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1/*
2 * Dynamic function tracer architecture backend.
3 *
4 * Copyright IBM Corp. 2009,2014
5 *
6 * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
7 * 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/cacheflush.h>
20#include "entry.h"
21
22/*
23 * The mcount code looks like this:
24 * stg %r14,8(%r15) # offset 0
25 * larl %r1,<&counter> # offset 6
26 * brasl %r14,_mcount # offset 12
27 * lg %r14,8(%r15) # offset 18
28 * Total length is 24 bytes. Only the first instruction will be patched
29 * by ftrace_make_call / ftrace_make_nop.
30 * The enabled ftrace code block looks like this:
31 * > brasl %r0,ftrace_caller # offset 0
32 * larl %r1,<&counter> # offset 6
33 * brasl %r14,_mcount # offset 12
34 * lg %r14,8(%r15) # offset 18
35 * The ftrace function gets called with a non-standard C function call ABI
36 * where r0 contains the return address. It is also expected that the called
37 * function only clobbers r0 and r1, but restores r2-r15.
38 * For module code we can't directly jump to ftrace caller, but need a
39 * trampoline (ftrace_plt), which clobbers also r1.
40 * The return point of the ftrace function has offset 24, so execution
41 * continues behind the mcount block.
42 * The disabled ftrace code block looks like this:
43 * > jg .+24 # offset 0
44 * larl %r1,<&counter> # offset 6
45 * brasl %r14,_mcount # offset 12
46 * lg %r14,8(%r15) # offset 18
47 * The jg instruction branches to offset 24 to skip as many instructions
48 * as possible.
49 * In case we use gcc's hotpatch feature the original and also the disabled
50 * function prologue contains only a single six byte instruction and looks
51 * like this:
52 * > brcl 0,0 # offset 0
53 * To enable ftrace the code gets patched like above and afterwards looks
54 * like this:
55 * > brasl %r0,ftrace_caller # offset 0
56 */
57
58unsigned long ftrace_plt;
59
60static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
61{
62#ifdef CC_USING_HOTPATCH
63 /* brcl 0,0 */
64 insn->opc = 0xc004;
65 insn->disp = 0;
66#else
67 /* stg r14,8(r15) */
68 insn->opc = 0xe3e0;
69 insn->disp = 0xf0080024;
70#endif
71}
72
73static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
74{
75#ifdef CONFIG_KPROBES
76 if (insn->opc == BREAKPOINT_INSTRUCTION)
77 return 1;
78#endif
79 return 0;
80}
81
82static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
83{
84#ifdef CONFIG_KPROBES
85 insn->opc = BREAKPOINT_INSTRUCTION;
86 insn->disp = KPROBE_ON_FTRACE_NOP;
87#endif
88}
89
90static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
91{
92#ifdef CONFIG_KPROBES
93 insn->opc = BREAKPOINT_INSTRUCTION;
94 insn->disp = KPROBE_ON_FTRACE_CALL;
95#endif
96}
97
98int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
99 unsigned long addr)
100{
101 return 0;
102}
103
104int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
105 unsigned long addr)
106{
107 struct ftrace_insn orig, new, old;
108
109 if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
110 return -EFAULT;
111 if (addr == MCOUNT_ADDR) {
112 /* Initial code replacement */
113 ftrace_generate_orig_insn(&orig);
114 ftrace_generate_nop_insn(&new);
115 } else if (is_kprobe_on_ftrace(&old)) {
116 /*
117 * If we find a breakpoint instruction, a kprobe has been
118 * placed at the beginning of the function. We write the
119 * constant KPROBE_ON_FTRACE_NOP into the remaining four
120 * bytes of the original instruction so that the kprobes
121 * handler can execute a nop, if it reaches this breakpoint.
122 */
123 ftrace_generate_kprobe_call_insn(&orig);
124 ftrace_generate_kprobe_nop_insn(&new);
125 } else {
126 /* Replace ftrace call with a nop. */
127 ftrace_generate_call_insn(&orig, rec->ip);
128 ftrace_generate_nop_insn(&new);
129 }
130 /* Verify that the to be replaced code matches what we expect. */
131 if (memcmp(&orig, &old, sizeof(old)))
132 return -EINVAL;
133 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
134 return 0;
135}
136
137int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
138{
139 struct ftrace_insn orig, new, old;
140
141 if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
142 return -EFAULT;
143 if (is_kprobe_on_ftrace(&old)) {
144 /*
145 * If we find a breakpoint instruction, a kprobe has been
146 * placed at the beginning of the function. We write the
147 * constant KPROBE_ON_FTRACE_CALL into the remaining four
148 * bytes of the original instruction so that the kprobes
149 * handler can execute a brasl if it reaches this breakpoint.
150 */
151 ftrace_generate_kprobe_nop_insn(&orig);
152 ftrace_generate_kprobe_call_insn(&new);
153 } else {
154 /* Replace nop with an ftrace call. */
155 ftrace_generate_nop_insn(&orig);
156 ftrace_generate_call_insn(&new, rec->ip);
157 }
158 /* Verify that the to be replaced code matches what we expect. */
159 if (memcmp(&orig, &old, sizeof(old)))
160 return -EINVAL;
161 s390_kernel_write((void *) rec->ip, &new, sizeof(new));
162 return 0;
163}
164
165int ftrace_update_ftrace_func(ftrace_func_t func)
166{
167 return 0;
168}
169
170int __init ftrace_dyn_arch_init(void)
171{
172 return 0;
173}
174
175static int __init ftrace_plt_init(void)
176{
177 unsigned int *ip;
178
179 ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
180 if (!ftrace_plt)
181 panic("cannot allocate ftrace plt\n");
182 ip = (unsigned int *) ftrace_plt;
183 ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
184 ip[1] = 0x100a0004;
185 ip[2] = 0x07f10000;
186 ip[3] = FTRACE_ADDR >> 32;
187 ip[4] = FTRACE_ADDR & 0xffffffff;
188 set_memory_ro(ftrace_plt, 1);
189 return 0;
190}
191device_initcall(ftrace_plt_init);
192
193#ifdef CONFIG_FUNCTION_GRAPH_TRACER
194/*
195 * Hook the return address and push it in the stack of return addresses
196 * in current thread info.
197 */
198unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
199{
200 struct ftrace_graph_ent trace;
201
202 if (unlikely(ftrace_graph_is_dead()))
203 goto out;
204 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
205 goto out;
206 ip -= MCOUNT_INSN_SIZE;
207 trace.func = ip;
208 trace.depth = current->curr_ret_stack + 1;
209 /* Only trace if the calling function expects to. */
210 if (!ftrace_graph_entry(&trace))
211 goto out;
212 if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
213 NULL) == -EBUSY)
214 goto out;
215 parent = (unsigned long) return_to_handler;
216out:
217 return parent;
218}
219NOKPROBE_SYMBOL(prepare_ftrace_return);
220
221/*
222 * Patch the kernel code at ftrace_graph_caller location. The instruction
223 * there is branch relative on condition. To enable the ftrace graph code
224 * block, we simply patch the mask field of the instruction to zero and
225 * turn the instruction into a nop.
226 * To disable the ftrace graph code the mask field will be patched to
227 * all ones, which turns the instruction into an unconditional branch.
228 */
229int ftrace_enable_ftrace_graph_caller(void)
230{
231 u8 op = 0x04; /* set mask field to zero */
232
233 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
234 return 0;
235}
236
237int ftrace_disable_ftrace_graph_caller(void)
238{
239 u8 op = 0xf4; /* set mask field to all ones */
240
241 s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
242 return 0;
243}
244
245#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