selftests: riscv: test ptrace vector interface

Add a test case to check ptrace behavior in the case when vector
extension is supported by the system, but vector context is not
yet enabled for the traced process.

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Reviewed-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Andy Chiu <andybnac@gmail.com>
Link: https://patch.msgid.link/20251214163537.1054292-6-geomatsi@gmail.com
[pjw@kernel.org: dropped duplicate sys/wait.h include]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

tools/testing/selftests/riscv/vector/.gitignore

@@ -2,3 +2,5 @@ vstate_exec_nolibc
 vstate_prctl
 v_initval
 v_exec_initval_nolibc
+vstate_ptrace
+validate_v_ptrace

tools/testing/selftests/riscv/vector/Makefile

@@ -2,11 +2,14 @@
 # Copyright (C) 2021 ARM Limited
 # Originally tools/testing/arm64/abi/Makefile
 
-TEST_GEN_PROGS := v_initval vstate_prctl vstate_ptrace
+TEST_GEN_PROGS := v_initval vstate_prctl vstate_ptrace validate_v_ptrace
 TEST_GEN_PROGS_EXTENDED := vstate_exec_nolibc v_exec_initval_nolibc
+TEST_GEN_LIBS := v_helpers.c sys_hwprobe.c
 
 include ../../lib.mk
 
+TEST_GEN_OBJ := $(patsubst %.c, $(OUTPUT)/%.o, $(TEST_GEN_LIBS))
+
 $(OUTPUT)/sys_hwprobe.o: ../hwprobe/sys_hwprobe.S
 	$(CC) -static -c -o$@ $(CFLAGS) $^
 
@@ -29,3 +32,8 @@ $(OUTPUT)/v_exec_initval_nolibc: v_exec_initval_nolibc.c
 
 $(OUTPUT)/vstate_ptrace: vstate_ptrace.c $(OUTPUT)/sys_hwprobe.o $(OUTPUT)/v_helpers.o
 	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
+
+$(OUTPUT)/validate_v_ptrace: validate_v_ptrace.c $(OUTPUT)/sys_hwprobe.o $(OUTPUT)/v_helpers.o
+	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
+
+EXTRA_CLEAN += $(TEST_GEN_OBJ)

tools/testing/selftests/riscv/vector/v_helpers.c

@@ -26,6 +26,29 @@ bool is_vector_supported(void)
 	return pair.value & RISCV_HWPROBE_EXT_ZVE32X;
 }
 
+unsigned long get_vr_len(void)
+{
+	unsigned long vlenb;
+
+	if (is_vector_supported()) {
+		asm volatile("csrr %[vlenb], vlenb" : [vlenb] "=r"(vlenb));
+		return vlenb;
+	}
+
+	if (is_xtheadvector_supported()) {
+		asm volatile (
+			// 0 | zimm[10:0] | rs1 | 1 1 1 | rd | 1010111 | vsetvli
+			// vsetvli	t4, x0, e8, m1, d1
+			".4byte		0b00000000000000000111111011010111\n\t"
+			"mv		%[vlenb], t4\n\t"
+			: [vlenb] "=r"(vlenb) : : "memory", "t4");
+		return vlenb;
+	}
+
+	printf("WARNING: vector not supported\n");
+	return 0;
+}
+
 int launch_test(char *next_program, int test_inherit, int xtheadvector)
 {
 	char *exec_argv[4], *exec_envp[1];

tools/testing/selftests/riscv/vector/v_helpers.h

@@ -5,4 +5,6 @@ bool is_xtheadvector_supported(void);
 
 bool is_vector_supported(void);
 
+unsigned long get_vr_len(void);
+
 int launch_test(char *next_program, int test_inherit, int xtheadvector);

tools/testing/selftests/riscv/vector/validate_v_ptrace.c

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <linux/ptrace.h>
+#include <linux/elf.h>
+
+#include "kselftest_harness.h"
+#include "v_helpers.h"
+
+volatile unsigned long chld_lock;
+
+TEST(ptrace_v_not_enabled)
+{
+	pid_t pid;
+
+	if (!(is_vector_supported() || is_xtheadvector_supported()))
+		SKIP(return, "Vector not supported");
+
+	chld_lock = 1;
+	pid = fork();
+	ASSERT_LE(0, pid)
+		TH_LOG("fork: %m");
+
+	if (pid == 0) {
+		while (chld_lock == 1)
+			asm volatile("" : : "g"(chld_lock) : "memory");
+
+		asm volatile ("ebreak" : : : );
+	} else {
+		struct __riscv_v_regset_state *regset_data;
+		unsigned long vlenb = get_vr_len();
+		size_t regset_size;
+		struct iovec iov;
+		int status;
+		int ret;
+
+		/* attach */
+
+		ASSERT_EQ(0, ptrace(PTRACE_ATTACH, pid, NULL, NULL));
+		ASSERT_EQ(pid, waitpid(pid, &status, 0));
+		ASSERT_TRUE(WIFSTOPPED(status));
+
+		/* unlock */
+
+		ASSERT_EQ(0, ptrace(PTRACE_POKEDATA, pid, &chld_lock, 0));
+
+		/* resume and wait for ebreak */
+
+		ASSERT_EQ(0, ptrace(PTRACE_CONT, pid, NULL, NULL));
+		ASSERT_EQ(pid, waitpid(pid, &status, 0));
+		ASSERT_TRUE(WIFSTOPPED(status));
+
+		/* try to read vector registers from the tracee */
+
+		regset_size = sizeof(*regset_data) + vlenb * 32;
+		regset_data = calloc(1, regset_size);
+
+		iov.iov_base = regset_data;
+		iov.iov_len = regset_size;
+
+		/* V extension is available, but not yet enabled for the tracee */
+
+		errno = 0;
+		ret = ptrace(PTRACE_GETREGSET, pid, NT_RISCV_VECTOR, &iov);
+		ASSERT_EQ(ENODATA, errno);
+		ASSERT_EQ(-1, ret);
+
+		/* cleanup */
+
+		ASSERT_EQ(0, kill(pid, SIGKILL));
+	}
+}
+
+TEST_HARNESS_MAIN