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 #ifdef HAVE_JUMP_LABEL
  20
  21 /*
  22  * Define parameters for the standard MIPS and the microMIPS jump
  23  * instruction encoding respectively:
  24  *
  25  * - the ISA bit of the target, either 0 or 1 respectively,
  26  *
  27  * - the amount the jump target address is shifted right to fit in the
  28  *   immediate field of the machine instruction, either 2 or 1,
  29  *
  30  * - the mask determining the size of the jump region relative to the
  31  *   delay-slot instruction, either 256MB or 128MB,
  32  *
  33  * - the jump target alignment, either 4 or 2 bytes.
  34  */
  35 #define J_ISA_BIT       IS_ENABLED(CONFIG_CPU_MICROMIPS)
  36 #define J_RANGE_SHIFT   (2 - J_ISA_BIT)
  37 #define J_RANGE_MASK    ((1ul << (26 + J_RANGE_SHIFT)) - 1)
  38 #define J_ALIGN_MASK    ((1ul << J_RANGE_SHIFT) - 1)
  39
  40 void arch_jump_label_transform(struct jump_entry *e,
  41                                enum jump_label_type type)
  42 {
  43         union mips_instruction *insn_p;
  44         union mips_instruction insn;
  45
  46         insn_p = (union mips_instruction *)msk_isa16_mode(e->code);
  47
  48         /* Jump only works within an aligned region its delay slot is in. */
  49         BUG_ON((e->target & ~J_RANGE_MASK) != ((e->code + 4) & ~J_RANGE_MASK));
  50
  51         /* Target must have the right alignment and ISA must be preserved. */
  52         BUG_ON((e->target & J_ALIGN_MASK) != J_ISA_BIT);
  53
  54         if (type == JUMP_LABEL_JMP) {
  55                 insn.j_format.opcode = J_ISA_BIT ? mm_j32_op : j_op;
  56                 insn.j_format.target = e->target >> J_RANGE_SHIFT;
  57         } else {
  58                 insn.word = 0; /* nop */
  59         }
  60
  61         mutex_lock(&text_mutex);
  62         if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
  63                 insn_p->halfword[0] = insn.word >> 16;
  64                 insn_p->halfword[1] = insn.word;
  65         } else
  66                 *insn_p = insn;
  67
  68         flush_icache_range((unsigned long)insn_p,
  69                            (unsigned long)insn_p + sizeof(*insn_p));
  70
  71         mutex_unlock(&text_mutex);
  72 }
  73
  74 #endif /* HAVE_JUMP_LABEL */