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-rw-r--r--tools/testing/selftests/x86/test_vsyscall.c535
1 files changed, 535 insertions, 0 deletions
diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
new file mode 100644
index 000000000000..f1c3df642352
--- /dev/null
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -0,0 +1,535 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <sys/time.h>
+#include <time.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <dlfcn.h>
+#include <string.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <sys/ucontext.h>
+#include <errno.h>
+#include <err.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <setjmp.h>
+#include <sys/uio.h>
+
+#include "helpers.h"
+#include "kselftest.h"
+
+#ifdef __x86_64__
+#define TOTAL_TESTS 13
+#else
+#define TOTAL_TESTS 8
+#endif
+
+#ifdef __x86_64__
+# define VSYS(x) (x)
+#else
+# define VSYS(x) 0
+#endif
+
+#ifndef SYS_getcpu
+# ifdef __x86_64__
+# define SYS_getcpu 309
+# else
+# define SYS_getcpu 318
+# endif
+#endif
+
+/* max length of lines in /proc/self/maps - anything longer is skipped here */
+#define MAPS_LINE_LEN 128
+
+/* vsyscalls and vDSO */
+bool vsyscall_map_r = false, vsyscall_map_x = false;
+
+typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
+const gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
+gtod_t vdso_gtod;
+
+typedef int (*vgettime_t)(clockid_t, struct timespec *);
+vgettime_t vdso_gettime;
+
+typedef long (*time_func_t)(time_t *t);
+const time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
+time_func_t vdso_time;
+
+typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
+const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
+getcpu_t vdso_getcpu;
+
+static void init_vdso(void)
+{
+ void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
+ if (!vdso)
+ vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
+ if (!vdso) {
+ ksft_print_msg("[WARN] failed to find vDSO\n");
+ return;
+ }
+
+ vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday");
+ if (!vdso_gtod)
+ ksft_print_msg("[WARN] failed to find gettimeofday in vDSO\n");
+
+ vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
+ if (!vdso_gettime)
+ ksft_print_msg("[WARN] failed to find clock_gettime in vDSO\n");
+
+ vdso_time = (time_func_t)dlsym(vdso, "__vdso_time");
+ if (!vdso_time)
+ ksft_print_msg("[WARN] failed to find time in vDSO\n");
+
+ vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
+ if (!vdso_getcpu)
+ ksft_print_msg("[WARN] failed to find getcpu in vDSO\n");
+}
+
+/* syscalls */
+static inline long sys_gtod(struct timeval *tv, struct timezone *tz)
+{
+ return syscall(SYS_gettimeofday, tv, tz);
+}
+
+static inline long sys_time(time_t *t)
+{
+ return syscall(SYS_time, t);
+}
+
+static inline long sys_getcpu(unsigned * cpu, unsigned * node,
+ void* cache)
+{
+ return syscall(SYS_getcpu, cpu, node, cache);
+}
+
+static double tv_diff(const struct timeval *a, const struct timeval *b)
+{
+ return (double)(a->tv_sec - b->tv_sec) +
+ (double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6;
+}
+
+static void check_gtod(const struct timeval *tv_sys1,
+ const struct timeval *tv_sys2,
+ const struct timezone *tz_sys,
+ const char *which,
+ const struct timeval *tv_other,
+ const struct timezone *tz_other)
+{
+ double d1, d2;
+
+ if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest ||
+ tz_sys->tz_dsttime != tz_other->tz_dsttime))
+ ksft_print_msg("%s tz mismatch\n", which);
+
+ d1 = tv_diff(tv_other, tv_sys1);
+ d2 = tv_diff(tv_sys2, tv_other);
+
+ ksft_print_msg("%s time offsets: %lf %lf\n", which, d1, d2);
+
+ ksft_test_result(!(d1 < 0 || d2 < 0), "%s gettimeofday()'s timeval\n", which);
+}
+
+static void test_gtod(void)
+{
+ struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys;
+ struct timezone tz_sys, tz_vdso, tz_vsys;
+ long ret_vdso = -1;
+ long ret_vsys = -1;
+
+ ksft_print_msg("test gettimeofday()\n");
+
+ if (sys_gtod(&tv_sys1, &tz_sys) != 0)
+ ksft_exit_fail_msg("syscall gettimeofday: %s\n", strerror(errno));
+ if (vdso_gtod)
+ ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
+ if (vsyscall_map_x)
+ ret_vsys = vgtod(&tv_vsys, &tz_vsys);
+ if (sys_gtod(&tv_sys2, &tz_sys) != 0)
+ ksft_exit_fail_msg("syscall gettimeofday: %s\n", strerror(errno));
+
+ if (vdso_gtod) {
+ if (ret_vdso == 0)
+ check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso);
+ else
+ ksft_test_result_fail("vDSO gettimeofday() failed: %ld\n", ret_vdso);
+ } else {
+ ksft_test_result_skip("vdso_gtod isn't set\n");
+ }
+
+ if (vsyscall_map_x) {
+ if (ret_vsys == 0)
+ check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
+ else
+ ksft_test_result_fail("vsys gettimeofday() failed: %ld\n", ret_vsys);
+ } else {
+ ksft_test_result_skip("vsyscall_map_x isn't set\n");
+ }
+}
+
+static void test_time(void)
+{
+ long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0;
+ long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1;
+
+ ksft_print_msg("test time()\n");
+ t_sys1 = sys_time(&t2_sys1);
+ if (vdso_time)
+ t_vdso = vdso_time(&t2_vdso);
+ if (vsyscall_map_x)
+ t_vsys = vtime(&t2_vsys);
+ t_sys2 = sys_time(&t2_sys2);
+ if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
+ ksft_print_msg("syscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n",
+ t_sys1, t2_sys1, t_sys2, t2_sys2);
+ ksft_test_result_skip("vdso_time\n");
+ ksft_test_result_skip("vdso_time\n");
+ return;
+ }
+
+ if (vdso_time) {
+ if (t_vdso < 0 || t_vdso != t2_vdso)
+ ksft_test_result_fail("vDSO failed (ret:%ld output:%ld)\n",
+ t_vdso, t2_vdso);
+ else if (t_vdso < t_sys1 || t_vdso > t_sys2)
+ ksft_test_result_fail("vDSO returned the wrong time (%ld %ld %ld)\n",
+ t_sys1, t_vdso, t_sys2);
+ else
+ ksft_test_result_pass("vDSO time() is okay\n");
+ } else {
+ ksft_test_result_skip("vdso_time isn't set\n");
+ }
+
+ if (vsyscall_map_x) {
+ if (t_vsys < 0 || t_vsys != t2_vsys)
+ ksft_test_result_fail("vsyscall failed (ret:%ld output:%ld)\n",
+ t_vsys, t2_vsys);
+ else if (t_vsys < t_sys1 || t_vsys > t_sys2)
+ ksft_test_result_fail("vsyscall returned the wrong time (%ld %ld %ld)\n",
+ t_sys1, t_vsys, t_sys2);
+ else
+ ksft_test_result_pass("vsyscall time() is okay\n");
+ } else {
+ ksft_test_result_skip("vsyscall_map_x isn't set\n");
+ }
+}
+
+static void test_getcpu(int cpu)
+{
+ unsigned int cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys;
+ long ret_sys, ret_vdso = -1, ret_vsys = -1;
+ unsigned int node = 0;
+ bool have_node = false;
+ cpu_set_t cpuset;
+
+ ksft_print_msg("getcpu() on CPU %d\n", cpu);
+
+ CPU_ZERO(&cpuset);
+ CPU_SET(cpu, &cpuset);
+ if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
+ ksft_print_msg("failed to force CPU %d\n", cpu);
+ ksft_test_result_skip("vdso_getcpu\n");
+ ksft_test_result_skip("vsyscall_map_x\n");
+
+ return;
+ }
+
+ ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
+ if (vdso_getcpu)
+ ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
+ if (vsyscall_map_x)
+ ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
+
+ if (ret_sys == 0) {
+ if (cpu_sys != cpu)
+ ksft_print_msg("syscall reported CPU %u but should be %d\n",
+ cpu_sys, cpu);
+
+ have_node = true;
+ node = node_sys;
+ }
+
+ if (vdso_getcpu) {
+ if (ret_vdso) {
+ ksft_test_result_fail("vDSO getcpu() failed\n");
+ } else {
+ if (!have_node) {
+ have_node = true;
+ node = node_vdso;
+ }
+
+ if (cpu_vdso != cpu || node_vdso != node) {
+ if (cpu_vdso != cpu)
+ ksft_print_msg("vDSO reported CPU %u but should be %d\n",
