[PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC

[PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC

[Nick Desaulniers]

A revert of the following two commits.
commit de3accdaec88 ("x86, build: Build 16-bit code with -m16 where
possible")
commit a9cfccee6604 ("x86, build: Change code16gcc.h from a C header to
an assembly header")

Since commit 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@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 1bf21746f4ce..7116da3980be 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 e19fd7536307..000000000000
--- 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
-- 
2.29.2.454.gaff20da3a2-goog

Re: [PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC

[Nathan Chancellor]

On Mon, Nov 30, 2020 at 05:13:06PM -0800, 'Nick Desaulniers' via Clang Built Linux wrote:
> A revert of the following two commits.
> commit de3accdaec88 ("x86, build: Build 16-bit code with -m16 where
> possible")
> commit a9cfccee6604 ("x86, build: Change code16gcc.h from a C header to
> an assembly header")
> 
> Since commit 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@google.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.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 1bf21746f4ce..7116da3980be 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 e19fd7536307..000000000000
> --- 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
> -- 
> 2.29.2.454.gaff20da3a2-goog
> 

Re: [PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC

[David Woodhouse]

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On Mon, 2020-11-30 at 17:13 -0800, Nick Desaulniers wrote:
> A revert of the following two commits.
> commit de3accdaec88 ("x86, build: Build 16-bit code with -m16 where
> possible")
> commit a9cfccee6604 ("x86, build: Change code16gcc.h from a C header to
> an assembly header")
> 
> Since commit 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@google.com>

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>

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

[tip-bot2 for Nick Desaulniers]

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@google.com>
AuthorDate:    Mon, 30 Nov 2020 17:13:06 -08:00
Committer:     Borislav Petkov <bp@suse.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@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: David Woodhouse <dwmw@amazon.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

Re: [PATCH] x86, build: remove -m16 workaround for unsupported versions of GCC

[hpa]

On November 30, 2020 5:13:06 PM PST, Nick Desaulniers <ndesaulniers@google.com> wrote:
>A revert of the following two commits.
>commit de3accdaec88 ("x86, build: Build 16-bit code with -m16 where
>possible")
>commit a9cfccee6604 ("x86, build: Change code16gcc.h from a C header to
>an assembly header")
>
>Since commit 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@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 1bf21746f4ce..7116da3980be 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 e19fd7536307..000000000000
>--- 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

With enthusiasm:

Acked-by: H. Peter Anvin <hpa@zytor.com>
-- 
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