From patchwork Mon Oct 9 12:09:08 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 731237 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 443FFE95A97 for ; Mon, 9 Oct 2023 12:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346612AbjJIMRL (ORCPT ); Mon, 9 Oct 2023 08:17:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346564AbjJIMQ4 (ORCPT ); Mon, 9 Oct 2023 08:16:56 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C7318F; Mon, 9 Oct 2023 05:14:34 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 299B9C433AB; Mon, 9 Oct 2023 12:14:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696853673; bh=GoX5+5TPWKMBeVX5ln3BsEwrTT7WlIZGkNrZpsUPmck=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=W0FSwNyqYZWNsOY3/ccw25GF3rzgDwnMk40GARdg5nA7BmNVFjlfiXp5Ppxrd+fL9 sKEF2cdqC8DpxBGQBRLxAAroWLmgJfjBDU8b3m1eWfhjOE3b/VAAbMW1jLl3d89wfi 2d/8HJPzISmQNXLyW2ZcbMYKqPGzq/OFlcI2XtNilb1m3bCCUCb6OA8G30F/sgKiU2 bpexuyb6Rt/imFxXl3SdUbvph5Rytpw7AuQV1CcftoZTiQD/tO8j62Y7kni0ad6vXI wCHeXD4dkJA/JXWHWgCa2QKEQepJGl2ED/cEJFNDvW7MDps9OI016UESOJf+gNUkld o2uMVrd6B3FnQ== From: Mark Brown Date: Mon, 09 Oct 2023 13:09:08 +0100 Subject: [PATCH v6 34/38] kselftest/arm64: Add a GCS test program built with the system libc MIME-Version: 1.0 Message-Id: <20231009-arm64-gcs-v6-34-78e55deaa4dd@kernel.org> References: <20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org> In-Reply-To: <20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org> To: Catalin Marinas , Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy Cc: "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Mark Brown X-Mailer: b4 0.13-dev-0438c X-Developer-Signature: v=1; a=openpgp-sha256; l=21534; i=broonie@kernel.org; h=from:subject:message-id; bh=GoX5+5TPWKMBeVX5ln3BsEwrTT7WlIZGkNrZpsUPmck=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBlI+2s3ZxHwCqqzhSo1a3a58tdnP9PUmH0mPnDeUuv PgKtKHCJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZSPtrAAKCRAk1otyXVSH0CIwB/ 9tWDmxl4OO+XrU+I3nLBXtcmPzmTHXbJyfrSkHIqAznge5tlKUC2VRqVbHtWhV4pvFmBpFddBOpTa4 Go8XyJylvmCfywK+UqxvkBJIYZfhy+FAocIB3jdamcPfsxXcrtYdsCEomj34AFBnhTJTp+kKUsqinE ptfcFzJyUF/omVPeFj4qlELtWgDteGIsd1c4TBkASJvrtEm8PrwEewthHZMhW1+E7WWYAzQzUk6wWl Ca4KmdvuA11aUmZSiMLP5CHvxc5I07QoRv7fwB50LpgIM3vM6wwElmbcDvTBKidjoOAk0cQbVWYoia q9fIBxsU82/nXfsY5mCf+/iQ6e8dM+ X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org There are things like threads which nolibc struggles with which we want to add coverage for, and the ABI allows us to test most of these even if libc itself does not understand GCS so add a test application built using the system libc. Signed-off-by: Mark Brown --- tools/testing/selftests/arm64/gcs/.gitignore | 1 + tools/testing/selftests/arm64/gcs/Makefile | 4 +- tools/testing/selftests/arm64/gcs/gcs-util.h | 10 + tools/testing/selftests/arm64/gcs/libc-gcs.c | 742 +++++++++++++++++++++++++++ 4 files changed, 756 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/arm64/gcs/.gitignore b/tools/testing/selftests/arm64/gcs/.gitignore index 0e5e695ecba5..5810c4a163d4 100644 --- a/tools/testing/selftests/arm64/gcs/.gitignore +++ b/tools/testing/selftests/arm64/gcs/.gitignore @@ -1 +1,2 @@ basic-gcs +libc-gcs diff --git a/tools/testing/selftests/arm64/gcs/Makefile b/tools/testing/selftests/arm64/gcs/Makefile index 61a30f483429..a8fdf21e9a47 100644 --- a/tools/testing/selftests/arm64/gcs/Makefile +++ b/tools/testing/selftests/arm64/gcs/Makefile @@ -6,7 +6,9 @@ # nolibc. # -TEST_GEN_PROGS := basic-gcs +TEST_GEN_PROGS := basic-gcs libc-gcs + +LDLIBS+=-lpthread include ../../lib.mk diff --git a/tools/testing/selftests/arm64/gcs/gcs-util.h