On Sat, Mar 25, 2023 at 3:05 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > On Fri, Mar 24, 2023 at 8:33 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > (cc BTF list and maintainer) > > > > On Thu, 23 Mar 2023 at 22:12, Aurelien Jarno <aurelien@xxxxxxxxxxx> wrote: > > > > > > Hi, > > > > > > On 2023-03-22 15:51, Ard Biesheuvel wrote: > > > > On Tue, 21 Mar 2023 at 23:26, Aurelien Jarno <aurelien@xxxxxxxxxxx> 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@xxxxxxxxxxxxxx/ > > > > > > Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > > > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > > > > > > --- > > > > > > > > > > > > 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
