arch/mips/kernel/jump_label.c

   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