[Bug target/99113] SHF_GNU_RETAIN doesn't work with Linux kernel

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99113

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@gcc.gnu.org>:

https://gcc.gnu.org/g:6347f4a0904fce17eedf5c071be6f3c118680290

commit r11-7284-g6347f4a0904fce17eedf5c071be6f3c118680290
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Mon Feb 15 11:31:12 2021 -0800

    Add retain attribute to place symbols in SHF_GNU_RETAIN section

    When building Linux kernel, ld in bninutils 2.36 with GCC 11 generates
    thousands of

    ld: warning: orphan section `.data.event_initcall_finish' from
`init/main.o' being placed in section `.data.event_initcall_finish'
    ld: warning: orphan section `.data.event_initcall_start' from `init/main.o'
being placed in section `.data.event_initcall_start'
    ld: warning: orphan section `.data.event_initcall_level' from `init/main.o'
being placed in section `.data.event_initcall_level'

    Since these sections are marked with SHF_GNU_RETAIN, they are placed in
    separate sections.  They become orphan sections since they aren't expected
    in the Linux kernel linker script. But orphan sections normally don't work
    well with the Linux kernel linker script and the resulting kernel crashed.

    Add the "retain" attribute to place symbols in separate SHF_GNU_RETAIN
    sections.  Issue a warning if the configured assembler/linker doesn't
    support SHF_GNU_RETAIN.

    gcc/

            PR target/99113
            * varasm.c (get_section): Replace SUPPORTS_SHF_GNU_RETAIN with
            looking up the retain attribute.
            (resolve_unique_section): Likewise.
            (get_variable_section): Likewise.
            (switch_to_section): Likewise.  Warn when a symbol without the
            retain attribute and a symbol with the retain attribute are
            placed in the section with the same name, instead of the used
            attribute.
            * doc/extend.texi: Document the "retain" attribute.

    gcc/c-family/

            PR target/99113
            * c-attribs.c (c_common_attribute_table): Add the "retain"
            attribute.
            (handle_retain_attribute): New function.

    gcc/testsuite/

            PR target/99113
            * c-c++-common/attr-retain-1.c: New test.
            * c-c++-common/attr-retain-2.c: Likewise.
            * c-c++-common/attr-retain-3.c: Likewise.
            * c-c++-common/attr-retain-4.c: Likewise.
            * c-c++-common/attr-retain-5.c: Likewise.
            * c-c++-common/attr-retain-6.c: Likewise.
            * c-c++-common/attr-retain-7.c: Likewise.
            * c-c++-common/attr-retain-8.c: Likewise.
            * c-c++-common/attr-retain-9.c: Likewise.
            * c-c++-common/pr99113.c: Likewise.
            * gcc.c-torture/compile/attr-retain-1.c: Likewise.
            * gcc.c-torture/compile/attr-retain-2.c: Likewise.
            * c-c++-common/attr-used.c: Don't expect SHF_GNU_RETAIN section.
            * c-c++-common/attr-used-2.c: Likewise.
            * c-c++-common/attr-used-3.c: Likewise.
            * c-c++-common/attr-used-4.c: Likewise.
            * c-c++-common/attr-used-9.c: Likewise.
            * gcc.c-torture/compile/attr-used-retain-1.c: Likewise.
            * gcc.c-torture/compile/attr-used-retain-2.c: Likewise.
            * c-c++-common/attr-used-5.c: Don't expect warning for the used
            attribute nor SHF_GNU_RETAIN section.
            * c-c++-common/attr-used-6.c: Likewise.
            * c-c++-common/attr-used-7.c: Likewise.
            * c-c++-common/attr-used-8.c: Likewise.