arm64/ptrace: Use saved floating point state type to determine SVE layout

The SVE register sets have two different formats, one of which is a wrapped
version of the standard FPSIMD register set and another with actual SVE
register data. At present we check TIF_SVE to see if full SVE register
state should be provided when reading the SVE regset but if we were in a
syscall we may have saved only floating point registers even though that is
set.

Fix this and simplify the logic by checking and using the format which we
recorded when deciding if we should use FPSIMD or SVE format.

Fixes: 8c845e27 ("arm64/sve: Leave SVE enabled on syscall if we don't context switch")
Cc: <stable@vger.kernel.org> # 6.2.x
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240325-arm64-ptrace-fp-type-v1-1-8dc846caf11f@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/ptrace.c

@@ -761,7 +761,6 @@ static void sve_init_header_from_task(struct user_sve_header *header,
 {
 	unsigned int vq;
 	bool active;
-	bool fpsimd_only;
 	enum vec_type task_type;
 
 	memset(header, 0, sizeof(*header));
@@ -777,12 +776,10 @@ static void sve_init_header_from_task(struct user_sve_header *header,
 	case ARM64_VEC_SVE:
 		if (test_tsk_thread_flag(target, TIF_SVE_VL_INHERIT))
 			header->flags |= SVE_PT_VL_INHERIT;
-		fpsimd_only = !test_tsk_thread_flag(target, TIF_SVE);
 		break;
 	case ARM64_VEC_SME:
 		if (test_tsk_thread_flag(target, TIF_SME_VL_INHERIT))
 			header->flags |= SVE_PT_VL_INHERIT;
-		fpsimd_only = false;
 		break;
 	default:
 		WARN_ON_ONCE(1);
@@ -790,7 +787,7 @@ static void sve_init_header_from_task(struct user_sve_header *header,
 	}
 
 	if (active) {
-		if (fpsimd_only) {
+		if (target->thread.fp_type == FP_STATE_FPSIMD) {
 			header->flags |= SVE_PT_REGS_FPSIMD;
 		} else {
 			header->flags |= SVE_PT_REGS_SVE;