Re: [PATCH] arm64: remove special treatment for the link order of head.o

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Ard Biesheuvel]

(cc BTF list and maintainer)

On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> Hi,
>
> On 2023-03-22 15:51, Ard Biesheuvel wrote:
> > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > >
> > > Hi,
> > >
> > > On 2022-10-13 08:35, Masahiro Yamada wrote:
> > > > In the previous discussion (see the Link tag), Ard pointed out that
> > > > arm/arm64/kernel/head.o does not need any special treatment - the only
> > > > piece that must appear right at the start of the binary image is the
> > > > image header which is emitted into .head.text.
> > > >
> > > > The linker script does the right thing to do. The build system does
> > > > not need to manipulate the link order of head.o.
> > > >
> > > > Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > ---
> > > >
> > > >  scripts/head-object-list.txt | 1 -
> > > >  1 file changed, 1 deletion(-)
> > > >
> > > > diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> > > > index b16326a92c45..f226e45e3b7b 100644
> > > > --- a/scripts/head-object-list.txt
> > > > +++ b/scripts/head-object-list.txt
> > > > @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
> > > >  arch/arc/kernel/head.o
> > > >  arch/arm/kernel/head-nommu.o
> > > >  arch/arm/kernel/head.o
> > > > -arch/arm64/kernel/head.o
> > > >  arch/csky/kernel/head.o
> > > >  arch/hexagon/kernel/head.o
> > > >  arch/ia64/kernel/head.o
> > >
> > > This patch causes a significant increase of the arch/arm64/boot/Image
> > > size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
> > > after this patch has been applied to the 6.1 stable tree.
> > >
> > > In turn this causes issues with some bootloaders, for instance U-Boot on
> > > a Raspberry Pi limits the kernel size to 36 MB.
> > >
> >
> > I cannot reproduce this with mainline
> >
> > With the patch
> >
> > $ size vmlinux
> >    text    data     bss     dec     hex filename
> > 24567309 14752630 621680 39941619 26175f3 vmlinux
> >
> > With the patch reverted
> >
> > $ size vmlinux
> >    text    data     bss     dec     hex filename
> > 24567309 14752694 621680 39941683 2617633 vmlinux
>
> I have tried with the current mainline, this is what I get, using GCC 12.2.0
> and binutils 2.40:
>
>    text    data     bss     dec     hex filename
> 32531655        8192996  621968 41346619        276e63b vmlinux.orig
> 25170610        8192996  621968 33985574        2069426 vmlinux.revert
>
> > It would help to compare the resulting vmlinux ELF images from both
> > builds to see where the extra space is being allocated
>
> At a first glance, it seems the extra space is allocated in the BTF
> section. I have uploaded the resulting files as well as the config file
> I used there:
> https://temp.aurel32.net/linux-arm64-size-head.o.tar.gz
>

Indeed. So we go from

  [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
       00000000005093d6  0000000000000000   A       0     0     1

to

  [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
       0000000000c0e5eb  0000000000000000   A       0     0     1

i.e, from 5 MiB to 12+ MiB of BTF metadata.

To me, it is not clear at all how one would be related to the other,
so it will leave it to the Kbuild and BTF experts to chew on this one.

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Alexei Starovoitov]

On Fri, Mar 24, 2023 at 4:39 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> (cc BTF list and maintainer)
>
> On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@aurel32.net> wrote:
> >
> > Hi,
> >
> > On 2023-03-22 15:51, Ard Biesheuvel wrote:
> > > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On 2022-10-13 08:35, Masahiro Yamada wrote:
> > > > > In the previous discussion (see the Link tag), Ard pointed out that
> > > > > arm/arm64/kernel/head.o does not need any special treatment - the only
> > > > > piece that must appear right at the start of the binary image is the
> > > > > image header which is emitted into .head.text.
> > > > >
> > > > > The linker script does the right thing to do. The build system does
> > > > > not need to manipulate the link order of head.o.
> > > > >
> > > > > Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> > > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > > ---
> > > > >
> > > > >  scripts/head-object-list.txt | 1 -
> > > > >  1 file changed, 1 deletion(-)
> > > > >
> > > > > diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> > > > > index b16326a92c45..f226e45e3b7b 100644
> > > > > --- a/scripts/head-object-list.txt
> > > > > +++ b/scripts/head-object-list.txt
> > > > > @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
> > > > >  arch/arc/kernel/head.o
> > > > >  arch/arm/kernel/head-nommu.o
> > > > >  arch/arm/kernel/head.o
> > > > > -arch/arm64/kernel/head.o
> > > > >  arch/csky/kernel/head.o
> > > > >  arch/hexagon/kernel/head.o
> > > > >  arch/ia64/kernel/head.o
> > > >
> > > > This patch causes a significant increase of the arch/arm64/boot/Image
> > > > size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
> > > > after this patch has been applied to the 6.1 stable tree.
> > > >
> > > > In turn this causes issues with some bootloaders, for instance U-Boot on
> > > > a Raspberry Pi limits the kernel size to 36 MB.
> > > >
> > >
> > > I cannot reproduce this with mainline
> > >
> > > With the patch
> > >
> > > $ size vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24567309 14752630 621680 39941619 26175f3 vmlinux
> > >
> > > With the patch reverted
> > >
> > > $ size vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24567309 14752694 621680 39941683 2617633 vmlinux
> >
> > I have tried with the current mainline, this is what I get, using GCC 12.2.0
> > and binutils 2.40:
> >
> >    text    data     bss     dec     hex filename
> > 32531655        8192996  621968 41346619        276e63b vmlinux.orig
> > 25170610        8192996  621968 33985574        2069426 vmlinux.revert
> >
> > > It would help to compare the resulting vmlinux ELF images from both
> > > builds to see where the extra space is being allocated
> >
> > At a first glance, it seems the extra space is allocated in the BTF
> > section. I have uploaded the resulting files as well as the config file
> > I used there:
> > https://temp.aurel32.net/linux-arm64-size-head.o.tar.gz
> >
>
> Indeed. So we go from
>
>   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
>        00000000005093d6  0000000000000000   A       0     0     1
>
> to
>
>   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
>        0000000000c0e5eb  0000000000000000   A       0     0     1
>
> i.e, from 5 MiB to 12+ MiB of BTF metadata.
>
> To me, it is not clear at all how one would be related to the other,
> so it will leave it to the Kbuild and BTF experts to chew on this one.