b/tools/testing/selftests/arm64/gcs/gcs-util.h index 65e6de583506..fd50d0523558 100644 --- a/tools/testing/selftests/arm64/gcs/gcs-util.h +++ b/tools/testing/selftests/arm64/gcs/gcs-util.h @@ -16,6 +16,16 @@ #define __NR_prctl 167 #endif +#ifndef NT_ARM_GCS +#define NT_ARM_GCS 0x40e + +struct user_gcs { + __u64 features_enabled; + __u64 features_locked; + __u64 gcspr_el0; +}; +#endif + /* Shadow Stack/Guarded Control Stack interface */ #define PR_GET_SHADOW_STACK_STATUS 71 #define PR_SET_SHADOW_STACK_STATUS 72 diff --git a/tools/testing/selftests/arm64/gcs/libc-gcs.c b/tools/testing/selftests/arm64/gcs/libc-gcs.c new file mode 100644 index 000000000000..58141d46f861 --- /dev/null +++ b/tools/testing/selftests/arm64/gcs/libc-gcs.c @@ -0,0 +1,742 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2023 ARM Limited. + */ + +#define _GNU_SOURCE + +#include +#include + +#include +#include +#include +#include +#include + +#include +#include + +#include + +#include "kselftest_harness.h" + +#include "gcs-util.h" + +#define my_syscall2(num, arg1, arg2) \ +({ \ + register long _num __asm__ ("x8") = (num); \ + register long _arg1 __asm__ ("x0") = (long)(arg1); \ + register long _arg2 __asm__ ("x1") = (long)(arg2); \ + register long _arg3 __asm__ ("x2") = 0; \ + register long _arg4 __asm__ ("x3") = 0; \ + register long _arg5 __asm__ ("x4") = 0; \ + \ + __asm__ volatile ( \ + "svc #0\n" \ + : "=r"(_arg1) \ + : "r"(_arg1), "r"(_arg2), \ + "r"(_arg3), "r"(_arg4), \ + "r"(_arg5), "r"(_num) \ + : "memory", "cc" \ + ); \ + _arg1; \ +}) + +static noinline void gcs_recurse(int depth) +{ + if (depth) + gcs_recurse(depth - 1); + + /* Prevent tail call optimization so we actually recurse */ + asm volatile("dsb sy" : : : "memory"); +} + +/* Smoke test that a function call and return works*/ +TEST(can_call_function) +{ + gcs_recurse(0); +} + +static void *gcs_test_thread(void *arg) +{ + int ret; + unsigned long mode; + + /* + * Some libcs don't seem to fill unused arguments with 0 but + * the kernel validates this so we supply all 5 arguments. + */ + ret = prctl(PR_GET_SHADOW_STACK_STATUS, &mode, 0, 0, 0); + if (ret != 0) { + ksft_print_msg("PR_GET_SHADOW_STACK_STATUS failed: %d\n", ret); + return NULL; + } + + if (!(mode & PR_SHADOW_STACK_ENABLE)) { + ksft_print_msg("GCS not enabled in thread, mode is %u\n", + mode); + return NULL; + } + + /* Just in case... */ + gcs_recurse(0); + + /* Use a non-NULL value to indicate a pass */ + return &gcs_test_thread; +} + +/* Verify that if we start a new thread it has GCS enabled */ +TEST(gcs_enabled_thread) +{ + pthread_t thread; + void *thread_ret; + int ret; + + ret = pthread_create(&thread, NULL, gcs_test_thread, NULL); + ASSERT_TRUE(ret == 0); + if (ret != 0) + return; + + ret = pthread_join(thread, &thread_ret); + ASSERT_TRUE(ret == 0); + if (ret != 0) + return; + + ASSERT_TRUE(thread_ret != NULL); +} + +/* Read the GCS until we find the terminator */ +TEST(gcs_find_terminator) +{ + unsigned long *gcs, *cur; + + gcs = get_gcspr(); + cur = gcs; + while (*cur) + cur++; + + ksft_print_msg("GCS in use from %p-%p\n", gcs, cur); + + /* + * We should have at least whatever called into this test so + * the two pointer should differ. + */ + ASSERT_TRUE(gcs != cur); +} + +/* + * We can access a GCS via ptrace + * + * This could usefully have a fixture but note that each test is + * fork()ed into a new child whcih causes issues. Might be better to + * lift at least some of this out into a separate, non-harness, test + * program. + */ +TEST(ptrace_read_write) +{ + pid_t child, pid; + int ret, status; + siginfo_t si; + uint64_t