On Wed, Aug 28, 2024 at 06:01:29PM -0700, Samuel Holland wrote:
> This test covers the behavior of the PR_SET_TAGGED_ADDR_CTRL and
> PR_GET_TAGGED_ADDR_CTRL prctl() operations, their effects on the
> userspace ABI, and their effects on the system call ABI.
>
> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
Reviewed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Tested-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> ---
>
> (no changes since v2)
>
> Changes in v2:
> - Rename "tags" directory to "pm" to avoid .gitignore rules
> - Add .gitignore file to ignore the compiled selftest binary
> - Write to a pipe to force dereferencing the user pointer
> - Handle SIGSEGV in the child process to reduce dmesg noise
>
> tools/testing/selftests/riscv/Makefile | 2 +-
> tools/testing/selftests/riscv/pm/.gitignore | 1 +
> tools/testing/selftests/riscv/pm/Makefile | 10 +
> .../selftests/riscv/pm/pointer_masking.c | 330 ++++++++++++++++++
> 4 files changed, 342 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/riscv/pm/.gitignore
> create mode 100644 tools/testing/selftests/riscv/pm/Makefile
> create mode 100644 tools/testing/selftests/riscv/pm/pointer_masking.c
>
> diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
> index 7ce03d832b64..2ee1d1548c5f 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 $(ARCH),riscv))
> -RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn
> +RISCV_SUBTARGETS ?= hwprobe mm pm sigreturn vector
> else
> RISCV_SUBTARGETS :=
> endif
> diff --git a/tools/testing/selftests/riscv/pm/.gitignore b/tools/testing/selftests/riscv/pm/.gitignore
> new file mode 100644
> index 000000000000..b38358f91c4d
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/pm/.gitignore
> @@ -0,0 +1 @@
> +pointer_masking
> diff --git a/tools/testing/selftests/riscv/pm/Makefile b/tools/testing/selftests/riscv/pm/Makefile
> new file mode 100644
> index 000000000000..ed82ff9c664e
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/pm/Makefile
> @@ -0,0 +1,10 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +CFLAGS += -I$(top_srcdir)/tools/include
> +
> +TEST_GEN_PROGS := pointer_masking
> +
> +include ../../lib.mk
> +
> +$(OUTPUT)/pointer_masking: pointer_masking.c
> + $(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
> diff --git a/tools/testing/selftests/riscv/pm/pointer_masking.c b/tools/testing/selftests/riscv/pm/pointer_masking.c
> new file mode 100644
> index 000000000000..0fe80f963ace
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/pm/pointer_masking.c
> @@ -0,0 +1,330 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <setjmp.h>
> +#include <signal.h>
> +#include <stdbool.h>
> +#include <sys/prctl.h>
> +#include <sys/wait.h>
> +#include <unistd.h>
> +
> +#include "../../kselftest.h"
> +
> +#ifndef PR_PMLEN_SHIFT
> +#define PR_PMLEN_SHIFT 24
> +#endif
> +#ifndef PR_PMLEN_MASK
> +#define PR_PMLEN_MASK (0x7fUL << PR_PMLEN_SHIFT)
> +#endif
> +
> +static int dev_zero;
> +
> +static int pipefd[2];
> +
> +static sigjmp_buf jmpbuf;
> +
> +static void sigsegv_handler(int sig)
> +{
> + siglongjmp(jmpbuf, 1);
> +}
> +
> +static int min_pmlen;
> +static int max_pmlen;
> +
> +static inline bool valid_pmlen(int pmlen)
> +{
> + return pmlen == 0 || pmlen == 7 || pmlen == 16;
> +}
> +
> +static void test_pmlen(void)
> +{
> + ksft_print_msg("Testing available PMLEN values\n");
> +
> + for (int request = 0; request <= 16; request++) {
> + int pmlen, ret;
> +
> + ret = prctl(PR_SET_TAGGED_ADDR_CTRL, request << PR_PMLEN_SHIFT, 0, 0, 0);
> + if (ret)
> + goto pr_set_error;
> +
> + ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
> + ksft_test_result(ret >= 0, "PMLEN=%d PR_GET_TAGGED_ADDR_CTRL\n", request);
> + if (ret < 0)
> + goto pr_get_error;
> +
> + pmlen = (ret & PR_PMLEN_MASK) >> PR_PMLEN_SHIFT;
> + ksft_test_result(pmlen >= request, "PMLEN=%d constraint\n", request);
> + ksft_test_result(valid_pmlen(pmlen), "PMLEN=%d validity\n", request);
> +
> + if (min_pmlen == 0)
> + min_pmlen = pmlen;
> + if (max_pmlen < pmlen)
> + max_pmlen = pmlen;
> +
> + continue;
> +
> +pr_set_error:
> + ksft_test_result_skip("PMLEN=%d PR_GET_TAGGED_ADDR_CTRL\n", request);
> +pr_get_error:
