| Message ID | 20240403234054.2020347-30-debug@rivosinc.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
| Series | riscv control-flow integrity for usermode | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/vmtest-fixes-PR | fail | merge-conflict |
On Wed, Apr 03, 2024 at 04:35:17PM -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 and > shadow stack for the binary and process are enabled or not. 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 recieving > 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 > As of today 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 > > Signed-off-by: Deepak Gupta <debug@rivosinc.com> > --- > tools/testing/selftests/riscv/Makefile | 2 +- > tools/testing/selftests/riscv/cfi/.gitignore | 3 + > tools/testing/selftests/riscv/cfi/Makefile | 10 + > .../testing/selftests/riscv/cfi/cfi_rv_test.h | 83 ++++ > .../selftests/riscv/cfi/riscv_cfi_test.c | 82 ++++ > .../testing/selftests/riscv/cfi/shadowstack.c | 362 ++++++++++++++++++ > .../testing/selftests/riscv/cfi/shadowstack.h | 37 ++ > 7 files changed, 578 insertions(+), 1 deletion(-) > create mode 100644 tools/testing/selftests/riscv/cfi/.gitignore > create mode 100644 tools/testing/selftests/riscv/cfi/Makefile > create mode 100644 tools/testing/selftests/riscv/cfi/cfi_rv_test.h > create mode 100644 tools/testing/selftests/riscv/cfi/riscv_cfi_test.c > create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.c > create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.h > > diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile > index 4a9ff515a3a0..867e5875b7ce 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 $(ARCH),riscv)) > -RISCV_SUBTARGETS ?= hwprobe vector mm > +RISCV_SUBTARGETS ?= hwprobe vector mm cfi > else > RISCV_SUBTARGETS := > endif > diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore > new file mode 100644 > index 000000000000..ce7623f9da28 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/.gitignore > @@ -0,0 +1,3 @@ > +cfitests > +riscv_cfi_test > +shadowstack > \ No newline at end of file > diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile > new file mode 100644 > index 000000000000..b65f7ff38a32 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/Makefile > @@ -0,0 +1,10 @@ > +CFLAGS += -I$(top_srcdir)/tools/include > + > +CFLAGS += -march=rv64gc_zicfilp_zicfiss > + > +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..fa1cf7183672 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h > @@ -0,0 +1,83 @@ > +/* 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 RISCV_CFI_SELFTEST_COUNT RISCV_SHADOW_STACK_TESTS > + > +#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..f22b3f0f24de > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c > @@ -0,0 +1,82 @@ > +// SPDX-License-Identifier: GPL-2.0-only > + > +#include "../../kselftest.h" > +#include <signal.h> > +#include <asm/ucontext.h> > +#include <linux/prctl.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) { > + printf("Control flow violation happened somewhere\n"); > + printf("pc where violation happened %lx\n", ctx->uc_mcontext.gregs[0]); > + exit(-1); > + } > + > + printf("In sigsegv handler\n"); > + /* 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)) { > + printf("registering signal handler for landing pad violation failed\n"); > + return false; > + } > + > + return true; > +} > + > +int main(int argc, char *argv[]) > +{ > + int ret = 0; > + unsigned long lpad_status = 0, ss_status = 0; > + > + ksft_print_header(); > + > + ksft_set_plan(RISCV_CFI_SELFTEST_COUNT); > + > + 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); There is an assumption here that the libc supports setting INDIR_BR_LP_STATUS but does not support the standard prctl interface defined in <sys/prctl.h>. my_syscall5() is defined to fill in gaps in the libc, so this test case should also set the status manually rather than relying on the libc. I don't think it's necessary to define my_syscall5() since every libc should have a prctl() definition. However, these CFI prctls are very new and glibc does not yet support (correct me if I am wrong) it so these prctls should be enabled by the test cases. - Charlie > + if (ret) > + ksft_exit_skip("Get landing pad status failed with %d\n", ret); > + > + if (!(lpad_status & PR_INDIR_BR_LP_ENABLE)) > + ksft_exit_skip("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_skip("Get shadow stack failed with %d\n", ret); > + > + if (!