From: John Millikin <[email protected]>
When cross-compiling with Clang, the `$(CLANG_FLAGS)' variable
contains additional flags needed to build C and assembly sources
for the target platform. Normally this variable is automatically
included in `$(KBUILD_CFLAGS)' by via the top-level Makefile.
The x86 real-mode makefile builds `$(REALMODE_CFLAGS)' from a
plain assignment and therefore drops the Clang flags. This causes
Clang to not recognize x86-specific assembler directives:
arch/x86/realmode/rm/header.S:36:1: error: unknown directive
.type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header
^
Explicit propagation of `$(CLANG_FLAGS)' to `$(REALMODE_CFLAGS)',
which is inherited by real-mode make rules, fixes cross-compilation
with Clang for x86 targets.
Relevant flags:
* `--target' sets the target architecture when cross-compiling. This
flag must be set for both compilation and assembly (`KBUILD_AFLAGS')
to support architecture-specific assembler directives.
* `-no-integrated-as' tells clang to assemble with GNU Assembler
instead of its built-in LLVM assembler. This flag is set by default
unless `LLVM_IAS=1' is set, because the LLVM assembler can't yet
parse certain GNU extensions.
Signed-off-by: John Millikin <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
arch/x86/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 2d6d5a28c3bf..9a73e0cea19c 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -33,6 +33,7 @@ REALMODE_CFLAGS += -ffreestanding
REALMODE_CFLAGS += -fno-stack-protector
REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member)
REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4))
+REALMODE_CFLAGS += $(CLANG_FLAGS)
export REALMODE_CFLAGS
# BITS is used as extension for files which are available in a 32 bit
--
2.31.0
On Fri, Mar 26, 2021 at 1:04 AM Nathan Chancellor <[email protected]> wrote:
>
> From: John Millikin <[email protected]>
>
> When cross-compiling with Clang, the `$(CLANG_FLAGS)' variable
> contains additional flags needed to build C and assembly sources
> for the target platform. Normally this variable is automatically
> included in `$(KBUILD_CFLAGS)' by via the top-level Makefile.
>
> The x86 real-mode makefile builds `$(REALMODE_CFLAGS)' from a
> plain assignment and therefore drops the Clang flags. This causes
> Clang to not recognize x86-specific assembler directives:
>
> arch/x86/realmode/rm/header.S:36:1: error: unknown directive
> .type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header
> ^
>
> Explicit propagation of `$(CLANG_FLAGS)' to `$(REALMODE_CFLAGS)',
> which is inherited by real-mode make rules, fixes cross-compilation
> with Clang for x86 targets.
>
> Relevant flags:
>
> * `--target' sets the target architecture when cross-compiling. This
> flag must be set for both compilation and assembly (`KBUILD_AFLAGS')
> to support architecture-specific assembler directives.
>
> * `-no-integrated-as' tells clang to assemble with GNU Assembler
> instead of its built-in LLVM assembler. This flag is set by default
> unless `LLVM_IAS=1' is set, because the LLVM assembler can't yet
> parse certain GNU extensions.
>
> Signed-off-by: John Millikin <[email protected]>
> Tested-by: Sedat Dilek <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
I had John's v2 of this patch in my custom 5.11 patchset.
Thanks for bringing this up again, Nathan.
Later, I will test the triple patchset series.
Feel free to add for this one:
Tested-by: Sedat Dilek <[email protected]>
- Sedat -
> ---
> arch/x86/Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 2d6d5a28c3bf..9a73e0cea19c 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -33,6 +33,7 @@ REALMODE_CFLAGS += -ffreestanding
> REALMODE_CFLAGS += -fno-stack-protector
> REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member)
> REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4))
> +REALMODE_CFLAGS += $(CLANG_FLAGS)
> export REALMODE_CFLAGS
>
> # BITS is used as extension for files which are available in a 32 bit
> --
> 2.31.0
>
The following commit has been merged into the x86/build branch of tip:
Commit-ID: 8abe7fc26ad8f28bfdf78adbed56acd1fa93f82d
Gitweb: https://git.kernel.org/tip/8abe7fc26ad8f28bfdf78adbed56acd1fa93f82d
Author: John Millikin <[email protected]>
AuthorDate: Thu, 25 Mar 2021 17:04:33 -07:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Fri, 26 Mar 2021 11:32:47 +01:00
x86/build: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS)
When cross-compiling with Clang, the `$(CLANG_FLAGS)' variable
contains additional flags needed to build C and assembly sources
for the target platform. Normally this variable is automatically
included in `$(KBUILD_CFLAGS)' via the top-level Makefile.
The x86 real-mode makefile builds `$(REALMODE_CFLAGS)' from a
plain assignment and therefore drops the Clang flags. This causes
Clang to not recognize x86-specific assembler directives:
arch/x86/realmode/rm/header.S:36:1: error: unknown directive
.type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header
^
Explicit propagation of `$(CLANG_FLAGS)' to `$(REALMODE_CFLAGS)',
which is inherited by real-mode make rules, fixes cross-compilation
with Clang for x86 targets.
Relevant flags:
* `--target' sets the target architecture when cross-compiling. This
flag must be set for both compilation and assembly (`KBUILD_AFLAGS')
to support architecture-specific assembler directives.
* `-no-integrated-as' tells clang to assemble with GNU Assembler
instead of its built-in LLVM assembler. This flag is set by default
unless `LLVM_IAS=1' is set, because the LLVM assembler can't yet
parse certain GNU extensions.
Signed-off-by: John Millikin <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 2d6d5a2..9a73e0c 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -33,6 +33,7 @@ REALMODE_CFLAGS += -ffreestanding
REALMODE_CFLAGS += -fno-stack-protector
REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member)
REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4))
+REALMODE_CFLAGS += $(CLANG_FLAGS)
export REALMODE_CFLAGS
# BITS is used as extension for files which are available in a 32 bit