From: Masahiro Yamada <masahiroy@kernel.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nicolas Schier <nicolas@fjasle.eu>,
Peter Zijlstra <peterz@infradead.org>,
linux-modules <linux-modules@vger.kernel.org>,
clang-built-linux <llvm@lists.linux.dev>,
Ard Biesheuvel <ardb@kernel.org>,
Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH v6 06/10] kbuild: check static EXPORT_SYMBOL* by script instead of modpost
Date: Wed, 25 May 2022 19:51:17 +0900 [thread overview]
Message-ID: <CAK7LNATifx2c877yEX5VkTQ5h7_7iSnTB0nkR5i98PEBHb=DuQ@mail.gmail.com> (raw)
In-Reply-To: <20220525083142.GA1952409@roeck-us.net>
On Wed, May 25, 2022 at 5:31 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, May 13, 2022 at 08:39:26PM +0900, Masahiro Yamada wrote:
> > The 'static' specifier and EXPORT_SYMBOL() are an odd combination.
> >
> > Commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL*
> > functions") tried to detect it, but this check has false negatives.
> >
> > Here is the sample code.
> >
> > Makefile:
> >
> > obj-y += foo1.o foo2.o
> >
> > foo1.c:
> >
> > #include <linux/export.h>
> > static void foo(void) {}
> > EXPORT_SYMBOL(foo);
> >
> > foo2.c:
> >
> > void foo(void) {}
> >
> > foo1.c exports the static symbol 'foo', but modpost cannot catch it
> > because it is fooled by foo2.c, which has a global symbol with the
> > same name.
> >
> > s->is_static is cleared if a global symbol with the same name is found
> > somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily
> > belong to the same compilation unit.
> >
> > This check should be done per compilation unit, but I do not know how
> > to do it in modpost. modpost runs against vmlinux.o or modules, which
> > merges multiple objects, then forgets their origin.
> >
> > It is true modpost gets access to the lists of all the member objects
> > (.vmlinux.objs and *.mod), but modpost cannot parse individual objects
> > because they may not be ELF but LLVM IR when CONFIG_LTO_CLANG=y.
> >
> > Add a simple bash script to parse the output from ${NM}. This works for
> > CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM IR files.
> >
>
> On parisc builds, this patch results in:
>
> Building parisc:allnoconfig ... failed
> --------------
> Error log:
> scripts/check-local-export: sh /opt/buildbot/slave/next-next/build/arch/parisc/nm failed
>
> Guenter
Thanks for the report.
parisc overrides NM:
NM = sh $(srctree)/arch/parisc/nm
I will fix the script to return the correct exit code.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2022-05-25 10:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-13 11:39 [PATCH v6 00/10] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 01/10] modpost: extract symbol versions from *.cmd files Masahiro Yamada
2022-05-28 22:47 ` Guenter Roeck
2022-05-29 4:27 ` Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 02/10] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS Masahiro Yamada
2022-08-20 10:02 ` Build/boot problem with 7b4537199a4a (Re: [PATCH v6 02/10] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS) Christophe Leroy
2022-08-20 12:05 ` Sedat Dilek
2022-08-20 14:10 ` Christophe Leroy
2022-08-20 12:51 ` Masahiro Yamada
2022-08-20 14:15 ` Christophe Leroy
2022-08-20 17:01 ` Masahiro Yamada
2022-08-20 17:51 ` Christophe Leroy
2022-05-13 11:39 ` [PATCH v6 03/10] kbuild: stop merging *.symversions Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 04/10] genksyms: adjust the output format to modpost Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 05/10] kbuild: do not create *.prelink.o for Clang LTO or IBT Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 06/10] kbuild: check static EXPORT_SYMBOL* by script instead of modpost Masahiro Yamada
2022-05-25 8:31 ` Guenter Roeck
2022-05-25 10:51 ` Masahiro Yamada [this message]
2022-06-07 14:22 ` Jon Hunter
2022-06-07 14:25 ` Nathan Chancellor
2022-06-07 14:34 ` Jon Hunter
2022-05-13 11:39 ` [PATCH v6 07/10] kbuild: make built-in.a rule robust against too long argument error Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 08/10] kbuild: make *.mod " Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 09/10] kbuild: add cmd_and_savecmd macro Masahiro Yamada
2022-05-13 11:39 ` [PATCH v6 10/10] kbuild: rebuild multi-object modules when objtool is updated Masahiro Yamada
2022-05-13 12:20 ` [PATCH v6 00/10] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
[not found] ` <CA+icZUUWww3fXvjQcefgFuq=tPO6+FYDbHE2E5PmL-BSJg4+cw@mail.gmail.com>
2022-05-22 6:49 ` Masahiro Yamada
2022-05-22 9:45 ` Sedat Dilek
2022-05-22 14:15 ` Sedat Dilek
2022-05-22 16:09 ` Masahiro Yamada
2022-05-22 16:18 ` Sedat Dilek
2022-05-22 22:34 ` Sedat Dilek
[not found] ` <2c496d24174e63b27ec047f383df6700@matoro.tk>
2022-08-06 7:23 ` Sedat Dilek
2022-08-06 13:12 ` matoro
2022-08-08 5:54 ` Masahiro Yamada
2022-08-08 13:26 ` matoro
2022-08-08 17:36 ` Masahiro Yamada
2022-08-08 18:42 ` matoro
2022-08-09 15:20 ` Masahiro Yamada
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