selftests: arm64: Add stress tests for FPSMID and SVE context switching

Add programs sve-test and fpsimd-test which spin reading and writing to
the SVE and FPSIMD registers, verifying the operations they perform. The
intended use is to leave them running to stress the context switch code's
handling of these registers which isn't compatible with what kselftest
does so they're not integrated into the framework but there's no other
obvious testsuite where they fit so let's store them here.

These tests were written by Dave Martin and lightly adapted 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/20200819114837.51466-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

Author: broonie

tools/testing/selftests/arm64/fp/asm-offsets.h

@@ -0,0 +1,11 @@
+#define sa_sz 32
+#define sa_flags 8
+#define sa_handler 0
+#define sa_mask_sz 8
+#define SIGUSR1 10
+#define SIGTERM 15
+#define SIGINT 2
+#define SIGABRT 6
+#define SA_NODEFER 1073741824
+#define SA_SIGINFO 4
+#define ucontext_regs 184

tools/testing/selftests/arm64/fp/assembler.h

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2015-2019 ARM Limited.
+// Original author: Dave Martin <Dave.Martin@arm.com>
+
+#ifndef ASSEMBLER_H
+#define ASSEMBLER_H
+
+.macro __for from:req, to:req
+	.if (\from) == (\to)
+		_for__body %\from
+	.else
+		__for \from, %(\from) + ((\to) - (\from)) / 2
+		__for %(\from) + ((\to) - (\from)) / 2 + 1, \to
+	.endif
+.endm
+
+.macro _for var:req, from:req, to:req, insn:vararg
+	.macro _for__body \var:req
+		.noaltmacro
+		\insn
+		.altmacro
+	.endm
+
+	.altmacro
+	__for \from, \to
+	.noaltmacro
+
+	.purgem _for__body
+.endm
+
+.macro function name
+	.macro endfunction
+		.type \name, @function
+		.purgem endfunction
+	.endm
+\name:
+.endm
+
+.macro define_accessor name, num, insn
+	.macro \name\()_entry n
+		\insn \n, 1
+		ret
+	.endm
+
+function \name
+	adr	x2, .L__accessor_tbl\@
+	add	x2, x2, x0, lsl #3
+	br	x2
+
+.L__accessor_tbl\@:
+	_for x, 0, (\num) - 1, \name\()_entry \x
+endfunction
+
+	.purgem \name\()_entry
+.endm
+
+#endif /* ! ASSEMBLER_H */