243 ftrace_plt = module_alloc(PAGE_SIZE);
244 if (!ftrace_plt)
245 panic("cannot allocate ftrace plt\n");
246
247 start = ftrace_shared_hotpatch_trampoline(&end);
248 memcpy(ftrace_plt, start, end - start);
249 set_memory_ro((unsigned long)ftrace_plt, 1);
250 return 0;
251}
252device_initcall(ftrace_plt_init);
253
254#endif /* CONFIG_MODULES */
255
256#ifdef CONFIG_FUNCTION_GRAPH_TRACER
257/*
258 * Hook the return address and push it in the stack of return addresses
259 * in current thread info.
260 */
261unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
262 unsigned long ip)
263{
264 if (unlikely(ftrace_graph_is_dead()))
265 goto out;
266 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
267 goto out;
268 ip -= MCOUNT_INSN_SIZE;
269 if (!function_graph_enter(ra, ip, 0, (void *) sp))
270 ra = (unsigned long) return_to_handler;
271out:
272 return ra;
273}
274NOKPROBE_SYMBOL(prepare_ftrace_return);
275
276/*
277 * Patch the kernel code at ftrace_graph_caller location. The instruction
278 * there is branch relative on condition. To enable the ftrace graph code
279 * block, we simply patch the mask field of the instruction to zero and
280 * turn the instruction into a nop.
281 * To disable the ftrace graph code the mask field will be patched to
282 * all ones, which turns the instruction into an unconditional branch.
283 */
284int ftrace_enable_ftrace_graph_caller(void)
285{
286 int rc;
287
288 /* Expect brc 0xf,... */
289 rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
290 if (rc)
291 return rc;
292 text_poke_sync_lock();
293 return 0;
294}
295
296int ftrace_disable_ftrace_graph_caller(void)
297{
298 int rc;
299
300 /* Expect brc 0x0,... */
301 rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
302 if (rc)
303 return rc;
304 text_poke_sync_lock();
305 return 0;
306}
307
308#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
309
310#ifdef CONFIG_KPROBES_ON_FTRACE
311void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
312 struct ftrace_ops *ops, struct ftrace_regs *fregs)
313{
314 struct kprobe_ctlblk *kcb;
315 struct pt_regs *regs;
316 struct kprobe *p;
317 int bit;
318
319 bit = ftrace_test_recursion_trylock(ip, parent_ip);
320 if (bit < 0)
321 return;
322
323 regs = ftrace_get_regs(fregs);
324 p = get_kprobe((kprobe_opcode_t *)ip);
325 if (!regs || unlikely(!p) || kprobe_disabled(p))
326 goto out;
327
328 if (kprobe_running()) {
329 kprobes_inc_nmissed_count(p);
330 goto out;
331 }
332
333 __this_cpu_write(current_kprobe, p);
334
335 kcb = get_kprobe_ctlblk();
336 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
337
338 instruction_pointer_set(regs, ip);
339
340 if (!p->pre_handler || !p->pre_handler(p, regs)) {
341
342 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
343
344 if (unlikely(p->post_handler)) {
345 kcb->kprobe_status = KPROBE_HIT_SSDONE;
346 p->post_handler(p, regs, 0);
347 }
348 }
349 __this_cpu_write(current_kprobe, NULL);
350out:
351 ftrace_test_recursion_unlock(bit);
352}
353NOKPROBE_SYMBOL(kprobe_ftrace_handler);
354
355int arch_prepare_kprobe_ftrace(struct kprobe *p)
356{
357 p->ainsn.insn = NULL;
358 return 0;
359}
360#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 * The mcount code looks like this:
26 * stg %r14,8(%r15) # offset 0
27 * larl %r1,<&counter> # offset 6
28 * brasl %r14,_mcount # offset 12
29 * lg %r14,8(%r15) # offset 18
30 * Total length is 24 bytes. Only the first instruction will be patched
31 * by ftrace_make_call / ftrace_make_nop.
32 * The enabled ftrace code block looks like this:
33 * > brasl %r0,ftrace_caller # offset 0
34 * larl %r1,<&counter> # offset 6
35 * brasl %r14,_mcount # offset 12
36 * lg %r14,8(%r15) # offset 18
37 * The ftrace function gets called with a non-standard C function call ABI
38 * where r0 contains the return address. It is also expected that the called
39 * function only clobbers r0 and r1, but restores r2-r15.
40 * For module code we can't directly jump to ftrace caller, but need a
41 * trampoline (ftrace_plt), which clobbers also r1.
42 * The return point of the ftrace function has offset 24, so execution
43 * continues behind the mcount block.
44 * The disabled ftrace code block looks like this:
45 * > jg .+24 # offset 0
46 * larl %r1,<&counter> # offset 6
47 * brasl %r14,_mcount # offset 12
48 * lg %r14,8(%r15) # offset 18
49 * The jg instruction branches to offset 24 to skip as many instructions
50 * as possible.
