* [BUG?] scripts/extract-vmlinux doesn't produce correct images
@ 2021-06-07 6:18 Grzegorz Zdanowski
0 siblings, 0 replies; only message in thread
From: Grzegorz Zdanowski @ 2021-06-07 6:18 UTC (permalink / raw)
To: linux-kernel, kernel-packagers
Hello!
To avoid a XY problem, I will say upfront that I want to:
1. unpack the x86_64 bzImage
2. byte-patch it (as the full source is not available)
3. recompress it back to bzImage to use w/GRUB
Neither the script, commit message
(#09d481270d445d98342d8ab872f05491b6d23f8b) nor LKML thread where the
script was discussed (https://lkml.org/lkml/2011/8/4/168) specified
which "vmlinux" is extracted. I compiled the kernel and ran some tests
after painstakingly analyzing Makefiles.
It looks like "scripts/extract-vmlinux arch/x86/boot/bzImage" extracts
an equivalent of arch/x86/boot/compressed/vmlinux.bin:
# file arch/x86/boot/compressed/vmlinux.bin test-extract
arch/x86/boot/compressed/vmlinux.bin: ELF 64-bit LSB executable,
x86-64, version 1 (SYSV), statically linked,
BuildID[sha1]=2cc29c8d102d8dac8a4cd29539f4364a334f88fd, stripped
test-extract: ELF 64-bit LSB executable,
x86-64, version 1 (SYSV), statically linked,
BuildID[sha1]=2cc29c8d102d8dac8a4cd29539f4364a334f88fd, stripped
However the extracted file doesn't match any other file I was able to
find analyzing compilation process. Even with the size of
vmlinux.relocs it will be significantly off.
# ls -1s ... | sort
11144 arch/x86/boot/compressed/vmlinux.bin.lz4
11148 arch/x86/boot/compressed/piggy.o
11200 arch/x86/boot/vmlinux.bin
11212 arch/x86/boot/compressed/vmlinux
11416 arch/x86/boot/bzImage
35752 arch/x86/boot/compressed/vmlinux.bin
43968 test-extract
4 arch/x86/boot/compressed/piggy.S
760924 vmlinux
1. Did I found a problem with extract-vmlinux, or is that script
extracting something else?
2. Is there any other way to binary patch a kernel where only the
bzImage is available?
Apologies if my questions are very basic, I'm just dipping my toes in
the kernel space.
--
Grzegorz "Greg" Zdanowski
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2021-06-07 6:18 [BUG?] scripts/extract-vmlinux doesn't produce correct images Grzegorz Zdanowski
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