1 /*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (c) 2010 Cavium Networks, Inc.
7 */
8
9 #include <linux/jump_label.h>
10 #include <linux/kernel.h>
11 #include <linux/memory.h>
12 #include <linux/mutex.h>
13 #include <linux/types.h>
14 #include <linux/cpu.h>
15
16 #include <asm/cacheflush.h>
17 #include <asm/inst.h>
18
19 /*
20 * Define parameters for the standard MIPS and the microMIPS jump
21 * instruction encoding respectively:
22 *
23 * - the ISA bit of the target, either 0 or 1 respectively,
24 *
25 * - the amount the jump target address is shifted right to fit in the
26 * immediate field of the machine instruction, either 2 or 1,
27 *
28 * - the mask determining the size of the jump region relative to the
29 * delay-slot instruction, either 256MB or 128MB,
30 *
31 * - the jump target alignment, either 4 or 2 bytes.
32 */
33 #define J_ISA_BIT IS_ENABLED(CONFIG_CPU_MICROMIPS)
34 #define J_RANGE_SHIFT (2 - J_ISA_BIT)
35 #define J_RANGE_MASK ((1ul << (26 + J_RANGE_SHIFT)) - 1)
36 #define J_ALIGN_MASK ((1ul << J_RANGE_SHIFT) - 1)
37
38 void arch_jump_label_transform(struct jump_entry *e,
39 enum jump_label_type type)
40 {
41 union mips_instruction *insn_p;
42 union mips_instruction insn;
43 long offset;
44
45 insn_p = (union mips_instruction *)msk_isa16_mode(e->code);
46
47 /* Target must have the right alignment and ISA must be preserved. */
48 BUG_ON((e->target & J_ALIGN_MASK) != J_ISA_BIT);
49
50 if (type == JUMP_LABEL_JMP) {
51 if (!IS_ENABLED(CONFIG_CPU_MICROMIPS) && MIPS_ISA_REV >= 6) {
52 offset = e->target - ((unsigned long)insn_p + 4);
53 offset >>= 2;
54
55 /*
56 * The branch offset must fit in the instruction's 26
57 * bit field.
58 */
59 WARN_ON((offset >= (long)BIT(25)) ||
60 (offset < -(long)BIT(25)));
61
62 insn.j_format.opcode = bc6_op;
63 insn.j_format.target = offset;
64 } else {
65 /*
66 * Jump only works within an aligned region its delay
67 * slot is in.
68 */
69 WARN_ON((e->target & ~J_RANGE_MASK) !=
70 ((e->code + 4) & ~J_RANGE_MASK));
71
72 insn.j_format.opcode = J_ISA_BIT ? mm_j32_op : j_op;
73 insn.j_format.target = e->target >> J_RANGE_SHIFT;
74 }
75 } else {
76 insn.word = 0; /* nop */
77 }
78
79 mutex_lock(&text_mutex);
80 if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
81 insn_p->halfword[0] = insn.word >> 16;
82 insn_p->halfword[1] = insn.word;
83 } else
84 *insn_p = insn;
85
86 flush_icache_range((unsigned long)insn_p,
87 (unsigned long)insn_p + sizeof(*insn_p));
88
89 mutex_unlock(&text_mutex);
90 }
91
92 #ifdef CONFIG_MODULES
93 void jump_label_apply_nops(struct module *mod)
94 {
95 struct jump_entry *iter_start = mod->jump_entries;
96 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
97 struct jump_entry *iter;
98
99 /* if the module doesn't have jump label entries, just return */
100 if (iter_start == iter_stop)
101 return;
102
103 for (iter = iter_start; iter < iter_stop; iter++) {
104 /* Only write NOPs for arch_branch_static(). */
105 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
106 arch_jump_label_transform(iter, JUMP_LABEL_NOP);
107 }
108 }
109 #endif
110
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.