arm64: bti: Import basic BTI tests

Import basic development tests for Branch Target Identification
(BTI, part of ARMv8.5-A).

Signed-off-by: Dave Martin <Dave.Martin@arm.com>

.gitignore

+*.[od]
+*~
+btitest
+nobtitest

COPYING

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+Public License instead of this License.

Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (C) 2019  Arm Limited
+# Original author: Dave Martin <Dave.Martin@arm.com>
+
+CFLAGS = -O2 -g
+CPPFLAGS =
+CROSS_COMPILE = aarch64-linux-gnu-
+CC = $(CROSS_COMPILE)gcc
+
+TESTS = btitest nobtitest
+
+CFLAGS_NOBTI = -DBTI=0
+CFLAGS_BTI = -mbranch-protection=standard -DBTI=1
+
+CFLAGS_COMMON = -ffreestanding -Wall -Wextra -MMD $(CFLAGS)
+
+BTI_CC_COMMAND = \
+	$(CC) $(CPPFLAGS) $(CFLAGS_BTI) $(CFLAGS_COMMON) -c -o $@ $<
+NOBTI_CC_COMMAND = \
+	$(CC) $(CPPFLAGS) $(CFLAGS_NOBTI) $(CFLAGS_COMMON) -c -o $@ $<
+
+all: FORCE $(TESTS) ;
+
+FORCE: ;
+
+-include *.d
+
+%-bti.o: %.c
+	$(BTI_CC_COMMAND)
+
+%-bti.o: %.S
+	$(BTI_CC_COMMAND)
+
+%-nobti.o: %.c
+	$(NOBTI_CC_COMMAND)
+
+%-nobti.o: %.S
+	$(NOBTI_CC_COMMAND)
+
+BTI_OBJS =					\
+	btitest-bti.o				\
+	signal-bti.o				\
+	start-bti.o				\
+	syscall-bti.o				\
+	system-bti.o				\
+	teststubs-bti.o				\
+	trampoline-bti.o
+btitest: $(BTI_OBJS)
+CFLAGS-btitest = $(CFLAGS_BTI)
+
+NOBTI_OBJS =					\
+	btitest-nobti.o				\
+	signal-nobti.o				\
+	start-nobti.o				\
+	syscall-nobti.o				\
+	system-nobti.o				\
+	teststubs-nobti.o			\
+	trampoline-nobti.o
+nobtitest: $(NOBTI_OBJS)
+CFLAGS-nobtitest = $(CFLAGS_NOBTI)
+
+$(TESTS):
+	$(CC) $(CPPFLAGS) $(CFLAGS-$@) $(CFLAGS_COMMON) -nostdlib -o $@ $^
+
+clean: FORCE
+	$(RM) $(TESTS) *.[od]

README

+Building
+========
+
+linux-tests$ make
+
+If your toolchain's headers are not sufficiently up to date to contain
+the BTI and Pointer authentication definitions, you may need to install
+the headers from a new enough kernel version, e.g.:
+
+linux$ make ARCH=arm64 headers_install
+linux-tests$ make CPPFLAGS=-I<path to linux directory>/usr/include
+
+
+Copy all the resulting binaries to your target filesystem:
+
+btitest:
+   checks that BTI-enabled binaries see BTI working as expected.
+
+nobtitest:
+   checks that non-BTI-enabled binaries do _not_ see BTI working.
+