val, rval, gcspr; + struct user_gcs child_gcs; + struct iovec iov, local_iov, remote_iov; + + child = fork(); + if (child == -1) { + ksft_print_msg("fork() failed: %d (%s)\n", + errno, strerror(errno)); + ASSERT_NE(child, -1); + } + + if (child == 0) { + /* + * In child, make sure there's something on the stack and + * ask to be traced. + */ + gcs_recurse(0); + if (ptrace(PTRACE_TRACEME, -1, NULL, NULL)) + ksft_exit_fail_msg("PTRACE_TRACEME", strerror(errno)); + + if (raise(SIGSTOP)) + ksft_exit_fail_msg("raise(SIGSTOP)", strerror(errno)); + + return; + } + + ksft_print_msg("Child: %d\n", child); + + /* Attach to the child */ + while (1) { + int sig; + + pid = wait(&status); + if (pid == -1) { + ksft_print_msg("wait() failed: %s", + strerror(errno)); + goto error; + } + + /* + * This should never happen but it's hard to flag in + * the framework. + */ + if (pid != child) + continue; + + if (WIFEXITED(status) || WIFSIGNALED(status)) + ksft_exit_fail_msg("Child died unexpectedly\n"); + + if (!WIFSTOPPED(status)) + goto error; + + sig = WSTOPSIG(status); + + if (ptrace(PTRACE_GETSIGINFO, pid, NULL, &si)) { + if (errno == ESRCH) { + ASSERT_NE(errno, ESRCH); + return; + } + + if (errno == EINVAL) { + sig = 0; /* bust group-stop */ + goto cont; + } + + ksft_print_msg("PTRACE_GETSIGINFO: %s\n", + strerror(errno)); + goto error; + } + + if (sig == SIGSTOP && si.si_code == SI_TKILL && + si.si_pid == pid) + break; + + cont: + if (ptrace(PTRACE_CONT, pid, NULL, sig)) { + if (errno == ESRCH) { + ASSERT_NE(errno, ESRCH); + return; + } + + ksft_print_msg("PTRACE_CONT: %s\n", strerror(errno)); + goto error; + } + } + + /* Where is the child GCS? */ + iov.iov_base = &child_gcs; + iov.iov_len = sizeof(child_gcs); + ret = ptrace(PTRACE_GETREGSET, child, NT_ARM_GCS, &iov); + if (ret != 0) { + ksft_print_msg("Failed to read child GCS state: %s (%d)\n", + strerror(errno), errno); + goto error; + } + + /* We should have inherited GCS over fork(), confirm */ + if (!(child_gcs.features_enabled & PR_SHADOW_STACK_ENABLE)) { + ASSERT_TRUE(child_gcs.features_enabled & + PR_SHADOW_STACK_ENABLE); + goto error; + } + + gcspr = child_gcs.gcspr_el0; + ksft_print_msg("Child GCSPR 0x%lx, flags %x, locked %x\n", + gcspr, child_gcs.features_enabled, + child_gcs.features_locked); + + /* Ideally we'd cross check with the child memory map */ + + errno = 0; + val = ptrace(PTRACE_PEEKDATA, child, (void *)gcspr, NULL); + ret = errno; + if (ret != 0) + ksft_print_msg("PTRACE_PEEKDATA failed: %s (%d)\n", + strerror(ret), ret); + EXPECT_EQ(ret, 0); + + /* The child should be in a function, the GCSPR shouldn't be 0 */ + EXPECT_NE(val, 0); + + /* Same thing via process_vm_readv() */ + local_iov.iov_base = &rval; + local_iov.iov_len = sizeof(rval); + remote_iov.iov_base = (void *)gcspr; + remote_iov.iov_len = sizeof(rval); + ret = process_vm_writev(child, &local_iov, 1, &remote_iov, 1, 0); + if (ret == -1) + ksft_print_msg("process_vm_readv() failed: %s (%d)\n", + strerror(errno), errno); + EXPECT_EQ(ret, sizeof(rval)); + EXPECT_EQ(val, rval); + + /* Write data via a peek */ + ret = ptrace(PTRACE_POKEDATA, child, (void *)gcspr, NULL); + if (ret == -1) + ksft_print_msg("PTRACE_POKEDATA failed: %s (%d)\n", + strerror(errno), errno); + EXPECT_EQ(ret, 0); + EXPECT_EQ(0, ptrace(PTRACE_PEEKDATA, child, (void *)gcspr, NULL)); + + /* Restore what we had before, this time with process_vm_writev() */ + local_iov.iov_base = &rval; + local_iov.iov_len = sizeof(val); + remote_iov.iov_base = (void *)gcspr; + remote_iov.iov_len = sizeof(rval); + ret = process_vm_readv(child, &local_iov, 1, &remote_iov, 1, 0); + if (ret == -1) + ksft_print_msg("process_vm_writev() failed: %s (%d)\n", + strerror(errno), errno); + EXPECT_EQ(ret, sizeof(rval)); + + EXPECT_EQ(val, ptrace(PTRACE_PEEKDATA, child, (void *)gcspr, NULL)); + + /* That's all, folks */ + kill(child, SIGKILL); + return; + +error: + kill(child, SIGKILL); + ASSERT_FALSE(true); +} + +FIXTURE(map_gcs) +{ + unsigned long *stack; +}; + +FIXTURE_VARIANT(map_gcs) +{ + size_t stack_size; + unsigned long flags; +}; + +FIXTURE_VARIANT_ADD(map_gcs, s2k_cap_marker) +{ + .stack_size = 2 * 1024, + .flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s2k_cap) +{ + .stack_size = 2 * 1024, + .flags = SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s2k_marker) +{ + .stack_size = 2 * 1024, + .flags = SHADOW_STACK_SET_MARKER, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s2k) +{ + .stack_size = 2 * 1024, + .flags = 0, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s4k_cap_marker) +{ + .stack_size = 4 * 1024, + .flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s4k_cap) +{ + .stack_size = 4 * 1024, + .flags = SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s3k_marker) +{ + .stack_size = 4 * 1024, + .flags = SHADOW_STACK_SET_MARKER, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s4k) +{ + .stack_size = 4 * 1024, + .flags = 0, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s16k_cap_marker) +{ + .stack_size = 16 * 1024, + .flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s16k_cap) +{ + .stack_size = 16 * 1024, + .flags = SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s16k_marker) +{ + .stack_size = 16 * 1024, + .flags = SHADOW_STACK_SET_MARKER, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s16k) +{ + .stack_size = 16 * 1024, + .flags = 0, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s64k_cap_marker) +{ + .stack_size = 64 * 1024, + .flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s64k_cap) +{ + .stack_size = 64 * 1024, + .flags = SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s64k_marker) +{ + .stack_size = 64 * 1024, + .flags = SHADOW_STACK_SET_MARKER, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s64k) +{ + .stack_size = 64 * 1024, + .flags = 0, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s128k_cap_marker) +{ + .stack_size = 128 * 1024, + .flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s128k_cap) +{ + .stack_size = 128 * 1024, + .flags = SHADOW_STACK_SET_TOKEN, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s128k_marker) +{ + .stack_size = 128 * 1024, + .flags = SHADOW_STACK_SET_MARKER, +}; + +FIXTURE_VARIANT_ADD(map_gcs, s128k) +{ + .stack_size = 128 * 1024, + .flags = 0, +}; + +FIXTURE_SETUP(map_gcs) +{ + self->stack = (void *)syscall(__NR_map_shadow_stack, 0, + variant->stack_size, + variant->flags); + ASSERT_FALSE(self->stack == MAP_FAILED); + ksft_print_msg("Allocated stack from %p-%p\n", self->stack, + (unsigned long)self->stack + variant->stack_size); +} + +FIXTURE_TEARDOWN(map_gcs) +{ + int ret; + + if (self->stack != MAP_FAILED) { + ret = munmap(self->stack, variant->stack_size); + ASSERT_EQ(ret, 0); + } +} + +/* The stack has a cap token */ +TEST_F(map_gcs, stack_capped) +{ + unsigned long *stack = self->stack; + size_t cap_index; + + cap_index = (variant->stack_size / sizeof(unsigned long)); + + switch (variant->flags & (SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN)) { + case SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN: + cap_index -= 2; + break; + case SHADOW_STACK_SET_TOKEN: + cap_index -= 1; + break; + case SHADOW_STACK_SET_MARKER: + case 0: + /* No cap, no test */ + return; + } + + ASSERT_EQ(stack[cap_index], GCS_CAP(&stack[cap_index])); +} + +/* The top of the stack is 0 */ +TEST_F(map_gcs, stack_terminated) +{ + unsigned long *stack = self->stack; + size_t term_index; + + if (!(variant->flags & SHADOW_STACK_SET_MARKER)) + return; + + term_index = (variant->stack_size / sizeof(unsigned long)) - 1; + + ASSERT_EQ(stack[term_index], 0); +} + +/* Writes should fault */ +TEST_F_SIGNAL(map_gcs, not_writeable, SIGSEGV) +{ + self->stack[0] = 0; +} + +/* Put it all together, we can safely switch to and from the stack */ +TEST_F(map_gcs, stack_switch) +{ + size_t cap_index; + cap_index = (variant->stack_size / sizeof(unsigned long)); + unsigned long *orig_gcspr_el0, *pivot_gcspr_el0; + + /* Skip over the stack terminator and point at the cap */ + switch (variant->flags & (SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN)) { + case SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN: + cap_index -= 2; + break; + case SHADOW_STACK_SET_TOKEN: + cap_index -= 1; + break; + case SHADOW_STACK_SET_MARKER: + case 0: + /* No cap, no test */ + return; + } + pivot_gcspr_el0 = &self->stack[cap_index]; + + /* Pivot to the new GCS */ + ksft_print_msg("Pivoting to %p from %p, target has value 0x%lx\n", + pivot_gcspr_el0, get_gcspr(), + *pivot_gcspr_el0); + gcsss1(pivot_gcspr_el0); + orig_gcspr_el0 = gcsss2(); + ksft_print_msg("Pivoted to %p from %p, target has value 0x%lx\n", + pivot_gcspr_el0, get_gcspr(), + *pivot_gcspr_el0); + + ksft_print_msg("Pivoted, GCSPR_EL0 now %p\n", get_gcspr()); + + /* New GCS must be in the new buffer */ + ASSERT_TRUE((unsigned long)get_gcspr() > (unsigned long)self->stack); + ASSERT_TRUE((unsigned long)get_gcspr() <= + (unsigned long)self->stack + variant->stack_size); + + /* We should be able to use all but 2 slots of the new stack */ + ksft_print_msg("Recursing %d levels\n", cap_index - 1); + gcs_recurse(cap_index - 1); + + /* Pivot back to the original GCS */ + gcsss1(orig_gcspr_el0); + pivot_gcspr_el0 = gcsss2(); + + gcs_recurse(0); + ksft_print_msg("Pivoted back to GCSPR_EL0 0x%lx\n", get_gcspr()); +} + +/* We fault if we try to go beyond the end of the stack */ +TEST_F_SIGNAL(map_gcs, stack_overflow, SIGSEGV) +{ + size_t cap_index; + cap_index = (variant->stack_size / sizeof(unsigned long)); + unsigned long *orig_gcspr_el0, *pivot_gcspr_el0; + + /* Skip over the stack terminator and point at the cap */ + switch (variant->flags & (SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN)) { + case SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN: + cap_index -= 2; + break; + case SHADOW_STACK_SET_TOKEN: + cap_index -= 1; + break; + case SHADOW_STACK_SET_MARKER: + case 0: + /* No cap, no test but we need to SEGV to avoid a false fail */ + orig_gcspr_el0 = get_gcspr(); + *orig_gcspr_el0 = 0; + return; + } + pivot_gcspr_el0 = &self->stack[cap_index]; + + /* Pivot to the new GCS */ + ksft_print_msg("Pivoting to %p from %p, target has value 0x%lx\n", + pivot_gcspr_el0, get_gcspr(), + *pivot_gcspr_el0); + gcsss1(pivot_gcspr_el0); + orig_gcspr_el0 = gcsss2(); + ksft_print_msg("Pivoted to %p from %p, target has value 0x%lx\n", + pivot_gcspr_el0, get_gcspr(), + *pivot_gcspr_el0); + + ksft_print_msg("Pivoted, GCSPR_EL0 now %p\n", get_gcspr()); + + /* New GCS must be in the new buffer */ + ASSERT_TRUE((unsigned long)get_gcspr() > (unsigned long)self->stack); + ASSERT_TRUE((unsigned long)get_gcspr() <= + (unsigned long)self->stack + variant->stack_size); + + /* Now try to recurse, we should fault doing this. */ + ksft_print_msg("Recursing %d levels...