text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
   *  Lennox Wu <lennox.wu@sunplusct.com>
   *  Chen Liqin <liqin.chen@sunplusct.com>
   * Copyright (C) 2013 Regents of the University of California
   */
  
  
  #include <linux/bitfield.h>
  #include <linux/extable.h>
  #include <linux/module.h>
  #include <linux/uaccess.h>
  #include <asm/asm-extable.h>
  #include <asm/ptrace.h>
  
  static inline unsigned long
  get_ex_fixup(const struct exception_table_entry *ex)
  {
  	return ((unsigned long)&ex->fixup + ex->fixup);
  }
  
  static bool ex_handler_fixup(const struct exception_table_entry *ex,
  			     struct pt_regs *regs)
  {
  	regs->epc = get_ex_fixup(ex);
  	return true;
  }
  
  static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
  				unsigned long val)
  {
  	if (unlikely(offset > MAX_REG_OFFSET))
  		return;
  
  	if (offset)
  		*(unsigned long *)((unsigned long)regs + offset) = val;
  }
  
  static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
  					struct pt_regs *regs)
  {
  	int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
  	int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
  
  	regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
  	regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
  
  	regs->epc = get_ex_fixup(ex);
  	return true;
  }
  
  bool fixup_exception(struct pt_regs *regs)
  {
  	const struct exception_table_entry *ex;
  
  	ex = search_exception_tables(regs->epc);
  	if (!ex)
  		return false;
  
  	switch (ex->type) {
  	case EX_TYPE_FIXUP:
  		return ex_handler_fixup(ex, regs);
  	case EX_TYPE_BPF:
  		return ex_handler_bpf(ex, regs);
  	case EX_TYPE_UACCESS_ERR_ZERO:
  		return ex_handler_uaccess_err_zero(ex, regs);
  	}
  
  	BUG();
  }
  