That's a huge increase.
It's not just that commit responsible, but the whole series ?
https://lore.kernel.org/lkml/20220906061313.1445810-1-masahiroy@kernel.org/
I'm guessing "Link vmlinux and modules in parallel" is related.
I'm not sure what "parallel link" means. Running 'ar' in parallel?
I cannot read makefile syntax, so no idea.

Jiri, Andrii, Alan, please take a look.

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Andrii Nakryiko]

On Fri, Mar 24, 2023 at 4:34 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Mar 24, 2023 at 4:39 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > (cc BTF list and maintainer)
> >
> > On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > >
> > > Hi,
> > >
> > > On 2023-03-22 15:51, Ard Biesheuvel wrote:
> > > > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > On 2022-10-13 08:35, Masahiro Yamada wrote:
> > > > > > In the previous discussion (see the Link tag), Ard pointed out that
> > > > > > arm/arm64/kernel/head.o does not need any special treatment - the only
> > > > > > piece that must appear right at the start of the binary image is the
> > > > > > image header which is emitted into .head.text.
> > > > > >
> > > > > > The linker script does the right thing to do. The build system does
> > > > > > not need to manipulate the link order of head.o.
> > > > > >
> > > > > > Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> > > > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > > > ---
> > > > > >
> > > > > >  scripts/head-object-list.txt | 1 -
> > > > > >  1 file changed, 1 deletion(-)
> > > > > >
> > > > > > diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> > > > > > index b16326a92c45..f226e45e3b7b 100644
> > > > > > --- a/scripts/head-object-list.txt
> > > > > > +++ b/scripts/head-object-list.txt
> > > > > > @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
> > > > > >  arch/arc/kernel/head.o
> > > > > >  arch/arm/kernel/head-nommu.o
> > > > > >  arch/arm/kernel/head.o
> > > > > > -arch/arm64/kernel/head.o
> > > > > >  arch/csky/kernel/head.o
> > > > > >  arch/hexagon/kernel/head.o
> > > > > >  arch/ia64/kernel/head.o
> > > > >
> > > > > This patch causes a significant increase of the arch/arm64/boot/Image
> > > > > size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
> > > > > after this patch has been applied to the 6.1 stable tree.
> > > > >
> > > > > In turn this causes issues with some bootloaders, for instance U-Boot on
> > > > > a Raspberry Pi limits the kernel size to 36 MB.
> > > > >
> > > >
> > > > I cannot reproduce this with mainline
> > > >
> > > > With the patch
> > > >
> > > > $ size vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24567309 14752630 621680 39941619 26175f3 vmlinux
> > > >
> > > > With the patch reverted
> > > >
> > > > $ size vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24567309 14752694 621680 39941683 2617633 vmlinux
> > >
> > > I have tried with the current mainline, this is what I get, using GCC 12.2.0
> > > and binutils 2.40:
> > >
> > >    text    data     bss     dec     hex filename
> > > 32531655        8192996  621968 41346619        276e63b vmlinux.orig
> > > 25170610        8192996  621968 33985574        2069426 vmlinux.revert
> > >
> > > > It would help to compare the resulting vmlinux ELF images from both
> > > > builds to see where the extra space is being allocated
> > >
> > > At a first glance, it seems the extra space is allocated in the BTF
> > > section. I have uploaded the resulting files as well as the config file
> > > I used there:
> > > https://temp.aurel32.net/linux-arm64-size-head.o.tar.gz
> > >
> >
> > Indeed. So we go from
> >
> >   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
> >        00000000005093d6  0000000000000000   A       0     0     1
> >
> > to
> >
> >   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
> >        0000000000c0e5eb  0000000000000000   A       0     0     1
> >
> > i.e, from 5 MiB to 12+ MiB of BTF metadata.
> >
> > To me, it is not clear at all how one would be related to the other,
> > so it will leave it to the Kbuild and BTF experts to chew on this one.
>
> That's a huge increase.
> It's not just that commit responsible, but the whole series ?
> https://lore.kernel.org/lkml/20220906061313.1445810-1-masahiroy@kernel.org/
> I'm guessing "Link vmlinux and modules in parallel" is related.
> I'm not sure what "parallel link" means. Running 'ar' in parallel?
> I cannot read makefile syntax, so no idea.
>
> Jiri, Andrii, Alan, please take a look.

