arch/riscv/mm/extable.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
   4  *  Lennox Wu <lennox.wu@sunplusct.com>
   5  *  Chen Liqin <liqin.chen@sunplusct.com>
   6  * Copyright (C) 2013 Regents of the University of California
   7  */
   8
   9
  10 #include <linux/bitfield.h>
  11 #include <linux/extable.h>
  12 #include <linux/module.h>
  13 #include <linux/uaccess.h>
  14 #include <asm/asm-extable.h>
  15 #include <asm/ptrace.h>
  16
  17 static inline unsigned long
  18 get_ex_fixup(const struct exception_table_entry *ex)
  19 {
  20         return ((unsigned long)&ex->fixup + ex->fixup);
  21 }
  22
  23 static bool ex_handler_fixup(const struct exception_table_entry *ex,
  24                              struct pt_regs *regs)
  25 {
  26         regs->epc = get_ex_fixup(ex);
  27         return true;
  28 }
  29
  30 static inline unsigned long regs_get_gpr(struct pt_regs *regs, unsigned int offset)
  31 {
  32         if (unlikely(!offset || offset > MAX_REG_OFFSET))
  33                 return 0;
  34
  35         return *(unsigned long *)((unsigned long)regs + offset);
  36 }
  37
  38 static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
  39                                 unsigned long val)
  40 {
  41         if (unlikely(offset > MAX_REG_OFFSET))
  42                 return;
  43
  44         if (offset)
  45                 *(unsigned long *)((unsigned long)regs + offset) = val;
  46 }
  47
  48 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
  49                                         struct pt_regs *regs)
  50 {
  51         int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
  52         int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
  53
  54         regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
  55         regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
  56
  57         regs->epc = get_ex_fixup(ex);
  58         return true;
  59 }
  60
  61 static bool
  62 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
  63                                   struct pt_regs *regs)
  64 {
  65         int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data);
  66         int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
  67         unsigned long data, addr, offset;
  68
  69         addr = regs_get_gpr(regs, reg_addr * sizeof(unsigned long));
  70
  71         offset = addr & 0x7UL;
  72         addr &= ~0x7UL;
  73
  74         data = *(unsigned long *)addr >> (offset * 8);
  75
  76         regs_set_gpr(regs, reg_data * sizeof(unsigned long), data);
  77
  78         regs->epc = get_ex_fixup(ex);
  79         return true;
  80 }
  81
  82 bool fixup_exception(struct pt_regs *regs)
  83 {
  84         const struct exception_table_entry *ex;
  85
  86         ex = search_exception_tables(regs->epc);
  87         if (!ex)
  88                 return false;
  89
  90         switch (ex->type) {
  91         case EX_TYPE_FIXUP:
  92                 return ex_handler_fixup(ex, regs);
  93         case EX_TYPE_BPF:
  94                 return ex_handler_bpf(ex, regs);
  95         case EX_TYPE_UACCESS_ERR_ZERO:
  96                 return ex_handler_uaccess_err_zero(ex, regs);
  97         case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
  98                 return ex_handler_load_unaligned_zeropad(ex, regs);
  99         }
 100
 101         BUG();
 102 }