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014dc90b66
linux_dsm_epyc7002/tools/testing/selftests/x86/ldt_gdt.c
Andy Lutomirski 014dc90b66 selftests/x86, x86/ldt: Add a selftest for modify_ldt() 
This tests general modify_ldt() behavior (only writes, so far) as
well as synchronous updates via IPI.  It fails on old kernels.

I called this ldt_gdt because I'll add set_thread_area() tests to
it at some point.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org <security@kernel.org>
Cc: xen-devel <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/dcfda65dad07ff5a3ea97a9172b5963bf8031b2e.1438291540.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31 10:24:37 +02:00

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/*
* ldt_gdt.c - Test cases for LDT and GDT access
* Copyright (c) 2015 Andrew Lutomirski
*/
#define _GNU_SOURCE
#include <err.h>
#include <stdio.h>
#include <stdint.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <asm/ldt.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdbool.h>
#include <pthread.h>
#include <sched.h>
#include <linux/futex.h>
#define AR_ACCESSED (1<<8)
#define AR_TYPE_RODATA (0 * (1<<9))
#define AR_TYPE_RWDATA (1 * (1<<9))
#define AR_TYPE_RODATA_EXPDOWN (2 * (1<<9))
#define AR_TYPE_RWDATA_EXPDOWN (3 * (1<<9))
#define AR_TYPE_XOCODE (4 * (1<<9))
#define AR_TYPE_XRCODE (5 * (1<<9))
#define AR_TYPE_XOCODE_CONF (6 * (1<<9))
#define AR_TYPE_XRCODE_CONF (7 * (1<<9))
#define AR_DPL3 (3 * (1<<13))
#define AR_S (1 << 12)
#define AR_P (1 << 15)
#define AR_AVL (1 << 20)
#define AR_L (1 << 21)
#define AR_DB (1 << 22)
#define AR_G (1 << 23)
static int nerrs;
static void check_invalid_segment(uint16_t index, int ldt)
{
uint32_t has_limit = 0, has_ar = 0, limit, ar;
uint32_t selector = (index << 3) | (ldt << 2) | 3;
asm ("lsl %[selector], %[limit]\n\t"
"jnz 1f\n\t"
"movl $1, %[has_limit]\n\t"
"1:"
: [limit] "=r" (limit), [has_limit] "+rm" (has_limit)
: [selector] "r" (selector));
asm ("larl %[selector], %[ar]\n\t"
"jnz 1f\n\t"
"movl $1, %[has_ar]\n\t"
"1:"
: [ar] "=r" (ar), [has_ar] "+rm" (has_ar)
: [selector] "r" (selector));
if (has_limit || has_ar) {
printf("[FAIL]\t%s entry %hu is valid but should be invalid\n",
(ldt ? "LDT" : "GDT"), index);
nerrs++;
} else {
printf("[OK]\t%s entry %hu is invalid\n",
(ldt ? "LDT" : "GDT"), index);
}
}
static void check_valid_segment(uint16_t index, int ldt,
uint32_t expected_ar, uint32_t expected_limit,
bool verbose)
{
uint32_t has_limit = 0, has_ar = 0, limit, ar;
uint32_t selector = (index << 3) | (ldt << 2) | 3;
asm ("lsl %[selector], %[limit]\n\t"
"jnz 1f\n\t"
"movl $1, %[has_limit]\n\t"
"1:"
: [limit] "=r" (limit), [has_limit] "+rm" (has_limit)
: [selector] "r" (selector));
asm ("larl %[selector], %[ar]\n\t"
"jnz 1f\n\t"
"movl $1, %[has_ar]\n\t"
"1:"
: [ar] "=r" (ar), [has_ar] "+rm" (has_ar)
: [selector] "r" (selector));
if (!has_limit || !has_ar) {
printf("[FAIL]\t%s entry %hu is invalid but should be valid\n",
(ldt ? "LDT" : "GDT"), index);
nerrs++;
return;
}
if (ar != expected_ar) {
printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n",
(ldt ? "LDT" : "GDT"), index, ar, expected_ar);
nerrs++;
} else if (limit != expected_limit) {
printf("[FAIL]\t%s entry %hu has limit 0x%08X but expected 0x%08X\n",
(ldt ? "LDT" : "GDT"), index, limit, expected_limit);
nerrs++;
} else if (verbose) {
