KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

7 files changed, 1179 insertions, 0 deletions

diff --git a/tools/testing/selftests/ptrace/.gitignore b/tools/testing/selftests/ptrace/.gitignore
new file mode 100644
index 000000000..f6be8efd5
--- /dev/null
+++ b/tools/testing/selftests/ptrace/.gitignore
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+get_syscall_info
+get_set_sud
+peeksiginfo
+vmaccess
+set_syscall_info
diff --git a/tools/testing/selftests/ptrace/Makefile b/tools/testing/selftests/ptrace/Makefile
new file mode 100644
index 000000000..c5e0b76ba
--- /dev/null
+++ b/tools/testing/selftests/ptrace/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -std=c99 -pthread -Wall $(KHDR_INCLUDES)
+
+TEST_GEN_PROGS := get_syscall_info set_syscall_info peeksiginfo vmaccess get_set_sud
+
+include ../lib.mk
diff --git a/tools/testing/selftests/ptrace/get_set_sud.c b/tools/testing/selftests/ptrace/get_set_sud.c
new file mode 100644
index 000000000..2e619c759
--- /dev/null
+++ b/tools/testing/selftests/ptrace/get_set_sud.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include "kselftest_harness.h"
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+#include <sys/prctl.h>
+
+#include "linux/ptrace.h"
+
+static int sys_ptrace(int request, pid_t pid, void *addr, void *data)
+{
+	return syscall(SYS_ptrace, request, pid, addr, data);
+}
+
+TEST(get_set_sud)
+{
+	struct ptrace_sud_config config;
+	pid_t child;
+	int ret = 0;
+	int status;
+
+	child = fork();
+	ASSERT_GE(child, 0);
+	if (child == 0) {
+		ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) {
+			TH_LOG("PTRACE_TRACEME: %m");
+		}
+		kill(getpid(), SIGSTOP);
+		_exit(1);
+	}
+
+	waitpid(child, &status, 0);
+
+	memset(&config, 0xff, sizeof(config));
+	config.mode = PR_SYS_DISPATCH_ON;
+
+	ret = sys_ptrace(PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG, child,
+			 (void *)sizeof(config), &config);
+
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(config.mode, PR_SYS_DISPATCH_OFF);
+	ASSERT_EQ(config.selector, 0);
+	ASSERT_EQ(config.offset, 0);
+	ASSERT_EQ(config.len, 0);
+
+	config.mode = PR_SYS_DISPATCH_ON;
+	config.selector = 0;
+	config.offset = 0x400000;
+	config.len = 0x1000;
+
+	ret = sys_ptrace(PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG, child,
+			 (void *)sizeof(config), &config);
+
+	ASSERT_EQ(ret, 0);
+
+	memset(&config, 1, sizeof(config));
+	ret = sys_ptrace(PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG, child,
+			 (void *)sizeof(config), &config);
+
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(config.mode, PR_SYS_DISPATCH_ON);
+	ASSERT_EQ(config.selector, 0);
+	ASSERT_EQ(config.offset, 0x400000);
+	ASSERT_EQ(config.len, 0x1000);
+
+	kill(child, SIGKILL);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/ptrace/get_syscall_info.c b/tools/testing/selftests/ptrace/get_syscall_info.c
new file mode 100644
index 000000000..3f5c3a9fd
--- /dev/null
+++ b/tools/testing/selftests/ptrace/get_syscall_info.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018 Dmitry V. Levin <ldv@altlinux.org>
+ * All rights reserved.
+ *
+ * Check whether PTRACE_GET_SYSCALL_INFO semantics implemented in the kernel
+ * matches userspace expectations.
