kselftest/arm64: Add test coverage for NT_ARM_TLS

In preparation for extending support for NT_ARM_TLS to cover additional
TPIDRs add some tests for the existing interface. Do this in a generic
ptrace test program to provide a place to collect additional tests in
the future.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154921.837871-2-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

tools/testing/selftests/arm64/abi/.gitignore

@@ -1,2 +1,3 @@
+ptrace
 syscall-abi
 tpidr2

tools/testing/selftests/arm64/abi/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Copyright (C) 2021 ARM Limited
 
-TEST_GEN_PROGS := syscall-abi tpidr2
+TEST_GEN_PROGS := ptrace syscall-abi tpidr2
 
 include ../../lib.mk
 

tools/testing/selftests/arm64/abi/ptrace.c

@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 ARM Limited.
+ */
+#include <errno.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/auxv.h>
+#include <sys/prctl.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/wait.h>
+#include <asm/sigcontext.h>
+#include <asm/ptrace.h>
+
+#include "../../kselftest.h"
+
+#define EXPECTED_TESTS 3
+
+#define MAX_TPIDRS 1
+
+static bool have_sme(void)
+{
+	return getauxval(AT_HWCAP2) & HWCAP2_SME;
+}
+
+static void test_tpidr(pid_t child)
+{
+	uint64_t read_val[MAX_TPIDRS];
+	uint64_t write_val[MAX_TPIDRS];
+	struct iovec read_iov, write_iov;
+	int ret;
+
+	read_iov.iov_base = read_val;
+	write_iov.iov_base = write_val;
+
+	/* Should be able to read a single TPIDR... */
+	read_iov.iov_len = sizeof(uint64_t);
+	ret = ptrace(PTRACE_GETREGSET, child, NT_ARM_TLS, &read_iov);
+	ksft_test_result(ret == 0, "read_tpidr_one\n");
+
+	/* ...write a new value.. */
+	write_iov.iov_len = sizeof(uint64_t);
+	write_val[0] = read_val[0]++;
+	ret = ptrace(PTRACE_SETREGSET, child, NT_ARM_TLS, &write_iov);
+	ksft_test_result(ret == 0, "write_tpidr_one\n");
+
+	/* ...then read it back */
+	ret = ptrace(PTRACE_GETREGSET, child, NT_ARM_TLS, &read_iov);
+	ksft_test_result(ret == 0 && write_val[0] == read_val[0],
+			 "verify_tpidr_one\n");
+}
+
+static int do_child(void)
+{
+	if (ptrace(PTRACE_TRACEME, -1, NULL, NULL))
+		ksft_exit_fail_msg("PTRACE_TRACEME", strerror(errno));
+
+	if (raise(SIGSTOP))
+		ksft_exit_fail_msg("raise(SIGSTOP)", strerror(errno));
+
+	return EXIT_SUCCESS;
+}
+
+static int do_parent(pid_t child)
+{
+	int ret = EXIT_FAILURE;
+	pid_t pid;
+	int status;
+	siginfo_t si;
+
+	/* Attach to the child */
+	while (1) {
+		int sig;
+
+		pid = wait(&status);
+		if (pid == -1) {
+			perror("wait");
+			goto error;
+		}
+
+		/*
+		 * This should never happen but it's hard to flag in
+		 * the framework.
+		 */
+		if (pid != child)
+			continue;
+
+		if (WIFEXITED(status) || WIFSIGNALED(status))
+			ksft_exit_fail_msg("Child died unexpectedly\n");
+
+		if (!WIFSTOPPED(status))
+			goto error;
+
+		sig = WSTOPSIG(status);
+
+		if (ptrace(PTRACE_GETSIGINFO, pid, NULL, &si)) {
+			if (errno == ESRCH)
+				goto disappeared;
+
+			if (errno == EINVAL) {
+				sig = 0; /* bust group-stop */
+				goto cont;
+			}
+
+			ksft_test_result_fail("PTRACE_GETSIGINFO: %s\n",
+					      strerror(errno));
+			goto error;
+		}
+
+		if (sig == SIGSTOP && si.si_code == SI_TKILL &&
+		    si.si_pid == pid)
+			break;
+
+	cont:
+		if (ptrace(PTRACE_CONT, pid, NULL, sig)) {
+			if (errno == ESRCH)
+				goto disappeared;
+
+			ksft_test_result_fail("PTRACE_CONT: %s\n",
+					      strerror(errno));
+			goto error;
+		}
+	}
+
+	ksft_print_msg("Parent is %d, child is %d\n", getpid(), child);
+
+	test_tpidr(child);
+
+	ret = EXIT_SUCCESS;
+
+error:
+	kill(child, SIGKILL);
+
+disappeared:
+	return ret;
+}
+
+int main(void)
+{
+	int ret = EXIT_SUCCESS;
+	pid_t child;
+
+	srandom(getpid());
+
+	ksft_print_header();
+
+	ksft_set_plan(EXPECTED_TESTS);
+
+	child = fork();
+	if (!child)
+		return do_child();
+
+	if (do_parent(child))
+		ret = EXIT_FAILURE;
+
+	ksft_print_cnts();
+
+	return ret;
+}