Using a custom LDFLAG for all objects and binaries

Using a custom LDFLAG for all objects and binaries

[Mahmood Naderan]

Hi
I would like to modify the kernel makefile in a way to include
--emit-relocs for every file that is linked during the process of
kernel make.
I see

KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
LDFLAGS_MODULE  =
LDFLAGS_vmlinux =
...

But I don't know which one is the main. Should I put that option in
front of every LD* variable? Or it is possible to apply one variable
for every file that is linked?
Appreciate your help.


Regards,
Mahmood

Re: Using a custom LDFLAG for all objects and binaries

[Randy Dunlap]

On 5/10/20 6:35 AM, Mahmood Naderan wrote:
> Hi
> I would like to modify the kernel makefile in a way to include
> --emit-relocs for every file that is linked during the process of
> kernel make.
> I see
> 
> KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
> LDFLAGS_MODULE  =
> LDFLAGS_vmlinux =
> ...
> 
> But I don't know which one is the main. Should I put that option in
> front of every LD* variable? Or it is possible to apply one variable
> for every file that is linked?
> Appreciate your help.
> 
> 
> Regards,
> Mahmood

Hi,

Have you read Documentation/kbuild/makefiles.rst ?

    LDFLAGS
	Generic $(LD) options

	Flags used for all invocations of the linker.


You could always build with V=1 to see all of the
command lines that are used in the build.

HTH.
-- 
~Randy

Re: Using a custom LDFLAG for all objects and binaries

[Mahmood Naderan]

> Have you read Documentation/kbuild/makefiles.rst ?
>
>     LDFLAGS
>         Generic $(LD) options
>
>         Flags used for all invocations of the linker.


What I see is this in Documentation/kbuild/makefiles.txt

    LDFLAGS             Generic $(LD) options

        Flags used for all invocations of the linker.
        Often specifying the emulation is sufficient.

        Example:
                #arch/s390/Makefile
                LDFLAGS         := -m elf_s390
        Note: ldflags-y can be used to further customise
        the flags used. See chapter 3.7.



I have two questions then:
1- Can I use that as a bash variable? Like "LDFLAGS=--emit-relocs make"
or
2- Editing arch/x86/Makefile with
   KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)

Thanks for your help.


Regards,
Mahmood

Re: Using a custom LDFLAG for all objects and binaries

[Randy Dunlap]

On 5/10/20 10:13 AM, Mahmood Naderan wrote:
>> Have you read Documentation/kbuild/makefiles.rst ?
>>
>>     LDFLAGS
>>         Generic $(LD) options
>>
>>         Flags used for all invocations of the linker.
> 
> 
> What I see is this in Documentation/kbuild/makefiles.txt
> 
>     LDFLAGS             Generic $(LD) options
> 
>         Flags used for all invocations of the linker.
>         Often specifying the emulation is sufficient.
> 
>         Example:
>                 #arch/s390/Makefile
>                 LDFLAGS         := -m elf_s390
>         Note: ldflags-y can be used to further customise
>         the flags used. See chapter 3.7.
> 
> 
> 
> I have two questions then:
> 1- Can I use that as a bash variable? Like "LDFLAGS=--emit-relocs make"

I don't know. You could experiment with it to see.
(again by using 'make V=1' to see the commands that are being used)

> or
> 2- Editing arch/x86/Makefile with
>    KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)

That should work.

> Thanks for your help.

It would be better to ask these questions on the linux-kbuild mailing list
(added now).

-- 
~Randy

Re: Using a custom LDFLAG for all objects and binaries

[Mahmood Naderan]

> > or
> > 2- Editing arch/x86/Makefile with
> >    KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)
>
> That should work.