+ */
+
+#include "kselftest_harness.h"
+#include <err.h>
+#include <signal.h>
+#include <asm/unistd.h>
+#include "linux/ptrace.h"
+
+static int
+kill_tracee(pid_t pid)
+{
+	if (!pid)
+		return 0;
+
+	int saved_errno = errno;
+
+	int rc = kill(pid, SIGKILL);
+
+	errno = saved_errno;
+	return rc;
+}
+
+static long
+sys_ptrace(int request, pid_t pid, unsigned long addr, unsigned long data)
+{
+	return syscall(__NR_ptrace, request, pid, addr, data);
+}
+
+#define LOG_KILL_TRACEE(fmt, ...)				\
+	do {							\
+		kill_tracee(pid);				\
+		TH_LOG("wait #%d: " fmt,			\
+		       ptrace_stop, ##__VA_ARGS__);		\
+	} while (0)
+
+TEST(get_syscall_info)
+{
+	static const unsigned long args[][7] = {
+		/* a sequence of architecture-agnostic syscalls */
+		{
+			__NR_chdir,
+			(unsigned long) "",
+			0xbad1fed1,
+			0xbad2fed2,
+			0xbad3fed3,
+			0xbad4fed4,
+			0xbad5fed5
+		},
+		{
+			__NR_gettid,
+			0xcaf0bea0,
+			0xcaf1bea1,
+			0xcaf2bea2,
+			0xcaf3bea3,
+			0xcaf4bea4,
+			0xcaf5bea5
+		},
+		{
+			__NR_exit_group,
+			0,
+			0xfac1c0d1,
+			0xfac2c0d2,
+			0xfac3c0d3,
+			0xfac4c0d4,
+			0xfac5c0d5
+		}
+	};
+	const unsigned long *exp_args;
+
+	pid_t pid = fork();
+
+	ASSERT_LE(0, pid) {
+		TH_LOG("fork: %m");
+	}
+
+	if (pid == 0) {
+		/* get the pid before PTRACE_TRACEME */
+		pid = getpid();
+		ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) {
+			TH_LOG("PTRACE_TRACEME: %m");
+		}
+		ASSERT_EQ(0, kill(pid, SIGSTOP)) {
+			/* cannot happen */
+			TH_LOG("kill SIGSTOP: %m");
+		}
+		for (unsigned int i = 0; i < ARRAY_SIZE(args); ++i) {
+			syscall(args[i][0],
+				args[i][1], args[i][2], args[i][3],
+				args[i][4], args[i][5], args[i][6]);
+		}
+		/* unreachable */
+		_exit(1);
+	}
+
+	const struct {
+		unsigned int is_error;
+		int rval;
+	} *exp_param, exit_param[] = {
+		{ 1, -ENOENT },	/* chdir */
+		{ 0, pid }	/* gettid */
+	};
+
+	unsigned int ptrace_stop;
+
+	for (ptrace_stop = 0; ; ++ptrace_stop) {
+		struct ptrace_syscall_info info = {
+			.op = 0xff	/* invalid PTRACE_SYSCALL_INFO_* op */
+		};
+		const size_t size = sizeof(info);
+		const int expected_none_size =
+			(void *) &info.entry - (void *) &info;
+		const int expected_entry_size =
+			(void *) &info.entry.args[6] - (void *) &info;
+		const int expected_exit_size =
+			(void *) (&info.exit.is_error + 1) -
+			(void *) &info;
+		int status;
+		long rc;
+
+		ASSERT_EQ(pid, wait(&status)) {
+			/* cannot happen */
+			LOG_KILL_TRACEE("wait: %m");
+		}
+		if (WIFEXITED(status)) {
+			pid = 0;	/* the tracee is no more */
+			ASSERT_EQ(0, WEXITSTATUS(status));
+			break;
+		}
+		ASSERT_FALSE(WIFSIGNALED(status)) {
+			pid = 0;	/* the tracee is no more */
+			LOG_KILL_TRACEE("unexpected signal %u",
+					WTERMSIG(status));
+		}
+		ASSERT_TRUE(WIFSTOPPED(status)) {
+			/* cannot happen */
+			LOG_KILL_TRACEE("unexpected wait status %#x", status);
+		}
+
+		switch (WSTOPSIG(status)) {
+		case SIGSTOP:
+			ASSERT_EQ(0, ptrace_stop) {
+				LOG_KILL_TRACEE("unexpected signal stop");
+			}
+			ASSERT_EQ(0, sys_ptrace(PTRACE_SETOPTIONS, pid, 0,
+						PTRACE_O_TRACESYSGOOD)) {
+				LOG_KILL_TRACEE("PTRACE_SETOPTIONS: %m");
+			}
+			ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+						      pid, size,
+						      (unsigned long) &info))) {
+				LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
+			}
+			ASSERT_EQ(expected_none_size, rc) {
+				LOG_KILL_TRACEE("signal stop mismatch");
+			}
+			ASSERT_EQ(PTRACE_SYSCALL_INFO_NONE, info.op) {
+				LOG_KILL_TRACEE("signal stop mismatch");
+			}
+			ASSERT_TRUE(info.arch) {
+				LOG_KILL_TRACEE("signal stop mismatch");
+			}
+			ASSERT_TRUE(info.instruction_pointer) {
+				LOG_KILL_TRACEE("signal stop mismatch");
+			}
+			ASSERT_TRUE(info.stack_pointer) {
+				LOG_KILL_TRACEE("signal stop mismatch");
+			}
+			break;
+
+		case SIGTRAP | 0x80:
+			ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+						      pid, size,
+						      (unsigned long) &info))) {
+				LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
+			}
+			switch (ptrace_stop) {
+			case 1: /* entering chdir */
+			case 3: /* entering gettid */
+			case 5: /* entering exit_group */
+				exp_args = args[ptrace_stop / 2];
+				ASSERT_EQ(expected_entry_size, rc) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(PTRACE_SYSCALL_INFO_ENTRY, info.op) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_TRUE(info.arch) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_TRUE(info.instruction_pointer) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_TRUE(info.stack_pointer) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[0], info.entry.nr) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[1], info.entry.args[0]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[2], info.entry.args[1]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[3], info.entry.args[2]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[4], info.entry.args[3]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[5], info.entry.args[4]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				ASSERT_EQ(exp_args[6], info.entry.args[5]) {
+					LOG_KILL_TRACEE("entry stop mismatch");
+				}
+				break;
+			case 2: /* exiting chdir */
+			case 4: /* exiting gettid */
+				exp_param = &exit_param[ptrace_stop / 2 - 1];
+				ASSERT_EQ(expected_exit_size, rc) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_EQ(PTRACE_SYSCALL_INFO_EXIT, info.op) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_TRUE(info.arch) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_TRUE(info.instruction_pointer) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_TRUE(info.stack_pointer) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_EQ(exp_param->is_error,
+					  info.exit.is_error) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				ASSERT_EQ(exp_param->rval, info.exit.rval) {
+					LOG_KILL_TRACEE("exit stop mismatch");
+				}
+				break;
+			default:
+				LOG_KILL_TRACEE("unexpected syscall stop");
+				abort();
+			}
+			break;
+
+		default:
+			LOG_KILL_TRACEE("unexpected stop signal %#x",
+					WSTOPSIG(status));
+			abort();
+		}
+
+		ASSERT_EQ(0, sys_ptrace(PTRACE_SYSCALL, pid, 0, 0)) {
+			LOG_KILL_TRACEE("PTRACE_SYSCALL: %m");
+		}
+	}
+
+	ASSERT_EQ(ARRAY_SIZE(args) * 2, ptrace_stop);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/ptrace/peeksiginfo.c b/tools/testing/selftests/ptrace/peeksiginfo.c
new file mode 100644
index 000000000..2f345d11e
--- /dev/null
+++ b/tools/testing/selftests/ptrace/peeksiginfo.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <linux/types.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+#include <sys/user.h>
+#include <sys/mman.h>
+
+#include "linux/ptrace.h"
+
+static int sys_rt_sigqueueinfo(pid_t tgid, int sig, siginfo_t *uinfo)
+{
+	return syscall(SYS_rt_sigqueueinfo, tgid, sig, uinfo);
+}
+
+static int sys_rt_tgsigqueueinfo(pid_t tgid, pid_t tid,
+					int sig, siginfo_t *uinfo)
+{
+	return syscall(SYS_rt_tgsigqueueinfo, tgid, tid, sig, uinfo);
+}
+
+static int sys_ptrace(int request, pid_t pid, void *addr, void *data)
+{
+	return syscall(SYS_ptrace, request, pid, addr, data);
+}
+
+#define SIGNR 10
+#define TEST_SICODE_PRIV	-1
+#define TEST_SICODE_SHARE	-2
+
+#ifndef PAGE_SIZE
+#define PAGE_SIZE sysconf(_SC_PAGESIZE)
+#endif
+
+#define err(fmt, ...)						\
+		fprintf(stderr,					\
+			"Error (%s:%d): " fmt,			\
+			__FILE__, __LINE__, ##__VA_ARGS__)
+
+static int check_error_paths(pid_t child)
+{
+	struct ptrace_peeksiginfo_args arg;
+	int ret, exit_code = -1;
+	void *addr_rw, *addr_ro;
+
+	/*
+	 * Allocate two contiguous pages. The first one is for read-write,
+	 * another is for read-only.
