• Trent Piepho's avatar
    [PATCH] symbol_put_addr() locks kernel · 5e376613
    Trent Piepho authored
    Even since a previous patch:
    
    Fix race between CONFIG_DEBUG_SLABALLOC and modules
    Sun, 27 Jun 2004 17:55:19 +0000 (17:55 +0000)
    http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=92b3db26d31cf21b70e3c1eadc56c179506d8fbe
    
    
    
    The function symbol_put_addr() will deadlock the kernel.
    
    symbol_put_addr() would acquire modlist_lock, then while holding the lock call
    two functions kernel_text_address() and module_text_address() which also try
    to acquire the same lock.  This deadlocks the kernel of course.
    
    This patch changes symbol_put_addr() to not acquire the modlist_lock, it
    doesn't need it since it never looks at the module list directly.  Also, it
    now uses core_kernel_text() instead of kernel_text_address().  The latter has
    an additional check for addr inside a module, but we don't need to do that
    since we call module_text_address() (the same function kernel_text_address
    uses) ourselves.
    Signed-off-by: default avatarTrent Piepho <xyzzy@speakeasy.org>
    Cc:...
    5e376613
extable.c 1.98 KB
/* 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/module.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/sections.h>

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

/* Sort the kernel's built-in exception table */
void __init sort_main_extable(void)
{
	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-1, addr);
	if (!e)
		e = search_module_extables(addr);
	return e;
}

int core_kernel_text(unsigned long addr)
{
	if (addr >= (unsigned long)_stext &&
	    addr <= (unsigned long)_etext)
		return 1;

	if (addr >= (unsigned long)_sinittext &&
	    addr <= (unsigned long)_einittext)
		return 1;
	return 0;
}

int __kernel_text_address(unsigned long addr)
{
	if (core_kernel_text(addr))
		return 1;
	return __module_text_address(addr) != NULL;
}

int kernel_text_address(unsigned long addr)
{
	if (core_kernel_text(addr))
		return 1;
	return module_text_address(addr) != NULL;
}