selftests: riscv: verify initial vector state with ptrace

Add a test case that attaches to a traced process immediately after its
first executed vector instructions to verify the initial vector context.

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/20251214163537.1054292-7-geomatsi@gmail.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: geomatsi

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

@@ -12,6 +12,9 @@
 #include "kselftest_harness.h"
 #include "v_helpers.h"
 
+#define SR_FS_DIRTY	0x00006000UL
+#define CSR_VXRM_SHIFT	1
+
 volatile unsigned long chld_lock;
 
 TEST(ptrace_v_not_enabled)
@@ -76,4 +79,136 @@ TEST(ptrace_v_not_enabled)
 	}
 }
 
+TEST(ptrace_v_early_debug)
+{
+	static volatile unsigned long vstart;
+	static volatile unsigned long vtype;
+	static volatile unsigned long vlenb;
+	static volatile unsigned long vcsr;
+	static volatile unsigned long vl;
+	bool xtheadvector;
+	pid_t pid;
+
+	if (!(is_vector_supported() || is_xtheadvector_supported()))
+		SKIP(return, "Vector not supported");
+
+	xtheadvector = is_xtheadvector_supported();
+
+	chld_lock = 1;
+	pid = fork();
+	ASSERT_LE(0, pid)
+		TH_LOG("fork: %m");
+
+	if (pid == 0) {
+		unsigned long vxsat, vxrm;
+
+		vlenb = get_vr_len();
+
+		while (chld_lock == 1)
+			asm volatile ("" : : "g"(chld_lock) : "memory");
+
+		asm volatile (
+			"csrr %[vstart], vstart\n"
+			"csrr %[vtype], vtype\n"
+			"csrr %[vl], vl\n"
+			: [vtype] "=r"(vtype), [vstart] "=r"(vstart), [vl] "=r"(vl)
+			:
+			: "memory");
+
+		/* no 'is_xtheadvector_supported()' here to avoid clobbering v-state by syscall */
+		if (xtheadvector) {
+			asm volatile (
+				"csrs sstatus, %[bit]\n"
+				"csrr %[vxsat], vxsat\n"
+				"csrr %[vxrm], vxrm\n"
+				: [vxsat] "=r"(vxsat), [vxrm] "=r"(vxrm)
+				: [bit] "r" (SR_FS_DIRTY)
+				: "memory");
+			vcsr = vxsat | vxrm << CSR_VXRM_SHIFT;
+		} else {
+			asm volatile (
+				"csrr %[vcsr], vcsr\n"
+				: [vcsr] "=r"(vcsr)
+				:
+				: "memory");
+		}
+
+		asm volatile (
+			".option push\n"
+			".option norvc\n"
+			"ebreak\n"
+			".option pop\n");
+	} else {
+		struct __riscv_v_regset_state *regset_data;
+		unsigned long vstart_csr;
+		unsigned long vlenb_csr;
+		unsigned long vtype_csr;
+		unsigned long vcsr_csr;
+		unsigned long vl_csr;
+		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 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 PEEKDATA */
+
+		errno = 0;
+		vstart_csr = ptrace(PTRACE_PEEKDATA, pid, &vstart, NULL);
+		ASSERT_FALSE((errno != 0) && (vstart_csr == -1));
+
+		errno = 0;
+		vl_csr = ptrace(PTRACE_PEEKDATA, pid, &vl, NULL);
+		ASSERT_FALSE((errno != 0) && (vl_csr == -1));
+
+		errno = 0;
+		vtype_csr = ptrace(PTRACE_PEEKDATA, pid, &vtype, NULL);
+		ASSERT_FALSE((errno != 0) && (vtype_csr == -1));
+
+		errno = 0;
+		vcsr_csr = ptrace(PTRACE_PEEKDATA, pid, &vcsr, NULL);
+		ASSERT_FALSE((errno != 0) && (vcsr_csr == -1));
+
+		errno = 0;
+		vlenb_csr = ptrace(PTRACE_PEEKDATA, pid, &vlenb, NULL);
+		ASSERT_FALSE((errno != 0) && (vlenb_csr == -1));
+
+		/* read tracee csr regs using ptrace GETREGSET */
+
+		regset_size = sizeof(*regset_data) + vlenb_csr * 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));
+
+		/* compare */
+
+		EXPECT_EQ(vstart_csr, regset_data->vstart);
+		EXPECT_EQ(vtype_csr, regset_data->vtype);
+		EXPECT_EQ(vlenb_csr, regset_data->vlenb);
+		EXPECT_EQ(vcsr_csr, regset_data->vcsr);
+		EXPECT_EQ(vl_csr, regset_data->vl);
+
+		/* cleanup */
+
+		ASSERT_EQ(0, kill(pid, SIGKILL));
+	}
+}
+
 TEST_HARNESS_MAIN