Seems not... I ran the following commands:

$ cp -v /boot/config-$(uname -r) .config
$ make menuconfig  -> Exit -> Save
$ vim arch/x86/Makefile
     KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)
$ make V=1

This is the error that I get

make -f ./scripts/Makefile.build obj=usr need-builtin=1
/bin/bash ./usr/gen_initramfs_list.sh -l -d > usr/.initramfs_data.cpio.d
(cat /dev/null; ) > usr/modules.order
make -f ./scripts/Makefile.build obj=arch/x86 need-builtin=1
make -f ./scripts/Makefile.build obj=arch/x86/crypto need-builtin=1
make -f ./scripts/Makefile.build obj=arch/x86/crypto/sha1-mb need-builtin=
(cat /dev/null;   echo kernel/arch/x86/crypto/sha1-mb/sha1-mb.ko;) >
arch/x86/crypto/sha1-mb/modules.order
  ld -m --emit-relocs elf_x86_64     -r -o
arch/x86/crypto/sha1-mb/sha1-mb.o arch/x86/crypto/sha1-mb/sha1_mb.o
arch/x86/crypto/sha1-mb/sha1_mb_mgr_flush_avx2.o
arch/x86/crypto/sha1-mb/sha1_mb_mgr_init_avx2.o
arch/x86/crypto/sha1-mb/sha1_mb_mgr_submit_avx2.o
arch/x86/crypto/sha1-mb/sha1_x8_avx2.o
ld: unrecognised emulation mode: --emit-relocs
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu
i386linux elf_l1om elf_k1om i386pep i386pe
scripts/Makefile.build:516: recipe for target
'arch/x86/crypto/sha1-mb/sha1-mb.o' failed
make[3]: *** [arch/x86/crypto/sha1-mb/sha1-mb.o] Error 1
scripts/Makefile.build:544: recipe for target 'arch/x86/crypto/sha1-mb' failed
make[2]: *** [arch/x86/crypto/sha1-mb] Error 2
scripts/Makefile.build:544: recipe for target 'arch/x86/crypto' failed
make[1]: *** [arch/x86/crypto] Error 2
Makefile:1053: recipe for target 'arch/x86' failed
make: *** [arch/x86] Error 2





ORIGINAL QUESTION:

>Hi
>I would like to modify the kernel makefile in a way to include
>--emit-relocs for every file that is linked during the process of
>kernel make.
>I see
>
>KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
>LDFLAGS_MODULE  =
>LDFLAGS_vmlinux =
>...
>
>But I don't know which one is the main. Should I put that option in
>front of every LD* variable? Or it is possible to apply one variable
>for every file that is linked?
>Appreciate your help.
>


Regards,
Mahmood

Re: Using a custom LDFLAG for all objects and binaries

[Randy Dunlap]

On 5/10/20 12:04 PM, Mahmood Naderan wrote:
>>> or
>>> 2- Editing arch/x86/Makefile with
>>>    KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)
>>
>> That should work.
> 
> 
> Seems not... I ran the following commands:
> 
> $ cp -v /boot/config-$(uname -r) .config
> $ make menuconfig  -> Exit -> Save
> $ vim arch/x86/Makefile
>      KBUILD_LDFLAGS := -m --emit-relocs elf_$(UTS_MACHINE)
> $ make V=1

OK, I suggest that you reorder the options like so:

	KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE) --emit-relocs

I.e., don't split -m and the machine type.