printf("[OK]\t%s entry %hu has AR 0x%08X and limit 0x%08X\n",
(ldt ? "LDT" : "GDT"), index, ar, limit);
}
}
static bool install_valid_mode(const struct user_desc *desc, uint32_t ar,
bool oldmode)
{
int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
desc, sizeof(*desc));
if (ret < -1)
errno = -ret;
if (ret == 0) {
uint32_t limit = desc->limit;
if (desc->limit_in_pages)
limit = (limit << 12) + 4095;
check_valid_segment(desc->entry_number, 1, ar, limit, true);
return true;
} else if (errno == ENOSYS) {
printf("[OK]\tmodify_ldt returned -ENOSYS\n");
return false;
} else {
if (desc->seg_32bit) {
printf("[FAIL]\tUnexpected modify_ldt failure %d\n",
errno);
nerrs++;
return false;
} else {
printf("[OK]\tmodify_ldt rejected 16 bit segment\n");
return false;
}
}
}
static bool install_valid(const struct user_desc *desc, uint32_t ar)
{
return install_valid_mode(desc, ar, false);
}
static void install_invalid(const struct user_desc *desc, bool oldmode)
{
int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
desc, sizeof(*desc));
if (ret < -1)
errno = -ret;
if (ret == 0) {
check_invalid_segment(desc->entry_number, 1);
} else if (errno == ENOSYS) {
printf("[OK]\tmodify_ldt returned -ENOSYS\n");
} else {
if (desc->seg_32bit) {
printf("[FAIL]\tUnexpected modify_ldt failure %d\n",
errno);
nerrs++;
} else {
printf("[OK]\tmodify_ldt rejected 16 bit segment\n");
}
}
}
static int safe_modify_ldt(int func, struct user_desc *ptr,
unsigned long bytecount)
{
int ret = syscall(SYS_modify_ldt, 0x11, ptr, bytecount);
if (ret < -1)
errno = -ret;
return ret;
}
static void fail_install(struct user_desc *desc)
{
if (safe_modify_ldt(0x11, desc, sizeof(*desc)) == 0) {
printf("[FAIL]\tmodify_ldt accepted a bad descriptor\n");
nerrs++;
} else if (errno == ENOSYS) {
printf("[OK]\tmodify_ldt returned -ENOSYS\n");
} else {
printf("[OK]\tmodify_ldt failure %d\n", errno);
}
}
static void do_simple_tests(void)
{
struct user_desc desc = {
.entry_number = 0,
.base_addr = 0,
.limit = 10,
.seg_32bit = 1,
.contents = 2, /* Code, not conforming */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 0,
.useable = 0
};
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB);
desc.limit_in_pages = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_P | AR_DB | AR_G);
check_invalid_segment(1, 1);
desc.entry_number = 2;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_P | AR_DB | AR_G);
check_invalid_segment(1, 1);
desc.base_addr = 0xf0000000;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_P | AR_DB | AR_G);
desc.useable = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_P | AR_DB | AR_G | AR_AVL);
desc.seg_not_present = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_DB | AR_G | AR_AVL);
desc.seg_32bit = 0;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_G | AR_AVL);
desc.seg_32bit = 1;
desc.contents = 0;
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA |
AR_S | AR_DB | AR_G | AR_AVL);
desc.read_exec_only = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA |
AR_S | AR_DB | AR_G | AR_AVL);
desc.contents = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA_EXPDOWN |
AR_S | AR_DB | AR_G | AR_AVL);
desc.read_exec_only = 0;
desc.limit_in_pages = 0;
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA_EXPDOWN |
AR_S | AR_DB | AR_AVL);
desc.contents = 3;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE_CONF |