(ss_status & PR_SHADOW_STACK_ENABLE)) > + ksft_exit_skip("shadow stack is not enabled, should be enabled via glibc\n"); > + > + if (!register_signal_handler()) > + ksft_exit_skip("registering signal handler for SIGSEGV failed\n"); > + > + ksft_print_msg("landing pad and shadow stack are enabled for binary\n"); > + ksft_print_msg("starting risc-v shadow stack tests\n"); > + execute_shadow_stack_tests(); > + > + ksft_finished(); > +} > + > +#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..2f65eb970c44 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c > @@ -0,0 +1,362 @@ > +// 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" > + > +/* 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); > + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); > +} > + > +void bar(void) > +{ > + printf("inside %s\n", __func__); > + zar(); > +} > + > +void foo(void) > +{ > + printf("inside %s\n", __func__); > + bar(); > +} > + > +void zar_child(void) > +{ > + unsigned long ssp = 0; > + > + ssp = csr_read(CSR_SSP); > + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); > +} > + > +void bar_child(void) > +{ > + printf("inside %s\n", __func__); > + zar_child(); > +} > + > +void foo_child(void) > +{ > + printf("inside %s\n", __func__); > + 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) > +{ > + if (parent) > + printf("call test for parent\n"); > + else > + printf("call test for child\n"); > + > + (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; > + > + printf("exercising shadow stack fork test\n"); > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); > + if (ret) { > + printf("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) { > + printf("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) { > + printf("waiting on child to finish\n"); > + wait(&child_status); > + } else { > + /* exit child gracefully */ > + exit(0); > + } > + > + if (pid && WIFSIGNALED(child_status)) { > + printf("child faulted"); > + 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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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) { > + printf("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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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) { > + printf("write suceeded\n"); > + return false; > + } > + > + /* if child reached here, then fail */ > + if (!pid) { > + printf("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) { > + printf("child wasn't signaled for write on shadow stack\n"); > + return false; > + } > + > + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE); > + if (ret) { > + printf("munmap failed with 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) { > + printf("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) { > + printf("writing shadow stack mem via gup failed\n"); > + return 1; > + } > + > + if (*shdw_addr != SS_MAGIC_WRITE_VAL) { > + printf("GUP write to shadow stack memory didn't happen\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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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)) { > + printf("gup tests failed\n"); > + goto out; > + } > + > + ret = true; > +out: > + if (shdw_addr && munmap(write_addr, SHADOW_STACK_ALLOC_SIZE)) { > + printf("munmap failed with error code %d\n", ret); > + ret = false; > + } > + > + return ret; > +} > + > +volatile bool break_loop; > + > +void sigusr1_handler(int signo) > +{ > + printf("In sigusr1 handler\n"); > + 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)) { > + printf("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; > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); > + if (ret) { > + printf("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"); > + > + /* this should be caught by signal handler and do an exit */ > + if (!sigusr1_signal_test()) { > + printf("registering sigusr1 handler failed\n"); > + exit(-1); > + } > + > + pid = fork(); > + > + if (pid == -1) { > + printf("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; > + > + printf("Executing RISC-V shadow stack self tests\n"); > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &shstk_status, 0, 0, 0); > + > + if (ret != 0) > + ksft_exit_skip("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 < ARRAY_SIZE(shstk_tests)) { > + ksft_test_result((*shstk_tests[test_count].t_func)(test_count, NULL), > + shstk_tests[test_count].name); > + test_count++; > + } > + > + 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..b43e74136a26 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/shadowstack.h > @@ -0,0 +1,37 @@ > +/* 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); > + > +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) > + > +int execute_shadow_stack_tests(void); > + > +#endif > -- > 2.43.2 >
