This is a note to let you know that I've just added the patch titled ARM: 8991/1: use VFP assembler mnemonics if available to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm-8991-1-use-vfp-assembler-mnemonics-if-available.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 24c661f203ea6f3af0495effbff3311408e225aa Author: Stefan Agner <stefan@xxxxxxxx> Date: Thu Jul 9 11:21:27 2020 +0100 ARM: 8991/1: use VFP assembler mnemonics if available commit 2cbd1cc3dcd3e84be1fc1987da24b190ddf24a70 upstream. The integrated assembler of Clang 10 and earlier do not allow to access the VFP registers through the coprocessor load/store instructions: arch/arm/vfp/vfpmodule.c:342:2: error: invalid operand for instruction fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK)); ^ arch/arm/vfp/vfpinstr.h:79:6: note: expanded from macro 'fmxr' asm("mcr p10, 7, %0, " vfpreg(_vfp_) ", cr0, 0 @ fmxr " #_vfp_ ", %0" ^ <inline asm>:1:6: note: instantiated into assembly here mcr p10, 7, r0, cr8, cr0, 0 @ fmxr FPEXC, r0 ^ This has been addressed with Clang 11 [0]. However, to support earlier versions of Clang and for better readability use of VFP assembler mnemonics still is preferred. Ideally we would replace this code with the unified assembler language mnemonics vmrs/vmsr on call sites along with .fpu assembler directives. The GNU assembler supports the .fpu directive at least since 2.17 (when documentation has been added). Since Linux requires binutils 2.21 it is safe to use .fpu directive. However, binutils does not allow to use FPINST or FPINST2 as an argument to vmrs/vmsr instructions up to binutils 2.24 (see binutils commit 16d02dc907c5): arch/arm/vfp/vfphw.S: Assembler messages: arch/arm/vfp/vfphw.S:162: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST,r6' arch/arm/vfp/vfphw.S:165: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST2,r8' arch/arm/vfp/vfphw.S:235: Error: operand 1 must be a VFP extension System Register -- `vmrs r3,FPINST' arch/arm/vfp/vfphw.S:238: Error: operand 1 must be a VFP extension System Register -- `vmrs r12,FPINST2' Use as-instr in Kconfig to check if FPINST/FPINST2 can be used. If they can be used make use of .fpu directives and UAL VFP mnemonics for register access. This allows to build vfpmodule.c with Clang and its integrated assembler. [0] https://reviews.llvm.org/D59733 Link: https://github.com/ClangBuiltLinux/linux/issues/905 Signed-off-by: Stefan Agner <stefan@xxxxxxxx> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> [nd: adjusted hunk from arch/arm/Kconfig due to missing commit 8a90a3228b6a ("arm: Unplug KVM from the build system")] Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 1877da816f65..5004a7871008 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -2198,3 +2198,4 @@ source "arch/arm/crypto/Kconfig" endif source "arch/arm/kvm/Kconfig" +source "arch/arm/Kconfig.assembler" diff --git a/arch/arm/Kconfig.assembler b/arch/arm/Kconfig.assembler new file mode 100644 index 000000000000..5cb31aae1188 --- /dev/null +++ b/arch/arm/Kconfig.assembler @@ -0,0 +1,6 @@ +# SPDX-License-Identifier: GPL-2.0 + +config AS_VFP_VMRS_FPINST + def_bool $(as-instr,.fpu vfpv2\nvmrs r0$(comma)FPINST) + help + Supported by binutils >= 2.24 and LLVM integrated assembler. diff --git a/arch/arm/include/asm/vfp.h b/arch/arm/include/asm/vfp.h index 7157d2a30a49..19928bfb4f9c 100644 --- a/arch/arm/include/asm/vfp.h +++ b/arch/arm/include/asm/vfp.h @@ -9,6 +9,7 @@ #ifndef __ASM_VFP_H #define __ASM_VFP_H +#ifndef CONFIG_AS_VFP_VMRS_FPINST #define FPSID cr0 #define FPSCR cr1 #define MVFR1 cr6 @@ -16,6 +17,7 @@ #define FPEXC cr8 #define FPINST cr9 #define FPINST2 cr10 +#endif /* FPSID bits */ #define FPSID_IMPLEMENTER_BIT (24) diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h index 947ee5395e1f..ba0d4cb5377e 100644 --- a/arch/arm/include/asm/vfpmacros.h +++ b/arch/arm/include/asm/vfpmacros.h @@ -8,7 +8,16 @@ #include <asm/vfp.h> -@ Macros to allow building with old toolkits (with no VFP support) +#ifdef CONFIG_AS_VFP_VMRS_FPINST + .macro VFPFMRX, rd, sysreg, cond + vmrs\cond \rd, \sysreg + .endm + + .macro VFPFMXR, sysreg, rd, cond + vmsr\cond \sysreg, \rd + .endm +#else + @ Macros to allow building with old toolkits (with no VFP support) .macro VFPFMRX, rd, sysreg, cond MRC\cond p10, 7, \rd, \sysreg, cr0, 0 @ FMRX \rd, \sysreg .endm @@ -16,6 +25,7 @@ .macro VFPFMXR, sysreg, rd, cond MCR\cond p10, 7, \rd, \sysreg, cr0, 0 @ FMXR \sysreg, \rd .endm +#endif @ read all the working registers back into the VFP .macro VFPFLDMIA, base, tmp diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index 64868a89a59f..6155ffae8603 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -81,6 +81,7 @@ ENTRY(vfp_support_entry) DBGSTR3 "instr %08x pc %08x state %p", r0, r2, r10 + .fpu vfpv2 ldr r3, [sp, #S_PSR] @ Neither lazy restore nor FP exceptions and r3, r3, #MODE_MASK @ are supported in kernel mode teq r3, #USR_MODE diff --git a/arch/arm/vfp/vfpinstr.h b/arch/arm/vfp/vfpinstr.h index 15b95b5ab97e..402b54d8fe28 100644 --- a/arch/arm/vfp/vfpinstr.h +++ b/arch/arm/vfp/vfpinstr.h @@ -65,10 +65,23 @@ #define FPSCR_C (1 << 29) #define FPSCR_V (1 << 28) -/* - * Since we aren't building with -mfpu=vfp, we need to code - * these instructions using their MRC/MCR equivalents. - */ +#ifdef CONFIG_AS_VFP_VMRS_FPINST + +#define fmrx(_vfp_) ({ \ + u32 __v; \ + asm(".fpu vfpv2\n" \ + "vmrs %0, " #_vfp_ \ + : "=r" (__v) : : "cc"); \ + __v; \ + }) + +#define fmxr(_vfp_,_var_) \ + asm(".fpu vfpv2\n" \ + "vmsr " #_vfp_ ", %0" \ + : : "r" (_var_) : "cc") + +#else + #define vfpreg(_vfp_) #_vfp_ #define fmrx(_vfp_) ({ \ @@ -82,6 +95,8 @@ asm("mcr p10, 7, %0, " vfpreg(_vfp_) ", cr0, 0 @ fmxr " #_vfp_ ", %0" \ : : "r" (_var_) : "cc") +#endif + u32 vfp_single_cpdo(u32 inst, u32 fpscr); u32 vfp_single_cprt(u32 inst, u32 fpscr, struct pt_regs *regs);