> This is the error that I get
> 
> make -f ./scripts/Makefile.build obj=usr need-builtin=1
> /bin/bash ./usr/gen_initramfs_list.sh -l -d > usr/.initramfs_data.cpio.d
> (cat /dev/null; ) > usr/modules.order
> make -f ./scripts/Makefile.build obj=arch/x86 need-builtin=1
> make -f ./scripts/Makefile.build obj=arch/x86/crypto need-builtin=1
> make -f ./scripts/Makefile.build obj=arch/x86/crypto/sha1-mb need-builtin=
> (cat /dev/null;   echo kernel/arch/x86/crypto/sha1-mb/sha1-mb.ko;) >
> arch/x86/crypto/sha1-mb/modules.order
>   ld -m --emit-relocs elf_x86_64     -r -o
> arch/x86/crypto/sha1-mb/sha1-mb.o arch/x86/crypto/sha1-mb/sha1_mb.o
> arch/x86/crypto/sha1-mb/sha1_mb_mgr_flush_avx2.o
> arch/x86/crypto/sha1-mb/sha1_mb_mgr_init_avx2.o
> arch/x86/crypto/sha1-mb/sha1_mb_mgr_submit_avx2.o
> arch/x86/crypto/sha1-mb/sha1_x8_avx2.o
> ld: unrecognised emulation mode: --emit-relocs
> Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu
> i386linux elf_l1om elf_k1om i386pep i386pe
> scripts/Makefile.build:516: recipe for target
> 'arch/x86/crypto/sha1-mb/sha1-mb.o' failed
> make[3]: *** [arch/x86/crypto/sha1-mb/sha1-mb.o] Error 1
> scripts/Makefile.build:544: recipe for target 'arch/x86/crypto/sha1-mb' failed
> make[2]: *** [arch/x86/crypto/sha1-mb] Error 2
> scripts/Makefile.build:544: recipe for target 'arch/x86/crypto' failed
> make[1]: *** [arch/x86/crypto] Error 2
> Makefile:1053: recipe for target 'arch/x86' failed
> make: *** [arch/x86] Error 2
> 
> 
> 
> 
> 
> ORIGINAL QUESTION:
> 
>> Hi
>> I would like to modify the kernel makefile in a way to include
>> --emit-relocs for every file that is linked during the process of
>> kernel make.
>> I see
>>
>> KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
>> LDFLAGS_MODULE  =
>> LDFLAGS_vmlinux =
>> ...
>>
>> But I don't know which one is the main. Should I put that option in
>> front of every LD* variable? Or it is possible to apply one variable
>> for every file that is linked?
>> Appreciate your help.
>>
> 
> 
> Regards,
> Mahmood
> 


-- 
~Randy

Re: Using a custom LDFLAG for all objects and binaries

[Mahmood Naderan]

>OK, I suggest that you reorder the options like so:
>
>        KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE) --emit-relocs


I did that. After

$ make V=1
$ sudo make modules_install V=1
$ sudo make install

I grepped for "emit-relocs" in the log and saw many instances such as

  gcc -Wp,-MD,drivers/rtc/.rtc-ds1305.o.d  -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/5/include -I./arch/x86/include
-I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi
-I./arch/x86/include/generated/uapi -I./include/uapi
-I./include/generated/uapi -include ./include/linux/kconfig.h -include
./include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
-fshort-wchar -Werror-implicit-function-declaration
-Wno-format-security -std=gnu89 -fno-PIE -mno-sse -mno-mmx -mno-sse2
-mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387
-mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup
-mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
-DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1
-DCONFIG_AS_AVX512=1 -DCONFIG_AS_SHA1_NI=1 -DCONFIG_AS_SHA256_NI=1
-pipe -Wno-sign-compare -fno-asynchronous-unwind-tables
-mindirect-branch=thunk-extern -mindirect-branch-register
-fno-jump-tables -fno-delete-null-pointer-checks -O2
--param=allow-store-data-races=0 -Wframe-larger-than=1024
-fstack-protector-strong -Wno-unused-but-set-variable
-fno-omit-frame-pointer -fno-optimize-sibling-calls
-fno-var-tracking-assignments -g -gdwarf-4 -pg -mrecord-mcount
-mfentry -DCC_USING_FENTRY -Wdeclaration-after-statement
-Wno-pointer-sign -fno-strict-overflow -fno-merge-all-constants
-fmerge-constants -fno-stack-check -fconserve-stack
-Werror=implicit-int -Werror=strict-prototypes -Werror=date-time
-Werror=incompatible-pointer-types -Werror=designated-init  -DMODULE
-DKBUILD_BASENAME='"rtc_ds1305"' -DKBUILD_MODNAME='"rtc_ds1305"' -c -o
drivers/rtc/rtc-ds1305.o drivers/rtc/rtc-ds1305.c
   ./tools/objtool/objtool check  --module --retpoline
"drivers/scsi/aacraid/dpcsup.o";