On Thu, May 09, 2024 at 11:21:15AM -0700, Charlie Jenkins wrote: >On Wed, Apr 03, 2024 at 04:35:17PM -0700, Deepak Gupta wrote: >> + >> +int main(int argc, char *argv[]) >> +{ >> + int ret = 0; >> + unsigned long lpad_status = 0, ss_status = 0; >> + >> + ksft_print_header(); >> + >> + ksft_set_plan(RISCV_CFI_SELFTEST_COUNT); >> + >> + 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); > >There is an assumption here that the libc supports setting >INDIR_BR_LP_STATUS but does not support the standard prctl interface >defined in <sys/prctl.h>. my_syscall5() is defined to fill in gaps in >the libc, so this test case should also set the status manually rather >than relying on the libc. > >I don't think it's necessary to define my_syscall5() since every libc >should have a prctl() definition. However, these CFI prctls are very new >and glibc does not yet support (correct me if I am wrong) it so these >prctls should be enabled by the test cases. In one of my previous patches, it was setting landing pad and shadow stack enabling directly via handcrafted prctl macro. I changed it to check for status for following reasons - If this binary is compiled with landing pad and shadow stack option then toolchain being used already has libc with shadow stack and landing pad enabling - Currently upstream glibc toolchain dont have support but libc with toolchain has the support. In case of shadow stack enabling, macro is needed and `prctl` function can't be used. Because you enter `prctl` function with no shadow stack but exit with shadow stack and will lead to fault in its epilog. Due to all these reasons, kselftests have to be compiled with toolchain with cfi codegen and thus libc should have support to light them up. Here tests only checks if they are already lit up, If not it fails. Although you're spot on one thing here, since this test is assuming libc already lit-up landing pad and shadow stack. It doesn't need macro here for status check of feature and can simply use `prctl` syscall interface. > >- Charlie > >> + if (ret)
On Wed, Apr 03, 2024 at 04:35:17PM -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 and > shadow stack for the binary and process are enabled or not. 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 recieving > 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 > As of today 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 > > Signed-off-by: Deepak Gupta <debug@rivosinc.com> > --- > tools/testing/selftests/riscv/Makefile | 2 +- > tools/testing/selftests/riscv/cfi/.gitignore | 3 + > tools/testing/selftests/riscv/cfi/Makefile | 10 + > .../testing/selftests/riscv/cfi/cfi_rv_test.h | 83 ++++ > .../selftests/riscv/cfi/riscv_cfi_test.c | 82 ++++ > .../testing/selftests/riscv/cfi/shadowstack.c | 362 ++++++++++++++++++ > .../testing/selftests/riscv/cfi/shadowstack.h | 37 ++ > 7 files changed, 578 insertions(+), 1 deletion(-) > create mode 100644 tools/testing/selftests/riscv/cfi/.gitignore > create mode 100644 tools/testing/selftests/riscv/cfi/Makefile > create mode 100644 tools/testing/selftests/riscv/cfi/cfi_rv_test.h > create mode 100644 tools/testing/selftests/riscv/cfi/riscv_cfi_test.c > create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.c > create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.h > > diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile > index 4a9ff515a3a0..867e5875b7ce 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 $(ARCH),riscv)) > -RISCV_SUBTARGETS ?= hwprobe vector mm > +RISCV_SUBTARGETS ?= hwprobe vector mm cfi > else > RISCV_SUBTARGETS := > endif > diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore > new file mode 100644 > index 000000000000..ce7623f9da28 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/.gitignore > @@ -0,0 +1,3 @@ > +cfitests > +riscv_cfi_test > +shadowstack > \ No newline at end of file > diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile > new file mode 100644 > index 000000000000..b65f7ff38a32 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/Makefile > @@ -0,0 +1,10 @@ > +CFLAGS += -I$(top_srcdir)/tools/include > + > +CFLAGS += -march=rv64gc_zicfilp_zicfiss > + > +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..fa1cf7183672 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h > @@ -0,0 +1,83 @@ > +/* 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 RISCV_CFI_SELFTEST_COUNT RISCV_SHADOW_STACK_TESTS > + > +#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..f22b3f0f24de > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c > @@ -0,0 +1,82 @@ > +// SPDX-License-Identifier: GPL-2.0-only > + > +#include "../../kselftest.h" > +#include <signal.h> > +#include <asm/ucontext.h> > +#include <linux/prctl.