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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2019-05-14 15:44:40 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-14 19:52:50 -0700 |
| commit | a6231d1993367cf48a9c5f1adc295a5a8b1c5731 (patch) | |
| tree | 9aad4cb6334c611b0c7e7bd6754815dcd92b27dc | |
| parent | d53ddd0181d1c284c28c0d70a3d7039db41c6f7e (diff) | |
| download | linux-a6231d1993367cf48a9c5f1adc295a5a8b1c5731.tar.bz2 | |
exec: move struct linux_binprm::buf
struct linux_binprm::buf is the first field and it is exactly 128 bytes
in size. It means that on x86_64 all accesses to other fields will go
though [r64 + disp32] addressing mode which is 3 bytes bloatier than
[r64 + disp8] addressing mode. Given that accesses to other fields
outnumber accesses to ->buf, move it down.
Space savings (x86_64 defconfig):
more on distro configs because LSMs actively dereference "bprm"
but do not care about first 128 bytes of the executable itself.
add/remove: 0/0 grow/shrink: 0/24 up/down: 0/-492 (-492)
Function old new delta
selinux_bprm_committing_creds 552 549 -3
finalize_exec 94 91 -3
__audit_log_bprm_fcaps 283 280 -3
__audit_bprm 39 36 -3
perf_trace_sched_process_exec 347 341 -6
install_exec_creds 105 99 -6
cap_bprm_set_creds.cold 60 54 -6
would_dump 137 128 -9
load_script 637 628 -9
bprm_change_interp 61 52 -9
trace_event_raw_event_sched_process_exec 260 250 -10
search_binary_handler 255 240 -15
remove_arg_zero 295 277 -18
free_bprm 119 101 -18
prepare_binprm 379 360 -19
setup_new_exec 336 315 -21
flush_old_exec 1638 1617 -21
copy_strings.isra 746 724 -22
setup_arg_pages 559 530 -29
load_misc_binary 1151 1118 -33
selinux_bprm_set_creds 792 753 -39
load_elf_binary 11111 11072 -39
cap_bprm_set_creds 1496 1454 -42
__do_execve_file.isra 2395 2286 -109
Link: http://lkml.kernel.org/r/20190421165025.GA26843@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/binfmts.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 688ab0de7810..b40fc633f3be 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -15,7 +15,6 @@ struct filename; * This structure is used to hold the arguments that are used when loading binaries. */ struct linux_binprm { - char buf[BINPRM_BUF_SIZE]; #ifdef CONFIG_MMU struct vm_area_struct *vma; unsigned long vma_pages; @@ -64,6 +63,8 @@ struct linux_binprm { unsigned long loader, exec; struct rlimit rlim_stack; /* Saved RLIMIT_STACK used during exec. */ + + char buf[BINPRM_BUF_SIZE]; } __randomize_layout; #define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0 |