linux-efi.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Arvind Sankar <nivedita@alum.mit.edu>
To: linux-efi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] efi/x86: Only copy the compressed kernel image in efi_relocate_kernel()
Date: Sun, 11 Oct 2020 10:20:12 -0400	[thread overview]
Message-ID: <20201011142012.96493-1-nivedita@alum.mit.edu> (raw)

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>
---
 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:[~2020-10-11 14:20 UTC|newest]

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201011142012.96493-1-nivedita@alum.mit.edu \
    --to=nivedita@alum.mit.edu \
    --cc=linux-efi@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).