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

7 files changed, 12 insertions, 7 deletions

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 9c5a67d1b9c1..f55420a67164 100644
--- 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
index 9b5adae9cc40..e2839b5c246c 100644
--- 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
index f491bbde8493..508cfa6828c5 100644
--- 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
index 96a6c7563538..0149e41d42c2 100644
--- 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
index 0d618ee634ac..bad8c51fee6e 100644
--- 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
index 4463fa72db94..96cb20de08af 100644
--- 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
index df8e11e26bc3..3bb980800c58 100644
--- 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