selftests: riscv: verify syscalls discard vector context

Add a test to v_ptrace test suite to verify that vector csr registers
are clobbered on syscalls.

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/20251214163537.1054292-8-geomatsi@gmail.com
[pjw@kernel.org: cleaned up a checkpatch issue]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: geomatsi

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

@@ -211,4 +211,127 @@ TEST(ptrace_v_early_debug)
 	}
 }
 
+TEST(ptrace_v_syscall_clobbering)
+{
+	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) {
+		unsigned long vl;
+
+		while (chld_lock == 1)
+			asm volatile("" : : "g"(chld_lock) : "memory");
+
+		if (is_xtheadvector_supported()) {
+			asm volatile (
+				// 0 | zimm[10:0] | rs1 | 1 1 1 | rd |1010111| vsetvli
+				// vsetvli	t4, x0, e16, m2, d1
+				".4byte		0b00000000010100000111111011010111\n"
+				"mv		%[new_vl], t4\n"
+				: [new_vl] "=r" (vl) : : "t4");
+		} else {
+			asm volatile (
+				".option push\n"
+				".option arch, +zve32x\n"
+				"vsetvli %[new_vl], x0, e16, m2, tu, mu\n"
+				".option pop\n"
+				: [new_vl] "=r"(vl) : : );
+		}
+
+		while (1) {
+			asm volatile (
+				".option push\n"
+				".option norvc\n"
+				"ebreak\n"
+				".option pop\n");
+
+			sleep(0);
+		}
+	} else {
+		struct __riscv_v_regset_state *regset_data;
+		unsigned long vlenb = get_vr_len();
+		struct user_regs_struct regs;
+		size_t regset_size;
+		struct iovec iov;
+		int status;
+
+		/* 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 the 1st ebreak */
+
+		ASSERT_EQ(0, ptrace(PTRACE_CONT, pid, NULL, NULL));
+		ASSERT_EQ(pid, waitpid(pid, &status, 0));
+		ASSERT_TRUE(WIFSTOPPED(status));
+
+		/* read tracee vector csr regs using ptrace GETREGSET */
+
+		regset_size = sizeof(*regset_data) + vlenb * 32;
+		regset_data = calloc(1, regset_size);
+
+		iov.iov_base = regset_data;
+		iov.iov_len = regset_size;
+
+		ASSERT_EQ(0, ptrace(PTRACE_GETREGSET, pid, NT_RISCV_VECTOR, &iov));
+
+		/* verify initial vsetvli settings */
+
+		if (is_xtheadvector_supported())
+			EXPECT_EQ(5UL, regset_data->vtype);
+		else
+			EXPECT_EQ(9UL, regset_data->vtype);
+
+		EXPECT_EQ(regset_data->vlenb, regset_data->vl);
+		EXPECT_EQ(vlenb, regset_data->vlenb);
+		EXPECT_EQ(0UL, regset_data->vstart);
+		EXPECT_EQ(0UL, regset_data->vcsr);
+
+		/* skip 1st ebreak, then resume and wait for the 2nd ebreak */
+
+		iov.iov_base = &regs;
+		iov.iov_len = sizeof(regs);
+
+		ASSERT_EQ(0, ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov));
+		regs.pc += 4;
+		ASSERT_EQ(0, ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov));
+
+		ASSERT_EQ(0, ptrace(PTRACE_CONT, pid, NULL, NULL));
+		ASSERT_EQ(pid, waitpid(pid, &status, 0));
+		ASSERT_TRUE(WIFSTOPPED(status));
+
+		/* read tracee vtype using ptrace GETREGSET */
+
+		iov.iov_base = regset_data;
+		iov.iov_len = regset_size;
+
+		ASSERT_EQ(0, ptrace(PTRACE_GETREGSET, pid, NT_RISCV_VECTOR, &iov));
+
+		/* verify that V state is illegal after syscall */
+
+		EXPECT_EQ((1UL << (__riscv_xlen - 1)), regset_data->vtype);
+		EXPECT_EQ(vlenb, regset_data->vlenb);
+		EXPECT_EQ(0UL, regset_data->vstart);
+		EXPECT_EQ(0UL, regset_data->vcsr);
+		EXPECT_EQ(0UL, regset_data->vl);
+
+		/* cleanup */
+
+		ASSERT_EQ(0, kill(pid, SIGKILL));
+	}
+}
+
 TEST_HARNESS_MAIN