/* Rewritten by Rusty Russell, on the backs of many others...
     Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
  
      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.
  
      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.
  
      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

  #include <linux/ftrace.h>

  #include <linux/memory.h>

  #include <linux/extable.h>

  #include <linux/module.h>

  #include <linux/mutex.h>

  #include <linux/init.h>

  #include <linux/kprobes.h>

  #include <linux/filter.h>

  #include <asm/sections.h>

  #include <linux/uaccess.h>

  
  /*
   * mutex protecting text section modification (dynamic code patching).
   * some users need to sleep (allocating memory...) while they hold this lock.
   *
   * NOT exported to modules - patching kernel text is a really delicate matter.
   */
  DEFINE_MUTEX(text_mutex);

  
  extern struct exception_table_entry __start___ex_table[];
  extern struct exception_table_entry __stop___ex_table[];

  /* Cleared by build time tools if the table is already sorted. */

  u32 __initdata __visible main_extable_sort_needed = 1;

  /* Sort the kernel's built-in exception table */
  void __init sort_main_extable(void)
  {

  	if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {

  		pr_notice("Sorting __ex_table...
  ");

  		sort_extable(__start___ex_table, __stop___ex_table);

  	}

  }
  
  /* Given an address, look for it in the exception tables. */
  const struct exception_table_entry *search_exception_tables(unsigned long addr)
  {
  	const struct exception_table_entry *e;

  	e = search_extable(__start___ex_table,
  			   __stop___ex_table - __start___ex_table, addr);

  	if (!e)
  		e = search_module_extables(addr);
  	return e;
  }

  static inline int init_kernel_text(unsigned long addr)
  {
  	if (addr >= (unsigned long)_sinittext &&

  	    addr < (unsigned long)_einittext)

  		return 1;
  	return 0;
  }

  int notrace core_kernel_text(unsigned long addr)

  {
  	if (addr >= (unsigned long)_stext &&

  	    addr < (unsigned long)_etext)

  		return 1;

  	if (system_state < SYSTEM_RUNNING &&

  	    init_kernel_text(addr))

  		return 1;
  	return 0;
  }

  /**
   * core_kernel_data - tell if addr points to kernel data
   * @addr: address to test
   *
   * Returns true if @addr passed in is from the core kernel data
   * section.
   *
   * Note: On some archs it may return true for core RODATA, and false
   *  for others. But will always be true for core RW data.
   */

  int core_kernel_data(unsigned long addr)
  {

  	if (addr >= (unsigned long)_sdata &&

  	    addr < (unsigned long)_edata)
  		return 1;
  	return 0;
  }

  int __kernel_text_address(unsigned long addr)

  {

  	if (kernel_text_address(addr))

  		return 1;

  	/*
  	 * There might be init symbols in saved stacktraces.
  	 * Give those symbols a chance to be printed in
  	 * backtraces (such as lockdep traces).
  	 *
  	 * Since we are after the module-symbols check, there's
  	 * no danger of address overlap:
  	 */
  	if (init_kernel_text(addr))
  		return 1;
  	return 0;

  }
  
  int kernel_text_address(unsigned long addr)
  {

  	bool no_rcu;
  	int ret = 1;

  	if (core_kernel_text(addr))
  		return 1;

  
  	/*
  	 * If a stack dump happens while RCU is not watching, then
  	 * RCU needs to be notified that it requires to start
  	 * watching again. This can happen either by tracing that
  	 * triggers a stack trace, or a WARN() that happens during
  	 * coming back from idle, or cpu on or offlining.
  	 *
  	 * is_module_text_address() as well as the kprobe slots
  	 * and is_bpf_text_address() require RCU to be watching.
  	 */
  	no_rcu = !rcu_is_watching();
  
  	/* Treat this like an NMI as it can happen anywhere */
  	if (no_rcu)
  		rcu_nmi_enter();

  	if (is_module_text_address(addr))

  		goto out;

  	if (is_ftrace_trampoline(addr))

  		goto out;

  	if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))

  		goto out;

  	if (is_bpf_text_address(addr))

  		goto out;
  	ret = 0;
  out:
  	if (no_rcu)
  		rcu_nmi_exit();
  
  	return ret;

  }

  
  /*
   * On some architectures (PPC64, IA64) function pointers
   * are actually only tokens to some data that then holds the
   * real function address. As a result, to find if a function
   * pointer is part of the kernel text, we need to do some
   * special dereferencing first.
   */
  int func_ptr_is_kernel_text(void *ptr)
  {
  	unsigned long addr;
  	addr = (unsigned long) dereference_function_descriptor(ptr);
  	if (core_kernel_text(addr))
  		return 1;

  	return is_module_text_address(addr);

  }