Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 927 insertions, 0 deletions

diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c
new file mode 100644
index 000000000..3a29346e1
--- /dev/null
+++ b/tools/testing/selftests/x86/ldt_gdt.c
@@ -0,0 +1,927 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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>
+#include <sys/mman.h>
+#include <asm/prctl.h>
+#include <sys/prctl.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)
+
+#ifdef __x86_64__
+# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
+#else
+# define INT80_CLOBBERS
+#endif
+
+static int nerrs;
+
+/* Points to an array of 1024 ints, each holding its own index. */
+static const unsigned int *counter_page;
+static struct user_desc *low_user_desc;
+static struct user_desc *low_user_desc_clear;  /* Use to delete GDT entry */
+static int gdt_entry_num;
+
+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;
+	}
+
+	/* The SDM says "bits 19:16 are undefined".  Thanks. */
+	ar &= ~0xF0000;
+
+	/*
+	 * NB: Different Linux versions do different things with the
+	 * accessed bit in set_thread_area().
+	 */
+	if (ar != expected_ar && ar != (expected_ar | AR_ACCESSED)) {
+		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 *d, uint32_t ar,
+			       bool oldmode, bool ldt)
+{
+	struct user_desc desc = *d;
+	int ret;
+
+	if (!ldt) {
+#ifndef __i386__
+		/* No point testing set_thread_area in a 64-bit build */
+		return false;
+#endif
+		if (!gdt_entry_num)
+			return false;
+		desc.entry_number = gdt_entry_num;
+
+		ret = syscall(SYS_set_thread_area, &desc);
+	} else {
+		ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
+			      &desc, sizeof(desc));
+
+		if (ret < -1)
+			errno = -ret;
+
+		if (ret != 0 && errno == ENOSYS) {
+			printf("[OK]\tmodify_ldt returned -ENOSYS\n");
+			return false;
+		}
+	}
+
+	if (ret == 0) {
+		uint32_t limit = desc.limit;
+		if (desc.limit_in_pages)
+			limit = (limit << 12) + 4095;
+		check_valid_segment(desc.entry_number, ldt, ar, limit, true);
+		return true;
+	} else {
+		if (desc.seg_32bit) {
+			printf("[FAIL]\tUnexpected %s failure %d\n",
+			       ldt ? "modify_ldt" : "set_thread_area",
+			       errno);
+			nerrs++;
+			return false;
+		} else {
+			printf("[OK]\t%s rejected 16 bit segment\n",
+			       ldt ? "modify_ldt" : "set_thread_area");
+			return false;
+		}
+	}
+}
+
+static bool install_valid(const struct user_desc *desc, uint32_t ar)
+{
+	bool ret = install_valid_mode(desc, ar, false, true);
+
+	if (desc->contents <= 1 && desc->seg_32bit &&
+	    !desc->seg_not_present) {
+		/* Should work in the GDT, too. */
+		install_valid_mode(desc, ar, false, false);
+	}
+
+	return ret;
+}
+
+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.seg_32bit = 1;
+	desc.read_exec_only = 0;
+	desc.limit = 0xfffff;
+
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB);
+
+	desc.limit_in_pages = 1;
+
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB | AR_G);
+	desc.read_exec_only = 1;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S | AR_P | AR_DB | AR_G);
+	desc.contents = 1;
+	desc.read_exec_only = 0;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA_EXPDOWN | AR_S | AR_P | AR_DB | AR_G);
+	desc.read_exec_only = 1;
+	install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA_EXPDOWN | AR_S | AR_P | AR_DB | AR_G);
+
+	desc.limit = 0;
+	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;
+	}
+}
+
+#ifdef __i386__
+
+#ifndef SA_RESTORE
+#define SA_RESTORER 0x04000000
+#endif
+
+/*
+ * The UAPI header calls this 'struct sigaction', which conflicts with
+ * glibc.  Sigh.
+ */
+struct fake_ksigaction {
+	void *handler;  /* the real type is nasty */
+	unsigned long sa_flags;
+	void (*sa_restorer)(void);
+	unsigned char sigset[8];
+};
+
+static void fix_sa_restorer(int sig)
+{
+	struct fake_ksigaction ksa;
+
+	if (syscall(SYS_rt_sigaction, sig, NULL, &ksa, 8) == 0) {
+		/*
+		 * glibc has a nasty bug: it sometimes writes garbage to
+		 * sa_restorer.  This interacts quite badly with anything
+		 * that fiddles with SS because it can trigger legacy
+		 * stack switching.  Patch it up.  See:
+		 *
+		 * https://sourceware.org/bugzilla/show_bug.cgi?id=21269
+		 */
+		if (!(ksa.sa_flags & SA_RESTORER) && ksa.sa_restorer) {
+			ksa.sa_restorer = NULL;
+			if (syscall(SYS_rt_sigaction, sig, &ksa, NULL,
+				    sizeof(ksa.sigset)) != 0)
+				err(1, "rt_sigaction");
+		}
+	}
+}
+#else
+static void fix_sa_restorer(int sig)
+{
+	/* 64-bit glibc works fine. */
+}
+#endif
+
+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");
+
+	fix_sa_restorer(sig);
+}
+
+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)
+{
+	/*
+	 * Older kernel versions did inherit the LDT on exec() which is
+	 * wrong because exec() starts from a clean state.
