The following commit has been merged into the x86/asm branch of tip: Commit-ID: 1a8770b746bd05ef68217989cd723b2c24d2208d Gitweb: https://git.kernel.org/tip/1a8770b746bd05ef68217989cd723b2c24d2208d Author: Jiri Slaby <[email protected]> AuthorDate: Thu, 03 Oct 2019 11:52:37 +02:00 Committer: Borislav Petkov <[email protected]> CommitterDate: Sat, 05 Oct 2019 12:11:00 +02:00
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 <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: x86-ml <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- arch/x86/kernel/head_64.S | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index f3d3e96..f00d7c0 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)
