This is the patch I'm using to evaluate the impact syscall user dispatch
has on native syscall (syscalls not redirected to userspace) when
enabled for the process and submiting syscalls though the unblocked
dispatch selector. It works by running a step to define a baseline of
the cost of executing sysinfo, then enabling SUD, and rerunning that
step.
On my test machine, an AMD Ryzen 5 1500X, I have the following results
with the latest version of syscall user dispatch patches.
root@olga:~# syscall_user_dispatch/sud_benchmark
Calibrating test set to last ~5 seconds...
test iterations = 37500000
Avg syscall time 134ns.
Caught sys_ff00
trapped_call_count 1, native_call_count 0.
Avg syscall time 147ns.
Interception overhead: 9.7% (+13ns).
Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
---
.../selftests/syscall_user_dispatch/Makefile | 2 +-
.../syscall_user_dispatch/sud_benchmark.c | 200 ++++++++++++++++++
2 files changed, 201 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
diff --git a/tools/testing/selftests/syscall_user_dispatch/Makefile b/tools/testing/selftests/syscall_user_dispatch/Makefile
index 8e15fa42bcda..03c120270953 100644
--- a/tools/testing/selftests/syscall_user_dispatch/Makefile
+++ b/tools/testing/selftests/syscall_user_dispatch/Makefile
@@ -5,5 +5,5 @@ LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
CFLAGS += -Wall -I$(LINUX_HDR_PATH)
-TEST_GEN_PROGS := sud_test
+TEST_GEN_PROGS := sud_test sud_benchmark
include ../lib.mk
diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
new file mode 100644
index 000000000000..6689f1183dbf
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020 Collabora Ltd.
+ *
+ * Benchmark and test syscall user dispatch
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <sys/sysinfo.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+
+#ifndef PR_SET_SYSCALL_USER_DISPATCH
+# define PR_SET_SYSCALL_USER_DISPATCH 59
+# define PR_SYS_DISPATCH_OFF 0
+# define PR_SYS_DISPATCH_ON 1
+#endif
+
+#ifdef __NR_syscalls
+# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */
+#else
+# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */
+#endif
+
+/*
+ * To test returning from a sigsys with selector blocked, the test
+ * requires some per-architecture support (i.e. knowledge about the
+ * signal trampoline address). On i386, we know it is on the vdso, and
+ * a small trampoline is open-coded for x86_64. Other architectures
+ * that have a trampoline in the vdso will support TEST_BLOCKED_RETURN
+ * out of the box, but don't enable them until they support syscall user
+ * dispatch.
+ */
+#if defined(__x86_64__) || defined(__i386__)
+#define TEST_BLOCKED_RETURN
+#endif
+
+#ifdef __x86_64__
+void* (syscall_dispatcher_start)(void);
+void* (syscall_dispatcher_end)(void);
+#else
+unsigned long syscall_dispatcher_start = 0;
+unsigned long syscall_dispatcher_end = 0;
+#endif
+
+unsigned long trapped_call_count = 0;
+unsigned long native_call_count = 0;
+
+char selector;
+#define SYSCALL_BLOCK (selector = PR_SYS_DISPATCH_ON)
+#define SYSCALL_UNBLOCK (selector = PR_SYS_DISPATCH_OFF)
+
+#define CALIBRATION_STEP 100000
+#define CALIBRATE_TO_SECS 5
+int factor;
+
+static double one_sysinfo_step(void)
+{
+ struct timespec t1, t2;
+ int i;
+ struct sysinfo info;
+
+ clock_gettime(CLOCK_MONOTONIC, &t1);
+ for (i = 0; i < CALIBRATION_STEP; i++)
+ sysinfo(&info);
+ clock_gettime(CLOCK_MONOTONIC, &t2);