AR_S | AR_DB | AR_AVL);
desc.read_exec_only = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE_CONF |
AR_S | AR_DB | AR_AVL);
desc.read_exec_only = 0;
desc.contents = 2;
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
AR_S | AR_DB | AR_AVL);
desc.read_exec_only = 1;
#ifdef __x86_64__
desc.lm = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE |
AR_S | AR_DB | AR_AVL);
desc.lm = 0;
#endif
bool entry1_okay = install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE |
AR_S | AR_DB | AR_AVL);
if (entry1_okay) {
printf("[RUN]\tTest fork\n");
pid_t child = fork();
if (child == 0) {
nerrs = 0;
check_valid_segment(desc.entry_number, 1,
AR_DPL3 | AR_TYPE_XOCODE |
AR_S | AR_DB | AR_AVL, desc.limit,
true);
check_invalid_segment(1, 1);
exit(nerrs ? 1 : 0);
} else {
int status;
if (waitpid(child, &status, 0) != child ||
!WIFEXITED(status)) {
printf("[FAIL]\tChild died\n");
nerrs++;
} else if (WEXITSTATUS(status) != 0) {
printf("[FAIL]\tChild failed\n");
nerrs++;
} else {
printf("[OK]\tChild succeeded\n");
}
}
printf("[RUN]\tTest size\n");
int i;
for (i = 0; i < 8192; i++) {
desc.entry_number = i;
desc.limit = i;
if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) {
printf("[FAIL]\tFailed to install entry %d\n", i);
nerrs++;
break;
}
}
for (int j = 0; j < i; j++) {
check_valid_segment(j, 1, AR_DPL3 | AR_TYPE_XOCODE |
AR_S | AR_DB | AR_AVL, j, false);
}
printf("[DONE]\tSize test\n");
} else {
printf("[SKIP]\tSkipping fork and size tests because we have no LDT\n");
}
/* Test entry_number too high. */
desc.entry_number = 8192;
fail_install(&desc);
/* Test deletion and actions mistakeable for deletion. */
memset(&desc, 0, sizeof(desc));
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P);
desc.seg_not_present = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S);
desc.seg_not_present = 0;
desc.read_exec_only = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S | AR_P);
desc.read_exec_only = 0;
desc.seg_not_present = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S);
desc.read_exec_only = 1;
desc.limit = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S);
desc.limit = 0;
desc.base_addr = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S);
desc.base_addr = 0;
install_invalid(&desc, false);
desc.seg_not_present = 0;
desc.read_exec_only = 0;
desc.seg_32bit = 1;
install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB);
install_invalid(&desc, true);
}
/*
* 0: thread is idle
* 1: thread armed
* 2: thread should clear LDT entry 0
* 3: thread should exit
*/
static volatile unsigned int ftx;
static void *threadproc(void *ctx)
{
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
CPU_SET(1, &cpuset);
if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
err(1, "sched_setaffinity to CPU 1"); /* should never fail */
while (1) {
syscall(SYS_futex, &ftx, FUTEX_WAIT, 0, NULL, NULL, 0);
while (ftx != 2) {
if (ftx >= 3)
return NULL;
}
/* clear LDT entry 0 */
const struct user_desc desc = {};
if (syscall(SYS_modify_ldt, 1, &desc, sizeof(desc)) != 0)
err(1, "modify_ldt");
/* If ftx == 2, set it to zero. If ftx == 100, quit. */
unsigned int x = -2;
asm volatile ("lock xaddl %[x], %[ftx]" :
[x] "+r" (x), [ftx] "+m" (ftx));
if (x != 2)
return NULL;
}
}
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static jmp_buf jmpbuf;
