arch/arm64/mm/extable.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Based on arch/arm/mm/extable.c
   4  */
   5
   6 #include <linux/bitfield.h>
   7 #include <linux/extable.h>
   8 #include <linux/uaccess.h>
   9
  10 #include <asm/asm-extable.h>
  11 #include <asm/ptrace.h>
  12
  13 static inline unsigned long
  14 get_ex_fixup(const struct exception_table_entry *ex)
  15 {
  16         return ((unsigned long)&ex->fixup + ex->fixup);
  17 }
  18
  19 static bool ex_handler_fixup(const struct exception_table_entry *ex,
  20                              struct pt_regs *regs)
  21 {
  22         regs->pc = get_ex_fixup(ex);
  23         return true;
  24 }
  25
  26 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
  27                                         struct pt_regs *regs)
  28 {
  29         int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
  30         int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
  31
  32         pt_regs_write_reg(regs, reg_err, -EFAULT);
  33         pt_regs_write_reg(regs, reg_zero, 0);
  34
  35         regs->pc = get_ex_fixup(ex);
  36         return true;
  37 }
  38
  39 static bool
  40 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
  41                                   struct pt_regs *regs)
  42 {
  43         int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type);
  44         int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type);
  45         unsigned long data, addr, offset;
  46
  47         addr = pt_regs_read_reg(regs, reg_addr);
  48
  49         offset = addr & 0x7UL;
  50         addr &= ~0x7UL;
  51
  52         data = *(unsigned long*)addr;
  53
  54 #ifndef __AARCH64EB__
  55         data >>= 8 * offset;
  56 #else
  57         data <<= 8 * offset;
  58 #endif
  59
  60         pt_regs_write_reg(regs, reg_data, data);
  61
  62         regs->pc = get_ex_fixup(ex);
  63         return true;
  64 }
  65
  66 bool fixup_exception(struct pt_regs *regs)
  67 {
  68         const struct exception_table_entry *ex;
  69
  70         ex = search_exception_tables(instruction_pointer(regs));
  71         if (!ex)
  72                 return false;
  73
  74         switch (ex->type) {
  75         case EX_TYPE_FIXUP:
  76                 return ex_handler_fixup(ex, regs);
  77         case EX_TYPE_BPF:
  78                 return ex_handler_bpf(ex, regs);
  79         case EX_TYPE_UACCESS_ERR_ZERO:
  80                 return ex_handler_uaccess_err_zero(ex, regs);
  81         case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
  82                 return ex_handler_load_unaligned_zeropad(ex, regs);
  83         }
  84
  85         BUG();
  86 }