+ return (t2.tv_sec - t1.tv_sec) + 1.0e-9 * (t2.tv_nsec - t1.tv_nsec);
+}
+
+static void calibrate_set(void)
+{
+ double elapsed = 0;
+
+ printf("Calibrating test set to last ~%d seconds...\n", CALIBRATE_TO_SECS);
+
+ while (elapsed < 1) {
+ elapsed += one_sysinfo_step();
+ factor += CALIBRATE_TO_SECS;
+ }
+
+ printf("test iterations = %d\n", CALIBRATION_STEP * factor);
+}
+
+static double perf_syscall(void)
+{
+ unsigned int i;
+ double partial = 0;
+
+ for (i = 0; i < factor; ++i)
+ partial += one_sysinfo_step()/(CALIBRATION_STEP*factor);
+ return partial;
+}
+
+static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
+{
+ char buf[1024];
+ int len;
+
+ SYSCALL_UNBLOCK;
+
+ /* printf and friends are not signal-safe. */
+ len = snprintf(buf, 1024, "Caught sys_%x\n", info->si_syscall);
+ write(1, buf, len);
+
+ if (info->si_syscall == MAGIC_SYSCALL_1)
+ trapped_call_count++;
+ else
+ native_call_count++;
+
+#ifdef TEST_BLOCKED_RETURN
+ SYSCALL_BLOCK;
+#endif
+
+#ifdef __x86_64__
+ __asm__ volatile("movq $0xf, %rax");
+ __asm__ volatile("leaveq");
+ __asm__ volatile("add $0x8, %rsp");
+ __asm__ volatile("syscall_dispatcher_start:");
+ __asm__ volatile("syscall");
+ __asm__ volatile("nop"); /* Landing pad within dispatcher area */
+ __asm__ volatile("syscall_dispatcher_end:");
+#endif
+
+}
+
+int main(void)
+{
+ struct sigaction act;
+ double time1, time2;
+ int ret;
+ sigset_t mask;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&mask);
+
+ act.sa_sigaction = handle_sigsys;
+ act.sa_flags = SA_SIGINFO;
+ act.sa_mask = mask;
+
+ calibrate_set();
+
+ time1 = perf_syscall();
+ printf("Avg syscall time %.0lfns.\n", time1 * 1.0e9);
+
+ ret = sigaction(SIGSYS, &act, NULL);
+ if (ret) {
+ perror("Error sigaction:");
+ exit(-1);
+ }
+
+ fprintf(stderr, "Enabling syscall trapping.\n");
+
+ if (prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON,
+ syscall_dispatcher_start,
+ (syscall_dispatcher_end - syscall_dispatcher_start + 1),
+ &selector)) {
+ perror("prctl failed\n");
+ exit(-1);
+ }
+
+ SYSCALL_BLOCK;
+ syscall(MAGIC_SYSCALL_1);
+
+#ifdef TEST_BLOCKED_RETURN
+ if (selector == PR_SYS_DISPATCH_OFF) {
+ fprintf(stderr, "Failed to return with selector blocked.\n");
+ exit(-1);
+ }
+#endif
+
+ SYSCALL_UNBLOCK;
+
+ if (!trapped_call_count) {
+ fprintf(stderr, "syscall trapping does not work.\n");
+ exit(-1);
+ }
+
+ time2 = perf_syscall();
+
+ if (native_call_count) {
+ perror("syscall trapping intercepted more syscalls than expected\n");
+ exit(-1);
+ }
+
+ printf("trapped_call_count %lu, native_call_count %lu.\n",
+ trapped_call_count, native_call_count);
+ printf("Avg syscall time %.0lfns.\n", time2 * 1.0e9);
+ printf("Interception overhead: %.1lf%% (+%.0lfns).\n",
+ 100.0 * (time2 / time1 - 1.0), 1.0e9 * (time2 - time1));
+ return 0;
+
+}
--
2.29.2
On Fri, Nov 27, 2020 at 02:32:37PM -0500, Gabriel Krisman Bertazi wrote:
> This is the patch I'm using to evaluate the impact syscall user dispatch
> has on native syscall (syscalls not redirected to userspace) when
> enabled for the process and submiting syscalls though the unblocked
> dispatch selector. It works by running a step to define a baseline of
> the cost of executing sysinfo, then enabling SUD, and rerunning that
> step.
>
> On my test machine, an AMD Ryzen 5 1500X, I have the following results
> with the latest version of syscall user dispatch patches.
