arm64: implement ARCH_HAS_KERNEL_FPU_SUPPORT

arm64 provides an equivalent to the common kernel-mode FPU API, but in a
different header and using different function names.  Add a wrapper
header, and export CFLAGS adjustments as found in lib/raid6/Makefile.

Link: https://lkml.kernel.org/r/20240329072441.591471-5-samuel.holland@sifive.com
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Xuerui <git@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 00cbb794aedaeac99442b6ece518f55eaae27fda..2f31376e85aa25e325fc1b0134e968d124e5a266 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -30,6 +30,7 @@ config ARM64
        select ARCH_HAS_GCOV_PROFILE_ALL
        select ARCH_HAS_GIGANTIC_PAGE
        select ARCH_HAS_KCOV
+       select ARCH_HAS_KERNEL_FPU_SUPPORT if KERNEL_MODE_NEON
        select ARCH_HAS_KEEPINITRD
        select ARCH_HAS_MEMBARRIER_SYNC_CORE
        select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b8b1d4f4a572b03aa6f47643321e6fb79f0e4c21..3f0f35fd5bb7b13210b4605a000514a35d26dfd8 100644 (file)
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -36,7 +36,14 @@ ifeq ($(CONFIG_BROKEN_GAS_INST),y)
 $(warning Detected assembler with broken .inst; disassembly will be unreliable)
 endif
 
-KBUILD_CFLAGS  += -mgeneral-regs-only  \
+# The GCC option -ffreestanding is required in order to compile code containing
+# ARM/NEON intrinsics in a non C99-compliant environment (such as the kernel)
+CC_FLAGS_FPU   := -ffreestanding
+# Enable <arm_neon.h>
+CC_FLAGS_FPU   += -isystem $(shell $(CC) -print-file-name=include)
+CC_FLAGS_NO_FPU        := -mgeneral-regs-only
+
+KBUILD_CFLAGS  += $(CC_FLAGS_NO_FPU) \
                   $(compat_vdso) $(cc_has_k_constraint)
 KBUILD_CFLAGS  += $(call cc-disable-warning, psabi)
 KBUILD_AFLAGS  += $(compat_vdso)

diff --git a/arch/arm64/include/asm/fpu.h b/arch/arm64/include/asm/fpu.h
new file mode 100644 (file)
index 0000000..2ae50bd
--- /dev/null
+++ b/arch/arm64/include/asm/fpu.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef __ASM_FPU_H
+#define __ASM_FPU_H
+
+#include <asm/neon.h>
+
+#define kernel_fpu_available() cpu_has_neon()
+#define kernel_fpu_begin()     kernel_neon_begin()
+#define kernel_fpu_end()       kernel_neon_end()
+
+#endif /* ! __ASM_FPU_H */