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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
	linux-efi <linux-efi@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] efi/x86: Only copy the compressed kernel image in efi_relocate_kernel()
Date: Sun, 25 Oct 2020 13:24:43 -0400	[thread overview]
Message-ID: <20201025172443.GA1222048@rani.riverdale.lan> (raw)
In-Reply-To: <CAMj1kXGBybyTOADr+PvC+ZVohw+aRZbEnfweHTECKKdX9JHXTw@mail.gmail.com>

On Sun, Oct 25, 2020 at 05:28:06PM +0100, Ard Biesheuvel wrote:
> On Sun, 25 Oct 2020 at 17:19, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> >
> > On Sun, Oct 11, 2020 at 10:20:12AM -0400, Arvind Sankar wrote:
> > > The image_size argument to efi_relocate_kernel() is currently specified
> > > as init_size, but this is unnecessarily large. The compressed kernel is
> > > much smaller, in fact, its image only extends up to the start of _bss,
> > > since at this point, the .bss section is still uninitialized.
> > >
> > > Depending on compression level, this can reduce the amount of data
> > > copied by 4-5x.
> > >
> > > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> >
> > Ping
> >
> 
> I'll pick this up as a fix once the merge window closes.

Thanks!

> 
> > > ---
> > >  drivers/firmware/efi/libstub/x86-stub.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
> > > index 3672539cb96e..f14c4ff5839f 100644
> > > --- a/drivers/firmware/efi/libstub/x86-stub.c
> > > +++ b/drivers/firmware/efi/libstub/x86-stub.c
> > > @@ -715,8 +715,11 @@ unsigned long efi_main(efi_handle_t handle,
> > >           (IS_ENABLED(CONFIG_X86_32) && buffer_end > KERNEL_IMAGE_SIZE)    ||
> > >           (IS_ENABLED(CONFIG_X86_64) && buffer_end > MAXMEM_X86_64_4LEVEL) ||
> > >           (image_offset == 0)) {
> > > +             extern char _bss[];
> > > +
> > >               status = efi_relocate_kernel(&bzimage_addr,
> > > -                                          hdr->init_size, hdr->init_size,
> > > +                                          (unsigned long)_bss - bzimage_addr,
> > > +                                          hdr->init_size,
> > >                                            hdr->pref_address,
> > >                                            hdr->kernel_alignment,
> > >                                            LOAD_PHYSICAL_ADDR);
> > > --
> > > 2.26.2
> > >

      reply	other threads:[~2020-10-25 17:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-11 14:20 [PATCH] efi/x86: Only copy the compressed kernel image in efi_relocate_kernel() Arvind Sankar
2020-10-25 16:19 ` Arvind Sankar
2020-10-25 16:28   ` Ard Biesheuvel
2020-10-25 17:24     ` Arvind Sankar [this message]

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