arch/parisc/include/asm/extable.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __PARISC_EXTABLE_H
   3 #define __PARISC_EXTABLE_H
   4
   5 #include <asm/ptrace.h>
   6 #include <linux/compiler.h>
   7
   8 /*
   9  * The exception table consists of three addresses:
  10  *
  11  * - A relative address to the instruction that is allowed to fault.
  12  * - A relative address at which the program should continue (fixup routine)
  13  * - An asm statement which specifies which CPU register will
  14  *   receive -EFAULT when an exception happens if the lowest bit in
  15  *   the fixup address is set.
  16  *
  17  * Note: The register specified in the err_opcode instruction will be
  18  * modified at runtime if a fault happens. Register %r0 will be ignored.
  19  *
  20  * Since relative addresses are used, 32bit values are sufficient even on
  21  * 64bit kernel.
  22  */
  23
  24 struct pt_regs;
  25 int fixup_exception(struct pt_regs *regs);
  26
  27 #define ARCH_HAS_RELATIVE_EXTABLE
  28 struct exception_table_entry {
  29         int insn;       /* relative address of insn that is allowed to fault. */
  30         int fixup;      /* relative address of fixup routine */
  31         int err_opcode; /* sample opcode with register which holds error code */
  32 };
  33
  34 #define ASM_EXCEPTIONTABLE_ENTRY( fault_addr, except_addr, opcode )\
  35         ".section __ex_table,\"aw\"\n"                     \
  36         ".align 4\n"                                       \
  37         ".word (" #fault_addr " - .), (" #except_addr " - .)\n" \
  38         opcode "\n"                                        \
  39         ".previous\n"
  40
  41 /*
  42  * ASM_EXCEPTIONTABLE_ENTRY_EFAULT() creates a special exception table entry
  43  * (with lowest bit set) for which the fault handler in fixup_exception() will
  44  * load -EFAULT on fault into the register specified by the err_opcode instruction,
  45  * and zeroes the target register in case of a read fault in get_user().
  46  */
  47 #define ASM_EXCEPTIONTABLE_VAR(__err_var)               \
  48         int __err_var = 0
  49 #define ASM_EXCEPTIONTABLE_ENTRY_EFAULT( fault_addr, except_addr, register )\
  50         ASM_EXCEPTIONTABLE_ENTRY( fault_addr, except_addr + 1, "or %%r0,%%r0," register)
  51
  52 static inline void swap_ex_entry_fixup(struct exception_table_entry *a,
  53                                        struct exception_table_entry *b,
  54                                        struct exception_table_entry tmp,
  55                                        int delta)
  56 {
  57         a->fixup = b->fixup + delta;
  58         b->fixup = tmp.fixup - delta;
  59         a->err_opcode = b->err_opcode;
  60         b->err_opcode = tmp.err_opcode;
  61 }
  62 #define swap_ex_entry_fixup swap_ex_entry_fixup
  63
  64 #endif