So it seems to come from the difference in return type for mm_struct's
get_unmapped_area callback:


struct mm_struct {
        struct {
                struct maple_tree mm_mt;
#ifdef CONFIG_MMU
                unsigned long (*get_unmapped_area) (struct file *filp,
                                unsigned long addr, unsigned long len,
                                unsigned long pgoff, unsigned long flags);
#endif


It seems that sometimes we have "unsigned long" as return type, but
sometimes it's just "void". I haven't debugged why this is happening.
But cc'ing Eduard, just in case it's related to the "unspecified type"
tracking in pahole, which he recently fixed. There could be some other
related bug lurking around.

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Masahiro Yamada]

On Fri, Mar 24, 2023 at 8:33 PM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> (cc BTF list and maintainer)
>
> On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@aurel32.net> wrote:
> >
> > Hi,
> >
> > On 2023-03-22 15:51, Ard Biesheuvel wrote:
> > > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On 2022-10-13 08:35, Masahiro Yamada wrote:
> > > > > In the previous discussion (see the Link tag), Ard pointed out that
> > > > > arm/arm64/kernel/head.o does not need any special treatment - the only
> > > > > piece that must appear right at the start of the binary image is the
> > > > > image header which is emitted into .head.text.
> > > > >
> > > > > The linker script does the right thing to do. The build system does
> > > > > not need to manipulate the link order of head.o.
> > > > >
> > > > > Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> > > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > > ---
> > > > >
> > > > >  scripts/head-object-list.txt | 1 -
> > > > >  1 file changed, 1 deletion(-)
> > > > >
> > > > > diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> > > > > index b16326a92c45..f226e45e3b7b 100644
> > > > > --- a/scripts/head-object-list.txt
> > > > > +++ b/scripts/head-object-list.txt
> > > > > @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
> > > > >  arch/arc/kernel/head.o
> > > > >  arch/arm/kernel/head-nommu.o
> > > > >  arch/arm/kernel/head.o
> > > > > -arch/arm64/kernel/head.o
> > > > >  arch/csky/kernel/head.o
> > > > >  arch/hexagon/kernel/head.o
> > > > >  arch/ia64/kernel/head.o
> > > >
> > > > This patch causes a significant increase of the arch/arm64/boot/Image
> > > > size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
> > > > after this patch has been applied to the 6.1 stable tree.
> > > >
> > > > In turn this causes issues with some bootloaders, for instance U-Boot on
> > > > a Raspberry Pi limits the kernel size to 36 MB.
> > > >
> > >
> > > I cannot reproduce this with mainline
> > >
> > > With the patch
> > >
> > > $ size vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24567309 14752630 621680 39941619 26175f3 vmlinux
> > >
> > > With the patch reverted
> > >
> > > $ size vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24567309 14752694 621680 39941683 2617633 vmlinux
> >
> > I have tried with the current mainline, this is what I get, using GCC 12.2.0
> > and binutils 2.40:
> >
> >    text    data     bss     dec     hex filename
> > 32531655        8192996  621968 41346619        276e63b vmlinux.orig
> > 25170610        8192996  621968 33985574        2069426 vmlinux.revert
> >
> > > It would help to compare the resulting vmlinux ELF images from both
> > > builds to see where the extra space is being allocated
> >
> > At a first glance, it seems the extra space is allocated in the BTF
> > section. I have uploaded the resulting files as well as the config file
> > I used there:
> > https://temp.aurel32.net/linux-arm64-size-head.o.tar.gz
> >
>
> Indeed. So we go from
>
>   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
>        00000000005093d6  0000000000000000   A       0     0     1
>
> to
>
>   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
>        0000000000c0e5eb  0000000000000000   A       0     0     1
>
> i.e, from 5 MiB to 12+ MiB of BTF metadata.
>
> To me, it is not clear at all how one would be related to the other,
> so it will leave it to the Kbuild and BTF experts to chew on this one.



Strange.

I used the .config file Aurelien provided, but
I still cannot reproduce this issue.


The vmlinux size is small
as-is in the current mainline.



[mainline]


masahiro@zoe:~/ref/linux(master)$ git log --oneline -1
65aca32efdcb (HEAD -> master, origin/master, origin/HEAD) Merge tag
'mm-hotfixes-stable-2023-03-24-17-09' of
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-size  vmlinux
   text    data     bss     dec     hex filename
24561282 8186912 622032 33370226 1fd3072 vmlinux
masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-readelf -S
vmlinux | grep -A1 BTF
  [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
       000000000048209c  0000000000000000   A       0     0     1
  [16] .BTF_ids          PROGBITS         ffff8000096427a4  016527a4
       0000000000000a1c  0000000000000000   A       0     0     1




[mainline + revert 994b7ac]

masahiro@zoe:~/ref/linux2(testing)$ git log --oneline -2
856c80dd789c (HEAD -> testing) Revert "arm64: remove special treatment
for the link order of head.o"
65aca32efdcb (origin/master, origin/HEAD, master) Merge tag
'mm-hotfixes-stable-2023-03-24-17-09' of
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-size  vmlinux
   text    data     bss     dec     hex filename
24561329 8186912 622032 33370273 1fd30a1 vmlinux
masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-readelf -S
vmlinux | grep -A1 BTF
  [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
       00000000004820cb  0000000000000000   A       0     0     1
  [16] .BTF_ids          PROGBITS         ffff8000096427d4  016527d4
       0000000000000a1c  0000000000000000   A       0     0     1



I still do not know what affects reproducibility.
(compiler version, pahole version, etc. ?)




