ELFNOTE_START allows callers to specify flags for .pushsection assembler
directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For
vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same
section is specified twice after preprocessing, once with "a" flag, once
without. Example:
.pushsection .note.Linux, "a", @note ;
.pushsection .note.Linux, "", @note ;
While GNU as allows this ordering, it warns for the opposite ordering,
making these directives position dependent. We'd prefer not to precisely
match this behavior in Clang's integrated assembler. Instead, the non
__ASSEMBLY__ definition of ELF_NOTE uses
__attribute__((section(".note.Linux"))) which is created with SHF_ALLOC,
so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C
and just always use "a" flag.
This allows Clang to assemble a working mainline (5.6) kernel via:
$ make CC=clang AS=clang
Link: https://github.com/ClangBuiltLinux/linux/issues/913
Cc: Jeremy Fitzhardinge <[email protected]>
Debugged-by: Ilie Halip <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
---
Ilie has further treewide cleanups:
https://github.com/ihalip/linux/commits/elfnote
This patch is the simplest to move us forwards.
include/linux/elfnote.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
index 594d4e78654f..69b136e4dd2b 100644
--- a/include/linux/elfnote.h
+++ b/include/linux/elfnote.h
@@ -54,7 +54,7 @@
.popsection ;
#define ELFNOTE(name, type, desc) \
- ELFNOTE_START(name, type, "") \
+ ELFNOTE_START(name, type, "a") \
desc ; \
ELFNOTE_END
--
2.26.0.rc2.310.g2932bb562d-goog
dropping Jeremy; I got bounceback from the email address. Ping for review?
On Wed, Mar 25, 2020 at 4:13 PM Nick Desaulniers
<[email protected]> wrote:
>
> ELFNOTE_START allows callers to specify flags for .pushsection assembler
> directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For
> vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same
> section is specified twice after preprocessing, once with "a" flag, once
> without. Example:
>
> .pushsection .note.Linux, "a", @note ;
> .pushsection .note.Linux, "", @note ;
>
> While GNU as allows this ordering, it warns for the opposite ordering,
> making these directives position dependent. We'd prefer not to precisely
> match this behavior in Clang's integrated assembler. Instead, the non
> __ASSEMBLY__ definition of ELF_NOTE uses
> __attribute__((section(".note.Linux"))) which is created with SHF_ALLOC,
> so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C
> and just always use "a" flag.
>
> This allows Clang to assemble a working mainline (5.6) kernel via:
> $ make CC=clang AS=clang
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/913
> Cc: Jeremy Fitzhardinge <[email protected]>
> Debugged-by: Ilie Halip <[email protected]>
> Signed-off-by: Nick Desaulniers <[email protected]>
> ---
> Ilie has further treewide cleanups:
> https://github.com/ihalip/linux/commits/elfnote
> This patch is the simplest to move us forwards.
>
> include/linux/elfnote.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
> index 594d4e78654f..69b136e4dd2b 100644
> --- a/include/linux/elfnote.h
> +++ b/include/linux/elfnote.h
> @@ -54,7 +54,7 @@
> .popsection ;
>
> #define ELFNOTE(name, type, desc) \
> - ELFNOTE_START(name, type, "") \
> + ELFNOTE_START(name, type, "a") \
> desc ; \
> ELFNOTE_END
>
> --
> 2.26.0.rc2.310.g2932bb562d-goog
>
--
Thanks,
~Nick Desaulniers
On Fri, Apr 03, 2020 at 03:13:34PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> dropping Jeremy; I got bounceback from the email address. Ping for review?
>
> On Wed, Mar 25, 2020 at 4:13 PM Nick Desaulniers
> <[email protected]> wrote:
> >
> > ELFNOTE_START allows callers to specify flags for .pushsection assembler
> > directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For
> > vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same
> > section is specified twice after preprocessing, once with "a" flag, once
> > without. Example:
> >
> > .pushsection .note.Linux, "a", @note ;
> > .pushsection .note.Linux, "", @note ;
> >
> > While GNU as allows this ordering, it warns for the opposite ordering,
> > making these directives position dependent. We'd prefer not to precisely
> > match this behavior in Clang's integrated assembler. Instead, the non
> > __ASSEMBLY__ definition of ELF_NOTE uses
> > __attribute__((section(".note.Linux"))) which is created with SHF_ALLOC,
> > so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C
> > and just always use "a" flag.
> >
> > This allows Clang to assemble a working mainline (5.6) kernel via:
> > $ make CC=clang AS=clang
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/913
> > Cc: Jeremy Fitzhardinge <[email protected]>
> > Debugged-by: Ilie Halip <[email protected]>
> > Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
> > ---
> > Ilie has further treewide cleanups:
> > https://github.com/ihalip/linux/commits/elfnote
> > This patch is the simplest to move us forwards.
> >
> > include/linux/elfnote.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
> > index 594d4e78654f..69b136e4dd2b 100644
> > --- a/include/linux/elfnote.h
> > +++ b/include/linux/elfnote.h
> > @@ -54,7 +54,7 @@
> > .popsection ;
> >
> > #define ELFNOTE(name, type, desc) \
> > - ELFNOTE_START(name, type, "") \
> > + ELFNOTE_START(name, type, "a") \
> > desc ; \
> > ELFNOTE_END
> >
> > --
> > 2.26.0.rc2.310.g2932bb562d-goog
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
On 2020-04-03, Nathan Chancellor wrote:
>On Fri, Apr 03, 2020 at 03:13:34PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
>> dropping Jeremy; I got bounceback from the email address. Ping for review?