+ cpu_vdso, cpu);
+ if (node_vdso != node)
+ ksft_print_msg("vDSO reported node %u but should be %u\n",
+ node_vdso, node);
+ ksft_test_result_fail("Wrong values\n");
+ } else {
+ ksft_test_result_pass("vDSO reported correct CPU and node\n");
+ }
+ }
+ } else {
+ ksft_test_result_skip("vdso_getcpu isn't set\n");
+ }
+
+ if (vsyscall_map_x) {
+ if (ret_vsys) {
+ ksft_test_result_fail("vsyscall getcpu() failed\n");
+ } else {
+ if (!have_node) {
+ have_node = true;
+ node = node_vsys;
+ }
+
+ if (cpu_vsys != cpu || node_vsys != node) {
+ if (cpu_vsys != cpu)
+ ksft_print_msg("vsyscall reported CPU %u but should be %d\n",
+ cpu_vsys, cpu);
+ if (node_vsys != node)
+ ksft_print_msg("vsyscall reported node %u but should be %u\n",
+ node_vsys, node);
+ ksft_test_result_fail("Wrong values\n");
+ } else {
+ ksft_test_result_pass("vsyscall reported correct CPU and node\n");
+ }
+ }
+ } else {
+ ksft_test_result_skip("vsyscall_map_x isn't set\n");
+ }
+}
+
+#ifdef __x86_64__
+
+static jmp_buf jmpbuf;
+static volatile unsigned long segv_err, segv_trapno;
+
+static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
+{
+ ucontext_t *ctx = (ucontext_t *)ctx_void;
+
+ segv_trapno = ctx->uc_mcontext.gregs[REG_TRAPNO];
+ segv_err = ctx->uc_mcontext.gregs[REG_ERR];
+ siglongjmp(jmpbuf, 1);
+}
+
+static void test_vsys_r(void)
+{
+ ksft_print_msg("Checking read access to the vsyscall page\n");
+ bool can_read;
+ if (sigsetjmp(jmpbuf, 1) == 0) {
+ *(volatile int *)0xffffffffff600000;
+ can_read = true;
+ } else {
+ can_read = false;
+ }
+
+ if (can_read && !vsyscall_map_r)
+ ksft_test_result_fail("We have read access, but we shouldn't\n");
+ else if (!can_read && vsyscall_map_r)
+ ksft_test_result_fail("We don't have read access, but we should\n");
+ else if (can_read)
+ ksft_test_result_pass("We have read access\n");
+ else
+ ksft_test_result_pass("We do not have read access (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
+}
+
+static void test_vsys_x(void)
+{
+ if (vsyscall_map_x) {
+ /* We already tested this adequately. */
+ ksft_test_result_pass("vsyscall_map_x is true\n");
+ return;
+ }
+
+ ksft_print_msg("Make sure that vsyscalls really cause a fault\n");
+
+ bool can_exec;
+ if (sigsetjmp(jmpbuf, 1) == 0) {
+ vgtod(NULL, NULL);
+ can_exec = true;
+ } else {
+ can_exec = false;
+ }
+
+ if (can_exec)
+ ksft_test_result_fail("Executing the vsyscall did not fault\n");
+ /* #GP or #PF (with X86_PF_INSTR) */
+ else if ((segv_trapno == 13) || ((segv_trapno == 14) && (segv_err & (1 << 4))))
+ ksft_test_result_pass("Executing the vsyscall page failed (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
+ else
+ ksft_test_result_fail("Execution failed with the wrong error (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
+}
+
+/*
+ * Debuggers expect ptrace() to be able to peek at the vsyscall page.
+ * Use process_vm_readv() as a proxy for ptrace() to test this. We
+ * want it to work in the vsyscall=emulate case and to fail in the
+ * vsyscall=xonly case.
+ *
+ * It's worth noting that this ABI is a bit nutty. write(2) can't
+ * read from the vsyscall page on any kernel version or mode. The
+ * fact that ptrace() ever worked was a nice courtesy of old kernels,
+ * but the code to support it is fairly gross.
+ */
+static void test_process_vm_readv(void)
+{
+ char buf[4096];
+ struct iovec local, remote;
+ int ret;
+
+ ksft_print_msg("process_vm_readv() from vsyscall page\n");
+
+ local.iov_base = buf;
+ local.iov_len = 4096;
+ remote.iov_base = (void *)0xffffffffff600000;
+ remote.iov_len = 4096;
+ ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
+ if (ret != 4096) {
+ /*
+ * We expect process_vm_readv() to work if and only if the
+ * vsyscall page is readable.