+	 */
+	check_invalid_segment(0, 1);
+
+	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");
+		}
+	}
+}
+
+static void setup_counter_page(void)
+{
+	unsigned int *page = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
+			 MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0);
+	if (page == MAP_FAILED)
+		err(1, "mmap");
+
+	for (int i = 0; i < 1024; i++)
+		page[i] = i;
+	counter_page = page;
+}
+
+static int invoke_set_thread_area(void)
+{
+	int ret;
+	asm volatile ("int $0x80"
+		      : "=a" (ret), "+m" (low_user_desc) :
+			"a" (243), "b" (low_user_desc)
+		      : INT80_CLOBBERS);
+	return ret;
+}
+
+static void setup_low_user_desc(void)
+{
+	low_user_desc = mmap(NULL, 2 * sizeof(struct user_desc),
+			     PROT_READ | PROT_WRITE,
+			     MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0);
+	if (low_user_desc == MAP_FAILED)
+		err(1, "mmap");
+
+	low_user_desc->entry_number	= -1;
+	low_user_desc->base_addr	= (unsigned long)&counter_page[1];
+	low_user_desc->limit		= 0xfffff;
+	low_user_desc->seg_32bit	= 1;
+	low_user_desc->contents		= 0; /* Data, grow-up*/
+	low_user_desc->read_exec_only	= 0;
+	low_user_desc->limit_in_pages	= 1;
+	low_user_desc->seg_not_present	= 0;
+	low_user_desc->useable		= 0;
+
+	if (invoke_set_thread_area() == 0) {
+		gdt_entry_num = low_user_desc->entry_number;
+		printf("[NOTE]\tset_thread_area is available; will use GDT index %d\n", gdt_entry_num);
+	} else {
+		printf("[NOTE]\tset_thread_area is unavailable\n");
+	}
+
+	low_user_desc_clear = low_user_desc + 1;
+	low_user_desc_clear->entry_number = gdt_entry_num;
+	low_user_desc_clear->read_exec_only = 1;
+	low_user_desc_clear->seg_not_present = 1;
+}
+
+static void test_gdt_invalidation(void)
+{
+	if (!gdt_entry_num)
+		return;	/* 64-bit only system -- we can't use set_thread_area */
+
+	unsigned short prev_sel;
+	unsigned short sel;
+	unsigned int eax;
+	const char *result;
+#ifdef __x86_64__
+	unsigned long saved_base;
+	unsigned long new_base;
+#endif
+
+	/* Test DS */
+	invoke_set_thread_area();
+	eax = 243;
+	sel = (gdt_entry_num << 3) | 3;
+	asm volatile ("movw %%ds, %[prev_sel]\n\t"
+		      "movw %[sel], %%ds\n\t"
+#ifdef __i386__
+		      "pushl %%ebx\n\t"
+#endif
+		      "movl %[arg1], %%ebx\n\t"
+		      "int $0x80\n\t"	/* Should invalidate ds */
+#ifdef __i386__
+		      "popl %%ebx\n\t"
+#endif
+		      "movw %%ds, %[sel]\n\t"
+		      "movw %[prev_sel], %%ds"
+		      : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
+			"+a" (eax)
+		      : "m" (low_user_desc_clear),
+			[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
+		      : INT80_CLOBBERS);
+
+	if (sel != 0) {
+		result = "FAIL";
+		nerrs++;
+	} else {
+		result = "OK";
+	}
+	printf("[%s]\tInvalidate DS with set_thread_area: new DS = 0x%hx\n",
+	       result, sel);
+
+	/* Test ES */
+	invoke_set_thread_area();
+	eax = 243;
+	sel = (gdt_entry_num << 3) | 3;
+	asm volatile ("movw %%es, %[prev_sel]\n\t"
+		      "movw %[sel], %%es\n\t"
+#ifdef __i386__
+		      "pushl %%ebx\n\t"
+#endif
+		      "movl %[arg1], %%ebx\n\t"
+		      "int $0x80\n\t"	/* Should invalidate es */
+#ifdef __i386__
+		      "popl %%ebx\n\t"
+#endif
+		      "movw %%es, %[sel]\n\t"
+		      "movw %[prev_sel], %%es"
+		      : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
