linux-kernel - Re: [PATCH v6 00/10] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL

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Date:   Sun, 22 May 2022 16:15:49 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-modules <linux-modules@...r.kernel.org>,
        clang-built-linux <llvm@...ts.linux.dev>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: [PATCH v6 00/10] kbuild: yet another series of cleanups (modpost,
 LTO, MODULE_REL_CRCS, export.h)

On Sun, May 22, 2022 at 11:45 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
>
> On Sun, May 22, 2022 at 8:50 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > On Sun, May 22, 2022 at 10:45 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
> > >
> > > On Fri, May 13, 2022 at 4:31 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > > >
> > > > On Fri, May 13, 2022 at 8:42 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > > > >
> > > > >
> > > > > This is the third batch of cleanups in this development cycle.
> > > > >
> > > >
> > > >
> > > > This series is available at
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git
> > > >  lto-cleanup-v6
> > > >
> > >
> > > Hi Masahiro,
> > >
> > > I cloned the repository on top of latest Linus Git.
> > >
> > > Not able to boot in Quemu - Not able to boot on bare metal.
> > >
> > > $ grep module_layout log_quemu-5.18.0-rc7-2-amd64-clang14-lto.txt
> > > 366:[    2.173265] floppy: disagrees about version of symbol module_layout
> > > 367:[    2.198746] scsi_common: disagrees about version of symbol module_layout
> > > 368:[    2.205573] i2c_piix4: disagrees about version of symbol module_layout
> > > 369:[    2.210610] psmouse: disagrees about version of symbol module_layout
> > > 370:[    2.225138] scsi_common: disagrees about version of symbol module_layout
> > > 371:[    2.235536] scsi_common: disagrees about version of symbol module_layout
> > > 375:Begin: Running /scripts/local-premount ... [    2.298555]
> > > crc32c_intel: disagrees about version of symbol module_layout
> > > 376:[    2.303335] crc32c_generic: disagrees about version of symbol
> > > module_layout
> > > 377:[    2.306667] libcrc32c: disagrees about version of symbol module_layout
> > >
> > > Infos: LLVM-14 + CONFIG_LTO_CLANG_THIN=y
> > >
> > > My linux-config and qemu-log are attached.
> > >
> >
> >
> > Thanks for your testing.
> >
> > I was also able to reproduce this issue.
> >
> >
> > The problematic parts are:
> >
> > [    2.298555] crc32c_intel: disagrees about version of symbol module_layout
> > [    2.303335] crc32c_generic: disagrees about version of symbol module_layout
> > [    2.306667] libcrc32c: disagrees about version of symbol module_layout
> >
> >
> >
> > When CONFIG_LTO_CLANG_THIN=y,
> > I cannot see any __crc_* symbols in "nm  vmlinux".
> >
> > Perhaps, LTO might have discarded all the __crc_* symbols
> > from vmlinux, but I am still checking the details...
> >
>
> Thanks for taking care.
>
> Just for the records:
>
> $ grep CONFIG_MODVERSIONS /boot/config-5.18.0-rc7-2-amd64-clang14-lto
> CONFIG_MODVERSIONS=y
>

Did not try CONFIG_MODVERSIONS=n.

We have a new file:

[ include/linux/export-internal.h ]
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Please do not include this explicitly.
* This is used by C files generated by modpost.
*/

#ifndef __LINUX_EXPORT_INTERNAL_H__
#define __LINUX_EXPORT_INTERNAL_H__

#include <linux/compiler.h>
#include <linux/types.h>

#define SYMBOL_CRC(sym, crc, sec)   \
       u32 __section("___kcrctab" sec "+" #sym) __crc_##sym = crc

#endif /* __LINUX_EXPORT_INTERNAL_H__ */

But we discard __kcrctab in scripts/module.lds.S file.

Maybe we need:

$ git diff scripts/module.lds.S
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 1d0e1e4dc3d2..c04b596c364b 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -21,8 +21,6 @@ SECTIONS {

       __ksymtab               0 : { *(SORT(___ksymtab+*)) }
       __ksymtab_gpl           0 : { *(SORT(___ksymtab_gpl+*)) }
-       __kcrctab               0 : { *(SORT(___kcrctab+*)) }
-       __kcrctab_gpl           0 : { *(SORT(___kcrctab_gpl+*)) }

       .ctors                  0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
       .init_array             0 : ALIGN(8) { *(SORT(.init_array.*))
*(.init_array) }

Or even?

$ git diff scripts/kallsyms.c
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 8caabddf817c..fb3601fe8aa3 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -109,7 +109,6 @@ static bool is_ignored_symbol(const char *name, char type)
       static const char * const ignored_prefixes[] = {
               "$",                    /* local symbols for ARM, MIPS, etc. */
               ".L",                   /* local labels,
.LBB,.Ltmpxxx,.L__unnamed_xx,.LASANPC, etc. */
-               "__crc_",               /* modversions */
               "__efistub_",           /* arm64 EFI stub namespace */
               "__kvm_nvhe_",          /* arm64 non-VHE KVM namespace */
               "__AArch64ADRPThunk_",  /* arm64 lld */

- Sedat -