+	 */
+	addr_rw = mmap(NULL, 2 * PAGE_SIZE, PROT_READ | PROT_WRITE,
+				MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (addr_rw == MAP_FAILED) {
+		err("mmap() failed: %m\n");
+		return 1;
+	}
+
+	addr_ro = mmap(addr_rw + PAGE_SIZE, PAGE_SIZE, PROT_READ,
+			MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
+	if (addr_ro == MAP_FAILED) {
+		err("mmap() failed: %m\n");
+		goto out;
+	}
+
+	arg.nr = SIGNR;
+	arg.off = 0;
+
+	/* Unsupported flags */
+	arg.flags = ~0;
+	ret = sys_ptrace(PTRACE_PEEKSIGINFO, child, &arg, addr_rw);
+	if (ret != -1 || errno != EINVAL) {
+		err("sys_ptrace() returns %d (expected -1),"
+				" errno %d (expected %d): %m\n",
+				ret, errno, EINVAL);
+		goto out;
+	}
+	arg.flags = 0;
+
+	/* A part of the buffer is read-only */
+	ret = sys_ptrace(PTRACE_PEEKSIGINFO, child, &arg,
+					addr_ro - sizeof(siginfo_t) * 2);
+	if (ret != 2) {
+		err("sys_ptrace() returns %d (expected 2): %m\n", ret);
+		goto out;
+	}
+
+	/* Read-only buffer */
+	ret = sys_ptrace(PTRACE_PEEKSIGINFO, child, &arg, addr_ro);
+	if (ret != -1 && errno != EFAULT) {
+		err("sys_ptrace() returns %d (expected -1),"
+				" errno %d (expected %d): %m\n",
+				ret, errno, EFAULT);
+		goto out;
+	}
+
+	exit_code = 0;
+out:
+	munmap(addr_rw, 2 * PAGE_SIZE);
+	return exit_code;
+}
+
+int check_direct_path(pid_t child, int shared, int nr)
+{
+	struct ptrace_peeksiginfo_args arg = {.flags = 0, .nr = nr, .off = 0};
+	int i, j, ret, exit_code = -1;
+	siginfo_t siginfo[SIGNR];
+	int si_code;
+
+	if (shared == 1) {
+		arg.flags = PTRACE_PEEKSIGINFO_SHARED;
+		si_code = TEST_SICODE_SHARE;
+	} else {
+		arg.flags = 0;
+		si_code = TEST_SICODE_PRIV;
+	}
+
+	for (i = 0; i < SIGNR; ) {
+		arg.off = i;
+		ret = sys_ptrace(PTRACE_PEEKSIGINFO, child, &arg, siginfo);
+		if (ret == -1) {
+			err("ptrace() failed: %m\n");
+			goto out;
+		}
+
+		if (ret == 0)
+			break;
+
+		for (j = 0; j < ret; j++, i++) {
+			if (siginfo[j].si_code == si_code &&
+			    siginfo[j].si_int == i)
+				continue;
+
+			err("%d: Wrong siginfo i=%d si_code=%d si_int=%d\n",
+			     shared, i, siginfo[j].si_code, siginfo[j].si_int);
+			goto out;
+		}
+	}
+
+	if (i != SIGNR) {
+		err("Only %d signals were read\n", i);
+		goto out;
+	}
+
+	exit_code = 0;
+out:
+	return exit_code;
+}
+
+int main(int argc, char *argv[])
+{
+	siginfo_t siginfo;
+	int i, exit_code = 1;
+	sigset_t blockmask;
+	pid_t child;
+
+	sigemptyset(&blockmask);
+	sigaddset(&blockmask, SIGRTMIN);
+	sigprocmask(SIG_BLOCK, &blockmask, NULL);
+
+	child = fork();
+	if (child == -1) {
+		err("fork() failed: %m");
+		return 1;
+	} else if (child == 0) {
+		pid_t ppid = getppid();
+		while (1) {
+			if (ppid != getppid())
+				break;
+			sleep(1);
+		}
+		return 1;
+	}
+
+	/* Send signals in process-wide and per-thread queues */
+	for (i = 0; i < SIGNR; i++) {
+		siginfo.si_code = TEST_SICODE_SHARE;
+		siginfo.si_int = i;
+		sys_rt_sigqueueinfo(child, SIGRTMIN, &siginfo);
+
+		siginfo.si_code = TEST_SICODE_PRIV;
+		siginfo.si_int = i;
+		sys_rt_tgsigqueueinfo(child, child, SIGRTMIN, &siginfo);
+	}
+
+	if (sys_ptrace(PTRACE_ATTACH, child, NULL, NULL) == -1)
+		return 1;
+
+	waitpid(child, NULL, 0);
+
+	/* Dump signals one by one*/
+	if (check_direct_path(child, 0, 1))
+		goto out;
+	/* Dump all signals for one call */
+	if (check_direct_path(child, 0, SIGNR))
+		goto out;
+
+	/*
+	 * Dump signal from the process-wide queue.
