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authorMichael Ellerman <michael@ellerman.id.au>2008-06-23 21:32:29 -0400
committerPaul Mackerras <paulus@samba.org>2008-06-30 21:28:21 -0400
commit411781a290b0d0a31fd73826b3ee110f1e3cc3b6 (patch)
tree4a5eb482d99916c17f19a013b52cf808161f32ea /arch/powerpc/lib
parent07630a37beefe8e4401c602f04e3e5bcbba50b31 (diff)
powerpc: Add new code patching routines
This commit adds some new routines for patching code, which will be used in a following commit. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/lib')
-rw-r--r--arch/powerpc/lib/code-patching.c107
1 files changed, 107 insertions, 0 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 430f4c15d786..27957c4ea9e0 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -41,3 +41,110 @@ unsigned int create_branch(const unsigned int *addr,
41 41
42 return instruction; 42 return instruction;
43} 43}
44
45unsigned int create_cond_branch(const unsigned int *addr,
46 unsigned long target, int flags)
47{
48 unsigned int instruction;
49 long offset;
50
51 offset = target;
52 if (! (flags & BRANCH_ABSOLUTE))
53 offset = offset - (unsigned long)addr;
54
55 /* Check we can represent the target in the instruction format */
56 if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
57 return 0;
58
59 /* Mask out the flags and target, so they don't step on each other. */
60 instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
61
62 return instruction;
63}
64
65static unsigned int branch_opcode(unsigned int instr)
66{
67 return (instr >> 26) & 0x3F;
68}
69
70static int instr_is_branch_iform(unsigned int instr)
71{
72 return branch_opcode(instr) == 18;
73}
74
75static int instr_is_branch_bform(unsigned int instr)
76{
77 return branch_opcode(instr) == 16;
78}
79
80int instr_is_relative_branch(unsigned int instr)
81{
82 if (instr & BRANCH_ABSOLUTE)
83 return 0;
84
85 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
86}
87
88static unsigned long branch_iform_target(const unsigned int *instr)
89{
90 signed long imm;
91
92 imm = *instr & 0x3FFFFFC;
93
94 /* If the top bit of the immediate value is set this is negative */
95 if (imm & 0x2000000)
96 imm -= 0x4000000;
97
98 if ((*instr & BRANCH_ABSOLUTE) == 0)
99 imm += (unsigned long)instr;
100
101 return (unsigned long)imm;
102}
103
104static unsigned long branch_bform_target(const unsigned int *instr)
105{
106 signed long imm;
107
108 imm = *instr & 0xFFFC;
109
110 /* If the top bit of the immediate value is set this is negative */
111 if (imm & 0x8000)
112 imm -= 0x10000;
113
114 if ((*instr & BRANCH_ABSOLUTE) == 0)
115 imm += (unsigned long)instr;
116
117 return (unsigned long)imm;
118}
119
120unsigned long branch_target(const unsigned int *instr)
121{
122 if (instr_is_branch_iform(*instr))
123 return branch_iform_target(instr);
124 else if (instr_is_branch_bform(*instr))
125 return branch_bform_target(instr);
126
127 return 0;
128}
129
130int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
131{
132 if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
133 return branch_target(instr) == addr;
134
135 return 0;
136}
137
138unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
139{
140 unsigned long target;
141
142 target = branch_target(src);
143
144 if (instr_is_branch_iform(*src))
145 return create_branch(dest, target, *src);
146 else if (instr_is_branch_bform(*src))
147 return create_cond_branch(dest, target, *src);
148
149 return 0;
150}