+			"+a" (eax)
+		      : "m" (low_user_desc_clear),
+			[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
+		      : INT80_CLOBBERS);
+
+	if (sel != 0) {
+		result = "FAIL";
+		nerrs++;
+	} else {
+		result = "OK";
+	}
+	printf("[%s]\tInvalidate ES with set_thread_area: new ES = 0x%hx\n",
+	       result, sel);
+
+	/* Test FS */
+	invoke_set_thread_area();
+	eax = 243;
+	sel = (gdt_entry_num << 3) | 3;
+#ifdef __x86_64__
+	syscall(SYS_arch_prctl, ARCH_GET_FS, &saved_base);
+#endif
+	asm volatile ("movw %%fs, %[prev_sel]\n\t"
+		      "movw %[sel], %%fs\n\t"
+#ifdef __i386__
+		      "pushl %%ebx\n\t"
+#endif
+		      "movl %[arg1], %%ebx\n\t"
+		      "int $0x80\n\t"	/* Should invalidate fs */
+#ifdef __i386__
+		      "popl %%ebx\n\t"
+#endif
+		      "movw %%fs, %[sel]\n\t"
+		      : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
+			"+a" (eax)
+		      : "m" (low_user_desc_clear),
+			[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
+		      : INT80_CLOBBERS);
+
+#ifdef __x86_64__
+	syscall(SYS_arch_prctl, ARCH_GET_FS, &new_base);
+#endif
+
+	/* Restore FS/BASE for glibc */
+	asm volatile ("movw %[prev_sel], %%fs" : : [prev_sel] "rm" (prev_sel));
+#ifdef __x86_64__
+	if (saved_base)
+		syscall(SYS_arch_prctl, ARCH_SET_FS, saved_base);
+#endif
+
+	if (sel != 0) {
+		result = "FAIL";
+		nerrs++;
+	} else {
+		result = "OK";
+	}
+	printf("[%s]\tInvalidate FS with set_thread_area: new FS = 0x%hx\n",
+	       result, sel);
+
+#ifdef __x86_64__
+	if (sel == 0 && new_base != 0) {
+		nerrs++;
+		printf("[FAIL]\tNew FSBASE was 0x%lx\n", new_base);
+	} else {
+		printf("[OK]\tNew FSBASE was zero\n");
+	}
+#endif
+
+	/* Test GS */
+	invoke_set_thread_area();
+	eax = 243;
+	sel = (gdt_entry_num << 3) | 3;
+#ifdef __x86_64__
+	syscall(SYS_arch_prctl, ARCH_GET_GS, &saved_base);
+#endif
+	asm volatile ("movw %%gs, %[prev_sel]\n\t"
+		      "movw %[sel], %%gs\n\t"
+#ifdef __i386__
+		      "pushl %%ebx\n\t"
+#endif
+		      "movl %[arg1], %%ebx\n\t"
+		      "int $0x80\n\t"	/* Should invalidate gs */
+#ifdef __i386__
+		      "popl %%ebx\n\t"
+#endif
+		      "movw %%gs, %[sel]\n\t"
+		      : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
+			"+a" (eax)
+		      : "m" (low_user_desc_clear),
+			[arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
+		      : INT80_CLOBBERS);
+
+#ifdef __x86_64__
+	syscall(SYS_arch_prctl, ARCH_GET_GS, &new_base);
+#endif
+
+	/* Restore GS/BASE for glibc */
+	asm volatile ("movw %[prev_sel], %%gs" : : [prev_sel] "rm" (prev_sel));
+#ifdef __x86_64__
+	if (saved_base)
+		syscall(SYS_arch_prctl, ARCH_SET_GS, saved_base);
+#endif
+
+	if (sel != 0) {
+		result = "FAIL";
+		nerrs++;
+	} else {
+		result = "OK";
+	}
+	printf("[%s]\tInvalidate GS with set_thread_area: new GS = 0x%hx\n",
+	       result, sel);
+
+#ifdef __x86_64__
+	if (sel == 0 && new_base != 0) {
+		nerrs++;
+		printf("[FAIL]\tNew GSBASE was 0x%lx\n", new_base);
+	} else {
+		printf("[OK]\tNew GSBASE was zero\n");
+	}
+#endif
+}
+
+int main(int argc, char **argv)
+{
+	if (argc == 1 && !strcmp(argv[0], "ldt_gdt_test_exec"))
+		return finish_exec_test();
+
+	setup_counter_page();
+	setup_low_user_desc();
+
+	do_simple_tests();
+
+	do_multicpu_tests();
+
+	do_exec_test();
+
+	test_gdt_invalidation();
+
+	return nerrs ? 1 : 0;
+}