assembler.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#ifndef ASSEMBLER_H
+#define ASSEMBLER_H
+
+#define NT_GNU_PROPERTY_TYPE_0	5
+#define GNU_PROPERTY_AARCH64_FEATURE_1_AND	0xc0000000
+
+/* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */
+#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI	(1U << 0)
+#define GNU_PROPERTY_AARCH64_FEATURE_1_PAC	(1U << 1)
+
+
+.macro startfn name:req
+	.globl \name
+\name:
+	.macro endfn
+		.size \name, . - \name
+		.type \name, @function
+		.purgem endfn
+	.endm
+.endm
+
+.macro emit_aarch64_feature_1_and
+	.pushsection .note.gnu.property, "a"
+	.align	3
+	.long	2f - 1f
+	.long	6f - 3f
+	.long	NT_GNU_PROPERTY_TYPE_0
+1:	.string	"GNU"
+2:
+	.align	3
+3:	.long	GNU_PROPERTY_AARCH64_FEATURE_1_AND
+	.long	5f - 4f
+4:
+#if BTI
+	.long	GNU_PROPERTY_AARCH64_FEATURE_1_PAC | \
+		GNU_PROPERTY_AARCH64_FEATURE_1_BTI
+#else
+	.long	0
+#endif
+5:
+	.align	3
+6:
+	.popsection
+.endm
+
+.macro paciasp
+	hint	0x19
+.endm
+
+.macro autiasp
+	hint	0x1d
+.endm
+
+.macro __bti_
+	hint	0x20
+.endm
+
+.macro __bti_c
+	hint	0x22
+.endm
+
+.macro __bti_j
+	hint	0x24
+.endm
+
+.macro __bti_jc
+	hint	0x26
+.endm
+
+.macro bti what=
+	__bti_\what
+.endm
+
+#endif /* ! ASSEMBLER_H */

