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_uaccess_err_zero(const struct exception_table_entry *ex,
  20                                         struct pt_regs *regs)
  21 {
  22         int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
  23         int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
  24
  25         pt_regs_write_reg(regs, reg_err, -EFAULT);
  26         pt_regs_write_reg(regs, reg_zero, 0);
  27
  28         regs->pc = get_ex_fixup(ex);
  29         return true;
  30 }
  31
  32 static bool
  33 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
  34                                   struct pt_regs *regs)
  35 {
  36         int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data);
  37         int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
  38         unsigned long data, addr, offset;
  39
  40         addr = pt_regs_read_reg(regs, reg_addr);
  41
  42         offset = addr & 0x7UL;
  43         addr &= ~0x7UL;
  44
  45         data = *(unsigned long*)addr;
  46
  47 #ifndef __AARCH64EB__
  48         data >>= 8 * offset;
  49 #else
  50         data <<= 8 * offset;
  51 #endif
  52
  53         pt_regs_write_reg(regs, reg_data, data);
  54
  55         regs->pc = get_ex_fixup(ex);
  56         return true;
  57 }
  58
  59 bool fixup_exception(struct pt_regs *regs)
  60 {
  61         const struct exception_table_entry *ex;
  62
  63         ex = search_exception_tables(instruction_pointer(regs));
  64         if (!ex)
  65                 return false;
  66
  67         switch (ex->type) {
  68         case EX_TYPE_BPF:
  69                 return ex_handler_bpf(ex, regs);
  70         case EX_TYPE_UACCESS_ERR_ZERO:
  71         case EX_TYPE_KACCESS_ERR_ZERO:
  72                 return ex_handler_uaccess_err_zero(ex, regs);
  73         case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
  74                 return ex_handler_load_unaligned_zeropad(ex, regs);
  75         }
  76
  77         BUG();
  78 }