[v3] modpost: Skip .llvm.call-graph-profile section check

[PATCH v3] modpost: Skip .llvm.call-graph-profile section check

Posted by Denis Nikitin 2 years, 3 months ago

.llvm.call-graph-profile section is added by clang when the kernel is
built with profiles (e.g. -fprofile-sample-use= or -fprofile-use=).
Note that .llvm.call-graph-profile intentionally uses REL relocations
to decrease the object size, for more details see
https://reviews.llvm.org/D104080.

The section contains edge information derived from text sections,
so .llvm.call-graph-profile itself doesn't need more analysis as
the text sections have been analyzed.

This change fixes the kernel build with clang and a sample profile
which currently fails with:

"FATAL: modpost: Please add code to calculate addend for this architecture"

Signed-off-by: Denis Nikitin <denik@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Fangrui Song <maskray@google.com>
---
 scripts/mod/modpost.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index b29b29707f10..64bd13f7199c 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -761,6 +761,7 @@ static const char *const section_white_list[] =
 	".fmt_slot*",			/* EZchip */
 	".gnu.lto*",
 	".discard.*",
+	".llvm.call-graph-profile",	/* call graph */
 	NULL
 };
 
-- 
2.42.0.rc1.204.g551eb34607-goog

Re: [PATCH v3] modpost: Skip .llvm.call-graph-profile section check

Posted by Masahiro Yamada 2 years, 3 months ago

On Mon, Aug 28, 2023 at 5:15 AM Denis Nikitin <denik@chromium.org> wrote:
>
> .llvm.call-graph-profile section is added by clang when the kernel is
> built with profiles (e.g. -fprofile-sample-use= or -fprofile-use=).
> Note that .llvm.call-graph-profile intentionally uses REL relocations
> to decrease the object size, for more details see
> https://reviews.llvm.org/D104080.
>
> The section contains edge information derived from text sections,
> so .llvm.call-graph-profile itself doesn't need more analysis as
> the text sections have been analyzed.
>
> This change fixes the kernel build with clang and a sample profile
> which currently fails with:
>
> "FATAL: modpost: Please add code to calculate addend for this architecture"
>
> Signed-off-by: Denis Nikitin <denik@chromium.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Fangrui Song <maskray@google.com>
> ---


Applied to linux-kbuild.
Thanks.


>  scripts/mod/modpost.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index b29b29707f10..64bd13f7199c 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -761,6 +761,7 @@ static const char *const section_white_list[] =
>         ".fmt_slot*",                   /* EZchip */
>         ".gnu.lto*",
>         ".discard.*",
> +       ".llvm.call-graph-profile",     /* call graph */
>         NULL
>  };
>
> --
> 2.42.0.rc1.204.g551eb34607-goog
>


-- 
Best Regards
Masahiro Yamada