btitest.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "system.h"
+
+#include <linux/errno.h>
+#include <linux/auxvec.h>
+#include <linux/signal.h>
+#include <asm/hwcap.h>
+#include <asm/sigcontext.h>
+#include <asm/ucontext.h>
+
+typedef struct ucontext ucontext_t;
+
+#include "btitest.h"
+#include "compiler.h"
+#include "signal.h"
+
+static void fdputs(int fd, const char *str)
+{
+	size_t len = 0;
+	const char *p = str;
+
+	while (*p++)
+		++len;
+
+	write(fd, str, len);
+}
+
+static void putstr(const char *str)
+{
+	fdputs(1, str);
+}
+
+#define puttestname(test_name, trampoline_name) do {	\
+	putstr(test_name);				\
+	putstr("/");					\
+	putstr(trampoline_name);			\
+} while (0)
+
+static const char *volatile current_test_name;
+static const char *volatile current_trampoline_name;
+static volatile int sigill_expected, sigill_received;
+
+static void handler(int n, siginfo_t *si __always_unused,
+		    void *uc_ __always_unused)
+{
+	ucontext_t *uc = uc_;
+
+	putstr("\t[SIGILL in ");
+	puttestname(current_test_name, current_trampoline_name);
+	putstr(", BTYPE=");
+	write(1, &"00011011"[((uc->uc_mcontext.pstate & PSR_BTYPE_MASK)
+			      >> PSR_BTYPE_SHIFT) * 2], 2);
+	if (!sigill_expected) {
+		putstr("]\n");
+		puttestname(current_test_name, current_trampoline_name);
+		putstr(":\tFAIL (unexpected SIGILL)\n");
+		exit(128 + n);
+	}
+
+	putstr(" (expected)]\n");
+	sigill_received = 1;
+	/* zap BTYPE so that resuming the faulting code will work */
+	uc->uc_mcontext.pstate &= ~PSR_BTYPE_MASK;
+}
+
+static int skip_all = 0;
+
+static void __do_test(void (*trampoline)(void (*)(void)),
+		      void (*fn)(void),
+		      const char *trampoline_name,
+		      const char *name,
+		      int expect_sigill)
+{
+	if (skip_all) {
+		puttestname(name, trampoline_name);
+		putstr(":\tSKIPPED\n");
+
+		return;
+	}
+
+	/* Branch Target exceptions should only happen in BTI binaries: */
+	if (!BTI)
+		expect_sigill = 0;
+
+	sigill_expected = expect_sigill;
+	sigill_received = 0;
+	current_test_name = name;
+	current_trampoline_name = trampoline_name;
+
+	trampoline(fn);
+
+	puttestname(name, trampoline_name);
+	if (expect_sigill && !sigill_received) {
+		putstr(":\tFAIL (no SIGILL)\n");
+		exit(1);
+	} else {
+		putstr(":\tPASS\n");
+	}
+}
+
+#define do_test(expect_sigill_br_x0,					\
+		expect_sigill_br_x16,					\
+		expect_sigill_blr,					\
+		name)							\
+do {									\
+	__do_test(call_using_br_x0, name, "call_using_br_x0", #name,	\
+		  expect_sigill_br_x0);					\
+	__do_test(call_using_br_x16, name, "call_using_br_x16", #name,	\
+		  expect_sigill_br_x16);				\
+	__do_test(call_using_blr, name, "call_using_blr", #name,	\
+		  expect_sigill_blr);					\
+} while (0)
+
+void start(int *argcp)
+{
+	struct sigaction sa;
+	void *const *p;
+	const struct auxv_entry {
+		unsigned long type;
+		unsigned long val;
+	} *auxv;
+	unsigned long hwcap = 0, hwcap2 = 0;
+
+	/* Gross hack for finding AT_HWCAP2 from the initial process stack: */
+	p = (void *const *)argcp + 1 + *argcp + 1; /* start of environment */
+	while (*p++) ; /* step over environment */
+	for (auxv = (const struct auxv_entry *)p; auxv->type != AT_NULL;
+			++auxv)
+		switch (auxv->type) {
+		case AT_HWCAP:	hwcap = auxv->val; break;
+		case AT_HWCAP2:	hwcap2 = auxv->val; break;
+		}
+
+	if (hwcap & HWCAP_PACA)
+		putstr("HWCAP_PACA present\n");
+	else
+		putstr("HWCAP_PACA not present\n");
+
+	if (hwcap2 & HWCAP2_BTI) {
+		putstr("HWCAP2_BTI present\n");
+		if (!(hwcap & HWCAP_PACA))
+			putstr("Bad hardware?  Expect problems.\n");
+	} else {
+		putstr("HWCAP2_BTI not present\n");
+		skip_all = 1;
+	}
+
+	putstr("Test binary");
+	if (!BTI)
+		putstr(" not");
+	putstr(" built for BTI\n");
+
+	putstr("---\n");
+
+	sa.sa_handler = (sighandler_t)(void *)handler;
+	sa.sa_flags = SA_SIGINFO;
+	sigemptyset(&sa.sa_mask);
+	sigaction(SIGILL, &sa, NULL);
+	sigaddset(&sa.sa_mask, SIGILL);
+	sigprocmask(SIG_UNBLOCK, &sa.sa_mask, NULL);
+
+	do_test(1, 1, 1, nohint_func);
+	do_test(1, 1, 1, bti_none_func);
+	do_test(1, 0, 0, bti_c_func);
+	do_test(0, 0, 1, bti_j_func);
+	do_test(0, 0, 0, bti_jc_func);
+	do_test(1, 0, 0, paciasp_func);
+
+	putstr("\nNo test failures.\n");
+	exit(0);
+}

btitest.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#ifndef BTITEST_H
+#define BTITEST_H
+
+/* Trampolines for calling the test stubs: */
+void call_using_br_x0(void (*)(void));
+void call_using_br_x16(void (*)(void));
+void call_using_blr(void (*)(void));
+
+/* Test stubs: */
+void nohint_func(void);
+void bti_none_func(void);
+void bti_c_func(void);
+void bti_j_func(void);
+void bti_jc_func(void);
+void paciasp_func(void);
+
+#endif /* !BTITEST_H */

compiler.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#ifndef COMPILER_H
+#define COMPILER_H
+
+#define __always_unused __attribute__((__unused__))
+#define __noreturn __attribute__((__noreturn__))
+#define __unreachable() __builtin_unreachable()
+
+/* curse(e) has value e, but the compiler cannot assume so */
+#define curse(e) ({				\
+	__typeof__(e) __curse_e = (e);		\
+	asm ("" : "+r" (__curse_e));		\
+	__curse_e;				\
+})
+
+#endif /* ! COMPILER_H */