>
> root@olga:~# syscall_user_dispatch/sud_benchmark
> Calibrating test set to last ~5 seconds...
> test iterations = 37500000
> Avg syscall time 134ns.
> Caught sys_ff00
> trapped_call_count 1, native_call_count 0.
> Avg syscall time 147ns.
> Interception overhead: 9.7% (+13ns).
>
> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
The following commit has been merged into the core/entry branch of tip:
Commit-ID: 3e8df777fbf4531a4ec740aae991090baed27856
Gitweb: https://git.kernel.org/tip/3e8df777fbf4531a4ec740aae991090baed27856
Author: Gabriel Krisman Bertazi <[email protected]>
AuthorDate: Fri, 27 Nov 2020 14:32:37 -05:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Wed, 02 Dec 2020 10:32:17 +01:00
selftests: Add benchmark for syscall user dispatch
This is the patch I'm using to evaluate the impact syscall user dispatch
has on native syscall (syscalls not redirected to userspace) when
enabled for the process and submiting syscalls though the unblocked
dispatch selector. It works by running a step to define a baseline of
the cost of executing sysinfo, then enabling SUD, and rerunning that
step.
On my test machine, an AMD Ryzen 5 1500X, I have the following results
with the latest version of syscall user dispatch patches.
root@olga:~# syscall_user_dispatch/sud_benchmark
Calibrating test set to last ~5 seconds...
test iterations = 37500000
Avg syscall time 134ns.
Caught sys_ff00
trapped_call_count 1, native_call_count 0.
Avg syscall time 147ns.
Interception overhead: 9.7% (+13ns).
Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Andy Lutomirski <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
tools/testing/selftests/syscall_user_dispatch/Makefile | 2 +-
tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c | 200 +++++++-
2 files changed, 201 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
diff --git a/tools/testing/selftests/syscall_user_dispatch/Makefile b/tools/testing/selftests/syscall_user_dispatch/Makefile
index 8e15fa4..03c1202 100644
--- a/tools/testing/selftests/syscall_user_dispatch/Makefile
+++ b/tools/testing/selftests/syscall_user_dispatch/Makefile
@@ -5,5 +5,5 @@ LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
CFLAGS += -Wall -I$(LINUX_HDR_PATH)
-TEST_GEN_PROGS := sud_test
+TEST_GEN_PROGS := sud_test sud_benchmark
include ../lib.mk
diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
new file mode 100644
index 0000000..6689f11
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020 Collabora Ltd.
+ *
+ * Benchmark and test syscall user dispatch
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <sys/sysinfo.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+
+#ifndef PR_SET_SYSCALL_USER_DISPATCH
+# define PR_SET_SYSCALL_USER_DISPATCH 59
+# define PR_SYS_DISPATCH_OFF 0
+# define PR_SYS_DISPATCH_ON 1
+#endif
+
+#ifdef __NR_syscalls
+# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */
+#else
+# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */
+#endif
+
+/*
+ * To test returning from a sigsys with selector blocked, the test
+ * requires some per-architecture support (i.e. knowledge about the
+ * signal trampoline address). On i386, we know it is on the vdso, and
+ * a small trampoline is open-coded for x86_64. Other architectures
+ * that have a trampoline in the vdso will support TEST_BLOCKED_RETURN
+ * out of the box, but don't enable them until they support syscall user
+ * dispatch.
