selftests: arm64: Add test for the SVE ptrace interface

Add a test case that does some basic verification of the SVE ptrace
interface, forking off a child with known values in the registers and
then using ptrace to inspect and manipulate the SVE registers of the
child, including in FPSIMD mode to account for sharing between the SVE
and FPSIMD registers.

This program was written by Dave Martin and modified for kselftest by
me.
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200819114837.51466-3-broonie@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

tools/testing/selftests/arm64/fp/sve-ptrace-asm.S

+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2015-2019 ARM Limited.
+// Original author: Dave Martin <Dave.Martin@arm.com>
+#include <asm/unistd.h>
+
+.arch_extension sve
+
+.globl sve_store_patterns
+
+sve_store_patterns:
+	mov	x1, x0
+
+	index	z0.b, #0, #1
+	str	q0, [x1]
+
+	mov	w8, #__NR_getpid
+	svc	#0
+	str	q0, [x1, #0x10]
+
+	mov	z1.d, z0.d
+	str	q0, [x1, #0x20]
+
+	mov	w8, #__NR_getpid
+	svc	#0
+	str	q0, [x1, #0x30]
+
+	mov	z1.d, z0.d
+	str	q0, [x1, #0x40]
+
+	ret
+
+.size	sve_store_patterns, . - sve_store_patterns
+.type	sve_store_patterns, @function