> + ksft_test_result_skip("PMLEN=%d constraint\n", request);
> + ksft_test_result_skip("PMLEN=%d validity\n", request);
> + }
> +
> + if (max_pmlen == 0)
> + ksft_exit_fail_msg("Failed to enable pointer masking\n");
> +}
> +
> +static int set_tagged_addr_ctrl(int pmlen, bool tagged_addr_abi)
> +{
> + int arg, ret;
> +
> + arg = pmlen << PR_PMLEN_SHIFT | tagged_addr_abi;
> + ret = prctl(PR_SET_TAGGED_ADDR_CTRL, arg, 0, 0, 0);
> + if (!ret) {
> + ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
> + if (ret == arg)
> + return 0;
> + }
> +
> + return ret < 0 ? -errno : -ENODATA;
> +}
> +
> +static void test_dereference_pmlen(int pmlen)
> +{
> + static volatile int i;
> + volatile int *p;
> + int ret;
> +
> + ret = set_tagged_addr_ctrl(pmlen, false);
> + if (ret)
> + return ksft_test_result_error("PMLEN=%d setup (%d)\n", pmlen, ret);
> +
> + i = pmlen;
> +
> + if (pmlen) {
> + p = (volatile int *)((uintptr_t)&i | 1UL << __riscv_xlen - pmlen);
> +
> + /* These dereferences should succeed. */
> + if (sigsetjmp(jmpbuf, 1))
> + return ksft_test_result_fail("PMLEN=%d valid tag\n", pmlen);
> + if (*p != pmlen)
> + return ksft_test_result_fail("PMLEN=%d bad value\n", pmlen);
> + *p++;
> + }
> +
> + p = (volatile int *)((uintptr_t)&i | 1UL << __riscv_xlen - pmlen - 1);
> +
> + /* These dereferences should raise SIGSEGV. */
> + if (sigsetjmp(jmpbuf, 1))
> + return ksft_test_result_pass("PMLEN=%d dereference\n", pmlen);
> + *p++;
> + ksft_test_result_fail("PMLEN=%d invalid tag\n", pmlen);
> +}
> +
> +static void test_dereference(void)
> +{
> + ksft_print_msg("Testing userspace pointer dereference\n");
> +
> + signal(SIGSEGV, sigsegv_handler);
> +
> + test_dereference_pmlen(0);
> + test_dereference_pmlen(min_pmlen);
> + test_dereference_pmlen(max_pmlen);
> +
> + signal(SIGSEGV, SIG_DFL);
> +}
> +
> +static void execve_child_sigsegv_handler(int sig)
> +{
> + exit(42);
> +}
> +
> +static int execve_child(void)
> +{
> + static volatile int i;
> + volatile int *p = (volatile int *)((uintptr_t)&i | 1UL << __riscv_xlen - 7);
> +
> + signal(SIGSEGV, execve_child_sigsegv_handler);
> +
> + /* This dereference should raise SIGSEGV. */
> + return *p;
> +}
> +
> +static void test_fork_exec(void)
> +{
> + int ret, status;
> +
> + ksft_print_msg("Testing fork/exec behavior\n");
> +
> + ret = set_tagged_addr_ctrl(min_pmlen, false);
> + if (ret)
> + return ksft_test_result_error("setup (%d)\n", ret);
> +
> + if (fork()) {
> + wait(&status);
> + ksft_test_result(WIFEXITED(status) && WEXITSTATUS(status) == 42,
> + "dereference after fork\n");
> + } else {
> + static volatile int i = 42;
> + volatile int *p = (volatile int *)((uintptr_t)&i | 1UL << __riscv_xlen - min_pmlen);
> +
> + /* This dereference should succeed. */
> + exit(*p);
> + }
> +
> + if (fork()) {
> + wait(&status);
> + ksft_test_result(WIFEXITED(status) && WEXITSTATUS(status) == 42,
> + "dereference after fork+exec\n");
> + } else {
> + /* Will call execve_child(). */
> + execve("/proc/self/exe", (char *const []) { "", NULL }, NULL);
> + }
> +}
> +
> +static void test_tagged_addr_abi_sysctl(void)
> +{
> + char value;
> + int fd;
> +
> + ksft_print_msg("Testing tagged address ABI sysctl\n");
> +
> + fd = open("/proc/sys/abi/tagged_addr_disabled", O_WRONLY);
> + if (fd < 0) {
> + ksft_test_result_skip("failed to open sysctl file\n");
> + ksft_test_result_skip("failed to open sysctl file\n");
> + return;
> + }
> +
> + value = '1';
> + pwrite(fd, &value, 1, 0);
> + ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
> + "sysctl disabled\n");
> +
> + value = '0';
> + pwrite(fd, &value, 1, 0);
> + ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == 0,
> + "sysctl enabled\n");
> +
> + set_tagged_addr_ctrl(0, false);
> +
> + close(fd);
> +}
> +
> +static void test_tagged_addr_abi_pmlen(int pmlen)
> +{
> + int i, *p, ret;
> +
> + i = ~pmlen;
> +
> + if (pmlen) {
> + p = (int *)((uintptr_t)&i | 1UL << __riscv_xlen - pmlen);
I am trying to put something together with
https://lore.kernel.org/linux-mm/20240905-patches-below_hint_mmap-v3-2-3cd5564efbbb@xxxxxxxxxxxx/T/
to ensure that the upper addresses aren't allocated. This is only
relevant on sv57 and PMLEN=16 hardware where addresses could overlap.