+ */
+ ksft_test_result(!vsyscall_map_r,
+ "process_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
+ return;
+ }
+
+ if (vsyscall_map_r)
+ ksft_test_result(!memcmp(buf, remote.iov_base, sizeof(buf)), "Read data\n");
+ else
+ ksft_test_result_fail("process_rm_readv() succeeded, but it should have failed in this configuration\n");
+}
+
+static void init_vsys(void)
+{
+ int nerrs = 0;
+ FILE *maps;
+ char line[MAPS_LINE_LEN];
+ bool found = false;
+
+ maps = fopen("/proc/self/maps", "r");
+ if (!maps) {
+ ksft_test_result_skip("Could not open /proc/self/maps -- assuming vsyscall is r-x\n");
+ vsyscall_map_r = true;
+ return;
+ }
+
+ while (fgets(line, MAPS_LINE_LEN, maps)) {
+ char r, x;
+ void *start, *end;
+ char name[MAPS_LINE_LEN];
+
+ /* sscanf() is safe here as strlen(name) >= strlen(line) */
+ if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
+ &start, &end, &r, &x, name) != 5)
+ continue;
+
+ if (strcmp(name, "[vsyscall]"))
+ continue;
+
+ ksft_print_msg("vsyscall map: %s", line);
+
+ if (start != (void *)0xffffffffff600000 ||
+ end != (void *)0xffffffffff601000) {
+ ksft_print_msg("address range is nonsense\n");
+ nerrs++;
+ }
+
+ ksft_print_msg("vsyscall permissions are %c-%c\n", r, x);
+ vsyscall_map_r = (r == 'r');
+ vsyscall_map_x = (x == 'x');
+
+ found = true;
+ break;
+ }
+
+ fclose(maps);
+
+ if (!found) {
+ ksft_print_msg("no vsyscall map in /proc/self/maps\n");
+ vsyscall_map_r = false;
+ vsyscall_map_x = false;
+ }
+
+ ksft_test_result(!nerrs, "vsyscall map\n");
+}
+
+static volatile sig_atomic_t num_vsyscall_traps;
+
+static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
+{
+ ucontext_t *ctx = (ucontext_t *)ctx_void;
+ unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP];
+
+ if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0)
+ num_vsyscall_traps++;
+}
+
+static void test_emulation(void)
+{
+ time_t tmp;
+ bool is_native;
+
+ if (!vsyscall_map_x) {
+ ksft_test_result_skip("vsyscall_map_x isn't set\n");
+ return;
+ }
+
+ ksft_print_msg("checking that vsyscalls are emulated\n");
+ sethandler(SIGTRAP, sigtrap, 0);
+ set_eflags(get_eflags() | X86_EFLAGS_TF);
+ vtime(&tmp);
+ set_eflags(get_eflags() & ~X86_EFLAGS_TF);
+
+ /*
+ * If vsyscalls are emulated, we expect a single trap in the
+ * vsyscall page -- the call instruction will trap with RIP
+ * pointing to the entry point before emulation takes over.
+ * In native mode, we expect two traps, since whatever code
+ * the vsyscall page contains will be more than just a ret
+ * instruction.
+ */
+ is_native = (num_vsyscall_traps > 1);
+
+ ksft_test_result(!is_native, "vsyscalls are %s (%d instructions in vsyscall page)\n",
+ (is_native ? "native" : "emulated"), (int)num_vsyscall_traps);
+}
+#endif
+
+int main(int argc, char **argv)
+{
+ int total_tests = TOTAL_TESTS;
+
+ ksft_print_header();
+ ksft_set_plan(total_tests);
+
+ init_vdso();
+#ifdef __x86_64__
+ init_vsys();
+#endif
+
+ test_gtod();
+ test_time();
+ test_getcpu(0);
+ test_getcpu(1);
+
+#ifdef __x86_64__
+ sethandler(SIGSEGV, sigsegv, 0);
+ test_vsys_r();
+ test_vsys_x();
+ test_process_vm_readv();
+ test_emulation();
+#endif
+
+ ksft_finished();
+}
generated by cgit (git 2.34.1) at 2025-12-25 10:08:51 +0000