On Wed, Oct 9, 2024 at 7:46 AM Deepak Gupta <debug@xxxxxxxxxxxx> 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 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 > > 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@xxxxxxxxxxxx> > --- > 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 | 84 +++++ > tools/testing/selftests/riscv/cfi/riscv_cfi_test.c | 78 +++++ > tools/testing/selftests/riscv/cfi/shadowstack.c | 373 +++++++++++++++++++++ > tools/testing/selftests/riscv/cfi/shadowstack.h | 37 ++ > 7 files changed, 586 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile > index 7ce03d832b64..6e142fe004ab 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 $(ARCH),riscv)) > -RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn > +RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn cfi > else > RISCV_SUBTARGETS := > endif > diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore > new file mode 100644 > index 000000000000..82545863bac6 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/.gitignore > @@ -0,0 +1,3 @@ > +cfitests > +riscv_cfi_test > +shadowstack > diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile > new file mode 100644 > index 000000000000..b65f7ff38a32 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/Makefile > @@ -0,0 +1,10 @@ > +CFLAGS += -I$(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..0fefdc33f71e > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h > @@ -0,0 +1,84 @@ > +/* 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..720a001f7c31 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c > @@ -0,0 +1,78 @@ > +// 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) { Hi Deepak, I got some errors when building this test, I suppose they should be fixed in the next version. riscv_cfi_test.c: In function 'sigsegv_handler': riscv_cfi_test.c:17:28: error: 'SEGV_CPERR' undeclared (first use in this function); did you mean 'SEGV_ACCERR'? 17 | if (si->si_code == SEGV_CPERR) { | ^~~~~~~~~~ | SEGV_ACCERR > + 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; > +} > + > +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"); > + 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..9d5301914578 > --- /dev/null > +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c > @@ -0,0 +1,373 @@ > +// 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); > + 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("Exercising 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\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("Write suceeded on shadow stack memory, shadow stack protection test" > + " failed\n"); > + return false; > + } > + > + /* if child reached here, then fail */ > + if (!pid) { > + ksft_print_msg("Shadow stack protection test: 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 protection test: child wasn't signaled for write on" > + " shadow stack\n"); > + return false; > + } > + > + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE); > + if (ret) { > + ksft_print_msg("Shadow stack protection test: 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) { > + 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 < ARRAY_SIZE(shstk_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..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[] = { shadowstack.h:25:34: warning: 'shstk_tests' defined but not used [-Wunused-variable] 25 | 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 > > -- > 2.45.0 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-riscv