signal.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "system.h"
+#include "signal.h"
+
+int sigemptyset(sigset_t *s)
+{
+	unsigned int i;
+
+	for (i = 0; i < _NSIG_WORDS; ++i)
+		s->sig[i] = 0;
+
+	return 0;
+}
+
+int sigaddset(sigset_t *s, int n)
+{
+	if (n < 1 || n > _NSIG)
+		return -EINVAL;
+
+	s->sig[(n - 1) / _NSIG_BPW] |= 1UL << (n - 1) % _NSIG_BPW;
+	return 0;
+}
+
+int sigaction(int n, struct sigaction *sa, const struct sigaction *old)
+{
+	return syscall(__NR_rt_sigaction, n, sa, old, sizeof sa->sa_mask);
+}
+
+int sigprocmask(int how, const sigset_t *mask, sigset_t *old)
+{
+	return syscall(__NR_rt_sigprocmask, how, mask, old, sizeof(*mask));
+}

signal.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#ifndef SIGNAL_H
+#define SIGNAL_H
+
+#include <linux/signal.h>
+
+#include "system.h"
+
+typedef __sighandler_t sighandler_t;
+
+int sigemptyset(sigset_t *s);
+int sigaddset(sigset_t *s, int n);
+int sigaction(int n, struct sigaction *sa, const struct sigaction *old);
+int sigprocmask(int how, const sigset_t *mask, sigset_t *old);
+
+#endif /* ! SIGNAL_H */

start.S

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "assembler.h"
+
+startfn _start
+	mov	x0, sp
+	b	start
+endfn
+
+emit_aarch64_feature_1_and

syscall.S

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "assembler.h"
+
+startfn syscall
+	bti	c
+	mov	w8, w0
+	mov	x0, x1
+	mov	x1, x2
+	mov	x2, x3
+	mov	x3, x4
+	mov	x4, x5
+	mov	x5, x6
+	mov	x6, x7
+	svc	#0
+	ret
+endfn
+
+emit_aarch64_feature_1_and

system.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "system.h"
+
+#include <asm/unistd.h>
+
+#include "compiler.h"
+
+void __noreturn exit(int n)
+{
+	syscall(__NR_exit, n);
+	__unreachable();
+}
+
+ssize_t write(int fd, const void *buf, size_t size)
+{
+	return syscall(__NR_write, fd, buf, size);
+}

system.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#ifndef SYSTEM_H
+#define SYSTEM_H
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+
+typedef __kernel_size_t size_t;
+typedef __kernel_ssize_t ssize_t;
+
+#define NULL ((void *)0)
+
+#include <linux/errno.h>
+#include <asm/hwcap.h>
+#include <asm/ptrace.h>
+#include <asm/unistd.h>
+
+#include "compiler.h"
+
+long syscall(int nr, ...);
+
+void __noreturn exit(int n);
+ssize_t write(int fd, const void *buf, size_t size);
+
+#ifndef PSR_BTYPE_SHIFT
+#define PSR_BTYPE_SHIFT 10
+#endif
+
+#endif /* ! SYSTEM_H */

teststubs.S

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "assembler.h"
+
+startfn bti_none_func
+	bti
+	ret
+endfn
+
+startfn bti_c_func
+	bti	c
+	ret
+endfn
+
+startfn bti_j_func
+	bti	j
+	ret
+endfn
+
+startfn bti_jc_func
+	bti	jc
+	ret
+endfn
+
+startfn paciasp_func
+	paciasp
+	autiasp
+	ret
+endfn
+
+startfn nohint_func
+	ret
+endfn
+
+emit_aarch64_feature_1_and

trampoline.S

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019  Arm Limited
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+
+#include "assembler.h"
+
+startfn call_using_br_x0
+	bti	c
+	br	x0
+endfn
+
+startfn call_using_br_x16
+	bti	c
+	mov	x16, x0
+	br	x16
+endfn
+
+startfn call_using_blr
+	paciasp
+	stp	x29, x30, [sp, #-16]!
+	blr	x0
+	ldp	x29, x30, [sp], #16
+	autiasp
+	ret
+endfn
+
+emit_aarch64_feature_1_and