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    SubjectRe: [PATCH 1/2] x86/boot/compressed/64: Remove .bss/.pgtable from bzImage
    On Tue, Feb 18, 2020 at 01:03:54PM -0500, Arvind Sankar wrote:
    > On Wed, Feb 05, 2020 at 11:29:21AM -0500, Arvind Sankar wrote:
    > > On Thu, Jan 09, 2020 at 10:02:17AM -0500, Arvind Sankar wrote:
    > > > Commit 5b11f1cee579 ("x86, boot: straighten out ranges to copy/zero in
    > > > compressed/head*.S") introduced a separate .pgtable section, splitting
    > > > it out from the rest of .bss. This section was added without the
    > > > writeable flag, marking it as read-only. This results in the linker
    > > > putting the .rela.dyn section (containing bogus dynamic relocations from
    > > > head_64.o) after the .bss and .pgtable sections.
    > > >
    > > > When we use objcopy to convert compressed/vmlinux into a binary for the
    > > > bzImage, the .bss and .pgtable sections get materialized as ~176KiB of
    > > > zero bytes in the binary in order to place .rela.dyn at the correct
    > > > location.
    > > >
    > > > Fix this by marking .pgtable as writeable. This moves the .rela.dyn
    > > > section earlier so that .bss and .pgtable are the last allocated
    > > > sections and so don't appear in bzImage.
    > > >
    > > > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
    > > > ---
    > > > arch/x86/boot/compressed/head_64.S | 2 +-
    > > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > > >
    > > > diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
    > > > index 58a512e33d8d..6eb30f8a3ce7 100644
    > > > --- a/arch/x86/boot/compressed/head_64.S
    > > > +++ b/arch/x86/boot/compressed/head_64.S
    > > > @@ -709,7 +709,7 @@ SYM_DATA_END_LABEL(boot_stack, SYM_L_LOCAL, boot_stack_end)
    > > > /*
    > > > * Space for page tables (not in .bss so not zeroed)
    > > > */
    > > > - .section ".pgtable","a",@nobits
    > > > + .section ".pgtable","aw",@nobits
    > > > .balign 4096
    > > > SYM_DATA_LOCAL(pgtable, .fill BOOT_PGT_SIZE, 1, 0)
    > > >
    > > > --
    > > > 2.24.1
    > > >
    > >
    > > Gentle reminder.
    > >
    > > https://lore.kernel.org/lkml/20200109150218.16544-1-nivedita@alum.mit.edu
    >
    > Ping.

    You keep pinging. Why? Is it a showstopper or what is the urgency here?

    This is shaving off some 100 - 200 KiB from the final bzImage, AFAICT. Or
    is there something more broken this is fixing?

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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