1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/kernel.h>
4 #include <linux/jump_label.h>
5
6 #include "asm/cacheflush.h"
7
8 #define JUMPLABEL_ERR "ARC: jump_label: ERROR: "
9
10 /* Halt system on fatal error to make debug easier */
11 #define arc_jl_fatal(format...) \
12 ({ \
13 pr_err(JUMPLABEL_ERR format); \
14 BUG(); \
15 })
16
17 static inline u32 arc_gen_nop(void)
18 {
19 /* 1x 32bit NOP in middle endian */
20 return 0x7000264a;
21 }
22
23 /*
24 * Atomic update of patched instruction is only available if this
25 * instruction doesn't cross L1 cache line boundary. You can read about
26 * the way we achieve this in arc/include/asm/jump_label.h
27 */
28 static inline void instruction_align_assert(void *addr, int len)
29 {
30 unsigned long a = (unsigned long)addr;
31
32 if ((a >> L1_CACHE_SHIFT) != ((a + len - 1) >> L1_CACHE_SHIFT))
33 arc_jl_fatal("instruction (addr %px) cross L1 cache line border",
34 addr);
35 }
36
37 /*
38 * ARCv2 'Branch unconditionally' instruction:
39 * 00000ssssssssss1SSSSSSSSSSNRtttt
40 * s S[n:0] lower bits signed immediate (number is bitfield size)
41 * S S[m:n+1] upper bits signed immediate (number is bitfield size)
42 * t S[24:21] upper bits signed immediate (branch unconditionally far)
43 * N N <.d> delay slot mode
44 * R R Reserved
45 */
46 static inline u32 arc_gen_branch(jump_label_t pc, jump_label_t target)
47 {
48 u32 instruction_l, instruction_r;
49 u32 pcl = pc & GENMASK(31, 2);
50 u32 u_offset = target - pcl;
51 u32 s, S, t;
52
53 /*
54 * Offset in 32-bit branch instruction must to fit into s25.
55 * Something is terribly broken if we get such huge offset within one
56 * function.
57 */
58 if ((s32)u_offset < -16777216 || (s32)u_offset > 16777214)
59 arc_jl_fatal("gen branch with offset (%d) not fit in s25",
60 (s32)u_offset);
61
62 /*
63 * All instructions are aligned by 2 bytes so we should never get offset
64 * here which is not 2 bytes aligned.
65 */
66 if (u_offset & 0x1)
67 arc_jl_fatal("gen branch with offset (%d) unaligned to 2 bytes",
68 (s32)u_offset);
69
70 s = (u_offset >> 1) & GENMASK(9, 0);
71 S = (u_offset >> 11) & GENMASK(9, 0);
72 t = (u_offset >> 21) & GENMASK(3, 0);
73
74 /* 00000ssssssssss1 */
75 instruction_l = (s << 1) | 0x1;
76 /* SSSSSSSSSSNRtttt */
77 instruction_r = (S << 6) | t;
78
79 return (instruction_r << 16) | (instruction_l & GENMASK(15, 0));
80 }
81
82 void arch_jump_label_transform(struct jump_entry *entry,
83 enum jump_label_type type)
84 {
85 jump_label_t *instr_addr = (jump_label_t *)entry->code;
86 u32 instr;
87
88 instruction_align_assert(instr_addr, JUMP_LABEL_NOP_SIZE);
89
90 if (type == JUMP_LABEL_JMP)
91 instr = arc_gen_branch(entry->code, entry->target);
92 else
93 instr = arc_gen_nop();
94
95 WRITE_ONCE(*instr_addr, instr);
96 flush_icache_range(entry->code, entry->code + JUMP_LABEL_NOP_SIZE);
97 }
98
99 #ifdef CONFIG_ARC_DBG_JUMP_LABEL
100 #define SELFTEST_MSG "ARC: instruction generation self-test: "
101
102 struct arc_gen_branch_testdata {
103 jump_label_t pc;
104 jump_label_t target_address;
105 u32 expected_instr;
106 };
107
108 static __init int branch_gen_test(const struct arc_gen_branch_testdata *test)
109 {
110 u32 instr_got;
111
112 instr_got = arc_gen_branch(test->pc, test->target_address);
113 if (instr_got == test->expected_instr)
114 return 0;
115
116 pr_err(SELFTEST_MSG "FAIL:\n arc_gen_branch(0x%08x, 0x%08x) != 0x%08x, got 0x%08x\n",
117 test->pc, test->target_address,
118 test->expected_instr, instr_got);
119
120 return -EFAULT;
121 }
122
123 /*
124 * Offset field in branch instruction is not continuous. Test all
125 * available offset field and sign combinations. Test data is generated
126 * from real working code.
127 */
128 static const struct arc_gen_branch_testdata arcgenbr_test_data[] __initconst = {
129 {0x90007548, 0x90007514, 0xffcf07cd}, /* tiny (-52) offs */
130 {0x9000c9c0, 0x9000c782, 0xffcf05c3}, /* tiny (-574) offs */
131 {0x9000cc1c, 0x9000c782, 0xffcf0367}, /* tiny (-1178) offs */
132 {0x9009dce0, 0x9009d106, 0xff8f0427}, /* small (-3034) offs */
133 {0x9000f5de, 0x90007d30, 0xfc0f0755}, /* big (-30892) offs */
134 {0x900a2444, 0x90035f64, 0xc9cf0321}, /* huge (-443616) offs */
135 {0x90007514, 0x9000752c, 0x00000019}, /* tiny (+24) offs */
136 {0x9001a578, 0x9001a77a, 0x00000203}, /* tiny (+514) offs */
137 {0x90031ed8, 0x90032634, 0x0000075d}, /* tiny (+1884) offs */
138 {0x9008c7f2, 0x9008d3f0, 0x00400401}, /* small (+3072) offs */
139 {0x9000bb38, 0x9003b340, 0x17c00009}, /* big (+194568) offs */
140 {0x90008f44, 0x90578d80, 0xb7c2063d} /* huge (+5701180) offs */
141 };
142
143 static __init int instr_gen_test(void)
144 {
145 int i;
146
147 for (i = 0; i < ARRAY_SIZE(arcgenbr_test_data); i++)
148 if (branch_gen_test(&arcgenbr_test_data[i]))
149 return -EFAULT;
150
151 pr_info(SELFTEST_MSG "OK\n");
152
153 return 0;
154 }
155 early_initcall(instr_gen_test);
156
157 #endif /* CONFIG_ARC_DBG_JUMP_LABEL */
158
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