mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-04-29 05:52:38 -04:00
4c6080cd6f
list_del() poisoning can generate 2 64-bit immediate loads but it also can generate one 64-bit immediate load and an addition: 48 b8 00 01 00 00 00 00 ad de movabs rax,0xdead000000000100 48 89 47 58 mov QWORD PTR [rdi+0x58],rax 48 05 00 01 00 00 <=====> add rax,0x100 48 89 47 60 mov QWORD PTR [rdi+0x60],rax However on x86_64 not all constants are equal: those within [-128, 127] range can be added with shorter "add r64, imm32" instruction: 48 b8 00 01 00 00 00 00 ad de movabs rax,0xdead000000000100 48 89 47 58 mov QWORD PTR [rdi+0x58],rax 48 83 c0 22 <======> add rax,0x22 48 89 47 60 mov QWORD PTR [rdi+0x60],rax Patch saves 2 bytes per some LIST_POISON2 usage. (Slightly disappointing) space savings on F29 x86_64 config: add/remove: 0/0 grow/shrink: 0/2164 up/down: 0/-5184 (-5184) Function old new delta zstd_get_workspace 548 546 -2 ... mlx4_delete_all_resources_for_slave 4826 4804 -22 Total: Before=83304131, After=83298947, chg -0.01% New constants are: 0xdead000000000100 0xdead000000000122 Note: LIST_POISON1 can't be changed to ...11 because something in page allocator requires low bit unset. Link: http://lkml.kernel.org/r/20190513191502.GA8492@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.