+	 * The number of signals is not multiple to the buffer size
+	 */
+	if (check_direct_path(child, 1, 3))
+		goto out;
+
+	if (check_error_paths(child))
+		goto out;
+
+	printf("PASS\n");
+	exit_code = 0;
+out:
+	if (sys_ptrace(PTRACE_KILL, child, NULL, NULL) == -1)
+		return 1;
+
+	waitpid(child, NULL, 0);
+
+	return exit_code;
+}
diff --git a/tools/testing/selftests/ptrace/set_syscall_info.c b/tools/testing/selftests/ptrace/set_syscall_info.c
new file mode 100644
index 000000000..1cc411a41
--- /dev/null
+++ b/tools/testing/selftests/ptrace/set_syscall_info.c
@@ -0,0 +1,519 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018-2025 Dmitry V. Levin <ldv@strace.io>
+ * All rights reserved.
+ *
+ * Check whether PTRACE_SET_SYSCALL_INFO semantics implemented in the kernel
+ * matches userspace expectations.
+ */
+
+#include "kselftest_harness.h"
+#include <err.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <asm/unistd.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+
+#if defined(_MIPS_SIM) && _MIPS_SIM == _MIPS_SIM_NABI32
+/*
+ * MIPS N32 is the only architecture where __kernel_ulong_t
+ * does not match the bitness of syscall arguments.
+ */
+typedef unsigned long long kernel_ulong_t;
+#else
+typedef __kernel_ulong_t kernel_ulong_t;
+#endif
+
+struct si_entry {
+	int nr;
+	kernel_ulong_t args[6];
+};
+struct si_exit {
+	unsigned int is_error;
+	int rval;
+};
+
+static unsigned int ptrace_stop;
+static pid_t tracee_pid;
+
+static int
+kill_tracee(pid_t pid)
+{
+	if (!pid)
+		return 0;
+
+	int saved_errno = errno;
+
+	int rc = kill(pid, SIGKILL);
+
+	errno = saved_errno;
+	return rc;
+}
+
+static long
+sys_ptrace(int request, pid_t pid, unsigned long addr, unsigned long data)
+{
+	return syscall(__NR_ptrace, request, pid, addr, data);
+}
+
+#define LOG_KILL_TRACEE(fmt, ...)				\
+	do {							\
+		kill_tracee(tracee_pid);			\
+		TH_LOG("wait #%d: " fmt,			\
+		       ptrace_stop, ##__VA_ARGS__);		\
+	} while (0)
+
+static void
+check_psi_entry(struct __test_metadata *_metadata,
+		const struct ptrace_syscall_info *info,
+		const struct si_entry *exp_entry,
+		const char *text)
+{
+	unsigned int i;
+	int exp_nr = exp_entry->nr;
+#if defined __s390__ || defined __s390x__
+	/* s390 is the only architecture that has 16-bit syscall numbers */
+	exp_nr &= 0xffff;
+#endif
+
+	ASSERT_EQ(PTRACE_SYSCALL_INFO_ENTRY, info->op) {
+		LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+	}
+	ASSERT_TRUE(info->arch) {
+		LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+	}
+	ASSERT_TRUE(info->instruction_pointer) {
+		LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+	}
+	ASSERT_TRUE(info->stack_pointer) {
+		LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+	}
+	ASSERT_EQ(exp_nr, info->entry.nr) {
+		LOG_KILL_TRACEE("%s: syscall nr mismatch", text);
+	}
+	for (i = 0; i < ARRAY_SIZE(exp_entry->args); ++i) {
+		ASSERT_EQ(exp_entry->args[i], info->entry.args[i]) {
+			LOG_KILL_TRACEE("%s: syscall arg #%u mismatch",
+					text, i);
+		}
+	}
+}
+
+static void
+check_psi_exit(struct __test_metadata *_metadata,
+	       const struct ptrace_syscall_info *info,
+	       const struct si_exit *exp_exit,
+	       const char *text)
+{
+	ASSERT_EQ(PTRACE_SYSCALL_INFO_EXIT, info->op) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+	ASSERT_TRUE(info->arch) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+	ASSERT_TRUE(info->instruction_pointer) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+	ASSERT_TRUE(info->stack_pointer) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+	ASSERT_EQ(exp_exit->is_error, info->exit.is_error) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+	ASSERT_EQ(exp_exit->rval, info->exit.rval) {
+		LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+	}
+}
+
+TEST(set_syscall_info)
+{
+	const pid_t tracer_pid = getpid();