Aurelien used GCC 12 + binutils 2.40, but
my toolchain is a bit older.



FWIW, I tested this on Ubuntu 22.04LTS.

masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-gcc --version
aarch64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

masahiro@zoe:~/ref/linux(master)$ pahole --version
v1.22

masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-as --version
GNU assembler (GNU Binutils for Ubuntu) 2.38
Copyright (C) 2022 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `aarch64-linux-gnu'.






--
Best Regards
Masahiro Yamada

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Masahiro Yamada]

On Sat, Mar 25, 2023 at 3:05 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Mar 24, 2023 at 8:33 PM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > (cc BTF list and maintainer)
> >
> > On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > >
> > > Hi,
> > >
> > > On 2023-03-22 15:51, Ard Biesheuvel wrote:
> > > > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > On 2022-10-13 08:35, Masahiro Yamada wrote:
> > > > > > In the previous discussion (see the Link tag), Ard pointed out that
> > > > > > arm/arm64/kernel/head.o does not need any special treatment - the only
> > > > > > piece that must appear right at the start of the binary image is the
> > > > > > image header which is emitted into .head.text.
> > > > > >
> > > > > > The linker script does the right thing to do. The build system does
> > > > > > not need to manipulate the link order of head.o.
> > > > > >
> > > > > > Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> > > > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > > > ---
> > > > > >
> > > > > >  scripts/head-object-list.txt | 1 -
> > > > > >  1 file changed, 1 deletion(-)
> > > > > >
> > > > > > diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> > > > > > index b16326a92c45..f226e45e3b7b 100644
> > > > > > --- a/scripts/head-object-list.txt
> > > > > > +++ b/scripts/head-object-list.txt
> > > > > > @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
> > > > > >  arch/arc/kernel/head.o
> > > > > >  arch/arm/kernel/head-nommu.o
> > > > > >  arch/arm/kernel/head.o
> > > > > > -arch/arm64/kernel/head.o
> > > > > >  arch/csky/kernel/head.o
> > > > > >  arch/hexagon/kernel/head.o
> > > > > >  arch/ia64/kernel/head.o
> > > > >
> > > > > This patch causes a significant increase of the arch/arm64/boot/Image
> > > > > size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
> > > > > after this patch has been applied to the 6.1 stable tree.
> > > > >
> > > > > In turn this causes issues with some bootloaders, for instance U-Boot on
> > > > > a Raspberry Pi limits the kernel size to 36 MB.
> > > > >
> > > >
> > > > I cannot reproduce this with mainline
> > > >
> > > > With the patch
> > > >
> > > > $ size vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24567309 14752630 621680 39941619 26175f3 vmlinux
> > > >
> > > > With the patch reverted
> > > >
> > > > $ size vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24567309 14752694 621680 39941683 2617633 vmlinux
> > >
> > > I have tried with the current mainline, this is what I get, using GCC 12.2.0
> > > and binutils 2.40:
> > >
> > >    text    data     bss     dec     hex filename
> > > 32531655        8192996  621968 41346619        276e63b vmlinux.orig
> > > 25170610        8192996  621968 33985574        2069426 vmlinux.revert
> > >
> > > > It would help to compare the resulting vmlinux ELF images from both
> > > > builds to see where the extra space is being allocated
> > >
> > > At a first glance, it seems the extra space is allocated in the BTF
> > > section. I have uploaded the resulting files as well as the config file
> > > I used there:
> > > https://temp.aurel32.net/linux-arm64-size-head.o.tar.gz
> > >
> >
> > Indeed. So we go from
> >
> >   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
> >        00000000005093d6  0000000000000000   A       0     0     1
> >
> > to
> >
> >   [15] .BTF              PROGBITS         ffff8000091d1ff4  011e1ff4
> >        0000000000c0e5eb  0000000000000000   A       0     0     1
> >
> > i.e, from 5 MiB to 12+ MiB of BTF metadata.
> >
> > To me, it is not clear at all how one would be related to the other,
> > so it will leave it to the Kbuild and BTF experts to chew on this one.
>
>
>
> Strange.
>
> I used the .config file Aurelien provided, but
> I still cannot reproduce this issue.
>
>
> The vmlinux size is small
> as-is in the current mainline.
>
>
>
> [mainline]
>
>
> masahiro@zoe:~/ref/linux(master)$ git log --oneline -1
> 65aca32efdcb (HEAD -> master, origin/master, origin/HEAD) Merge tag
> 'mm-hotfixes-stable-2023-03-24-17-09' of
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-size  vmlinux
>    text    data     bss     dec     hex filename
> 24561282 8186912 622032 33370226 1fd3072 vmlinux
> masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-readelf -S
> vmlinux | grep -A1 BTF
>   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
>        000000000048209c  0000000000000000   A       0     0     1
>   [16] .BTF_ids          PROGBITS         ffff8000096427a4  016527a4
>        0000000000000a1c  0000000000000000   A       0     0     1
>
>
>
>
> [mainline + revert 994b7ac]
>
> masahiro@zoe:~/ref/linux2(testing)$ git log --oneline -2
> 856c80dd789c (HEAD -> testing) Revert "arm64: remove special treatment
> for the link order of head.o"
> 65aca32efdcb (origin/master, origin/HEAD, master) Merge tag
> 'mm-hotfixes-stable-2023-03-24-17-09' of
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-size  vmlinux
>    text    data     bss     dec     hex filename
> 24561329 8186912 622032 33370273 1fd30a1 vmlinux
> masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-readelf -S
> vmlinux | grep -A1 BTF
>   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
>        00000000004820cb  0000000000000000   A       0     0     1
>   [16] .BTF_ids          PROGBITS         ffff8000096427d4  016527d4
>        0000000000000a1c  0000000000000000   A       0     0     1
>
>
>
> I still do not know what affects reproducibility.
> (compiler version, pahole version, etc. ?)
>
>
>
>
> Aurelien used GCC 12 + binutils 2.40, but
> my toolchain is a bit older.
>
>
>
> FWIW, I tested this on Ubuntu 22.04LTS.
>
> masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-gcc --version
> aarch64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
> Copyright (C) 2021 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>
> masahiro@zoe:~/ref/linux(master)$ pahole --version
> v1.22
>
> masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-as --version
> GNU assembler (GNU Binutils for Ubuntu) 2.38
> Copyright (C) 2022 Free Software Foundation, Inc.
> This program is free software; you may redistribute it under the terms of
> the GNU General Public License version 3 or later.
> This program has absolutely no warranty.
> This assembler was configured for a target of `aarch64-linux-gnu'.