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) { > + printf("Control flow violation happened somewhere\n"); > + printf("pc where violation happened %lx\n", ctx->uc_mcontext.gregs[0]); > + exit(-1); > + } > + > + printf("In sigsegv handler\n"); > + /* 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)) { > + printf("registering signal handler for landing pad violation failed\n"); > + return false; > + } > + > + return true; > +} > + > +int main(int argc, char *argv[]) > +{ > + int ret = 0; > + unsigned long lpad_status = 0, ss_status = 0; > + > + ksft_print_header(); > + > + ksft_set_plan(RISCV_CFI_SELFTEST_COUNT); > + > + 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_skip("Get landing pad status failed with %d\n", ret); > + > + if (!(lpad_status & PR_INDIR_BR_LP_ENABLE)) > + ksft_exit_skip("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_skip("Get shadow stack failed with %d\n", ret); > + > + if (!(ss_status & PR_SHADOW_STACK_ENABLE)) > + ksft_exit_skip("shadow stack is not enabled, should be enabled via glibc\n"); > + > + if (!register_signal_handler()) > + ksft_exit_skip("registering signal handler for SIGSEGV failed\n"); > + > + ksft_print_msg("landing pad and shadow stack are enabled for binary\n"); > + ksft_print_msg("starting risc-v shadow stack tests\n"); > + execute_shadow_stack_tests(); > + > + ksft_finished(); The test case framework is based off of static variables, so these tests actually report that nothing passed because the setup is in this file and the actual test cases are in a different file. This can be remedied by moving ksft_set_plan(RISCV_CFI_SELFTEST_COUNT) and ksft_finished() into execute_shadow_stack_tests(). There are two versions of the kselftest framework and the one that this is using is the low-level version that has the note in the header: kselftest.h: low-level kselftest framework to include from selftest programs. When possible, please use kselftest_harness.h instead. There is not a good enough reason for you to change up this code to use kselftest_harness.h instead, but just something to think about for any future test cases you may write. - Charlie > +} > + > +#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..2f65eb970c44 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c > @@ -0,0 +1,362 @@ > +// 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" > + > +/* 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); > + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); > +} > + > +void bar(void) > +{ > + printf("inside %s\n", __func__); > + zar(); > +} > + > +void foo(void) > +{ > + printf("inside %s\n", __func__); > + bar(); > +} > + > +void zar_child(void) > +{ > + unsigned long ssp = 0; > + > + ssp = csr_read(CSR_SSP); > + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); > +} > + > +void bar_child(void) > +{ > + printf("inside %s\n", __func__); > + zar_child(); > +} > + > +void foo_child(void) > +{ > + printf("inside %s\n", __func__); > + 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) > +{ > + if (parent) > + printf("call test for parent\n"); > + else > + printf("call test for child\n"); > + > + (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; > + > + printf("exercising shadow stack fork test\n"); > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); > + if (ret) { > + printf("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) { > + printf("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) { > + printf("waiting on child to finish\n"); > + wait(&child_status); > + } else { > + /* exit child gracefully */ > + exit(0); > + } > + > + if (pid && WIFSIGNALED(child_status)) { > + printf("child faulted"); > + 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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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) { > + printf("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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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) { > + printf("write suceeded\n"); > + return false; > + } > + > + /* if child reached here, then fail */ > + if (!pid) { > + printf("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) { > + printf("child wasn't signaled for write on shadow stack\n"); > + return false; > + } > + > + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE); > + if (ret) { > + printf("munmap failed with 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) { > + printf("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) { > + printf("writing shadow stack mem via gup failed\n"); > + return 1; > + } > + > + if (*shdw_addr != SS_MAGIC_WRITE_VAL) { > + printf("GUP write to shadow stack memory didn't happen\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; > + > + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); > + > + if (((long) shdw_addr) <= 0) { > + printf("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)) { > + printf("gup tests failed\n"); > + goto out; > + } > + > + ret = true; > +out: > + if (shdw_addr && munmap(write_addr, SHADOW_STACK_ALLOC_SIZE)) { > + printf("munmap