1 /*
2 * ftrace graph code
3 *
4 * Copyright (C) 2009-2010 Analog Devices Inc.
5 * Licensed under the GPL-2 or later.
6 */
7
8 #include <linux/ftrace.h>
9 #include <linux/kernel.h>
10 #include <linux/sched.h>
11 #include <linux/uaccess.h>
12 #include <linux/atomic.h>
13 #include <asm/cacheflush.h>
14
15 #ifdef CONFIG_DYNAMIC_FTRACE
16
17 static const unsigned char mnop[] = {
18 0x03, 0xc0, 0x00, 0x18, /* MNOP; */
19 0x03, 0xc0, 0x00, 0x18, /* MNOP; */
20 };
21
bfin_make_pcrel24(unsigned char * insn,unsigned long src,unsigned long dst)22 static void bfin_make_pcrel24(unsigned char *insn, unsigned long src,
23 unsigned long dst)
24 {
25 uint32_t pcrel = (dst - src) >> 1;
26 insn[0] = pcrel >> 16;
27 insn[1] = 0xe3;
28 insn[2] = pcrel;
29 insn[3] = pcrel >> 8;
30 }
31 #define bfin_make_pcrel24(insn, src, dst) bfin_make_pcrel24(insn, src, (unsigned long)(dst))
32
ftrace_modify_code(unsigned long ip,const unsigned char * code,unsigned long len)33 static int ftrace_modify_code(unsigned long ip, const unsigned char *code,
34 unsigned long len)
35 {
36 int ret = probe_kernel_write((void *)ip, (void *)code, len);
37 flush_icache_range(ip, ip + len);
38 return ret;
39 }
40
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)41 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
42 unsigned long addr)
43 {
44 /* Turn the mcount call site into two MNOPs as those are 32bit insns */
45 return ftrace_modify_code(rec->ip, mnop, sizeof(mnop));
46 }
47
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)48 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
49 {
50 /* Restore the mcount call site */
51 unsigned char call[8];
52 call[0] = 0x67; /* [--SP] = RETS; */
53 call[1] = 0x01;
54 bfin_make_pcrel24(&call[2], rec->ip + 2, addr);
55 call[6] = 0x27; /* RETS = [SP++]; */
56 call[7] = 0x01;
57 return ftrace_modify_code(rec->ip, call, sizeof(call));
58 }
59
ftrace_update_ftrace_func(ftrace_func_t func)60 int ftrace_update_ftrace_func(ftrace_func_t func)
61 {
62 unsigned char call[4];
63 unsigned long ip = (unsigned long)&ftrace_call;
64 bfin_make_pcrel24(call, ip, func);
65 return ftrace_modify_code(ip, call, sizeof(call));
66 }
67
ftrace_dyn_arch_init(void * data)68 int __init ftrace_dyn_arch_init(void *data)
69 {
70 /* return value is done indirectly via data */
71 *(unsigned long *)data = 0;
72
73 return 0;
74 }
75
76 #endif
77
78 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
79
80 # ifdef CONFIG_DYNAMIC_FTRACE
81
82 extern void ftrace_graph_call(void);
83
ftrace_enable_ftrace_graph_caller(void)84 int ftrace_enable_ftrace_graph_caller(void)
85 {
86 unsigned long ip = (unsigned long)&ftrace_graph_call;
87 uint16_t jump_pcrel12 = ((unsigned long)&ftrace_graph_caller - ip) >> 1;
88 jump_pcrel12 |= 0x2000;
89 return ftrace_modify_code(ip, (void *)&jump_pcrel12, sizeof(jump_pcrel12));
90 }
91
ftrace_disable_ftrace_graph_caller(void)92 int ftrace_disable_ftrace_graph_caller(void)
93 {
94 return ftrace_modify_code((unsigned long)&ftrace_graph_call, empty_zero_page, 2);
95 }
96
97 # endif
98
99 /*
100 * Hook the return address and push it in the stack of return addrs
101 * in current thread info.
102 */
prepare_ftrace_return(unsigned long * parent,unsigned long self_addr,unsigned long frame_pointer)103 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
104 unsigned long frame_pointer)
105 {
106 struct ftrace_graph_ent trace;
107 unsigned long return_hooker = (unsigned long)&return_to_handler;
108
109 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
110 return;
111
112 if (ftrace_push_return_trace(*parent, self_addr, &trace.depth,
113 frame_pointer) == -EBUSY)
114 return;
115
116 trace.func = self_addr;
117
118 /* Only trace if the calling function expects to */
119 if (!ftrace_graph_entry(&trace)) {
120 current->curr_ret_stack--;
121 return;
122 }
123
124 /* all is well in the world ! hijack RETS ... */
125 *parent = return_hooker;
126 }
127
128 #endif
129