I did the same things in Deiban sid
in order to use newer versions of tools.



Yup, I saw a huge increase in the .BTF section,
and observed the difference w/wo 994b7ac.

masahiro@3e9802d667e3:~/ref/linux2$ aarch64-linux-gnu-readelf -S
vmlinux | grep -A1 BTF
  [15] .BTF              PROGBITS         ffff8000091d26c4  011e26c4
       000000000093e626  0000000000000000   A       0     0     1
  [16] .BTF_ids          PROGBITS         ffff800009b10cec  01b20cec
       0000000000000a1c  0000000000000000   A       0     0     1


I guess some tool might be affecting this.
Even with 994b7ac reverted, the .BTF section
is much bigger.


At the same time, I saw a ton of warnings
while building BTF.


masahiro@3e9802d667e3:~/ref/linux2$ cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux bookworm/sid"
NAME="Debian GNU/Linux"
VERSION_CODENAME=bookworm
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"



  LD      vmlinux
  BTFIDS  vmlinux
WARN: multiple IDs found for 'task_struct': 177, 16690 - using 177
WARN: multiple IDs found for 'file': 517, 16712 - using 517
WARN: multiple IDs found for 'vm_area_struct': 524, 16714 - using 524
WARN: multiple IDs found for 'inode': 586, 16773 - using 586
WARN: multiple IDs found for 'path': 618, 16802 - using 618
WARN: multiple IDs found for 'task_struct': 177, 17267 - using 177
WARN: multiple IDs found for 'file': 517, 17312 - using 517
WARN: multiple IDs found for 'vm_area_struct': 524, 17315 - using 524
WARN: multiple IDs found for 'seq_file': 1029, 17376 - using 1029
WARN: multiple IDs found for 'inode': 586, 17494 - using 586
WARN: multiple IDs found for 'path': 618, 17523 - using 618
WARN: multiple IDs found for 'cgroup': 704, 17532 - using 704
WARN: multiple IDs found for 'task_struct': 177, 18652 - using 177
WARN: multiple IDs found for 'file': 517, 18704 - using 517
WARN: multiple IDs found for 'vm_area_struct': 524, 18707 - using 524
WARN: multiple IDs found for 'seq_file': 1029, 18781 - using 1029
WARN: multiple IDs found for 'inode': 586, 18911 - using 586
WARN: multiple IDs found for 'path': 618, 18940 - using 618
WARN: multiple IDs found for 'cgroup': 704, 18949 - using 704
WARN: multiple IDs found for 'task_struct': 177, 20514 - using 177
WARN: multiple IDs found for 'file': 517, 20515 - using 517
WARN: multiple IDs found for 'vm_area_struct': 524, 20541 - using 524
WARN: multiple IDs found for 'inode': 586, 20595 - using 586
WARN: multiple IDs found for 'path': 618, 20624 - using 618
WARN: multiple IDs found for 'cgroup': 704, 20639 - using 704
WARN: multiple IDs found for 'seq_file': 1029, 20801 - using 1029
   ...




I am not sure whether these warnings are related to
the current issue or not.


