Commit edeed305 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar

x86: add testcases for RODATA and NX protections/attributes

Latest update; I now have 4 NX tests, but 2 fail so they're #if 0'd.
I also cleaned up the NX test code quite a bit, and got rid of the ugly
exception table sorting stuff.

From: Arjan van de Ven <arjan@linux.intel.com>

This patch adds testcases for the CONFIG_DEBUG_RODATA configuration option
as well as the NX CPU feature/mappings. Both testcases can move to tests/
once that patch gets merged into mainline.
(I'm half considering moving the rodata test into mm/init.c but I'll
wait with that until init.c is unified)

As part of this I had to fix a not-quite-right alignment in the vmlinux.lds.h
for the RODATA sections, which lead to 1 page less being marked read only.
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent adafdf6a
/*
* 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>");
/*
* test_rodata.c: functional test for mark_rodata_ro function
*
* (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 <asm/sections.h>
extern int rodata_test_data;
int rodata_test(void)
{
unsigned long result;
unsigned long start, end;
/* test 1: read the value */
/* If this test fails, some previous testrun has clobbered the state */
if (!rodata_test_data) {
printk(KERN_ERR "rodata_test: test 1 fails (start data)\n");
return -ENODEV;
}
/* test 2: write to the variable; this should fault */
/*
* If this test fails, we managed to overwrite the data
*
* This is written in assembly to be able to catch the
* exception that is supposed to happen in the correct
* case
*/
result = 1;
asm volatile(
"0: mov %[zero],(%[rodata_test])\n"
" mov %[zero], %[rslt]\n"
"1:\n"
".section .fixup,\"ax\"\n"
"2: jmp 1b\n"
".previous\n"
".section __ex_table,\"a\"\n"
" .align 16\n"
#ifdef CONFIG_X86_32
" .long 0b,2b\n"
#else
" .quad 0b,2b\n"
#endif
".previous"
: [rslt] "=r" (result)
: [rodata_test] "r" (&rodata_test_data), [zero] "r" (0UL)
);
if (!result) {
printk(KERN_ERR "rodata_test: test data was not read only\n");
return -ENODEV;
}
/* test 3: check the value hasn't changed */
/* If this test fails, we managed to overwrite the data */
if (!rodata_test_data) {
printk(KERN_ERR "rodata_test: Test 3 failes (end data)\n");
return -ENODEV;
}
/* test 4: check if the rodata section is 4Kb aligned */
start = (unsigned long)__start_rodata;
end = (unsigned long)__end_rodata;
if (start & (PAGE_SIZE - 1)) {
printk(KERN_ERR "rodata_test: .rodata is not 4k aligned\n");
return -ENODEV;
}
if (end & (PAGE_SIZE - 1)) {
printk(KERN_ERR "rodata_test: .rodata end is not 4k aligned\n");
return -ENODEV;
}
return 0;
}
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
...@@ -736,6 +736,8 @@ static int noinline do_test_wp_bit(void) ...@@ -736,6 +736,8 @@ static int noinline do_test_wp_bit(void)
} }
#ifdef CONFIG_DEBUG_RODATA #ifdef CONFIG_DEBUG_RODATA
const int rodata_test_data = 0xC3;
EXPORT_SYMBOL_GPL(rodata_test_data);
void mark_rodata_ro(void) void mark_rodata_ro(void)
{ {
...@@ -765,6 +767,7 @@ void mark_rodata_ro(void) ...@@ -765,6 +767,7 @@ void mark_rodata_ro(void)
set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT); set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
printk("Write protecting the kernel read-only data: %luk\n", printk("Write protecting the kernel read-only data: %luk\n",
size >> 10); size >> 10);
rodata_test();
#ifdef CONFIG_CPA_DEBUG #ifdef CONFIG_CPA_DEBUG
printk("Testing CPA: undo %lx-%lx\n", start, start + size); printk("Testing CPA: undo %lx-%lx\n", start, start + size);
......
...@@ -573,6 +573,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end) ...@@ -573,6 +573,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
set_memory_rw(begin, (end - begin)/PAGE_SIZE); set_memory_rw(begin, (end - begin)/PAGE_SIZE);
set_memory_np(begin, (end - begin)/PAGE_SIZE); set_memory_np(begin, (end - begin)/PAGE_SIZE);
set_memory_nx(begin, (end - begin)/PAGE_SIZE); set_memory_nx(begin, (end - begin)/PAGE_SIZE);
rodata_test();
} }
#endif #endif
} }
...@@ -585,6 +586,8 @@ void free_initmem(void) ...@@ -585,6 +586,8 @@ void free_initmem(void)
} }
#ifdef CONFIG_DEBUG_RODATA #ifdef CONFIG_DEBUG_RODATA
const int rodata_test_data = 0xC3;
EXPORT_SYMBOL_GPL(rodata_test_data);
void mark_rodata_ro(void) void mark_rodata_ro(void)
{ {
......
...@@ -184,6 +184,7 @@ ...@@ -184,6 +184,7 @@
VMLINUX_SYMBOL(__start___param) = .; \ VMLINUX_SYMBOL(__start___param) = .; \
*(__param) \ *(__param) \
VMLINUX_SYMBOL(__stop___param) = .; \ VMLINUX_SYMBOL(__stop___param) = .; \
. = ALIGN((align)); \
VMLINUX_SYMBOL(__end_rodata) = .; \ VMLINUX_SYMBOL(__end_rodata) = .; \
} \ } \
. = ALIGN((align)); . = ALIGN((align));
......
...@@ -47,5 +47,12 @@ void clflush_cache_range(void *addr, int size); ...@@ -47,5 +47,12 @@ void clflush_cache_range(void *addr, int size);
#ifdef CONFIG_DEBUG_RODATA #ifdef CONFIG_DEBUG_RODATA
void mark_rodata_ro(void); void mark_rodata_ro(void);
#endif #endif
#ifdef CONFIG_DEBUG_RODATA_TEST
void rodata_test(void);
#else
static inline void rodata_test(void)
{
}
#endif
#endif #endif
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment