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Message-ID: <aC0VI-LqC6lQHv64@debug.ba.rivosinc.com>
Date: Tue, 20 May 2025 16:49:55 -0700
From: Deepak Gupta <debug@...osinc.com>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor@...nel.org>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Christian Brauner <brauner@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Oleg Nesterov <oleg@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
Jann Horn <jannh@...gle.com>, Conor Dooley <conor+dt@...nel.org>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
devicetree@...r.kernel.org, linux-arch@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
alistair.francis@....com, richard.henderson@...aro.org,
jim.shu@...ive.com, andybnac@...il.com, kito.cheng@...ive.com,
atishp@...osinc.com, evan@...osinc.com, cleger@...osinc.com,
alexghiti@...osinc.com, samitolvanen@...gle.com, broonie@...nel.org,
rick.p.edgecombe@...el.com, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v15 27/27] kselftest/riscv: kselftest for user mode cfi
On Mon, May 19, 2025 at 11:02:17PM -0700, Charlie Jenkins wrote:
>On Fri, May 02, 2025 at 04:30:58PM -0700, Deepak Gupta wrote:
>> Adds kselftest for RISC-V control flow integrity implementation for user
>> mode. There is not a lot going on in kernel for enabling landing pad for
>> user mode. cfi selftest are intended to be compiled with zicfilp and
>> zicfiss enabled compiler. Thus kselftest simply checks if landing pad /
>> shadow stack for the process are enabled or not and executes ptrace
>> selftests on cfi. selftest then register a signal handler for SIGSEGV.
>> Any control flow violation are reported as SIGSEGV with si_code =
>> SEGV_CPERR. Test will fail on receiving any SEGV_CPERR. Shadow stack part
>> has more changes in kernel and thus there are separate tests for that
>>
>> - Exercise `map_shadow_stack` syscall
>> - `fork` test to make sure COW works for shadow stack pages
>> - gup tests
>> Kernel uses FOLL_FORCE when access happens to memory via
>> /proc/<pid>/mem. Not breaking that for shadow stack.
>> - signal test. Make sure signal delivery results in token creation on
>> shadow stack and consumes (and verifies) token on sigreturn
>> - shadow stack protection test. attempts to write using regular store
>> instruction on shadow stack memory must result in access faults
>> - ptrace test: adds landing pad violation, clears ELP and continues
>>
>> Test outut
>> ==========
>>
>> """
>> TAP version 13
>> 1..5
>> This is to ensure shadow stack is indeed enabled and working
>> This is to ensure shadow stack is indeed enabled and working
>> ok 1 shstk fork test
>> ok 2 map shadow stack syscall
>> ok 3 shadow stack gup tests
>> ok 4 shadow stack signal tests
>> ok 5 memory protections of shadow stack memory
>> """
>>
>> Signed-off-by: Deepak Gupta <debug@...osinc.com>
>>
>> squash
>>
>> Signed-off-by: Deepak Gupta <debug@...osinc.com>
>> ---
>> tools/testing/selftests/riscv/Makefile | 2 +-
>> tools/testing/selftests/riscv/cfi/.gitignore | 3 +
>> tools/testing/selftests/riscv/cfi/Makefile | 10 +
>> tools/testing/selftests/riscv/cfi/cfi_rv_test.h | 82 +++++
>> tools/testing/selftests/riscv/cfi/riscv_cfi_test.c | 173 +++++++++
>> tools/testing/selftests/riscv/cfi/shadowstack.c | 385 +++++++++++++++++++++
>> tools/testing/selftests/riscv/cfi/shadowstack.h | 27 ++
>> 7 files changed, 681 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
>> index 099b8c1f46f8..5671b4405a12 100644
>> --- a/tools/testing/selftests/riscv/Makefile
>> +++ b/tools/testing/selftests/riscv/Makefile
>> @@ -5,7 +5,7 @@
>> ARCH ?= $(shell uname -m 2>/dev/null || echo not)
>>
>> ifneq (,$(filter $(ARCH),riscv))
>> -RISCV_SUBTARGETS ?= abi hwprobe mm sigreturn vector
>> +RISCV_SUBTARGETS ?= abi hwprobe mm sigreturn vector cfi
>> else
>> RISCV_SUBTARGETS :=
>> endif
>> diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore
>> new file mode 100644
>> index 000000000000..82545863bac6
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/.gitignore
>> @@ -0,0 +1,3 @@
>> +cfitests
>> +riscv_cfi_test
>> +shadowstack
>> diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile
>> new file mode 100644
>> index 000000000000..1fa27cc10fb5
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/Makefile
>> @@ -0,0 +1,10 @@
>> +CFLAGS += -I$(top_srcdir)/tools/include
>> +
>> +CFLAGS += -march=rv64gc_zicfilp_zicfiss -fcf-protection=full
>
>I am worried about the developer workflows that this will impact. Trying
>to build kselftest with TARGETS=riscv will fail if the toolchain does
>not support -fcf-protection=full. How about we skip these tests if the
>compiler can't compile it instead?
>
>Something like:
Yeah make sense to me.
Alex,
You want me to spin up a v16 with this change?
-Deepak
>
>>From 334f5c821d84751494d269272a875636a9e0d68f Mon Sep 17 00:00:00 2001
>From: Charlie Jenkins <charlie@...osinc.com>
>Date: Mon, 19 May 2025 22:44:05 -0700
>Subject: [PATCH] fixup! kselftest/riscv: kselftest for user mode cfi
>
>---
> tools/testing/selftests/riscv/cfi/Makefile | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile
>index 1fa27cc10fb5..55165a93845f 100644
>--- a/tools/testing/selftests/riscv/cfi/Makefile
>+++ b/tools/testing/selftests/riscv/cfi/Makefile
>@@ -2,9 +2,15 @@ CFLAGS += -I$(top_srcdir)/tools/include
>
> CFLAGS += -march=rv64gc_zicfilp_zicfiss -fcf-protection=full
>
>+ifeq ($(shell $(CC) $(CFLAGS) -nostdlib -xc /dev/null -o /dev/null > /dev/null 2>&1; echo $$?),0)
> TEST_GEN_PROGS := cfitests
>
> include ../../lib.mk
>
> $(OUTPUT)/cfitests: riscv_cfi_test.c shadowstack.c
> $(CC) -o$@ $(CFLAGS) $(LDFLAGS) $^
>+else
>+include ../../lib.mk
>+
>+$(shell echo "Toolchain doesn't support CFI, skipping CFI kselftest." >&2)
>+endif
>--
>2.43.0
>
>
>> +
>> +TEST_GEN_PROGS := cfitests
>> +
>> +include ../../lib.mk
>> +
>> +$(OUTPUT)/cfitests: riscv_cfi_test.c shadowstack.c
>> + $(CC) -o$@ $(CFLAGS) $(LDFLAGS) $^
>> diff --git a/tools/testing/selftests/riscv/cfi/cfi_rv_test.h b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h
>> new file mode 100644
>> index 000000000000..1c8043f2b778
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h
>> @@ -0,0 +1,82 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +
>> +#ifndef SELFTEST_RISCV_CFI_H
>> +#define SELFTEST_RISCV_CFI_H
>> +#include <stddef.h>
>> +#include <sys/types.h>
>> +#include "shadowstack.h"
>> +
>> +#define CHILD_EXIT_CODE_SSWRITE 10
>> +#define CHILD_EXIT_CODE_SIG_TEST 11
>> +
>> +#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
>> +({ \
>> + register long _num __asm__ ("a7") = (num); \
>> + register long _arg1 __asm__ ("a0") = (long)(arg1); \
>> + register long _arg2 __asm__ ("a1") = (long)(arg2); \
>> + register long _arg3 __asm__ ("a2") = (long)(arg3); \
>> + register long _arg4 __asm__ ("a3") = (long)(arg4); \
>> + register long _arg5 __asm__ ("a4") = (long)(arg5); \
>> + \
>> + __asm__ volatile( \
>> + "ecall\n" \
>> + : "+r" \
>> + (_arg1) \
>> + : "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
>> + "r"(_num) \
>> + : "memory", "cc" \
>> + ); \
>> + _arg1; \
>> +})
>> +
>> +#define my_syscall3(num, arg1, arg2, arg3) \
>> +({ \
>> + register long _num __asm__ ("a7") = (num); \
>> + register long _arg1 __asm__ ("a0") = (long)(arg1); \
>> + register long _arg2 __asm__ ("a1") = (long)(arg2); \
>> + register long _arg3 __asm__ ("a2") = (long)(arg3); \
>> + \
>> + __asm__ volatile( \
>> + "ecall\n" \
>> + : "+r" (_arg1) \
>> + : "r"(_arg2), "r"(_arg3), \
>> + "r"(_num) \
>> + : "memory", "cc" \
>> + ); \
>> + _arg1; \
>> +})
>> +
>> +#ifndef __NR_prctl
>> +#define __NR_prctl 167
>> +#endif
>> +
>> +#ifndef __NR_map_shadow_stack
>> +#define __NR_map_shadow_stack 453
>> +#endif
>> +
>> +#define CSR_SSP 0x011
>> +
>> +#ifdef __ASSEMBLY__
>> +#define __ASM_STR(x) x
>> +#else
>> +#define __ASM_STR(x) #x
>> +#endif
>> +
>> +#define csr_read(csr) \
>> +({ \
>> + register unsigned long __v; \
>> + __asm__ __volatile__ ("csrr %0, " __ASM_STR(csr) \
>> + : "=r" (__v) : \
>> + : "memory"); \
>> + __v; \
>> +})
>> +
>> +#define csr_write(csr, val) \
>> +({ \
>> + unsigned long __v = (unsigned long)(val); \
>> + __asm__ __volatile__ ("csrw " __ASM_STR(csr) ", %0" \
>> + : : "rK" (__v) \
>> + : "memory"); \
>> +})
>> +
>> +#endif
>> diff --git a/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c
>> new file mode 100644
>> index 000000000000..486a2e779053
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c
>> @@ -0,0 +1,173 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +
>> +#include "../../kselftest.h"
>> +#include <sys/signal.h>
>> +#include <asm/ucontext.h>
>> +#include <linux/prctl.h>
>> +#include <errno.h>
>> +#include <linux/ptrace.h>
>> +#include <sys/wait.h>
>> +#include <linux/elf.h>
>> +#include <sys/uio.h>
>> +#include <asm-generic/unistd.h>
>> +
>> +#include "cfi_rv_test.h"
>> +
>> +/* do not optimize cfi related test functions */
>> +#pragma GCC push_options
>> +#pragma GCC optimize("O0")
>> +
>> +void sigsegv_handler(int signum, siginfo_t *si, void *uc)
>> +{
>> + struct ucontext *ctx = (struct ucontext *)uc;
>> +
>> + if (si->si_code == SEGV_CPERR) {
>> + ksft_print_msg("Control flow violation happened somewhere\n");
>> + ksft_print_msg("PC where violation happened %lx\n", ctx->uc_mcontext.gregs[0]);
>> + exit(-1);
>> + }
>> +
>> + /* all other cases are expected to be of shadow stack write case */
>> + exit(CHILD_EXIT_CODE_SSWRITE);
>> +}
>> +
>> +bool register_signal_handler(void)
>> +{
>> + struct sigaction sa = {};
>> +
>> + sa.sa_sigaction = sigsegv_handler;
>> + sa.sa_flags = SA_SIGINFO;
>> + if (sigaction(SIGSEGV, &sa, NULL)) {
>> + ksft_print_msg("Registering signal handler for landing pad violation failed\n");
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +long ptrace(int request, pid_t pid, void *addr, void *data);
>> +
>> +bool cfi_ptrace_test(void)
>> +{
>> + pid_t pid;
>> + int status, ret = 0;
>> + unsigned long ptrace_test_num = 0, total_ptrace_tests = 2;
>> +
>> + struct user_cfi_state cfi_reg;
>> + struct iovec iov;
>> +
>> + pid = fork();
>> +
>> + if (pid == -1) {
>> + ksft_exit_fail_msg("%s: fork failed\n", __func__);
>> + exit(1);
>> + }
>> +
>> + if (pid == 0) {
>> + /* allow to be traced */
>> + ptrace(PTRACE_TRACEME, 0, NULL, NULL);
>> + raise(SIGSTOP);
>> + asm volatile (
>> + "la a5, 1f\n"
>> + "jalr a5 \n"
>> + "nop \n"
>> + "nop \n"
>> + "1: nop\n"
>> + : : : "a5");
>> + exit(11);
>> + /* child shouldn't go beyond here */
>> + }
>> +
>> + /* parent's code goes here */
>> + iov.iov_base = &cfi_reg;
>> + iov.iov_len = sizeof(cfi_reg);
>> +
>> + while (ptrace_test_num < total_ptrace_tests) {
>> + memset(&cfi_reg, 0, sizeof(cfi_reg));
>> + waitpid(pid, &status, 0);
>> + if (WIFSTOPPED(status)) {
>> + errno = 0;
>> + ret = ptrace(PTRACE_GETREGSET, pid, (void *)NT_RISCV_USER_CFI, &iov);
>> + if (ret == -1 && errno)
>> + ksft_exit_fail_msg("%s: PTRACE_GETREGSET failed\n", __func__);
>> + } else
>> + ksft_exit_fail_msg("%s: child didn't stop, failed\n", __func__);
>> +
>> + switch (ptrace_test_num) {
>> +#define CFI_ENABLE_MASK (PTRACE_CFI_LP_EN_STATE | \
>> + PTRACE_CFI_SS_EN_STATE | \
>> + PTRACE_CFI_SS_PTR_STATE)
>> + case 0:
>> + if ((cfi_reg.cfi_status.cfi_state & CFI_ENABLE_MASK) != CFI_ENABLE_MASK)
>> + ksft_exit_fail_msg("%s: ptrace_getregset failed, %llu\n", __func__,
>> + cfi_reg.cfi_status.cfi_state);
>> + if (!cfi_reg.shstk_ptr)
>> + ksft_exit_fail_msg("%s: NULL shadow stack pointer, test failed\n",
>> + __func__);
>> + break;
>> + case 1:
>> + if (!(cfi_reg.cfi_status.cfi_state & PTRACE_CFI_ELP_STATE))
>> + ksft_exit_fail_msg("%s: elp must have been set\n", __func__);
>> + /* clear elp state. not interested in anything else */
>> + cfi_reg.cfi_status.cfi_state = 0;
>> +
>> + ret = ptrace(PTRACE_SETREGSET, pid, (void *)NT_RISCV_USER_CFI, &iov);
>> + if (ret == -1 && errno)
>> + ksft_exit_fail_msg("%s: PTRACE_GETREGSET failed\n", __func__);
>> + break;
>> + default:
>> + ksft_exit_fail_msg("%s: unreachable switch case\n", __func__);
>> + break;
>> + }
>> + ptrace(PTRACE_CONT, pid, NULL, NULL);
>> + ptrace_test_num++;
>> + }
>> +
>> + waitpid(pid, &status, 0);
>> + if (WEXITSTATUS(status) != 11)
>> + ksft_print_msg("%s, bad return code from child\n", __func__);
>> +
>> + ksft_print_msg("%s, ptrace test succeeded\n", __func__);
>> + return true;
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> + int ret = 0;
>> + unsigned long lpad_status = 0, ss_status = 0;
>> +
>> + ksft_print_header();
>> +
>> + ksft_print_msg("Starting risc-v tests\n");
>> +
>> + /*
>> + * Landing pad test. Not a lot of kernel changes to support landing
>> + * pad for user mode except lighting up a bit in senvcfg via a prctl
>> + * Enable landing pad through out the execution of test binary
>> + */
>> + ret = my_syscall5(__NR_prctl, PR_GET_INDIR_BR_LP_STATUS, &lpad_status, 0, 0, 0);
>> + if (ret)
>> + ksft_exit_fail_msg("Get landing pad status failed with %d\n", ret);
>> +
>> + if (!(lpad_status & PR_INDIR_BR_LP_ENABLE))
>> + ksft_exit_fail_msg("Landing pad is not enabled, should be enabled via glibc\n");
>> +
>> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
>> + if (ret)
>> + ksft_exit_fail_msg("Get shadow stack failed with %d\n", ret);
>> +
>> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
>> + ksft_exit_fail_msg("Shadow stack is not enabled, should be enabled via glibc\n");
>> +
>> + if (!register_signal_handler())
>> + ksft_exit_fail_msg("Registering signal handler for SIGSEGV failed\n");
>> +
>> + ksft_print_msg("Landing pad and shadow stack are enabled for binary\n");
>> + cfi_ptrace_test();
>> +
>> + execute_shadow_stack_tests();
>> +
>> + return 0;
>> +}
>> +
>> +#pragma GCC pop_options
>> diff --git a/tools/testing/selftests/riscv/cfi/shadowstack.c b/tools/testing/selftests/riscv/cfi/shadowstack.c
>> new file mode 100644
>> index 000000000000..53387dbd9cf5
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c
>> @@ -0,0 +1,385 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +
>> +#include "../../kselftest.h"
>> +#include <sys/wait.h>
>> +#include <signal.h>
>> +#include <fcntl.h>
>> +#include <asm-generic/unistd.h>
>> +#include <sys/mman.h>
>> +#include "shadowstack.h"
>> +#include "cfi_rv_test.h"
>> +
>> +static struct shadow_stack_tests shstk_tests[] = {
>> + { "shstk fork test\n", shadow_stack_fork_test },
>> + { "map shadow stack syscall\n", shadow_stack_map_test },
>> + { "shadow stack gup tests\n", shadow_stack_gup_tests },
>> + { "shadow stack signal tests\n", shadow_stack_signal_test},
>> + { "memory protections of shadow stack memory\n", shadow_stack_protection_test }
>> +};
>> +
>> +#define RISCV_SHADOW_STACK_TESTS ARRAY_SIZE(shstk_tests)
>> +
>> +/* do not optimize shadow stack related test functions */
>> +#pragma GCC push_options
>> +#pragma GCC optimize("O0")
>> +
>> +void zar(void)
>> +{
>> + unsigned long ssp = 0;
>> +
>> + ssp = csr_read(CSR_SSP);
>> + ksft_print_msg("Spewing out shadow stack ptr: %lx\n"
>> + " This is to ensure shadow stack is indeed enabled and working\n",
>> + ssp);
>> +}
>> +
>> +void bar(void)
>> +{
>> + zar();
>> +}
>> +
>> +void foo(void)
>> +{
>> + bar();
>> +}
>> +
>> +void zar_child(void)
>> +{
>> + unsigned long ssp = 0;
>> +
>> + ssp = csr_read(CSR_SSP);
>> + ksft_print_msg("Spewing out shadow stack ptr: %lx\n"
>> + " This is to ensure shadow stack is indeed enabled and working\n",
>> + ssp);
>> +}
>> +
>> +void bar_child(void)
>> +{
>> + zar_child();
>> +}
>> +
>> +void foo_child(void)
>> +{
>> + bar_child();
>> +}
>> +
>> +typedef void (call_func_ptr)(void);
>> +/*
>> + * call couple of functions to test push pop.
>> + */
>> +int shadow_stack_call_tests(call_func_ptr fn_ptr, bool parent)
>> +{
>> + ksft_print_msg("dummy calls for sspush and sspopchk in context of %s\n",
>> + parent ? "parent" : "child");
>> +
>> + (fn_ptr)();
>> +
>> + return 0;
>> +}
>> +
>> +/* forks a thread, and ensure shadow stacks fork out */
>> +bool shadow_stack_fork_test(unsigned long test_num, void *ctx)
>> +{
>> + int pid = 0, child_status = 0, parent_pid = 0, ret = 0;
>> + unsigned long ss_status = 0;
>> +
>> + ksft_print_msg("Exercising shadow stack fork test\n");
>> +
>> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
>> + if (ret) {
>> + ksft_exit_skip("Shadow stack get status prctl failed with errorcode %d\n", ret);
>> + return false;
>> + }
>> +
>> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
>> + ksft_exit_skip("Shadow stack is not enabled, should be enabled via glibc\n");
>> +
>> + parent_pid = getpid();
>> + pid = fork();
>> +
>> + if (pid) {
>> + ksft_print_msg("Parent pid %d and child pid %d\n", parent_pid, pid);
>> + shadow_stack_call_tests(&foo, true);
>> + } else {
>> + shadow_stack_call_tests(&foo_child, false);
>> + }
>> +
>> + if (pid) {
>> + ksft_print_msg("Waiting on child to finish\n");
>> + wait(&child_status);
>> + } else {
>> + /* exit child gracefully */
>> + exit(0);
>> + }
>> +
>> + if (pid && WIFSIGNALED(child_status)) {
>> + ksft_print_msg("Child faulted, fork test failed\n");
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +/* exercise `map_shadow_stack`, pivot to it and call some functions to ensure it works */
>> +#define SHADOW_STACK_ALLOC_SIZE 4096
>> +bool shadow_stack_map_test(unsigned long test_num, void *ctx)
>> +{
>> + unsigned long shdw_addr;
>> + int ret = 0;
>> +
>> + ksft_print_msg("Exercising shadow stack map test\n");
>> +
>> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
>> +
>> + if (((long)shdw_addr) <= 0) {
>> + ksft_print_msg("map_shadow_stack failed with error code %d\n",
>> + (int)shdw_addr);
>> + return false;
>> + }
>> +
>> + ret = munmap((void *)shdw_addr, SHADOW_STACK_ALLOC_SIZE);
>> +
>> + if (ret) {
>> + ksft_print_msg("munmap failed with error code %d\n", ret);
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +/*
>> + * shadow stack protection tests. map a shadow stack and
>> + * validate all memory protections work on it
>> + */
>> +bool shadow_stack_protection_test(unsigned long test_num, void *ctx)
>> +{
>> + unsigned long shdw_addr;
>> + unsigned long *write_addr = NULL;
>> + int ret = 0, pid = 0, child_status = 0;
>> +
>> + ksft_print_msg("Exercising shadow stack protection test (WPT)\n");
>> +
>> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
>> +
>> + if (((long)shdw_addr) <= 0) {
>> + ksft_print_msg("map_shadow_stack failed with error code %d\n",
>> + (int)shdw_addr);
>> + return false;
>> + }
>> +
>> + write_addr = (unsigned long *)shdw_addr;
>> + pid = fork();
>> +
>> + /* no child was created, return false */
>> + if (pid == -1)
>> + return false;
>> +
>> + /*
>> + * try to perform a store from child on shadow stack memory
>> + * it should result in SIGSEGV
>> + */
>> + if (!pid) {
>> + /* below write must lead to SIGSEGV */
>> + *write_addr = 0xdeadbeef;
>> + } else {
>> + wait(&child_status);
>> + }
>> +
>> + /* test fail, if 0xdeadbeef present on shadow stack address */
>> + if (*write_addr == 0xdeadbeef) {
>> + ksft_print_msg("Shadow stack WPT failed\n");
>> + return false;
>> + }
>> +
>> + /* if child reached here, then fail */
>> + if (!pid) {
>> + ksft_print_msg("Shadow stack WPT failed: child reached unreachable state\n");
>> + return false;
>> + }
>> +
>> + /* if child exited via signal handler but not for write on ss */
>> + if (WIFEXITED(child_status) &&
>> + WEXITSTATUS(child_status) != CHILD_EXIT_CODE_SSWRITE) {
>> + ksft_print_msg("Shadow stack WPT failed: child wasn't signaled for write\n");
>> + return false;
>> + }
>> +
>> + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE);
>> + if (ret) {
>> + ksft_print_msg("Shadow stack WPT failed: munmap failed, error code %d\n",
>> + ret);
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +#define SS_MAGIC_WRITE_VAL 0xbeefdead
>> +
>> +int gup_tests(int mem_fd, unsigned long *shdw_addr)
>> +{
>> + unsigned long val = 0;
>> +
>> + lseek(mem_fd, (unsigned long)shdw_addr, SEEK_SET);
>> + if (read(mem_fd, &val, sizeof(val)) < 0) {
>> + ksft_print_msg("Reading shadow stack mem via gup failed\n");
>> + return 1;
>> + }
>> +
>> + val = SS_MAGIC_WRITE_VAL;
>> + lseek(mem_fd, (unsigned long)shdw_addr, SEEK_SET);
>> + if (write(mem_fd, &val, sizeof(val)) < 0) {
>> + ksft_print_msg("Writing shadow stack mem via gup failed\n");
>> + return 1;
>> + }
>> +
>> + if (*shdw_addr != SS_MAGIC_WRITE_VAL) {
>> + ksft_print_msg("GUP write to shadow stack memory failed\n");
>> + return 1;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +bool shadow_stack_gup_tests(unsigned long test_num, void *ctx)
>> +{
>> + unsigned long shdw_addr = 0;
>> + unsigned long *write_addr = NULL;
>> + int fd = 0;
>> + bool ret = false;
>> +
>> + ksft_print_msg("Exercising shadow stack gup tests\n");
>> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
>> +
>> + if (((long)shdw_addr) <= 0) {
>> + ksft_print_msg("map_shadow_stack failed with error code %d\n", (int)shdw_addr);
>> + return false;
>> + }
>> +
>> + write_addr = (unsigned long *)shdw_addr;
>> +
>> + fd = open("/proc/self/mem", O_RDWR);
>> + if (fd == -1)
>> + return false;
>> +
>> + if (gup_tests(fd, write_addr)) {
>> + ksft_print_msg("gup tests failed\n");
>> + goto out;
>> + }
>> +
>> + ret = true;
>> +out:
>> + if (shdw_addr && munmap(write_addr, SHADOW_STACK_ALLOC_SIZE)) {
>> + ksft_print_msg("munmap failed with error code %d\n", ret);
>> + ret = false;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +volatile bool break_loop;
>> +
>> +void sigusr1_handler(int signo)
>> +{
>> + break_loop = true;
>> +}
>> +
>> +bool sigusr1_signal_test(void)
>> +{
>> + struct sigaction sa = {};
>> +
>> + sa.sa_handler = sigusr1_handler;
>> + sa.sa_flags = 0;
>> + sigemptyset(&sa.sa_mask);
>> + if (sigaction(SIGUSR1, &sa, NULL)) {
>> + ksft_print_msg("Registering signal handler for SIGUSR1 failed\n");
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +/*
>> + * shadow stack signal test. shadow stack must be enabled.
>> + * register a signal, fork another thread which is waiting
>> + * on signal. Send a signal from parent to child, verify
>> + * that signal was received by child. If not test fails
>> + */
>> +bool shadow_stack_signal_test(unsigned long test_num, void *ctx)
>> +{
>> + int pid = 0, child_status = 0, ret = 0;
>> + unsigned long ss_status = 0;
>> +
>> + ksft_print_msg("Exercising shadow stack signal test\n");
>> +
>> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
>> + if (ret) {
>> + ksft_print_msg("Shadow stack get status prctl failed with errorcode %d\n", ret);
>> + return false;
>> + }
>> +
>> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
>> + ksft_print_msg("Shadow stack is not enabled, should be enabled via glibc\n");
>> +
>> + /* this should be caught by signal handler and do an exit */
>> + if (!sigusr1_signal_test()) {
>> + ksft_print_msg("Registering sigusr1 handler failed\n");
>> + exit(-1);
>> + }
>> +
>> + pid = fork();
>> +
>> + if (pid == -1) {
>> + ksft_print_msg("Signal test: fork failed\n");
>> + goto out;
>> + }
>> +
>> + if (pid == 0) {
>> + while (!break_loop)
>> + sleep(1);
>> +
>> + exit(11);
>> + /* child shouldn't go beyond here */
>> + }
>> +
>> + /* send SIGUSR1 to child */
>> + kill(pid, SIGUSR1);
>> + wait(&child_status);
>> +
>> +out:
>> +
>> + return (WIFEXITED(child_status) &&
>> + WEXITSTATUS(child_status) == 11);
>> +}
>> +
>> +int execute_shadow_stack_tests(void)
>> +{
>> + int ret = 0;
>> + unsigned long test_count = 0;
>> + unsigned long shstk_status = 0;
>> + bool test_pass = false;
>> +
>> + ksft_print_msg("Executing RISC-V shadow stack self tests\n");
>> + ksft_set_plan(RISCV_SHADOW_STACK_TESTS);
>> +
>> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &shstk_status, 0, 0, 0);
>> +
>> + if (ret != 0)
>> + ksft_exit_fail_msg("Get shadow stack status failed with %d\n", ret);
>> +
>> + /*
>> + * If we are here that means get shadow stack status succeeded and
>> + * thus shadow stack support is baked in the kernel.
>> + */
>> + while (test_count < RISCV_SHADOW_STACK_TESTS) {
>> + test_pass = (*shstk_tests[test_count].t_func)(test_count, NULL);
>> + ksft_test_result(test_pass, shstk_tests[test_count].name);
>> + test_count++;
>> + }
>> +
>> + ksft_finished();
>> +
>> + return 0;
>> +}
>> +
>> +#pragma GCC pop_options
>> diff --git a/tools/testing/selftests/riscv/cfi/shadowstack.h b/tools/testing/selftests/riscv/cfi/shadowstack.h
>> new file mode 100644
>> index 000000000000..0be510167de3
>> --- /dev/null
>> +++ b/tools/testing/selftests/riscv/cfi/shadowstack.h
>> @@ -0,0 +1,27 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +
>> +#ifndef SELFTEST_SHADOWSTACK_TEST_H
>> +#define SELFTEST_SHADOWSTACK_TEST_H
>> +#include <stddef.h>
>> +#include <linux/prctl.h>
>> +
>> +/*
>> + * a cfi test returns true for success or false for fail
>> + * takes a number for test number to index into array and void pointer.
>> + */
>> +typedef bool (*shstk_test_func)(unsigned long test_num, void *);
>> +
>> +struct shadow_stack_tests {
>> + char *name;
>> + shstk_test_func t_func;
>> +};
>> +
>> +bool shadow_stack_fork_test(unsigned long test_num, void *ctx);
>> +bool shadow_stack_map_test(unsigned long test_num, void *ctx);
>> +bool shadow_stack_protection_test(unsigned long test_num, void *ctx);
>> +bool shadow_stack_gup_tests(unsigned long test_num, void *ctx);
>> +bool shadow_stack_signal_test(unsigned long test_num, void *ctx);
>> +
>> +int execute_shadow_stack_tests(void);
>> +
>> +#endif
>>
>> --
>> 2.43.0
>>
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