I did not look into it any further.
I may not be seeing a sane build result.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Eduard Zingerman]

On Sat, 2023-03-25 at 20:42 +0900, Masahiro Yamada wrote:
[...]
> > Strange.
> > 
> > I used the .config file Aurelien provided, but
> > I still cannot reproduce this issue.
> > 
> > 
> > The vmlinux size is small
> > as-is in the current mainline.
> > 
> > 
> > 
> > [mainline]
> > 
> > 
> > masahiro@zoe:~/ref/linux(master)$ git log --oneline -1
> > 65aca32efdcb (HEAD -> master, origin/master, origin/HEAD) Merge tag
> > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-size  vmlinux
> >    text    data     bss     dec     hex filename
> > 24561282 8186912 622032 33370226 1fd3072 vmlinux
> > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-readelf -S
> > vmlinux | grep -A1 BTF
> >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> >        000000000048209c  0000000000000000   A       0     0     1
> >   [16] .BTF_ids          PROGBITS         ffff8000096427a4  016527a4
> >        0000000000000a1c  0000000000000000   A       0     0     1
> > 
> > 
> > 
> > 
> > [mainline + revert 994b7ac]
> > 
> > masahiro@zoe:~/ref/linux2(testing)$ git log --oneline -2
> > 856c80dd789c (HEAD -> testing) Revert "arm64: remove special treatment
> > for the link order of head.o"
> > 65aca32efdcb (origin/master, origin/HEAD, master) Merge tag
> > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-size  vmlinux
> >    text    data     bss     dec     hex filename
> > 24561329 8186912 622032 33370273 1fd30a1 vmlinux
> > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-readelf -S
> > vmlinux | grep -A1 BTF
> >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> >        00000000004820cb  0000000000000000   A       0     0     1
> >   [16] .BTF_ids          PROGBITS         ffff8000096427d4  016527d4
> >        0000000000000a1c  0000000000000000   A       0     0     1
> > 
> > 
> > 
> > I still do not know what affects reproducibility.
> > (compiler version, pahole version, etc. ?)
> > 
> > 
> > 
> > 
> > Aurelien used GCC 12 + binutils 2.40, but
> > my toolchain is a bit older.
> > 
> > 
> > 
> > FWIW, I tested this on Ubuntu 22.04LTS.
> > 
> > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-gcc --version
> > aarch64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
> > Copyright (C) 2021 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > 
> > masahiro@zoe:~/ref/linux(master)$ pahole --version
> > v1.22
> > 
> > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-as --version
> > GNU assembler (GNU Binutils for Ubuntu) 2.38
> > Copyright (C) 2022 Free Software Foundation, Inc.
> > This program is free software; you may redistribute it under the terms of
> > the GNU General Public License version 3 or later.
> > This program has absolutely no warranty.
> > This assembler was configured for a target of `aarch64-linux-gnu'.
> 
> 
> 
> 
> 
> I did the same things in Deiban sid
> in order to use newer versions of tools.


Hi Masahiro,

An upgrade from gcc 11 to gcc 12, BTF section increase and a number of
duplicate IDs reported by resolve_btfids matches the description of
the following thread:

https://lore.kernel.org/bpf/Y%2FP1yxAuV6Wj3A0K@google.com/

The issue is caused by change in GNU assembler DWARF generation.
I've sent a patch to fix it a few weeks ago and it is merged in
dwarves master:

a9498899109d ("dwarf_loader: Fix for BTF id drift caused by adding unspecified types")

Could you please grab a fresh version of dwarves from:

git@github.com:acmel/dwarves.git

compile 'pahole' and try with?

Thanks,
Eduard

> 
> 
> 
> Yup, I saw a huge increase in the .BTF section,
> and observed the difference w/wo 994b7ac.
> 
> masahiro@3e9802d667e3:~/ref/linux2$ aarch64-linux-gnu-readelf -S
> vmlinux | grep -A1 BTF
>   [15] .BTF              PROGBITS         ffff8000091d26c4  011e26c4
>        000000000093e626  0000000000000000   A       0     0     1
>   [16] .BTF_ids          PROGBITS         ffff800009b10cec  01b20cec
>        0000000000000a1c  0000000000000000   A       0     0     1
> 
> 
> I guess some tool might be affecting this.
> Even with 994b7ac reverted, the .BTF section
> is much bigger.
> 
> 
> At the same time, I saw a ton of warnings
> while building BTF.
> 
> 
> masahiro@3e9802d667e3:~/ref/linux2$ cat /etc/os-release
> PRETTY_NAME="Debian GNU/Linux bookworm/sid"
> NAME="Debian GNU/Linux"
> VERSION_CODENAME=bookworm
> ID=debian
> HOME_URL="https://www.debian.org/"
> SUPPORT_URL="https://www.debian.org/support"
> BUG_REPORT_URL="https://bugs.debian.org/"
> 
> 
> 
>   LD      vmlinux
>   BTFIDS  vmlinux
> WARN: multiple IDs found for 'task_struct': 177, 16690 - using 177
> WARN: multiple IDs found for 'file': 517, 16712 - using 517
> WARN: multiple IDs found for 'vm_area_struct': 524, 16714 - using 524
> WARN: multiple IDs found for 'inode': 586, 16773 - using 586
> WARN: multiple IDs found for 'path': 618, 16802 - using 618
> WARN: multiple IDs found for 'task_struct': 177, 17267 - using 177
> WARN: multiple IDs found for 'file': 517, 17312 - using 517
> WARN: multiple IDs found for 'vm_area_struct': 524, 17315 - using 524
> WARN: multiple IDs found for 'seq_file': 1029, 17376 - using 1029
> WARN: multiple IDs found for 'inode': 586, 17494 - using 586
> WARN: multiple IDs found for 'path': 618, 17523 - using 618
> WARN: multiple IDs found for 'cgroup': 704, 17532 - using 704
> WARN: multiple IDs found for 'task_struct': 177, 18652 - using 177
> WARN: multiple IDs found for 'file': 517, 18704 - using 517
> WARN: multiple IDs found for 'vm_area_struct': 524, 18707 - using 524
> WARN: multiple IDs found for 'seq_file': 1029, 18781 - using 1029
> WARN: multiple IDs found for 'inode': 586, 18911 - using 586
> WARN: multiple IDs found for 'path': 618, 18940 - using 618
> WARN: multiple IDs found for 'cgroup': 704, 18949 - using 704
> WARN: multiple IDs found for 'task_struct': 177, 20514 - using 177
> WARN: multiple IDs found for 'file': 517, 20515 - using 517
> WARN: multiple IDs found for 'vm_area_struct': 524, 20541 - using 524
> WARN: multiple IDs found for 'inode': 586, 20595 - using 586
> WARN: multiple IDs found for 'path': 618, 20624 - using 618
> WARN: multiple IDs found for 'cgroup': 704, 20639 - using 704
> WARN: multiple IDs found for 'seq_file': 1029, 20801 - using 1029
>    ...
> 
> 
> 
> 
> I am not sure whether these warnings are related to
> the current issue or not.
> 
> 
> I did not look into it any further.
> I may not be seeing a sane build result.
> 
> 

