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1 #include <linux/spinlock.h>
2 #include <linux/hardirq.h>
3 #include <linux/ftrace.h>
4 #include <linux/percpu.h>
5 #include <linux/init.h>
6 #include <linux/list.h>
7 
8 #include <asm/ftrace.h>
9 
10 static const u32 ftrace_nop = 0x01000000;
11 
ftrace_nop_replace(void)12 unsigned char *ftrace_nop_replace(void)
13 {
14 	return (char *)&ftrace_nop;
15 }
16 
ftrace_call_replace(unsigned long ip,unsigned long addr)17 unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
18 {
19 	static u32 call;
20 	s32 off;
21 
22 	off = ((s32)addr - (s32)ip);
23 	call = 0x40000000 | ((u32)off >> 2);
24 
25 	return (unsigned char *) &call;
26 }
27 
28 int
ftrace_modify_code(unsigned long ip,unsigned char * old_code,unsigned char * new_code)29 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
30 		   unsigned char *new_code)
31 {
32 	u32 old = *(u32 *)old_code;
33 	u32 new = *(u32 *)new_code;
34 	u32 replaced;
35 	int faulted;
36 
37 	__asm__ __volatile__(
38 	"1:	cas	[%[ip]], %[old], %[new]\n"
39 	"	flush	%[ip]\n"
40 	"	mov	0, %[faulted]\n"
41 	"2:\n"
42 	"	.section .fixup,#alloc,#execinstr\n"
43 	"	.align	4\n"
44 	"3:	sethi	%%hi(2b), %[faulted]\n"
45 	"	jmpl	%[faulted] + %%lo(2b), %%g0\n"
46 	"	 mov	1, %[faulted]\n"
47 	"	.previous\n"
48 	"	.section __ex_table,\"a\"\n"
49 	"	.align	4\n"
50 	"	.word	1b, 3b\n"
51 	"	.previous\n"
52 	: "=r" (replaced), [faulted] "=r" (faulted)
53 	: [new] "0" (new), [old] "r" (old), [ip] "r" (ip)
54 	: "memory");
55 
56 	if (replaced != old && replaced != new)
57 		faulted = 2;
58 
59 	return faulted;
60 }
61 
ftrace_update_ftrace_func(ftrace_func_t func)62 int ftrace_update_ftrace_func(ftrace_func_t func)
63 {
64 	unsigned long ip = (unsigned long)(&ftrace_call);
65 	unsigned char old[MCOUNT_INSN_SIZE], *new;
66 
67 	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
68 	new = ftrace_call_replace(ip, (unsigned long)func);
69 	return ftrace_modify_code(ip, old, new);
70 }
71 
ftrace_dyn_arch_init(void * data)72 int __init ftrace_dyn_arch_init(void *data)
73 {
74 	ftrace_mcount_set(data);
75 	return 0;
76 }
77