OR

  ld -r -m elf_x86_64 --emit-relocs  -z max-page-size=0x200000 -T
./scripts/module-common.lds  --build-id  -o
sound/usb/line6/snd-usb-line6.ko sound/usb/line6/snd-usb-line6.o
sound/usb/line6/snd-usb-line6.mod.o ;  true



I guess that all kernel modules are now use --emit-relocs.
I would like to be sure that libc and those files related to syscalls
are also using that.

I grepped for "libc.so" but it seems that there is no such match.
Did I miss something?


Regards,
Mahmood

Re: Using a custom LDFLAG for all objects and binaries

[Randy Dunlap]

On 5/10/20 12:53 PM, Mahmood Naderan wrote:
>> OK, I suggest that you reorder the options like so:
>>
>>        KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE) --emit-relocs
> 
> 
> I did that. After
> 
> $ make V=1
> $ sudo make modules_install V=1
> $ sudo make install
> 
> I grepped for "emit-relocs" in the log and saw many instances such as
> 
>   gcc -Wp,-MD,drivers/rtc/.rtc-ds1305.o.d  -nostdinc -isystem
> /usr/lib/gcc/x86_64-linux-gnu/5/include -I./arch/x86/include
> -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi
> -I./arch/x86/include/generated/uapi -I./include/uapi
> -I./include/generated/uapi -include ./include/linux/kconfig.h -include
> ./include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef
> -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
> -fshort-wchar -Werror-implicit-function-declaration
> -Wno-format-security -std=gnu89 -fno-PIE -mno-sse -mno-mmx -mno-sse2
> -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387
> -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup
> -mtune=generic -mno-red-zone -mcmodel=kernel -funit-at-a-time
> -DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
> -DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
> -DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1
> -DCONFIG_AS_AVX512=1 -DCONFIG_AS_SHA1_NI=1 -DCONFIG_AS_SHA256_NI=1
> -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables
> -mindirect-branch=thunk-extern -mindirect-branch-register
> -fno-jump-tables -fno-delete-null-pointer-checks -O2
> --param=allow-store-data-races=0 -Wframe-larger-than=1024
> -fstack-protector-strong -Wno-unused-but-set-variable
> -fno-omit-frame-pointer -fno-optimize-sibling-calls
> -fno-var-tracking-assignments -g -gdwarf-4 -pg -mrecord-mcount
> -mfentry -DCC_USING_FENTRY -Wdeclaration-after-statement
> -Wno-pointer-sign -fno-strict-overflow -fno-merge-all-constants
> -fmerge-constants -fno-stack-check -fconserve-stack
> -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time
> -Werror=incompatible-pointer-types -Werror=designated-init  -DMODULE
> -DKBUILD_BASENAME='"rtc_ds1305"' -DKBUILD_MODNAME='"rtc_ds1305"' -c -o
> drivers/rtc/rtc-ds1305.o drivers/rtc/rtc-ds1305.c
>    ./tools/objtool/objtool check  --module --retpoline
> "drivers/scsi/aacraid/dpcsup.o";
> 
> OR
> 
>   ld -r -m elf_x86_64 --emit-relocs  -z max-page-size=0x200000 -T
> ./scripts/module-common.lds  --build-id  -o
> sound/usb/line6/snd-usb-line6.ko sound/usb/line6/snd-usb-line6.o
> sound/usb/line6/snd-usb-line6.mod.o ;  true
> 
> 
> 
> I guess that all kernel modules are now use --emit-relocs.
> I would like to be sure that libc and those files related to syscalls
> are also using that.
> 
> I grepped for "libc.so" but it seems that there is no such match.
> Did I miss something?

The kernel doesn't use libc...

-- 
~Randy