\n", cap_index + 1); + gcs_recurse(cap_index + 1); + ksft_print_msg("...done\n"); + + /* Clean up properly to try to guard against spurious passes. */ + gcsss1(orig_gcspr_el0); + pivot_gcspr_el0 = gcsss2(); + ksft_print_msg("Pivoted back to GCSPR_EL0 0x%lx\n", get_gcspr()); +} + +FIXTURE(map_invalid_gcs) +{ +}; + +FIXTURE_VARIANT(map_invalid_gcs) +{ + size_t stack_size; +}; + +FIXTURE_SETUP(map_invalid_gcs) +{ +} + +FIXTURE_TEARDOWN(map_invalid_gcs) +{ +} + +/* GCS must be larger than 16 bytes */ +FIXTURE_VARIANT_ADD(map_invalid_gcs, too_small) +{ + .stack_size = 8, +}; + +/* GCS size must be 16 byte aligned */ +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_1) { .stack_size = 1024 + 1 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_2) { .stack_size = 1024 + 2 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_3) { .stack_size = 1024 + 3 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_4) { .stack_size = 1024 + 4 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_5) { .stack_size = 1024 + 5 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_6) { .stack_size = 1024 + 6 }; +FIXTURE_VARIANT_ADD(map_invalid_gcs, unligned_7) { .stack_size = 1024 + 7 }; + +TEST_F(map_invalid_gcs, do_map) +{ + void *stack; + + stack = (void *)syscall(__NR_map_shadow_stack, 0, + variant->stack_size, 0); + ASSERT_TRUE(stack == MAP_FAILED); + if (stack != MAP_FAILED) + munmap(stack, variant->stack_size); +} + +FIXTURE(invalid_mprotect) +{ + unsigned long *stack; + size_t stack_size; +}; + +FIXTURE_VARIANT(invalid_mprotect) +{ + unsigned long flags; +}; + +FIXTURE_SETUP(invalid_mprotect) +{ + self->stack_size = sysconf(_SC_PAGE_SIZE); + self->stack = (void *)syscall(__NR_map_shadow_stack, 0, + self->stack_size, 0); + ASSERT_FALSE(self->stack == MAP_FAILED); + ksft_print_msg("Allocated stack from %p-%p\n", self->stack, + (unsigned long)self->stack + self->stack_size); +} + +FIXTURE_TEARDOWN(invalid_mprotect) +{ + int ret; + + if (self->stack != MAP_FAILED) { + ret = munmap(self->stack, self->stack_size); + ASSERT_EQ(ret, 0); + } +} + +FIXTURE_VARIANT_ADD(invalid_mprotect, exec) +{ + .flags = PROT_EXEC, +}; + +FIXTURE_VARIANT_ADD(invalid_mprotect, bti) +{ + .flags = PROT_BTI, +}; + +FIXTURE_VARIANT_ADD(invalid_mprotect, exec_bti) +{ + .flags = PROT_EXEC | PROT_BTI, +}; + +TEST_F(invalid_mprotect, do_map) +{ + int ret; + + ret = mprotect(self->stack, self->stack_size, variant->flags); + ASSERT_EQ(ret, -1); +} + +TEST_F(invalid_mprotect, do_map_read) +{ + int ret; + + ret = mprotect(self->stack, self->stack_size, + variant->flags | PROT_READ); + ASSERT_EQ(ret, -1); +} + +int main(int argc, char **argv) +{ + unsigned long gcs_mode; + int ret; + + if (!(getauxval(AT_HWCAP2) & HWCAP2_GCS)) + ksft_exit_skip("SKIP GCS not supported\n"); + + /* + * Force shadow stacks on, our tests *should* be fine with or + * without libc support and with or without this having ended + * up tagged for GCS and enabled by the dynamic linker. We + * can't use the libc prctl() function since we can't return + * from enabling the stack. Also lock GCS if not already + * locked so we can test behaviour when it's locked. + */ + ret = my_syscall2(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &gcs_mode); + if (ret) { + ksft_print_msg("Failed to read GCS state: %d\n", ret); + return EXIT_FAILURE; + } + + if (!(gcs_mode & PR_SHADOW_STACK_ENABLE)) { + gcs_mode = PR_SHADOW_STACK_ENABLE; + ret = my_syscall2(__NR_prctl, PR_SET_SHADOW_STACK_STATUS, + gcs_mode); + if (ret) { + ksft_print_msg("Failed to configure GCS: %d\n", ret); + return EXIT_FAILURE; + } + } + + /* Avoid returning in case libc doesn't understand GCS */ + exit(test_harness_run(argc, argv)); +}