+ */
+#if defined(__x86_64__) || defined(__i386__)
+#define TEST_BLOCKED_RETURN
+#endif
+
+#ifdef __x86_64__
+void* (syscall_dispatcher_start)(void);
+void* (syscall_dispatcher_end)(void);
+#else
+unsigned long syscall_dispatcher_start = 0;
+unsigned long syscall_dispatcher_end = 0;
+#endif
+
+unsigned long trapped_call_count = 0;
+unsigned long native_call_count = 0;
+
+char selector;
+#define SYSCALL_BLOCK (selector = PR_SYS_DISPATCH_ON)
+#define SYSCALL_UNBLOCK (selector = PR_SYS_DISPATCH_OFF)
+
+#define CALIBRATION_STEP 100000
+#define CALIBRATE_TO_SECS 5
+int factor;
+
+static double one_sysinfo_step(void)
+{
+ struct timespec t1, t2;
+ int i;
+ struct sysinfo info;
+
+ clock_gettime(CLOCK_MONOTONIC, &t1);
+ for (i = 0; i < CALIBRATION_STEP; i++)
+ sysinfo(&info);
+ clock_gettime(CLOCK_MONOTONIC, &t2);
+ return (t2.tv_sec - t1.tv_sec) + 1.0e-9 * (t2.tv_nsec - t1.tv_nsec);
+}
+
+static void calibrate_set(void)
+{
+ double elapsed = 0;
+
+ printf("Calibrating test set to last ~%d seconds...\n", CALIBRATE_TO_SECS);
+
+ while (elapsed < 1) {
+ elapsed += one_sysinfo_step();
+ factor += CALIBRATE_TO_SECS;
+ }
+
+ printf("test iterations = %d\n", CALIBRATION_STEP * factor);
+}
+
+static double perf_syscall(void)
+{
+ unsigned int i;
+ double partial = 0;
+
+ for (i = 0; i < factor; ++i)
+ partial += one_sysinfo_step()/(CALIBRATION_STEP*factor);
+ return partial;
+}
+
+static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
+{
+ char buf[1024];
+ int len;
+
+ SYSCALL_UNBLOCK;
+
+ /* printf and friends are not signal-safe. */
+ len = snprintf(buf, 1024, "Caught sys_%x\n", info->si_syscall);
+ write(1, buf, len);
+
+ if (info->si_syscall == MAGIC_SYSCALL_1)
+ trapped_call_count++;
+ else
+ native_call_count++;
+
+#ifdef TEST_BLOCKED_RETURN
+ SYSCALL_BLOCK;
+#endif
+
+#ifdef __x86_64__
+ __asm__ volatile("movq $0xf, %rax");
+ __asm__ volatile("leaveq");
+ __asm__ volatile("add $0x8, %rsp");
+ __asm__ volatile("syscall_dispatcher_start:");
+ __asm__ volatile("syscall");
+ __asm__ volatile("nop"); /* Landing pad within dispatcher area */
+ __asm__ volatile("syscall_dispatcher_end:");
+#endif
+
+}
+
+int main(void)
+{
+ struct sigaction act;
+ double time1, time2;
+ int ret;
+ sigset_t mask;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&mask);
+
+ act.sa_sigaction = handle_sigsys;
+ act.sa_flags = SA_SIGINFO;
+ act.sa_mask = mask;
+
+ calibrate_set();
+
+ time1 = perf_syscall();
+ printf("Avg syscall time %.0lfns.\n", time1 * 1.0e9);
+
+ ret = sigaction(SIGSYS, &act, NULL);
+ if (ret) {
+ perror("Error sigaction:");
+ exit(-1);
+ }
+
+ fprintf(stderr, "Enabling syscall trapping.\n");
+
+ if (prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON,
+ syscall_dispatcher_start,
+ (syscall_dispatcher_end - syscall_dispatcher_start + 1),
+ &selector)) {
+ perror("prctl failed\n");
+ exit(-1);
+ }
+
+ SYSCALL_BLOCK;
+ syscall(MAGIC_SYSCALL_1);
+
+#ifdef TEST_BLOCKED_RETURN
+ if (selector == PR_SYS_DISPATCH_OFF) {
+ fprintf(stderr, "Failed to return with selector blocked.\n");
+ exit(-1);
+ }
+#endif
+
+ SYSCALL_UNBLOCK;
+
+ if (!trapped_call_count) {
+ fprintf(stderr, "syscall trapping does not work.\n");
+ exit(-1);
+ }
+
+ time2 = perf_syscall();
+
+ if (native_call_count) {
+ perror("syscall trapping intercepted more syscalls than expected\n");
+ exit(-1);
+ }
+
+ printf("trapped_call_count %lu, native_call_count %lu.\n",
+ trapped_call_count, native_call_count);
+ printf("Avg syscall time %.0lfns.\n", time2 * 1.0e9);
+ printf("Interception overhead: %.1lf%% (+%.0lfns).\n",
+ 100.0 * (time2 / time1 - 1.0), 1.0e9 * (time2 - time1));
+ return 0;
+
+}
The following commit has been merged into the core/entry branch of tip:
Commit-ID: d87ae0fa21c26db2d7c66f22dee9c27ecda48ce2
Gitweb: https://git.kernel.org/tip/d87ae0fa21c26db2d7c66f22dee9c27ecda48ce2
Author: Gabriel Krisman Bertazi <[email protected]>
AuthorDate: Fri, 27 Nov 2020 14:32:37 -05:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Wed, 02 Dec 2020 15:07:57 +01:00
selftests: Add benchmark for syscall user dispatch
This is the patch I'm using to evaluate the impact syscall user dispatch
has on native syscall (syscalls not redirected to userspace) when
enabled for the process and submiting syscalls though the unblocked
dispatch selector. It works by running a step to define a baseline of
the cost of executing sysinfo, then enabling SUD, and rerunning that
step.
