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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 * 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#ifdef CC_USING_HOTPATCH
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 parent, unsigned long ip)
205{
206 struct ftrace_graph_ent trace;
207
208 if (unlikely(ftrace_graph_is_dead()))
209 goto out;
210 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
211 goto out;
212 ip -= MCOUNT_INSN_SIZE;
213 trace.func = ip;
214 trace.depth = current->curr_ret_stack + 1;
215 /* Only trace if the calling function expects to. */
216 if (!ftrace_graph_entry(&trace))
217 goto out;
218 if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
219 NULL) == -EBUSY)
220 goto out;
221 parent = (unsigned long) return_to_handler;
222out:
223 return parent;
224}
225NOKPROBE_SYMBOL(prepare_ftrace_return);
226
227/*
228 * Patch the kernel code at ftrace_graph_caller location. The instruction
229 * there is branch relative on condition. To enable the ftrace graph code
230 * block, we simply patch the mask field of the instruction to zero and
231 * turn the instruction into a nop.
232 * To disable the ftrace graph code the mask field will be patched to
233 * all ones, which turns the instruction into an unconditional branch.
234 */
235int ftrace_enable_ftrace_graph_caller(void)
236{
237 u8 op = 0x04; /* set mask field to zero */
238
239 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
240 return 0;
241}
242
243int ftrace_disable_ftrace_graph_caller(void)
244{
245 u8 op = 0xf4; /* set mask field to all ones */
246
247 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
248 return 0;
249}
250
251#endif /* CONFIG_FUNCTION_GRAPH_TRACER */