From: Alexander Kuleshov <kuleshovmail@xxxxxxxxx> commit a4733143085d6c782ac1e6c85778655b6bac1d4e upstream We are using %rax as temporary register to check the kernel address alignment. We don't really have to since the TEST instruction does not clobber the destination operand. Suggested-by: Brian Gerst <brgerst@xxxxxxxxx> Signed-off-by: Alexander Kuleshov <kuleshovmail@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Alexander Popov <alpopov@xxxxxxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1453531828-19291-1-git-send-email-kuleshovmail@xxxxxxxxx Link: http://lkml.kernel.org/r/1453842730-28463-11-git-send-email-bp@xxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Srivatsa S. Bhat <srivatsa@xxxxxxxxxxxxx> Reviewed-by: Matt Helsley (VMware) <matt.helsley@xxxxxxxxx> Reviewed-by: Alexey Makhalov <amakhalov@xxxxxxxxxx> Reviewed-by: Bo Gan <ganb@xxxxxxxxxx> --- arch/x86/kernel/head_64.S | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4034e90..734ba1d 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -76,9 +76,7 @@ startup_64: subq $_text - __START_KERNEL_map, %rbp /* Is the address not 2M aligned? */ - movq %rbp, %rax - andl $~PMD_PAGE_MASK, %eax - testl %eax, %eax + testl $~PMD_PAGE_MASK, %ebp jnz bad_address /*