+	const kernel_ulong_t dummy[] = {
+		(kernel_ulong_t) 0xdad0bef0bad0fed0ULL,
+		(kernel_ulong_t) 0xdad1bef1bad1fed1ULL,
+		(kernel_ulong_t) 0xdad2bef2bad2fed2ULL,
+		(kernel_ulong_t) 0xdad3bef3bad3fed3ULL,
+		(kernel_ulong_t) 0xdad4bef4bad4fed4ULL,
+		(kernel_ulong_t) 0xdad5bef5bad5fed5ULL,
+	};
+	int splice_in[2], splice_out[2];
+
+	ASSERT_EQ(0, pipe(splice_in));
+	ASSERT_EQ(0, pipe(splice_out));
+	ASSERT_EQ(sizeof(dummy), write(splice_in[1], dummy, sizeof(dummy)));
+
+	const struct {
+		struct si_entry entry[2];
+		struct si_exit exit[2];
+	} si[] = {
+		/* change scno, keep non-error rval */
+		{
+			{
+				{
+					__NR_gettid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_getppid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 0, tracer_pid }, { 0, tracer_pid }
+			}
+		},
+
+		/* set scno to -1, keep error rval */
+		{
+			{
+				{
+					__NR_chdir,
+					{
+						(uintptr_t) ".",
+						dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					-1,
+					{
+						(uintptr_t) ".",
+						dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 1, -ENOSYS }, { 1, -ENOSYS }
+			}
+		},
+
+		/* keep scno, change non-error rval */
+		{
+			{
+				{
+					__NR_getppid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_getppid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 0, tracer_pid }, { 0, tracer_pid + 1 }
+			}
+		},
+
+		/* change arg1, keep non-error rval */
+		{
+			{
+				{
+					__NR_chdir,
+					{
+						(uintptr_t) "",
+						dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_chdir,
+					{
+						(uintptr_t) ".",
+						dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 0, 0 }, { 0, 0 }
+			}
+		},
+
+		/* set scno to -1, change error rval to non-error */
+		{
+			{
+				{
+					__NR_gettid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					-1,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 1, -ENOSYS }, { 0, tracer_pid }
+			}
+		},
+
+		/* change scno, change non-error rval to error */
+		{
+			{
+				{
+					__NR_chdir,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_getppid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 0, tracer_pid }, { 1, -EISDIR }
+			}
+		},
+
+		/* change scno and all args, change non-error rval */
+		{
+			{
+				{
+					__NR_gettid,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_splice,
+					{
+						splice_in[0], 0, splice_out[1], 0,
+						sizeof(dummy), SPLICE_F_NONBLOCK
+					}
+				}
+			}, {
+				{ 0, sizeof(dummy) }, { 0, sizeof(dummy) + 1 }
+			}
+		},
+
+		/* change arg1, no exit stop */
+		{
+			{
+				{
+					__NR_exit_group,
+					{
+						dummy[0], dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}, {
+					__NR_exit_group,
+					{
+						0, dummy[1], dummy[2],
+						dummy[3], dummy[4], dummy[5]
+					}
+				}
+			}, {
+				{ 0, 0 }, { 0, 0 }
+			}
+		},
+	};
+
+	long rc;
+	unsigned int i;
+
+	tracee_pid = fork();
+
+	ASSERT_LE(0, tracee_pid) {
+		TH_LOG("fork: %m");
+	}
+
+	if (tracee_pid == 0) {
+		/* get the pid before PTRACE_TRACEME */
+		tracee_pid = getpid();
+		ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) {
+			TH_LOG("PTRACE_TRACEME: %m");
+		}
+		ASSERT_EQ(0, kill(tracee_pid, SIGSTOP)) {
+			/* cannot happen */
+			TH_LOG("kill SIGSTOP: %m");
+		}
+		for (i = 0; i < ARRAY_SIZE(si); ++i) {
+			rc = syscall(si[i].entry[0].nr,
+				     si[i].entry[0].args[0],
+				     si[i].entry[0].args[1],
+				     si[i].entry[0].args[2],
+				     si[i].entry[0].args[3],
+				     si[i].entry[0].args[4],
+				     si[i].entry[0].args[5]);
+			if (si[i].exit[1].is_error) {
+				if (rc != -1 || errno != -si[i].exit[1].rval)
+					break;
+			} else {
+				if (rc != si[i].exit[1].rval)
+					break;
+			}
+		}
+		/*
+		 * Something went wrong, but in this state tracee
+		 * cannot reliably issue syscalls, so just crash.
