linux-kernel - [tip: x86/build] x86/build: Remove -m16 workaround for unsupported versions of GCC

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Date:   Tue, 01 Dec 2020 16:43:39 -0000
From:   "tip-bot2 for Nick Desaulniers" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        David Woodhouse <dwmw@...zon.co.uk>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/build] x86/build: Remove -m16 workaround for unsupported
 versions of GCC

The following commit has been merged into the x86/build branch of tip:

Commit-ID:     2838307b019dfec0c309c4e8e589658736cff4c9
Gitweb:        https://git.kernel.org/tip/2838307b019dfec0c309c4e8e589658736cff4c9
Author:        Nick Desaulniers <ndesaulniers@...gle.com>
AuthorDate:    Mon, 30 Nov 2020 17:13:06 -08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 01 Dec 2020 17:17:18 +01:00

x86/build: Remove -m16 workaround for unsupported versions of GCC

Revert the following two commits:

  de3accdaec88 ("x86, build: Build 16-bit code with -m16 where possible")
  a9cfccee6604 ("x86, build: Change code16gcc.h from a C header to an assembly header")

Since

  0bddd227f3dc ("Documentation: update for gcc 4.9 requirement")

the minimum supported version of GCC is gcc-4.9. It's now safe to remove
this code.

Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>
Link: https://lkml.kernel.org/r/20201201011307.3676986-1-ndesaulniers@google.com
---
 arch/x86/Makefile         |  9 +--------
 arch/x86/boot/code16gcc.h | 12 ------------
 2 files changed, 1 insertion(+), 20 deletions(-)
 delete mode 100644 arch/x86/boot/code16gcc.h

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 154259f..b891066 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -24,14 +24,7 @@ endif
 
 # How to compile the 16-bit code.  Note we always compile for -march=i386;
 # that way we can complain to the user if the CPU is insufficient.
-#
-# The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
-# older versions of GCC, include an *assembly* header to make sure that
-# gcc doesn't play any games behind our back.
-CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h
-M16_CFLAGS	 := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
-
-REALMODE_CFLAGS	:= $(M16_CFLAGS) -g -Os -DDISABLE_BRANCH_PROFILING \
+REALMODE_CFLAGS	:= -m16 -g -Os -DDISABLE_BRANCH_PROFILING \
 		   -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
 		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
 		   -mno-mmx -mno-sse
diff --git a/arch/x86/boot/code16gcc.h b/arch/x86/boot/code16gcc.h
deleted file mode 100644
index e19fd75..0000000
--- a/arch/x86/boot/code16gcc.h
+++ /dev/null
@@ -1,12 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#
-# code16gcc.h
-#
-# This file is added to the assembler via -Wa when compiling 16-bit C code.
-# This is done this way instead via asm() to make sure gcc does not reorder
-# things around us.
-#
-# gcc 4.9+ has a real -m16 option so we can drop this hack long term.
-#
-
-	.code16gcc