> +
> + ret = set_tagged_addr_ctrl(pmlen, false);
> + if (ret)
> + return ksft_test_result_error("PMLEN=%d ABI disabled setup (%d)\n",
> + pmlen, ret);
> +
> + ret = write(pipefd[1], p, sizeof(*p));
> + if (ret >= 0 || errno != EFAULT)
> + return ksft_test_result_fail("PMLEN=%d ABI disabled write\n", pmlen);
> +
> + ret = read(dev_zero, p, sizeof(*p));
> + if (ret >= 0 || errno != EFAULT)
> + return ksft_test_result_fail("PMLEN=%d ABI disabled read\n", pmlen);
> +
> + if (i != ~pmlen)
> + return ksft_test_result_fail("PMLEN=%d ABI disabled value\n", pmlen);
> +
> + ret = set_tagged_addr_ctrl(pmlen, true);
> + if (ret)
> + return ksft_test_result_error("PMLEN=%d ABI enabled setup (%d)\n",
> + pmlen, ret);
> +
> + ret = write(pipefd[1], p, sizeof(*p));
> + if (ret != sizeof(*p))
> + return ksft_test_result_fail("PMLEN=%d ABI enabled write\n", pmlen);
> +
> + ret = read(dev_zero, p, sizeof(*p));
> + if (ret != sizeof(*p))
> + return ksft_test_result_fail("PMLEN=%d ABI enabled read\n", pmlen);
> +
> + if (i)
> + return ksft_test_result_fail("PMLEN=%d ABI enabled value\n", pmlen);
> +
> + i = ~pmlen;
> + } else {
> + /* The tagged address ABI cannot be enabled when PMLEN == 0. */
> + ret = set_tagged_addr_ctrl(pmlen, true);
> + if (ret != -EINVAL)
> + return ksft_test_result_error("PMLEN=%d ABI setup (%d)\n",
> + pmlen, ret);
> + }
> +
> + p = (int *)((uintptr_t)&i | 1UL << __riscv_xlen - pmlen - 1);
> +
> + ret = write(pipefd[1], p, sizeof(*p));
> + if (ret >= 0 || errno != EFAULT)
> + return ksft_test_result_fail("PMLEN=%d invalid tag write (%d)\n", pmlen, errno);
> +
> + ret = read(dev_zero, p, sizeof(*p));
> + if (ret >= 0 || errno != EFAULT)
> + return ksft_test_result_fail("PMLEN=%d invalid tag read\n", pmlen);
> +
> + if (i != ~pmlen)
> + return ksft_test_result_fail("PMLEN=%d invalid tag value\n", pmlen);
> +
> + ksft_test_result_pass("PMLEN=%d tagged address ABI\n", pmlen);
> +}
> +
> +static void test_tagged_addr_abi(void)
> +{
> + ksft_print_msg("Testing tagged address ABI\n");
> +
> + test_tagged_addr_abi_pmlen(0);
> + test_tagged_addr_abi_pmlen(min_pmlen);
> + test_tagged_addr_abi_pmlen(max_pmlen);
> +}
> +
> +static struct test_info {
> + unsigned int nr_tests;
> + void (*test_fn)(void);
> +} tests[] = {
> + { .nr_tests = 17 * 3, test_pmlen },
> + { .nr_tests = 3, test_dereference },
> + { .nr_tests = 2, test_fork_exec },
> + { .nr_tests = 2, test_tagged_addr_abi_sysctl },
> + { .nr_tests = 3, test_tagged_addr_abi },
> +};
> +
> +int main(int argc, char **argv)
> +{
> + unsigned int plan = 0;
> + int ret;
> +
> + /* Check if this is the child process after execve(). */
> + if (!argv[0][0])
> + return execve_child();
> +
> + dev_zero = open("/dev/zero", O_RDWR);
> + if (dev_zero < 0)
> + return 1;
> +
> + /* Write to a pipe so the kernel must dereference the buffer pointer. */
> + ret = pipe(pipefd);
> + if (ret)
> + return 1;
> +
> + ksft_print_header();
> +
> + for (int i = 0; i < ARRAY_SIZE(tests); ++i)
> + plan += tests[i].nr_tests;
> +
> + ksft_set_plan(plan);
> +
> + for (int i = 0; i < ARRAY_SIZE(tests); ++i)
> + tests[i].test_fn();
> +
> + ksft_finished();
> +}
> --
> 2.45.1
>
>
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