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Diffstat (limited to 'arch/x86/kernel/test_nx.c')
| -rw-r--r-- | arch/x86/kernel/test_nx.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/arch/x86/kernel/test_nx.c b/arch/x86/kernel/test_nx.c new file mode 100644 index 000000000000..6d7ef11e7975 --- /dev/null +++ b/arch/x86/kernel/test_nx.c @@ -0,0 +1,176 @@ +/* + * test_nx.c: functional test for NX functionality + * + * (C) Copyright 2008 Intel Corporation + * Author: Arjan van de Ven <arjan@linux.intel.com> + * + * 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; version 2 + * of the License. + */ +#include <linux/module.h> +#include <linux/sort.h> +#include <asm/uaccess.h> + +extern int rodata_test_data; + +/* + * This file checks 4 things: + * 1) Check if the stack is not executable + * 2) Check if kmalloc memory is not executable + * 3) Check if the .rodata section is not executable + * 4) Check if the .data section of a module is not executable + * + * To do this, the test code tries to execute memory in stack/kmalloc/etc, + * and then checks if the expected trap happens. + * + * Sadly, this implies having a dynamic exception handling table entry. + * ... which can be done (and will make Rusty cry)... but it can only + * be done in a stand-alone module with only 1 entry total. + * (otherwise we'd have to sort and that's just too messy) + */ + + + +/* + * We want to set up an exception handling point on our stack, + * which means a variable value. This function is rather dirty + * and walks the exception table of the module, looking for a magic + * marker and replaces it with a specific function. + */ +static void fudze_exception_table(void *marker, void *new) +{ + struct module *mod = THIS_MODULE; + struct exception_table_entry *extable; + + /* + * Note: This module has only 1 exception table entry, + * so searching and sorting is not needed. If that changes, + * this would be the place to search and re-sort the exception + * table. + */ + if (mod->num_exentries > 1) { + printk(KERN_ERR "test_nx: too many exception table entries!\n"); + printk(KERN_ERR "test_nx: test results are not reliable.\n"); + return; + } + extable = (struct exception_table_entry *)mod->extable; + extable[0].insn = (unsigned long)new; +} + + +/* + * exception tables get their symbols translated so we need + * to use a fake function to put in there, which we can then + * replace at runtime. + */ +void foo_label(void); + +/* + * returns 0 for not-executable, negative for executable + * + * Note: we cannot allow this function to be inlined, because + * that would give us more than 1 exception table entry. + * This in turn would break the assumptions above. + */ +static noinline int test_address(void *address) +{ + unsigned long result; + + /* Set up an exception table entry for our address */ + fudze_exception_table(&foo_label, address); + result = 1; + asm volatile( + "foo_label:\n" + "0: call *%[fake_code]\n" + "1:\n" + ".section .fixup,\"ax\"\n" + "2: mov %[zero], %[rslt]\n" + " ret\n" + ".previous\n" + ".section __ex_table,\"a\"\n" + " .align 8\n" + " .quad 0b\n" + " .quad 2b\n" + ".previous\n" + : [rslt] "=r" (result) + : [fake_code] "r" (address), [zero] "r" (0UL), "0" (result) + ); + /* change the exception table back for the next round */ + fudze_exception_table(address, &foo_label); + + if (result) + return -ENODEV; + return 0; +} + +static unsigned char test_data = 0xC3; /* 0xC3 is the opcode for "ret" */ + +static int test_NX(void) +{ + int ret = 0; + /* 0xC3 is the opcode for "ret" */ + char stackcode[] = {0xC3, 0x90, 0 }; + char *heap; + + test_data = 0xC3; + + printk(KERN_INFO "Testing NX protection\n"); + + /* Test 1: check if the stack is not executable */ + if (test_address(&stackcode)) { + printk(KERN_ERR "test_nx: stack was executable\n"); + ret = -ENODEV; + } + + + /* Test 2: Check if the heap is executable */ + heap = kmalloc(64, GFP_KERNEL); + if (!heap) + return -ENOMEM; + heap[0] = 0xC3; /* opcode for "ret" */ + + if (test_address(heap)) { + printk(KERN_ERR "test_nx: heap was executable\n"); + ret = -ENODEV; + } + kfree(heap); + + /* + * The following 2 tests currently fail, this needs to get fixed + * Until then, don't run them to avoid too many people getting scared + * by the error message + */ +#if 0 + +#ifdef CONFIG_DEBUG_RODATA + /* Test 3: Check if the .rodata section is executable */ + if (rodata_test_data != 0xC3) { + printk(KERN_ERR "test_nx: .rodata marker has invalid value\n"); + ret = -ENODEV; + } else if (test_address(&rodata_test_data)) { + printk(KERN_ERR "test_nx: .rodata section is executable\n"); + ret = -ENODEV; + } +#endif + + /* Test 4: Check if the .data section of a module is executable */ + if (test_address(&test_data)) { + printk(KERN_ERR "test_nx: .data section is executable\n"); + ret = -ENODEV; + } + +#endif + return 0; +} + +static void test_exit(void) +{ +} + +module_init(test_NX); +module_exit(test_exit); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Testcase for the NX infrastructure"); +MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>"); |