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Arnaldo Carvalho de Melo]

Em Tue, Mar 28, 2023 at 01:33:29PM +0300, Eduard Zingerman escreveu:
> On Sat, 2023-03-25 at 20:42 +0900, Masahiro Yamada wrote:
> [...]
> > > Strange.
> > > 
> > > I used the .config file Aurelien provided, but
> > > I still cannot reproduce this issue.
> > > 
> > > The vmlinux size is small as-is in the current mainline.
> > > 
> > > [mainline]
> > > 
> > > masahiro@zoe:~/ref/linux(master)$ git log --oneline -1
> > > 65aca32efdcb (HEAD -> master, origin/master, origin/HEAD) Merge tag
> > > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-size  vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24561282 8186912 622032 33370226 1fd3072 vmlinux
> > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-readelf -S
> > > vmlinux | grep -A1 BTF
> > >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> > >        000000000048209c  0000000000000000   A       0     0     1
> > >   [16] .BTF_ids          PROGBITS         ffff8000096427a4  016527a4
> > >        0000000000000a1c  0000000000000000   A       0     0     1
> > > 
> > > [mainline + revert 994b7ac]
> > > 
> > > masahiro@zoe:~/ref/linux2(testing)$ git log --oneline -2
> > > 856c80dd789c (HEAD -> testing) Revert "arm64: remove special treatment
> > > for the link order of head.o"
> > > 65aca32efdcb (origin/master, origin/HEAD, master) Merge tag
> > > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-size  vmlinux
> > >    text    data     bss     dec     hex filename
> > > 24561329 8186912 622032 33370273 1fd30a1 vmlinux
> > > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-readelf -S
> > > vmlinux | grep -A1 BTF
> > >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> > >        00000000004820cb  0000000000000000   A       0     0     1
> > >   [16] .BTF_ids          PROGBITS         ffff8000096427d4  016527d4
> > >        0000000000000a1c  0000000000000000   A       0     0     1
> > > 
> > > 
> > > 
> > > I still do not know what affects reproducibility.
> > > (compiler version, pahole version, etc. ?)
> > > 
> > > 
> > > 
> > > 
> > > Aurelien used GCC 12 + binutils 2.40, but
> > > my toolchain is a bit older.
> > > 
> > > FWIW, I tested this on Ubuntu 22.04LTS.
> > > 
> > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-gcc --version
> > > aarch64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
> > > Copyright (C) 2021 Free Software Foundation, Inc.
> > > This is free software; see the source for copying conditions.  There is NO
> > > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > > 
> > > masahiro@zoe:~/ref/linux(master)$ pahole --version
> > > v1.22
> > > 
> > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-as --version
> > > GNU assembler (GNU Binutils for Ubuntu) 2.38
> > > Copyright (C) 2022 Free Software Foundation, Inc.
> > > This program is free software; you may redistribute it under the terms of
> > > the GNU General Public License version 3 or later.
> > > This program has absolutely no warranty.
> > > This assembler was configured for a target of `aarch64-linux-gnu'.
> > 
> > I did the same things in Deiban sid
> > in order to use newer versions of tools.
> 
> 
> Hi Masahiro,
> 
> An upgrade from gcc 11 to gcc 12, BTF section increase and a number of
> duplicate IDs reported by resolve_btfids matches the description of
> the following thread:
> 
> https://lore.kernel.org/bpf/Y%2FP1yxAuV6Wj3A0K@google.com/
> 
> The issue is caused by change in GNU assembler DWARF generation.
> I've sent a patch to fix it a few weeks ago and it is merged in
> dwarves master:
> 
> a9498899109d ("dwarf_loader: Fix for BTF id drift caused by adding unspecified types")
> 
> Could you please grab a fresh version of dwarves from:
> 
> git@github.com:acmel/dwarves.git
> 
> compile 'pahole' and try with?

