diff options
| author | Jiri Slaby <jslaby@suse.cz> | 2019-10-03 11:52:37 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2019-10-05 12:11:00 +0200 |
| commit | 1a8770b746bd05ef68217989cd723b2c24d2208d (patch) | |
| tree | fb92d76ed9da9997521d4ff092d5bde8eedb9eee /arch/x86/kernel/head_64.S | |
| parent | 54ecb8f7028c5eb3d740bb82b0f1d90f2df63c5c (diff) | |
x86/asm: Reorder early variables
Moving early_recursion_flag (4 bytes) after early_level4_pgt (4k) and
early_dynamic_pgts (256k) saves 4k which are used for alignment of
early_level4_pgt after early_recursion_flag.
The real improvement is merely on the source code side. Previously it
was:
* __INITDATA + .balign
* early_recursion_flag variable
* a ton of CPP MACROS
* __INITDATA (again)
* early_top_pgt and early_recursion_flag variables
* .data
Now, it is a bit simpler:
* a ton of CPP MACROS
* __INITDATA + .balign
* early_top_pgt and early_recursion_flag variables
* early_recursion_flag variable
* .data
On the binary level the change looks like this:
Before:
(sections)
12 .init.data 00042000 0000000000000000 0000000000000000 00008000 2**12
(symbols)
000000 4 OBJECT GLOBAL DEFAULT 22 early_recursion_flag
001000 4096 OBJECT GLOBAL DEFAULT 22 early_top_pgt
002000 0x40000 OBJECT GLOBAL DEFAULT 22 early_dynamic_pgts
After:
(sections)
12 .init.data 00041004 0000000000000000 0000000000000000 00008000 2**12
(symbols)
000000 4096 OBJECT GLOBAL DEFAULT 22 early_top_pgt
001000 0x40000 OBJECT GLOBAL DEFAULT 22 early_dynamic_pgts
041000 4 OBJECT GLOBAL DEFAULT 22 early_recursion_flag
So the resulting vmlinux is smaller by 4k with my toolchain as many
other variables can be placed after early_recursion_flag to fill the
rest of the page. Note that this is only .init data, so it is freed
right after being booted anyway. Savings on-disk are none -- compression
of zeros is easy, so the size of bzImage is the same pre and post the
change.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191003095238.29831-1-jslaby@suse.cz
Diffstat (limited to 'arch/x86/kernel/head_64.S')
| -rw-r--r-- | arch/x86/kernel/head_64.S | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index f3d3e9646a99..f00d7c0c1c86 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -335,12 +335,6 @@ early_idt_handler_common: jmp restore_regs_and_return_to_kernel END(early_idt_handler_common) - __INITDATA - - .balign 4 -GLOBAL(early_recursion_flag) - .long 0 - #define NEXT_PAGE(name) \ .balign PAGE_SIZE; \ GLOBAL(name) @@ -375,6 +369,8 @@ GLOBAL(name) .endr __INITDATA + .balign 4 + NEXT_PGD_PAGE(early_top_pgt) .fill 512,8,0 .fill PTI_USER_PGD_FILL,8,0 @@ -382,6 +378,9 @@ NEXT_PGD_PAGE(early_top_pgt) NEXT_PAGE(early_dynamic_pgts) .fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0 +GLOBAL(early_recursion_flag) + .long 0 + .data #if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH) |