Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 10 Apr 2020 12:12:18 -0700 | Subject | Re: [PATCH] elfnote: mark all .note sections SHF_ALLOC |
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(bumping for review)
On Fri, Apr 3, 2020 at 5:40 PM Fangrui Song <maskray@google.com> 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 > >> <ndesaulniers@google.com> 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 <jeremy@xensource.com> > >> > Debugged-by: Ilie Halip <ilie.halip@gmail.com> > >> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > > > >Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > > I asked on binutils@sourceware.org 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 <maskray@google.com> > > >> > --- > >> > 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
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