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 <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: Ingo Molnar <[email protected]>
CC: Borislav Petkov <[email protected]>
CC: "H. Peter Anvin" <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Frederic Weisbecker <[email protected]>
CC: Alexei Starovoitov <[email protected]>
CC: Will Drewry <[email protected]>
CC: Kees Cook <[email protected]>
CC: [email protected]
CC: [email protected]
---
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 8f8b22a..60705b03 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:
--
1.8.1.4
--
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