pahole 1.25 is long overdue, so let see if this got fixed with what is
in master, please take a look, you can as well get it from:

git://git.kernel.org/pub/scm/devel/pahole/pahole.git

- Arnald o

Re: [PATCH] arm64: remove special treatment for the link order of head.o

[Aurelien Jarno]

On 2023-03-28 16:52, Arnaldo Carvalho de Melo wrote:
> Em Tue, Mar 28, 2023 at 01:33:29PM +0300, Eduard Zingerman escreveu:
> > On Sat, 2023-03-25 at 20:42 +0900, Masahiro Yamada wrote:
> > [...]
> > > > Strange.
> > > > 
> > > > I used the .config file Aurelien provided, but
> > > > I still cannot reproduce this issue.
> > > > 
> > > > The vmlinux size is small as-is in the current mainline.
> > > > 
> > > > [mainline]
> > > > 
> > > > masahiro@zoe:~/ref/linux(master)$ git log --oneline -1
> > > > 65aca32efdcb (HEAD -> master, origin/master, origin/HEAD) Merge tag
> > > > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-size  vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24561282 8186912 622032 33370226 1fd3072 vmlinux
> > > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-readelf -S
> > > > vmlinux | grep -A1 BTF
> > > >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> > > >        000000000048209c  0000000000000000   A       0     0     1
> > > >   [16] .BTF_ids          PROGBITS         ffff8000096427a4  016527a4
> > > >        0000000000000a1c  0000000000000000   A       0     0     1
> > > > 
> > > > [mainline + revert 994b7ac]
> > > > 
> > > > masahiro@zoe:~/ref/linux2(testing)$ git log --oneline -2
> > > > 856c80dd789c (HEAD -> testing) Revert "arm64: remove special treatment
> > > > for the link order of head.o"
> > > > 65aca32efdcb (origin/master, origin/HEAD, master) Merge tag
> > > > 'mm-hotfixes-stable-2023-03-24-17-09' of
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > > > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-size  vmlinux
> > > >    text    data     bss     dec     hex filename
> > > > 24561329 8186912 622032 33370273 1fd30a1 vmlinux
> > > > masahiro@zoe:~/ref/linux2(testing)$ aarch64-linux-gnu-readelf -S
> > > > vmlinux | grep -A1 BTF
> > > >   [15] .BTF              PROGBITS         ffff8000091c0708  011d0708
> > > >        00000000004820cb  0000000000000000   A       0     0     1
> > > >   [16] .BTF_ids          PROGBITS         ffff8000096427d4  016527d4
> > > >        0000000000000a1c  0000000000000000   A       0     0     1
> > > > 
> > > > 
> > > > 
> > > > I still do not know what affects reproducibility.
> > > > (compiler version, pahole version, etc. ?)
> > > > 
> > > > 
> > > > 
> > > > 
> > > > Aurelien used GCC 12 + binutils 2.40, but
> > > > my toolchain is a bit older.
> > > > 
> > > > FWIW, I tested this on Ubuntu 22.04LTS.
> > > > 
> > > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-gcc --version
> > > > aarch64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
> > > > Copyright (C) 2021 Free Software Foundation, Inc.
> > > > This is free software; see the source for copying conditions.  There is NO
> > > > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > > > 
> > > > masahiro@zoe:~/ref/linux(master)$ pahole --version
> > > > v1.22
> > > > 
> > > > masahiro@zoe:~/ref/linux(master)$ aarch64-linux-gnu-as --version
> > > > GNU assembler (GNU Binutils for Ubuntu) 2.38
> > > > Copyright (C) 2022 Free Software Foundation, Inc.
> > > > This program is free software; you may redistribute it under the terms of
> > > > the GNU General Public License version 3 or later.
> > > > This program has absolutely no warranty.
> > > > This assembler was configured for a target of `aarch64-linux-gnu'.
> > > 
> > > I did the same things in Deiban sid
> > > in order to use newer versions of tools.
> > 
> > 
> > Hi Masahiro,
> > 
> > An upgrade from gcc 11 to gcc 12, BTF section increase and a number of
> > duplicate IDs reported by resolve_btfids matches the description of
> > the following thread:
> > 
> > https://lore.kernel.org/bpf/Y%2FP1yxAuV6Wj3A0K@google.com/
> > 
> > The issue is caused by change in GNU assembler DWARF generation.
> > I've sent a patch to fix it a few weeks ago and it is merged in
> > dwarves master:
> > 
> > a9498899109d ("dwarf_loader: Fix for BTF id drift caused by adding unspecified types")
> > 
> > Could you please grab a fresh version of dwarves from:
> > 
> > git@github.com:acmel/dwarves.git
> > 
> > compile 'pahole' and try with?
> 
> pahole 1.25 is long overdue, so let see if this got fixed with what is
> in master, please take a look, you can as well get it from:
> 
> git://git.kernel.org/pub/scm/devel/pahole/pahole.git
> 

pahole 1.25 has been released, so I have tried a kernel build with it,
and I confirm it fixes the issue. Thanks for the help.

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net