static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
{
siglongjmp(jmpbuf, 1);
}
static void do_multicpu_tests(void)
{
cpu_set_t cpuset;
pthread_t thread;
int failures = 0, iters = 5, i;
unsigned short orig_ss;
CPU_ZERO(&cpuset);
CPU_SET(1, &cpuset);
if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
printf("[SKIP]\tCannot set affinity to CPU 1\n");
return;
}
CPU_ZERO(&cpuset);
CPU_SET(0, &cpuset);
if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
printf("[SKIP]\tCannot set affinity to CPU 0\n");
return;
}
sethandler(SIGSEGV, sigsegv, 0);
#ifdef __i386__
/* True 32-bit kernels send SIGILL instead of SIGSEGV on IRET faults. */
sethandler(SIGILL, sigsegv, 0);
#endif
printf("[RUN]\tCross-CPU LDT invalidation\n");
if (pthread_create(&thread, 0, threadproc, 0) != 0)
err(1, "pthread_create");
asm volatile ("mov %%ss, %0" : "=rm" (orig_ss));
for (i = 0; i < 5; i++) {
if (sigsetjmp(jmpbuf, 1) != 0)
continue;
/* Make sure the thread is ready after the last test. */
while (ftx != 0)
;
struct user_desc desc = {
.entry_number = 0,
.base_addr = 0,
.limit = 0xfffff,
.seg_32bit = 1,
.contents = 0, /* Data */
.read_exec_only = 0,
.limit_in_pages = 1,
.seg_not_present = 0,
.useable = 0
};
if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) {
if (errno != ENOSYS)
err(1, "modify_ldt");
printf("[SKIP]\tmodify_ldt unavailable\n");
break;
}
/* Arm the thread. */
ftx = 1;
syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);
asm volatile ("mov %0, %%ss" : : "r" (0x7));
/* Go! */
ftx = 2;
while (ftx != 0)
;
/*
* On success, modify_ldt will segfault us synchronously,
* and we'll escape via siglongjmp.
*/
failures++;
asm volatile ("mov %0, %%ss" : : "rm" (orig_ss));
};
ftx = 100; /* Kill the thread. */
syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);
if (pthread_join(thread, NULL) != 0)
err(1, "pthread_join");
if (failures) {
printf("[FAIL]\t%d of %d iterations failed\n", failures, iters);
nerrs++;
} else {
printf("[OK]\tAll %d iterations succeeded\n", iters);
}
}
static int finish_exec_test(void)
{
/*
* In a sensible world, this would be check_invalid_segment(0, 1);
* For better or for worse, though, the LDT is inherited across exec.
* We can probably change this safely, but for now we test it.
*/
check_valid_segment(0, 1,
AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB,
42, true);
return nerrs ? 1 : 0;
}
static void do_exec_test(void)
{
printf("[RUN]\tTest exec\n");
struct user_desc desc = {
.entry_number = 0,
.base_addr = 0,
.limit = 42,
.seg_32bit = 1,
.contents = 2, /* Code, not conforming */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 0,
.useable = 0
};
install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB);
pid_t child = fork();
if (child == 0) {
execl("/proc/self/exe", "ldt_gdt_test_exec", NULL);
printf("[FAIL]\tCould not exec self\n");
exit(1); /* exec failed */
} else {
int status;
if (waitpid(child, &status, 0) != child ||
!WIFEXITED(status)) {
printf("[FAIL]\tChild died\n");
nerrs++;
} else if (WEXITSTATUS(status) != 0) {
printf("[FAIL]\tChild failed\n");
nerrs++;
} else {
printf("[OK]\tChild succeeded\n");
}
}
}
int main(int argc, char **argv)
{
if (argc == 1 && !strcmp(argv[0], "ldt_gdt_test_exec"))
return finish_exec_test();
do_simple_tests();
do_multicpu_tests();
do_exec_test();
return nerrs ? 1 : 0;
}
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