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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): 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
75static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
76{
77#ifdef CONFIG_KPROBES
78 if (insn->opc == BREAKPOINT_INSTRUCTION)
79 return 1;
80#endif
81 return 0;
82}
83
84static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
85{
86#ifdef CONFIG_KPROBES
87 insn->opc = BREAKPOINT_INSTRUCTION;
88 insn->disp = KPROBE_ON_FTRACE_NOP;
89#endif
90}
91
92static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
93{
94#ifdef CONFIG_KPROBES
95 insn->opc = BREAKPOINT_INSTRUCTION;
96 insn->disp = KPROBE_ON_FTRACE_CALL;
97#endif
98}
99
100int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
101 unsigned long addr)
102{
103 return 0;
104}
105
106int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
107 unsigned long addr)
108{
109 struct ftrace_insn orig, new, old;
110
111 if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
112 return -EFAULT;
113 if (addr == MCOUNT_ADDR) {
114 /* Initial code replacement */
115 ftrace_generate_orig_insn(&orig);
116 ftrace_generate_nop_insn(&new);
117 } else if (is_kprobe_on_ftrace(&old)) {
118 /*
119 * If we find a breakpoint instruction, a kprobe has been
120 * placed at the beginning of the function. We write the
121 * constant KPROBE_ON_FTRACE_NOP into the remaining four
122 * bytes of the original instruction so that the kprobes
123 * handler can execute a nop, if it reaches this breakpoint.
124 */
125 ftrace_generate_kprobe_call_insn(&orig);
126 ftrace_generate_kprobe_nop_insn(&new);
127 } else {
128 /* Replace ftrace call with a nop. */
129 ftrace_generate_call_insn(&orig, rec->ip);
130 ftrace_generate_nop_insn(&new);
131 }
132 /* Verify that the to be replaced code matches what we expect. */
133 if (memcmp(&orig, &old, sizeof(old)))
134 return -EINVAL;
135 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
136 return 0;
137}
138
139int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
140{
141 struct ftrace_insn orig, new, old;
142
143 if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
144 return -EFAULT;
145 if (is_kprobe_on_ftrace(&old)) {
146 /*
147 * If we find a breakpoint instruction, a kprobe has been
148 * placed at the beginning of the function. We write the
149 * constant KPROBE_ON_FTRACE_CALL into the remaining four
150 * bytes of the original instruction so that the kprobes
151 * handler can execute a brasl if it reaches this breakpoint.
152 */
153 ftrace_generate_kprobe_nop_insn(&orig);
154 ftrace_generate_kprobe_call_insn(&new);
155 } else {
156 /* Replace nop with an ftrace call. */
157 ftrace_generate_nop_insn(&orig);
158 ftrace_generate_call_insn(&new, rec->ip);
159 }
160 /* Verify that the to be replaced code matches what we expect. */
161 if (memcmp(&orig, &old, sizeof(old)))
162 return -EINVAL;
163 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
164 return 0;
165}
166
167int ftrace_update_ftrace_func(ftrace_func_t func)
168{
169 return 0;
170}
171
172int __init ftrace_dyn_arch_init(void)
173{
174 return 0;
175}
176
177#ifdef CONFIG_MODULES
178
179static int __init ftrace_plt_init(void)
180{
181 unsigned int *ip;
182
183 ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
184 if (!ftrace_plt)
185 panic("cannot allocate ftrace plt\n");
186 ip = (unsigned int *) ftrace_plt;
187 ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
188 ip[1] = 0x100a0004;
189 ip[2] = 0x07f10000;
190 ip[3] = FTRACE_ADDR >> 32;
191 ip[4] = FTRACE_ADDR & 0xffffffff;
192 set_memory_ro(ftrace_plt, 1);
193 return 0;
194}
195device_initcall(ftrace_plt_init);
196
197#endif /* CONFIG_MODULES */
198
199#ifdef CONFIG_FUNCTION_GRAPH_TRACER
200/*
201 * Hook the return address and push it in the stack of return addresses
202 * in current thread info.
203 */
204unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
205 unsigned long ip)
206{
207 if (unlikely(ftrace_graph_is_dead()))
208 goto out;
209 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
210 goto out;
211 ip -= MCOUNT_INSN_SIZE;
212 if (!function_graph_enter(ra, ip, 0, (void *) sp))
213 ra = (unsigned long) return_to_handler;
214out:
215 return ra;
216}
217NOKPROBE_SYMBOL(prepare_ftrace_return);
218
219/*
220 * Patch the kernel code at ftrace_graph_caller location. The instruction
221 * there is branch relative on condition. To enable the ftrace graph code
222 * block, we simply patch the mask field of the instruction to zero and
223 * turn the instruction into a nop.
224 * To disable the ftrace graph code the mask field will be patched to
225 * all ones, which turns the instruction into an unconditional branch.
226 */
227int ftrace_enable_ftrace_graph_caller(void)
228{
229 u8 op = 0x04; /* set mask field to zero */
230
231 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
232 return 0;
233}
234
235int ftrace_disable_ftrace_graph_caller(void)
236{
237 u8 op = 0xf4; /* set mask field to all ones */
238
239 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
240 return 0;
241}
242
243#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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