[mirror_ubuntu-artful-kernel.git] / kernel / extable.c

/* 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...\n");
		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);
}
Commit	Line	Data
	1	/* Rewritten by Rusty Russell, on the backs of many others...
	2	Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
	3
	4	This program is free software; you can redistribute it and/or modify
	5	it under the terms of the GNU General Public License as published by
	6	the Free Software Foundation; either version 2 of the License, or
	7	(at your option) any later version.
	8
	9	This program is distributed in the hope that it will be useful,
	10	but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	GNU General Public License for more details.
	13
	14	You should have received a copy of the GNU General Public License
	15	along with this program; if not, write to the Free Software
	16	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	17	*/
	18	#include <linux/ftrace.h>
	19	#include <linux/memory.h>
	20	#include <linux/extable.h>
	21	#include <linux/module.h>
	22	#include <linux/mutex.h>
	23	#include <linux/init.h>
	24	#include <linux/kprobes.h>
	25	#include <linux/filter.h>
	26
	27	#include <asm/sections.h>
	28	#include <linux/uaccess.h>
	29
	30	/*
	31	* mutex protecting text section modification (dynamic code patching).
	32	* some users need to sleep (allocating memory...) while they hold this lock.
	33	*
	34	* NOT exported to modules - patching kernel text is a really delicate matter.
	35	*/
	36	DEFINE_MUTEX(text_mutex);
	37
	38	extern struct exception_table_entry __start___ex_table[];
	39	extern struct exception_table_entry __stop___ex_table[];
	40
	41	/* Cleared by build time tools if the table is already sorted. */
	42	u32 __initdata __visible main_extable_sort_needed = 1;
	43
	44	/* Sort the kernel's built-in exception table */
	45	void __init sort_main_extable(void)
	46	{
	47	if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
	48	pr_notice("Sorting __ex_table...\n");
	49	sort_extable(__start___ex_table, __stop___ex_table);
	50	}
	51	}
	52
	53	/* Given an address, look for it in the exception tables. */
	54	const struct exception_table_entry *search_exception_tables(unsigned long addr)
	55	{
	56	const struct exception_table_entry *e;
	57
	58	e = search_extable(__start___ex_table,
	59	__stop___ex_table - __start___ex_table, addr);
	60	if (!e)
	61	e = search_module_extables(addr);
	62	return e;
	63	}
	64
	65	static inline int init_kernel_text(unsigned long addr)
	66	{
	67	if (addr >= (unsigned long)_sinittext &&
	68	addr < (unsigned long)_einittext)
	69	return 1;
	70	return 0;
	71	}
	72
	73	int notrace core_kernel_text(unsigned long addr)
	74	{
	75	if (addr >= (unsigned long)_stext &&
	76	addr < (unsigned long)_etext)
	77	return 1;
	78
	79	if (system_state < SYSTEM_RUNNING &&
	80	init_kernel_text(addr))
	81	return 1;
	82	return 0;
	83	}
	84
	85	/**
	86	* core_kernel_data - tell if addr points to kernel data
	87	* @addr: address to test
	88	*
	89	* Returns true if @addr passed in is from the core kernel data
	90	* section.
	91	*
	92	* Note: On some archs it may return true for core RODATA, and false
	93	* for others. But will always be true for core RW data.
	94	*/
	95	int core_kernel_data(unsigned long addr)
	96	{
	97	if (addr >= (unsigned long)_sdata &&
	98	addr < (unsigned long)_edata)
	99	return 1;
	100	return 0;
	101	}
	102
	103	int __kernel_text_address(unsigned long addr)
	104	{
	105	if (kernel_text_address(addr))
	106	return 1;
	107	/*
	108	* There might be init symbols in saved stacktraces.
	109	* Give those symbols a chance to be printed in
	110	* backtraces (such as lockdep traces).
	111	*
	112	* Since we are after the module-symbols check, there's
	113	* no danger of address overlap:
	114	*/
	115	if (init_kernel_text(addr))
	116	return 1;
	117	return 0;
	118	}
	119
	120	int kernel_text_address(unsigned long addr)
	121	{
	122	bool no_rcu;
	123	int ret = 1;
	124
	125	if (core_kernel_text(addr))
	126	return 1;
	127
	128	/*
	129	* If a stack dump happens while RCU is not watching, then
	130	* RCU needs to be notified that it requires to start
	131	* watching again. This can happen either by tracing that
	132	* triggers a stack trace, or a WARN() that happens during
	133	* coming back from idle, or cpu on or offlining.
	134	*
	135	* is_module_text_address() as well as the kprobe slots
	136	* and is_bpf_text_address() require RCU to be watching.
	137	*/
	138	no_rcu = !rcu_is_watching();
	139
	140	/* Treat this like an NMI as it can happen anywhere */
	141	if (no_rcu)
	142	rcu_nmi_enter();
	143
	144	if (is_module_text_address(addr))
	145	goto out;
	146	if (is_ftrace_trampoline(addr))
	147	goto out;
	148	if (is_kprobe_optinsn_slot(addr) \|\| is_kprobe_insn_slot(addr))
	149	goto out;
	150	if (is_bpf_text_address(addr))
	151	goto out;
	152	ret = 0;
	153	out:
	154	if (no_rcu)
	155	rcu_nmi_exit();
	156
	157	return ret;
	158	}
	159
	160	/*
	161	* On some architectures (PPC64, IA64) function pointers
	162	* are actually only tokens to some data that then holds the
	163	* real function address. As a result, to find if a function
	164	* pointer is part of the kernel text, we need to do some
	165	* special dereferencing first.
	166	*/
	167	int func_ptr_is_kernel_text(void *ptr)
	168	{
	169	unsigned long addr;
	170	addr = (unsigned long) dereference_function_descriptor(ptr);
	171	if (core_kernel_text(addr))
	172	return 1;
	173	return is_module_text_address(addr);
	174	}