>>
>> On Wed, Mar 25, 2020 at 4:13 PM Nick Desaulniers
>> <[email protected]> wrote:
>> >
>> > ELFNOTE_START allows callers to specify flags for .pushsection assembler
>> > directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For
>> > vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same
>> > section is specified twice after preprocessing, once with "a" flag, once
>> > without. Example:
>> >
>> > .pushsection .note.Linux, "a", @note ;
>> > .pushsection .note.Linux, "", @note ;
>> >
>> > While GNU as allows this ordering, it warns for the opposite ordering,
>> > making these directives position dependent. We'd prefer not to precisely
>> > match this behavior in Clang's integrated assembler. Instead, the non
>> > __ASSEMBLY__ definition of ELF_NOTE uses
>> > __attribute__((section(".note.Linux"))) which is created with SHF_ALLOC,
>> > so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C
>> > and just always use "a" flag.
>> >
>> > This allows Clang to assemble a working mainline (5.6) kernel via:
>> > $ make CC=clang AS=clang
>> >
>> > Link: https://github.com/ClangBuiltLinux/linux/issues/913
>> > Cc: Jeremy Fitzhardinge <[email protected]>
>> > Debugged-by: Ilie Halip <[email protected]>
>> > Signed-off-by: Nick Desaulniers <[email protected]>
>
>Reviewed-by: Nathan Chancellor <[email protected]>
I asked on [email protected] whether GNU as is willing to change.
https://sourceware.org/pipermail/binutils/2020-March/109997.html
I'll also ping that thread.
Reviewed-by: Fangrui Song <[email protected]>
>> > ---
>> > Ilie has further treewide cleanups:
>> > https://github.com/ihalip/linux/commits/elfnote
>> > This patch is the simplest to move us forwards.
>> >
>> > include/linux/elfnote.h | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
>> > index 594d4e78654f..69b136e4dd2b 100644
>> > --- a/include/linux/elfnote.h
>> > +++ b/include/linux/elfnote.h
>> > @@ -54,7 +54,7 @@
>> > .popsection ;
>> >
>> > #define ELFNOTE(name, type, desc) \
>> > - ELFNOTE_START(name, type, "") \
>> > + ELFNOTE_START(name, type, "a") \
>> > desc ; \
>> > ELFNOTE_END
>> >
>> > --
>> > 2.26.0.rc2.310.g2932bb562d-goog
>> >
>>
>>
>> --
>> Thanks,
>> ~Nick Desaulniers
>
>
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(bumping for review)
On Fri, Apr 3, 2020 at 5:40 PM Fangrui Song <[email protected]> wrote:
>
> On 2020-04-03, Nathan Chancellor wrote:
> >On Fri, Apr 03, 2020 at 03:13:34PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> >> dropping Jeremy; I got bounceback from the email address. Ping for review?
> >>
> >> On Wed, Mar 25, 2020 at 4:13 PM Nick Desaulniers
> >> <[email protected]> wrote:
> >> >
> >> > ELFNOTE_START allows callers to specify flags for .pushsection assembler
> >> > directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For
> >> > vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same
> >> > section is specified twice after preprocessing, once with "a" flag, once
> >> > without. Example:
> >> >
> >> > .pushsection .note.Linux, "a", @note ;
> >> > .pushsection .note.Linux, "", @note ;
> >> >
> >> > While GNU as allows this ordering, it warns for the opposite ordering,
> >> > making these directives position dependent. We'd prefer not to precisely
> >> > match this behavior in Clang's integrated assembler. Instead, the non
> >> > __ASSEMBLY__ definition of ELF_NOTE uses
> >> > __attribute__((section(".note.Linux"))) which is created with SHF_ALLOC,
> >> > so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C
> >> > and just always use "a" flag.
> >> >
> >> > This allows Clang to assemble a working mainline (5.6) kernel via:
> >> > $ make CC=clang AS=clang
> >> >
> >> > Link: https://github.com/ClangBuiltLinux/linux/issues/913
> >> > Cc: Jeremy Fitzhardinge <[email protected]>
> >> > Debugged-by: Ilie Halip <[email protected]>
> >> > Signed-off-by: Nick Desaulniers <[email protected]>
> >
> >Reviewed-by: Nathan Chancellor <[email protected]>
>
> I asked on [email protected] whether GNU as is willing to change.
> https://sourceware.org/pipermail/binutils/2020-March/109997.html
> I'll also ping that thread.
>
>
> Reviewed-by: Fangrui Song <[email protected]>
>
> >> > ---
> >> > Ilie has further treewide cleanups:
> >> > https://github.com/ihalip/linux/commits/elfnote
> >> > This patch is the simplest to move us forwards.
> >> >
> >> > include/linux/elfnote.h | 2 +-
> >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
> >> > index 594d4e78654f..69b136e4dd2b 100644
> >> > --- a/include/linux/elfnote.h
> >> > +++ b/include/linux/elfnote.h
> >> > @@ -54,7 +54,7 @@
> >> > .popsection ;
> >> >
> >> > #define ELFNOTE(name, type, desc) \
> >> > - ELFNOTE_START(name, type, "") \
> >> > + ELFNOTE_START(name, type, "a") \
> >> > desc ; \
> >> > ELFNOTE_END
> >> >
> >> > --
--
Thanks,
~Nick Desaulniers