failed with error code %d\n", ret); > + ret = false; > + } > + > + return ret; > +} > + > +volatile bool break_loop; > + > +void sigusr1_handler(int signo) > +{ > + printf("In sigusr1 handler\n"); > + 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)) { > + printf("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; > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); > + if (ret) { > + printf("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"); > + > + /* this should be caught by signal handler and do an exit */ > + if (!sigusr1_signal_test()) { > + printf("registering sigusr1 handler failed\n"); > + exit(-1); > + } > + > + pid = fork(); > + > + if (pid == -1) { > + printf("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; > + > + printf("Executing RISC-V shadow stack self tests\n"); > + > + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &shstk_status, 0, 0, 0); > + > + if (ret != 0) > + ksft_exit_skip("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 < ARRAY_SIZE(shstk_tests)) { > + ksft_test_result((*shstk_tests[test_count].t_func)(test_count, NULL), > + shstk_tests[test_count].name); > + test_count++; > + } > + > + 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..b43e74136a26 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/shadowstack.h > @@ -0,0 +1,37 @@ > +/* 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); > + > +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) > + > +int execute_shadow_stack_tests(void); > + > +#endif > -- > 2.43.2 >
diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile index 4a9ff515a3a0..867e5875b7ce 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 $(ARCH),riscv)) -RISCV_SUBTARGETS ?= hwprobe vector mm +RISCV_SUBTARGETS ?= hwprobe vector mm cfi else RISCV_SUBTARGETS := endif diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore new file mode 100644 index 000000000000..ce7623f9da28 --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/.gitignore @@ -0,0 +1,3 @@ +cfitests +riscv_cfi_test +shadowstack \ No newline at end of file diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile new file mode 100644 index 000000000000..b65f7ff38a32 --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/Makefile @@ -0,0 +1,10 @@ +CFLAGS += -I$(top_srcdir)/tools/include + +CFLAGS += -march=rv64gc_zicfilp_zicfiss + +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..fa1cf7183672 --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h @@ -0,0 +1,83 @@ +/* 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 RISCV_CFI_SELFTEST_COUNT RISCV_SHADOW_STACK_TESTS + +#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..f22b3f0f24de --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include "../../kselftest.h" +#include <signal.h> +#include <asm/ucontext.h> +#include <linux/prctl.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) { + printf("Control flow violation happened somewhere\n"); + printf("pc where violation happened %lx\n", ctx->uc_mcontext.gregs[0]); + exit(-1); + } + + printf("In sigsegv handler\n"); + /* 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)) { + printf("registering signal handler for landing pad violation failed\n"); + return false; + } + + return true; +} + +int main(int argc, char *argv[]) +{ + int ret = 0; + unsigned long lpad_status = 0, ss_status = 0; + + ksft_print_header(); + + ksft_set_plan(RISCV_CFI_SELFTEST_COUNT); + + 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_skip("Get landing pad status failed with %d\n", ret); + + if (!(lpad_status & PR_INDIR_BR_LP_ENABLE)) + ksft_exit_skip("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_skip("Get shadow stack failed with %d\n", ret); + + if (!(ss_status & PR_SHADOW_STACK_ENABLE)) + ksft_exit_skip("shadow stack is not enabled, should be enabled via glibc\n"); + + if (!register_signal_handler()) + ksft_exit_skip("registering signal handler for SIGSEGV failed\n"); + + ksft_print_msg("landing pad and shadow stack are enabled for binary\n"); + ksft_print_msg("starting risc-v shadow stack tests\n"); + execute_shadow_stack_tests(); + + ksft_finished(); +} + +#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..2f65eb970c44 --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c @@ -0,0 +1,362 @@ +// 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" + +/* 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); + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); +} + +void bar(void) +{ + printf("inside %s\n", __func__); + zar(); +} + +void foo(void) +{ + printf("inside %s\n", __func__); + bar(); +} + +void zar_child(void) +{ + unsigned long ssp = 0; + + ssp = csr_read(CSR_SSP); + printf("inside %s and shadow stack ptr is %lx\n", __func__, ssp); +} + +void bar_child(void) +{ + printf("inside %s\n", __func__); + zar_child(); +} + +void foo_child(void) +{ + printf("inside %s\n", __func__); + 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) +{ + if (parent) + printf("call test for parent\n"); + else + printf("call test for child\n"); + + (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; + + printf("exercising shadow stack fork test\n"); + + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); + if (ret) { + printf("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) { + printf("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) { + printf("waiting on child to finish\n"); + wait(&child_status); + } else { + /* exit child gracefully */ + exit(0); + } + + if (pid && WIFSIGNALED(child_status)) { + printf("child faulted"); + 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; + + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); + + if (((long) shdw_addr) <= 0) { + printf("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) { + printf("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; + + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); + + if (((long) shdw_addr) <= 0) { + printf("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) { + printf("write suceeded\n"); + return false; + } + + /* if child reached here, then fail */ + if (!pid) { + printf("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) { + printf("child wasn't signaled for write on shadow stack\n"); + return false; + } + + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE); + if (ret) { + printf("munmap failed with 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) { + printf("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) { + printf("writing shadow stack mem via gup failed\n"); + return 1; + } + + if (*shdw_addr != SS_MAGIC_WRITE_VAL) { + printf("GUP write to shadow stack memory didn't happen\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; + + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0); + + if (((long) shdw_addr) <= 0) { + printf("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)) { + printf("gup tests failed\n"); + goto out; + } + + ret = true; +out: + if (shdw_addr && munmap(write_addr, SHADOW_STACK_ALLOC_SIZE)) { + printf("munmap failed with error code %d\n", ret); + ret = false; + } + + return ret; +} + +volatile bool break_loop; + +void sigusr1_handler(int signo) +{ + printf("In sigusr1 handler\n"); + 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)) { + printf("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; + + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0); + if (ret) { + printf("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"); + + /* this should be caught by signal handler and do an exit */ + if (!sigusr1_signal_test()) { + printf("registering sigusr1 handler failed\n"); + exit(-1); + } + + pid = fork(); + + if (pid == -1) { + printf("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; + + printf("Executing RISC-V shadow stack self tests\n"); + + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &shstk_status, 0, 0, 0); + + if (ret != 0) + ksft_exit_skip("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 < ARRAY_SIZE(shstk_tests)) { + ksft_test_result((*shstk_tests[test_count].t_func)(test_count, NULL), + shstk_tests[test_count].name); + test_count++; + } + + 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..b43e74136a26 --- /dev/null +++ b/tools/testing/selftests/riscv/cfi/shadowstack.h @@ -0,0 +1,37 @@ +/* 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); + +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) + +int execute_shadow_stack_tests(void); + +#endif
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 and shadow stack for the binary and process are enabled or not. 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 recieving 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 As of today 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 Signed-off-by: Deepak Gupta <debug@rivosinc.com> --- tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/cfi/.gitignore | 3 + tools/testing/selftests/riscv/cfi/Makefile | 10 + .../testing/selftests/riscv/cfi/cfi_rv_test.h | 83 ++++ .../selftests/riscv/cfi/riscv_cfi_test.c | 82 ++++ .../testing/selftests/riscv/cfi/shadowstack.c | 362 ++++++++++++++++++ .../testing/selftests/riscv/cfi/shadowstack.h | 37 ++ 7 files changed, 578 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/riscv/cfi/.gitignore create mode 100644 tools/testing/selftests/riscv/cfi/Makefile create mode 100644 tools/testing/selftests/riscv/cfi/cfi_rv_test.h create mode 100644 tools/testing/selftests/riscv/cfi/riscv_cfi_test.c create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.c create mode 100644 tools/testing/selftests/riscv/cfi/shadowstack.h