tools/testing/selftests/arm64/fp/sve-ptrace.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2015-2020 ARM Limited.
+ * Original author: Dave Martin <Dave.Martin@arm.com>
+ */
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/auxv.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"
+
+/* <linux/elf.h> and <sys/auxv.h> don't like each other, so: */
+#ifndef NT_ARM_SVE
+#define NT_ARM_SVE 0x405
+#endif
+
+/* Number of registers filled in by sve_store_patterns */
+#define NR_VREGS 5
+
+void sve_store_patterns(__uint128_t v[NR_VREGS]);
+
+static void dump(const void *buf, size_t size)
+{
+	size_t i;
+	const unsigned char *p = buf;
+
+	for (i = 0; i < size; ++i)
+		printf(" %.2x", *p++);
+}
+
+static int check_vregs(const __uint128_t vregs[NR_VREGS])
+{
+	int i;
+	int ok = 1;
+
+	for (i = 0; i < NR_VREGS; ++i) {
+		printf("# v[%d]:", i);
+		dump(&vregs[i], sizeof vregs[i]);
+		putchar('\n');
+
+		if (vregs[i] != vregs[0])
+			ok = 0;
+	}
+
+	return ok;
+}
+
+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 struct user_sve_header *get_sve(pid_t pid, void **buf, size_t *size)
+{
+	struct user_sve_header *sve;
+	void *p;
+	size_t sz = sizeof *sve;
+	struct iovec iov;
+
+	while (1) {
+		if (*size < sz) {
+			p = realloc(*buf, sz);
+			if (!p) {
+				errno = ENOMEM;
+				goto error;
+			}
+
+			*buf = p;
+			*size = sz;
+		}
+
+		iov.iov_base = *buf;
+		iov.iov_len = sz;
+		if (ptrace(PTRACE_GETREGSET, pid, NT_ARM_SVE, &iov))
+			goto error;
+
+		sve = *buf;
+		if (sve->size <= sz)
+			break;
+
+		sz = sve->size;
+	}
+
+	return sve;
+
+error:
+	return NULL;
+}
+
+static int set_sve(pid_t pid, const struct user_sve_header *sve)
+{
+	struct iovec iov;
+
+	iov.iov_base = (void *)sve;
+	iov.iov_len = sve->size;
+	return ptrace(PTRACE_SETREGSET, pid, NT_ARM_SVE, &iov);
+}
+
+static void dump_sve_regs(const struct user_sve_header *sve, unsigned int num,
+			  unsigned int vlmax)
+{
+	unsigned int vq;
+	unsigned int i;
+
+	if ((sve->flags & SVE_PT_REGS_MASK) != SVE_PT_REGS_SVE)
+		ksft_exit_fail_msg("Dumping non-SVE register\n");
+
+	if (vlmax > sve->vl)
+		vlmax = sve->vl;
+
+	vq = sve_vq_from_vl(sve->vl);
+	for (i = 0; i < num; ++i) {
+		printf("# z%u:", i);
+		dump((const char *)sve + SVE_PT_SVE_ZREG_OFFSET(vq, i),
+		     vlmax);
+		printf("%s\n", vlmax == sve->vl ? "" : " ...");
+	}
+}
+
+static int do_parent(pid_t child)
+{
+	int ret = EXIT_FAILURE;
+	pid_t pid;
+	int status;
+	siginfo_t si;
+	void *svebuf = NULL, *newsvebuf;
+	size_t svebufsz = 0, newsvebufsz;
+	struct user_sve_header *sve, *new_sve;
+	struct user_fpsimd_state *fpsimd;
+	unsigned int i, j;
+	unsigned char *p;
+	unsigned int vq;
+
+	/* 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");
+
+		ksft_test_result(WIFSTOPPED(status), "WIFSTOPPED(%d)\n",
+				 status);
+		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;
+		}
+	}
+
+	sve = get_sve(pid, &svebuf, &svebufsz);
+	if (!sve) {
+		int e = errno;
+
+		ksft_test_result_fail("get_sve: %s\n", strerror(errno));
+		if (e == ESRCH)
+			goto disappeared;
+
+		goto error;
+	} else {
+		ksft_test_result_pass("get_sve\n");
+	}
+
+	ksft_test_result((sve->flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_FPSIMD,
+			 "FPSIMD registers\n");
+	if ((sve->flags & SVE_PT_REGS_MASK) != SVE_PT_REGS_FPSIMD)
+		goto error;
+
+	fpsimd = (struct user_fpsimd_state *)((char *)sve +
+					      SVE_PT_FPSIMD_OFFSET);
+	for (i = 0; i < 32; ++i) {
+		p = (unsigned char *)&fpsimd->vregs[i];
+
+		for (j = 0; j < sizeof fpsimd->vregs[i]; ++j)
+			p[j] = j;
+	}
+
+	if (set_sve(pid, sve)) {
+		int e = errno;
+
+		ksft_test_result_fail("set_sve(FPSIMD): %s\n",
+				      strerror(errno));
+		if (e == ESRCH)
+			goto disappeared;
+
+		goto error;
+	}
+
+	vq = sve_vq_from_vl(sve->vl);
+
+	newsvebufsz = SVE_PT_SVE_ZREG_OFFSET(vq, 1);
+	new_sve = newsvebuf = malloc(newsvebufsz);
+	if (!new_sve) {
+		errno = ENOMEM;
+		perror(NULL);
+		goto error;
+	}
+
+	*new_sve = *sve;
+	new_sve->flags &= ~SVE_PT_REGS_MASK;
+	new_sve->flags |= SVE_PT_REGS_SVE;
+	memset((char *)new_sve + SVE_PT_SVE_ZREG_OFFSET(vq, 0),
+	       0, SVE_PT_SVE_ZREG_SIZE(vq));
+	new_sve->size = SVE_PT_SVE_ZREG_OFFSET(vq, 1);
+	if (set_sve(pid, new_sve)) {
+		int e = errno;
+
+		ksft_test_result_fail("set_sve(ZREG): %s\n", strerror(errno));
+		if (e == ESRCH)
+			goto disappeared;
+
+		goto error;
+	}
+
+	new_sve = get_sve(pid, &newsvebuf, &newsvebufsz);
+	if (!new_sve) {
+		int e = errno;
+
+		ksft_test_result_fail("get_sve(ZREG): %s\n", strerror(errno));
+		if (e == ESRCH)
+			goto disappeared;
+
+		goto error;
+	}
+
+	ksft_test_result((new_sve->flags & SVE_PT_REGS_MASK) == SVE_PT_REGS_SVE,
+			 "SVE registers\n");
+	if ((new_sve->flags & SVE_PT_REGS_MASK) != SVE_PT_REGS_SVE)
+		goto error;
+
+	dump_sve_regs(new_sve, 3, sizeof fpsimd->vregs[0]);
+
+	p = (unsigned char *)new_sve + SVE_PT_SVE_ZREG_OFFSET(vq, 1);
+	for (i = 0; i < sizeof fpsimd->vregs[0]; ++i) {
+		unsigned char expected = i;
+
+		if (__BYTE_ORDER == __BIG_ENDIAN)
+			expected = sizeof fpsimd->vregs[0] - 1 - expected;
+
+		ksft_test_result(p[i] == expected, "p[%d] == expected\n", i);
+		if (p[i] != expected)
+			goto error;
+	}
+
+	ret = EXIT_SUCCESS;
+
+error:
+	kill(child, SIGKILL);
+
+disappeared:
+	return ret;
+}
+
+int main(void)
+{
+	int ret = EXIT_SUCCESS;
+	__uint128_t v[NR_VREGS];
+	pid_t child;
+
+	ksft_print_header();
+	ksft_set_plan(20);
+
+	if (!(getauxval(AT_HWCAP) & HWCAP_SVE))
+		ksft_exit_skip("SVE not available\n");
+
+	sve_store_patterns(v);
+
+	if (!check_vregs(v))
+		ksft_exit_fail_msg("Initial check_vregs() failed\n");
+
+	child = fork();
+	if (!child)
+		return do_child();
+
+	if (do_parent(child))
+		ret = EXIT_FAILURE;
+
+	ksft_print_cnts();
+
+	return 0;
+}