51 * In case we use gcc's hotpatch feature the original and also the disabled
52 * function prologue contains only a single six byte instruction and looks
53 * like this:
54 * > brcl 0,0 # offset 0
55 * To enable ftrace the code gets patched like above and afterwards looks
56 * like this:
57 * > brasl %r0,ftrace_caller # offset 0
58 */
59
60unsigned long ftrace_plt;
61
62static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
63{
64#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
65 /* brcl 0,0 */
66 insn->opc = 0xc004;
67 insn->disp = 0;
68#else
69 /* stg r14,8(r15) */
70 insn->opc = 0xe3e0;
71 insn->disp = 0xf0080024;
72#endif
73}
74
75int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
76 unsigned long addr)
77{
78 return 0;
79}
80
81int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
82 unsigned long addr)
83{
84 struct ftrace_insn orig, new, old;
85
86 if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
87 return -EFAULT;
88 if (addr == MCOUNT_ADDR) {
89 /* Initial code replacement */
90 ftrace_generate_orig_insn(&orig);
91 ftrace_generate_nop_insn(&new);
92 } else {
93 /* Replace ftrace call with a nop. */
94 ftrace_generate_call_insn(&orig, rec->ip);
95 ftrace_generate_nop_insn(&new);
96 }
97 /* Verify that the to be replaced code matches what we expect. */
98 if (memcmp(&orig, &old, sizeof(old)))
99 return -EINVAL;
100 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
101 return 0;
102}
103
104int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
105{
106 struct ftrace_insn orig, new, old;
107
108 if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
109 return -EFAULT;
110 /* Replace nop with an ftrace call. */
111 ftrace_generate_nop_insn(&orig);
112 ftrace_generate_call_insn(&new, rec->ip);
113
114 /* Verify that the to be replaced code matches what we expect. */
115 if (memcmp(&orig, &old, sizeof(old)))
116 return -EINVAL;
117 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
118 return 0;
119}
120
121int ftrace_update_ftrace_func(ftrace_func_t func)
122{
123 return 0;
124}
125
126int __init ftrace_dyn_arch_init(void)
127{
128 return 0;
129}
130
131#ifdef CONFIG_MODULES
132
133static int __init ftrace_plt_init(void)
134{
135 unsigned int *ip;
136
137 ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
138 if (!ftrace_plt)
139 panic("cannot allocate ftrace plt\n");
140 ip = (unsigned int *) ftrace_plt;
141 ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
142 ip[1] = 0x100a0004;
143 ip[2] = 0x07f10000;
144 ip[3] = FTRACE_ADDR >> 32;
145 ip[4] = FTRACE_ADDR & 0xffffffff;
146 set_memory_ro(ftrace_plt, 1);
147 return 0;
148}
149device_initcall(ftrace_plt_init);
150
151#endif /* CONFIG_MODULES */
152
153#ifdef CONFIG_FUNCTION_GRAPH_TRACER
154/*
155 * Hook the return address and push it in the stack of return addresses
156 * in current thread info.
157 */
158unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
159 unsigned long ip)
160{
161 if (unlikely(ftrace_graph_is_dead()))
162 goto out;
163 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
164 goto out;
165 ip -= MCOUNT_INSN_SIZE;
166 if (!function_graph_enter(ra, ip, 0, (void *) sp))
167 ra = (unsigned long) return_to_handler;
168out:
169 return ra;
170}
171NOKPROBE_SYMBOL(prepare_ftrace_return);
172
173/*
174 * Patch the kernel code at ftrace_graph_caller location. The instruction
175 * there is branch relative on condition. To enable the ftrace graph code
176 * block, we simply patch the mask field of the instruction to zero and
177 * turn the instruction into a nop.
178 * To disable the ftrace graph code the mask field will be patched to
179 * all ones, which turns the instruction into an unconditional branch.
180 */
181int ftrace_enable_ftrace_graph_caller(void)
182{
183 u8 op = 0x04; /* set mask field to zero */
184
185 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
186 return 0;
187}
188
189int ftrace_disable_ftrace_graph_caller(void)
190{
191 u8 op = 0xf4; /* set mask field to all ones */
192
193 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
194 return 0;
195}
196
197#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
198
199#ifdef CONFIG_KPROBES_ON_FTRACE
200void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
201 struct ftrace_ops *ops, struct pt_regs *regs)
202{
203 struct kprobe_ctlblk *kcb;
204 struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
205
206 if (unlikely(!p) || kprobe_disabled(p))
207 return;
208
209 if (kprobe_running()) {
210 kprobes_inc_nmissed_count(p);
211 return;
212 }
213
214 __this_cpu_write(current_kprobe, p);
215
216 kcb = get_kprobe_ctlblk();
217 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
218
219 instruction_pointer_set(regs, ip);
220
221 if (!p->pre_handler || !p->pre_handler(p, regs)) {
222
223 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
224
225 if (unlikely(p->post_handler)) {
226 kcb->kprobe_status = KPROBE_HIT_SSDONE;
227 p->post_handler(p, regs, 0);
228 }
229 }
230 __this_cpu_write(current_kprobe, NULL);
231}
232NOKPROBE_SYMBOL(kprobe_ftrace_handler);
233
234int arch_prepare_kprobe_ftrace(struct kprobe *p)
235{
236 p->ainsn.insn = NULL;
237 return 0;
238}
239#endif