whiterose

linux unikernel
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commit f14b5f05cde1e22f4a99d7bc0f9d61f024f21f70
parent 37d18565e4c2d691286b88a5a4e70bcf563768f4
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu,  7 Mar 2019 13:38:27 -0800

Merge branch 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Ingo Molnar:
 "Misc cleanups and a retpoline code generation optimization"

* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, retpolines: Raise limit for generating indirect calls from switch-case
  x86/build: Use the single-argument OUTPUT_FORMAT() linker script command
  x86/build: Specify elf_i386 linker emulation explicitly for i386 objects
  x86/build: Mark per-CPU symbols as absolute explicitly for LLD

Diffstat:
March/x86/Makefile | 5+++++
March/x86/boot/Makefile | 2+-
March/x86/boot/compressed/vmlinux.lds.S | 2+-
March/x86/boot/setup.ld | 2+-
March/x86/kernel/vmlinux.lds.S | 4++--
March/x86/realmode/rm/Makefile | 2+-
March/x86/realmode/rm/realmode.lds.S | 2+-
7 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile @@ -217,6 +217,11 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables # Avoid indirect branches in kernel to deal with Spectre ifdef CONFIG_RETPOLINE KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) + # Additionally, avoid generating expensive indirect jumps which + # are subject to retpolines for small number of switch cases. + # clang turns off jump table generation by default when under + # retpoline builds, however, gcc does not for x86. + KBUILD_CFLAGS += $(call cc-option,--param=case-values-threshold=20) endif archscripts: scripts_basic diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile @@ -100,7 +100,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE AFLAGS_header.o += -I$(objtree)/$(obj) $(obj)/header.o: $(obj)/zoffset.h -LDFLAGS_setup.elf := -T +LDFLAGS_setup.elf := -m elf_i386 -T $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE $(call if_changed,ld) diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S @@ -1,7 +1,7 @@ /* SPDX-License-Identifier: GPL-2.0 */ #include <asm-generic/vmlinux.lds.h> -OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT) +OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT) #undef i386 diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld @@ -3,7 +3,7 @@ * * Linker script for the i386 setup code */ -OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386") +OUTPUT_FORMAT("elf32-i386") OUTPUT_ARCH(i386) ENTRY(_start) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S @@ -31,7 +31,7 @@ #undef i386 /* in case the preprocessor is a 32bit one */ -OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT) +OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT) #ifdef CONFIG_X86_32 OUTPUT_ARCH(i386) @@ -401,7 +401,7 @@ SECTIONS * Per-cpu symbols which need to be offset from __per_cpu_load * for the boot processor. */ -#define INIT_PER_CPU(x) init_per_cpu__##x = x + __per_cpu_load +#define INIT_PER_CPU(x) init_per_cpu__##x = ABSOLUTE(x) + __per_cpu_load INIT_PER_CPU(gdt_page); INIT_PER_CPU(irq_stack_union); diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile @@ -47,7 +47,7 @@ $(obj)/pasyms.h: $(REALMODE_OBJS) FORCE targets += realmode.lds $(obj)/realmode.lds: $(obj)/pasyms.h -LDFLAGS_realmode.elf := --emit-relocs -T +LDFLAGS_realmode.elf := -m elf_i386 --emit-relocs -T CPPFLAGS_realmode.lds += -P -C -I$(objtree)/$(obj) targets += realmode.elf diff --git a/arch/x86/realmode/rm/realmode.lds.S b/arch/x86/realmode/rm/realmode.lds.S @@ -9,7 +9,7 @@ #undef i386 -OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386") +OUTPUT_FORMAT("elf32-i386") OUTPUT_ARCH(i386) SECTIONS