arch/loongarch/mm/extable.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
   4  */
   5 #include <linux/bitfield.h>
   6 #include <linux/extable.h>
   7 #include <linux/uaccess.h>
   8 #include <asm/asm-extable.h>
   9 #include <asm/branch.h>
  10
  11 static inline unsigned long
  12 get_ex_fixup(const struct exception_table_entry *ex)
  13 {
  14         return ((unsigned long)&ex->fixup + ex->fixup);
  15 }
  16
  17 static inline void regs_set_gpr(struct pt_regs *regs,
  18                                 unsigned int offset, unsigned long val)
  19 {
  20         if (offset && offset <= MAX_REG_OFFSET)
  21                 *(unsigned long *)((unsigned long)regs + offset) = val;
  22 }
  23
  24 static bool ex_handler_fixup(const struct exception_table_entry *ex,
  25                              struct pt_regs *regs)
  26 {
  27         regs->csr_era = get_ex_fixup(ex);
  28
  29         return true;
  30 }
  31
  32 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
  33                                         struct pt_regs *regs)
  34 {
  35         int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
  36         int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
  37
  38         regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
  39         regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
  40         regs->csr_era = get_ex_fixup(ex);
  41
  42         return true;
  43 }
  44
  45 bool fixup_exception(struct pt_regs *regs)
  46 {
  47         const struct exception_table_entry *ex;
  48
  49         ex = search_exception_tables(exception_era(regs));
  50         if (!ex)
  51                 return false;
  52
  53         switch (ex->type) {
  54         case EX_TYPE_FIXUP:
  55                 return ex_handler_fixup(ex, regs);
  56         case EX_TYPE_UACCESS_ERR_ZERO:
  57                 return ex_handler_uaccess_err_zero(ex, regs);
  58         case EX_TYPE_BPF:
  59                 return ex_handler_bpf(ex, regs);
  60         }
  61
  62         BUG();
  63 }