On my test machine, an AMD Ryzen 5 1500X, I have the following results
with the latest version of syscall user dispatch patches.
root@olga:~# syscall_user_dispatch/sud_benchmark
Calibrating test set to last ~5 seconds...
test iterations = 37500000
Avg syscall time 134ns.
Caught sys_ff00
trapped_call_count 1, native_call_count 0.
Avg syscall time 147ns.
Interception overhead: 9.7% (+13ns).
Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Andy Lutomirski <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
tools/testing/selftests/syscall_user_dispatch/Makefile | 2 +-
tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c | 200 +++++++-
2 files changed, 201 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
diff --git a/tools/testing/selftests/syscall_user_dispatch/Makefile b/tools/testing/selftests/syscall_user_dispatch/Makefile
index 8e15fa4..03c1202 100644
--- a/tools/testing/selftests/syscall_user_dispatch/Makefile
+++ b/tools/testing/selftests/syscall_user_dispatch/Makefile
@@ -5,5 +5,5 @@ LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
CFLAGS += -Wall -I$(LINUX_HDR_PATH)
-TEST_GEN_PROGS := sud_test
+TEST_GEN_PROGS := sud_test sud_benchmark
include ../lib.mk
diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
new file mode 100644
index 0000000..6689f11
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020 Collabora Ltd.
+ *
+ * Benchmark and test syscall user dispatch
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <sys/sysinfo.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+
+#ifndef PR_SET_SYSCALL_USER_DISPATCH
+# define PR_SET_SYSCALL_USER_DISPATCH 59
+# define PR_SYS_DISPATCH_OFF 0
+# define PR_SYS_DISPATCH_ON 1
+#endif
+
+#ifdef __NR_syscalls
+# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */
+#else
+# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */
+#endif
+
+/*
+ * To test returning from a sigsys with selector blocked, the test
+ * requires some per-architecture support (i.e. knowledge about the
+ * signal trampoline address). On i386, we know it is on the vdso, and
+ * a small trampoline is open-coded for x86_64. Other architectures
+ * that have a trampoline in the vdso will support TEST_BLOCKED_RETURN
+ * out of the box, but don't enable them until they support syscall user
+ * dispatch.