+		 */
+		*(volatile unsigned char *) (uintptr_t) i = 42;
+		/* unreachable */
+		_exit(i + 1);
+	}
+
+	for (ptrace_stop = 0; ; ++ptrace_stop) {
+		struct ptrace_syscall_info info = {
+			.op = 0xff	/* invalid PTRACE_SYSCALL_INFO_* op */
+		};
+		const size_t size = sizeof(info);
+		const int expected_entry_size =
+			(void *) &info.entry.args[6] - (void *) &info;
+		const int expected_exit_size =
+			(void *) (&info.exit.is_error + 1) -
+			(void *) &info;
+		int status;
+
+		ASSERT_EQ(tracee_pid, wait(&status)) {
+			/* cannot happen */
+			LOG_KILL_TRACEE("wait: %m");
+		}
+		if (WIFEXITED(status)) {
+			tracee_pid = 0;	/* the tracee is no more */
+			ASSERT_EQ(0, WEXITSTATUS(status)) {
+				LOG_KILL_TRACEE("unexpected exit status %u",
+						WEXITSTATUS(status));
+			}
+			break;
+		}
+		ASSERT_FALSE(WIFSIGNALED(status)) {
+			tracee_pid = 0;	/* the tracee is no more */
+			LOG_KILL_TRACEE("unexpected signal %u",
+					WTERMSIG(status));
+		}
+		ASSERT_TRUE(WIFSTOPPED(status)) {
+			/* cannot happen */
+			LOG_KILL_TRACEE("unexpected wait status %#x", status);
+		}
+
+		ASSERT_LT(ptrace_stop, ARRAY_SIZE(si) * 2) {
+			LOG_KILL_TRACEE("ptrace stop overflow");
+		}
+
+		switch (WSTOPSIG(status)) {
+		case SIGSTOP:
+			ASSERT_EQ(0, ptrace_stop) {
+				LOG_KILL_TRACEE("unexpected signal stop");
+			}
+			ASSERT_EQ(0, sys_ptrace(PTRACE_SETOPTIONS, tracee_pid,
+						0, PTRACE_O_TRACESYSGOOD)) {
+				LOG_KILL_TRACEE("PTRACE_SETOPTIONS: %m");
+			}
+			break;
+
+		case SIGTRAP | 0x80:
+			ASSERT_LT(0, ptrace_stop) {
+				LOG_KILL_TRACEE("unexpected syscall stop");
+			}
+			ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+						      tracee_pid, size,
+						      (uintptr_t) &info))) {
+				LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1: %m");
+			}
+			if (ptrace_stop & 1) {
+				/* entering syscall */
+				const struct si_entry *exp_entry =
+					&si[ptrace_stop / 2].entry[0];
+				const struct si_entry *set_entry =
+					&si[ptrace_stop / 2].entry[1];
+
+				/* check ptrace_syscall_info before the changes */
+				ASSERT_EQ(expected_entry_size, rc) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1"
+							": entry stop mismatch");
+				}
+				check_psi_entry(_metadata, &info, exp_entry,
+						"PTRACE_GET_SYSCALL_INFO #1");
+
+				/* apply the changes */
+				info.entry.nr = set_entry->nr;
+				for (i = 0; i < ARRAY_SIZE(set_entry->args); ++i)
+					info.entry.args[i] = set_entry->args[i];
+				ASSERT_EQ(0, sys_ptrace(PTRACE_SET_SYSCALL_INFO,
+							tracee_pid, size,
+							(uintptr_t) &info)) {
+					LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m");
+				}
+
+				/* check ptrace_syscall_info after the changes */
+				memset(&info, 0, sizeof(info));
+				info.op = 0xff;
+				ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+							      tracee_pid, size,
+							      (uintptr_t) &info))) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
+				}
+				ASSERT_EQ(expected_entry_size, rc) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2"
+							": entry stop mismatch");
+				}
+				check_psi_entry(_metadata, &info, set_entry,
+						"PTRACE_GET_SYSCALL_INFO #2");
+			} else {
+				/* exiting syscall */
+				const struct si_exit *exp_exit =
+					&si[ptrace_stop / 2 - 1].exit[0];
+				const struct si_exit *set_exit =
+					&si[ptrace_stop / 2 - 1].exit[1];
