From 03335e95e27fc1f2b17b05b27342ad76986b3cf0 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Mon, 27 Apr 2015 15:21:52 +0200 Subject: [PATCH] x86/asm/entry/64: Clean up usage of TEST insns By the nature of TEST operation, it is often possible to test a narrower part of the operand: "testl $3, mem" -> "testb $3, mem" This results in shorter insns, because TEST insn has no sign-entending byte-immediate forms unlike other ALU ops. text data bss dec hex filename 11674 0 0 11674 2d9a entry_64.o.before 11658 0 0 11658 2d8a entry_64.o Changes in object code: - f7 84 24 88 00 00 00 03 00 00 00 testl $0x3,0x88(%rsp) + f6 84 24 88 00 00 00 03 testb $0x3,0x88(%rsp) - f7 44 24 68 03 00 00 00 testl $0x3,0x68(%rsp) + f6 44 24 68 03 testb $0x3,0x68(%rsp) - f7 84 24 90 00 00 00 03 00 00 00 testl $0x3,0x90(%rsp) + f6 84 24 90 00 00 00 03 testb $0x3,0x90(%rsp) Signed-off-by: Denys Vlasenko Acked-by: Andy Lutomirski Cc: Alexei Starovoitov Cc: Borislav Petkov Cc: Brian Gerst Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Will Drewry Link: http://lkml.kernel.org/r/1430140912-7960-2-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 8f8b22a361df..60705b032521 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -601,7 +601,7 @@ ENTRY(ret_from_fork) RESTORE_EXTRA_REGS - testl $3,CS(%rsp) # from kernel_thread? + testb $3, CS(%rsp) # from kernel_thread? /* * By the time we get here, we have no idea whether our pt_regs, @@ -665,7 +665,7 @@ END(irq_entries_start) leaq -RBP(%rsp),%rdi /* arg1 for \func (pointer to pt_regs) */ - testl $3, CS-RBP(%rsp) + testb $3, CS-RBP(%rsp) jz 1f SWAPGS 1: @@ -720,7 +720,7 @@ ret_from_intr: CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET RBP - testl $3,CS(%rsp) + testb $3, CS(%rsp) jz retint_kernel /* Interrupt came from user space */ @@ -968,7 +968,7 @@ ENTRY(\sym) .if \paranoid .if \paranoid == 1 CFI_REMEMBER_STATE - testl $3, CS(%rsp) /* If coming from userspace, switch */ + testb $3, CS(%rsp) /* If coming from userspace, switch */ jnz 1f /* stacks. */ .endif call paranoid_entry @@ -1309,7 +1309,7 @@ ENTRY(error_entry) SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 xorl %ebx,%ebx - testl $3,CS+8(%rsp) + testb $3, CS+8(%rsp) jz error_kernelspace error_swapgs: SWAPGS @@ -1606,7 +1606,6 @@ end_repeat_nmi: je 1f movq %r12, %cr2 1: - testl %ebx,%ebx /* swapgs needed? */ jnz nmi_restore nmi_swapgs: -- 2.39.2