+ */
+#if defined(__x86_64__) || defined(__i386__)
+#define TEST_BLOCKED_RETURN
+#endif
+
+#ifdef __x86_64__
+void* (syscall_dispatcher_start)(void);
+void* (syscall_dispatcher_end)(void);
+#else
+unsigned long syscall_dispatcher_start = 0;
+unsigned long syscall_dispatcher_end = 0;
+#endif
+
+unsigned long trapped_call_count = 0;
+unsigned long native_call_count = 0;
+
+char selector;
+#define SYSCALL_BLOCK (selector = PR_SYS_DISPATCH_ON)
+#define SYSCALL_UNBLOCK (selector = PR_SYS_DISPATCH_OFF)
+
+#define CALIBRATION_STEP 100000
+#define CALIBRATE_TO_SECS 5
+int factor;
+
+static double one_sysinfo_step(void)
+{
+ struct timespec t1, t2;
+ int i;
+ struct sysinfo info;
+
+ clock_gettime(CLOCK_MONOTONIC, &t1);
+ for (i = 0; i < CALIBRATION_STEP; i++)
+ sysinfo(&info);
+ clock_gettime(CLOCK_MONOTONIC, &t2);
+ return (t2.tv_sec - t1.tv_sec) + 1.0e-9 * (t2.tv_nsec - t1.tv_nsec);
+}
+
+static void calibrate_set(void)
+{
+ double elapsed = 0;
+
+ printf("Calibrating test set to last ~%d seconds...\n", CALIBRATE_TO_SECS);
+
+ while (elapsed < 1) {
+ elapsed += one_sysinfo_step();
+ factor += CALIBRATE_TO_SECS;
+ }
+
+ printf("test iterations = %d\n", CALIBRATION_STEP * factor);
+}
+
+static double perf_syscall(void)
+{
+ unsigned int i;
+ double partial = 0;
+
+ for (i = 0; i < factor; ++i)
+ partial += one_sysinfo_step()/(CALIBRATION_STEP*factor);
+ return partial;
+}
+
+static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
+{
+ char buf[1024];
+ int len;
+
+ SYSCALL_UNBLOCK;
+
+ /* printf and friends are not signal-safe. */
+ len = snprintf(buf, 1024, "Caught sys_%x\n", info->si_syscall);
+ write(1, buf, len);
+
+ if (info->si_syscall == MAGIC_SYSCALL_1)
+ trapped_call_count++;
+ else
+ native_call_count++;
+
+#ifdef TEST_BLOCKED_RETURN
+ SYSCALL_BLOCK;
+#endif
+
+#ifdef __x86_64__
+ __asm__ volatile("movq $0xf, %rax");
+ __asm__ volatile("leaveq");
+ __asm__ volatile("add $0x8, %rsp");
+ __asm__ volatile("syscall_dispatcher_start:");
+ __asm__ volatile("syscall");
+ __asm__ volatile("nop"); /* Landing pad within dispatcher area */
+ __asm__ volatile("syscall_dispatcher_end:");
+#endif
+
+}
+
+int main(void)
+{
+ struct sigaction act;
+ double time1, time2;
+ int ret;
+ sigset_t mask;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&mask);
+
+ act.sa_sigaction = handle_sigsys;
+ act.sa_flags = SA_SIGINFO;
+ act.sa_mask = mask;
+
+ calibrate_set();
+
+ time1 = perf_syscall();
+ printf("Avg syscall time %.0lfns.\n", time1 * 1.0e9);
+
+ ret = sigaction(SIGSYS, &act, NULL);
+ if (ret) {
+ perror("Error sigaction:");
+ exit(-1);
+ }
+
+ fprintf(stderr, "Enabling syscall trapping.\n");
+
+ if (prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON,
+ syscall_dispatcher_start,
+ (syscall_dispatcher_end - syscall_dispatcher_start + 1),
+ &selector)) {
+ perror("prctl failed\n");
+ exit(-1);
+ }
+
+ SYSCALL_BLOCK;
+ syscall(MAGIC_SYSCALL_1);
+
+#ifdef TEST_BLOCKED_RETURN
+ if (selector == PR_SYS_DISPATCH_OFF) {
+ fprintf(stderr, "Failed to return with selector blocked.\n");
+ exit(-1);
+ }
+#endif
+
+ SYSCALL_UNBLOCK;
+
+ if (!trapped_call_count) {
+ fprintf(stderr, "syscall trapping does not work.\n");
+ exit(-1);
+ }
+
+ time2 = perf_syscall();
+
+ if (native_call_count) {
+ perror("syscall trapping intercepted more syscalls than expected\n");
+ exit(-1);
+ }
+
+ printf("trapped_call_count %lu, native_call_count %lu.\n",
+ trapped_call_count, native_call_count);
+ printf("Avg syscall time %.0lfns.\n", time2 * 1.0e9);
+ printf("Interception overhead: %.1lf%% (+%.0lfns).\n",
+ 100.0 * (time2 / time1 - 1.0), 1.0e9 * (time2 - time1));
+ return 0;
+
+}