+
+				/* check ptrace_syscall_info before the changes */
+				ASSERT_EQ(expected_exit_size, rc) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1"
+							": exit stop mismatch");
+				}
+				check_psi_exit(_metadata, &info, exp_exit,
+						"PTRACE_GET_SYSCALL_INFO #1");
+
+				/* apply the changes */
+				info.exit.is_error = set_exit->is_error;
+				info.exit.rval = set_exit->rval;
+				ASSERT_EQ(0, sys_ptrace(PTRACE_SET_SYSCALL_INFO,
+							tracee_pid, size,
+							(uintptr_t) &info)) {
+					LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m");
+				}
+
+				/* check ptrace_syscall_info after the changes */
+				memset(&info, 0, sizeof(info));
+				info.op = 0xff;
+				ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+							      tracee_pid, size,
+							      (uintptr_t) &info))) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2: %m");
+				}
+				ASSERT_EQ(expected_exit_size, rc) {
+					LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2"
+							": exit stop mismatch");
+				}
+				check_psi_exit(_metadata, &info, set_exit,
+						"PTRACE_GET_SYSCALL_INFO #2");
+			}
+			break;
+
+		default:
+			LOG_KILL_TRACEE("unexpected stop signal %u",
+					WSTOPSIG(status));
+			abort();
+		}
+
+		ASSERT_EQ(0, sys_ptrace(PTRACE_SYSCALL, tracee_pid, 0, 0)) {
+			LOG_KILL_TRACEE("PTRACE_SYSCALL: %m");
+		}
+	}
+
+	ASSERT_EQ(ptrace_stop, ARRAY_SIZE(si) * 2);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/ptrace/vmaccess.c b/tools/testing/selftests/ptrace/vmaccess.c
new file mode 100644
index 000000000..3801b5831
--- /dev/null
+++ b/tools/testing/selftests/ptrace/vmaccess.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2020 Bernd Edlinger <bernd.edlinger@hotmail.de>
+ * All rights reserved.
+ *
+ * Check whether /proc/$pid/mem can be accessed without causing deadlocks
+ * when de_thread is blocked with ->cred_guard_mutex held.
+ */
+
+#include "kselftest_harness.h"
+#include <stdio.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+
+static void *thread(void *arg)
+{
+	ptrace(PTRACE_TRACEME, 0, 0L, 0L);
+	return NULL;
+}
+
+TEST(vmaccess)
+{
+	int f, pid = fork();
+	char mm[64];
+
+	if (!pid) {
+		pthread_t pt;
+
+		pthread_create(&pt, NULL, thread, NULL);
+		pthread_join(pt, NULL);
+		execlp("true", "true", NULL);
+	}
+
+	sleep(1);
+	sprintf(mm, "/proc/%d/mem", pid);
+	f = open(mm, O_RDONLY);
+	ASSERT_GE(f, 0);
+	close(f);
+	f = kill(pid, SIGCONT);
+	ASSERT_EQ(f, 0);
+}
+
+TEST(attach)
+{
+	int s, k, pid = fork();
+
+	if (!pid) {
+		pthread_t pt;
+
+		pthread_create(&pt, NULL, thread, NULL);
+		pthread_join(pt, NULL);
+		execlp("sleep", "sleep", "2", NULL);
+	}
+
+	sleep(1);
+	k = ptrace(PTRACE_ATTACH, pid, 0L, 0L);
+	ASSERT_EQ(errno, EAGAIN);
+	ASSERT_EQ(k, -1);
+	k = waitpid(-1, &s, WNOHANG);
+	ASSERT_NE(k, -1);
+	ASSERT_NE(k, 0);
+	ASSERT_NE(k, pid);
+	ASSERT_EQ(WIFEXITED(s), 1);
+	ASSERT_EQ(WEXITSTATUS(s), 0);
+	sleep(1);
+	k = ptrace(PTRACE_ATTACH, pid, 0L, 0L);
+	ASSERT_EQ(k, 0);
+	k = waitpid(-1, &s, 0);
+	ASSERT_EQ(k, pid);
+	ASSERT_EQ(WIFSTOPPED(s), 1);
+	ASSERT_EQ(WSTOPSIG(s), SIGSTOP);
+	k = ptrace(PTRACE_DETACH, pid, 0L, 0L);
+	ASSERT_EQ(k, 0);
+	k = waitpid(-1, &s, 0);
+	ASSERT_EQ(k, pid);
+	ASSERT_EQ(WIFEXITED(s), 1);
+	ASSERT_EQ(WEXITSTATUS(s), 0);
+	k = waitpid(-1, NULL, 0);
+	ASSERT_EQ(k, -1);
+	ASSERT_EQ(errno, ECHILD);
+}
+
+TEST_HARNESS_MAIN