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 <[email protected]>
---
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
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 <[email protected]>
Ping
> ---
> 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
>
On Sun, 25 Oct 2020 at 17:19, Arvind Sankar <[email protected]> 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 <[email protected]>
>
> Ping
>
I'll pick this up as a fix once the merge window closes.
> > ---
> > 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
> >
On Sun, Oct 25, 2020 at 05:28:06PM +0100, Ard Biesheuvel wrote:
> On Sun, 25 Oct 2020 at 17:19, Arvind Sankar <[email protected]> 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 <[email protected]>
> >
> > 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
> > >
The following commit has been merged into the efi/core branch of tip:
Commit-ID: 688eb28211abdf82a3f51e8997f1c8137947227d
Gitweb: https://git.kernel.org/tip/688eb28211abdf82a3f51e8997f1c8137947227d
Author: Arvind Sankar <[email protected]>
AuthorDate: Sun, 11 Oct 2020 10:20:12 -04:00
Committer: Ard Biesheuvel <[email protected]>
CommitterDate: Mon, 26 Oct 2020 08:06:36 +01:00
efi/x86: Only copy the compressed kernel image in efi_relocate_kernel()
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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ard Biesheuvel <[email protected]>
---
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 3672539..f14c4ff 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);