[PATCH v9 10/10] x86: jump-labels: use macros instead of inline assembly

Nadav Amit
2018-10-03T21:32:51Z

Use assembly macros for jump-labels and call them from inline assembly.
This not only makes the code more readable, but also improves
compilation decision, specifically inline decisions which GCC base on
the number of new lines in inline assembly.

As a result the code size is slightly increased.

text data bss dec hex filename
18163528 10226300 2957312 31347140 1de51c4 ./vmlinux before
18163608 10227348 2957312 31348268 1de562c ./vmlinux after (+1128)

And functions such as intel_pstate_adjust_policy_max(),
kvm_cpu_accept_dm_intr(), kvm_register_readl() are inlined.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
arch/x86/entry/calling.h | 2 +-
arch/x86/include/asm/jump_label.h | 77 +++++++++++--------------------
arch/x86/kernel/macros.S | 1 +
3 files changed, 30 insertions(+), 50 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 352e70cd33e8..708b46a54578 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -338,7 +338,7 @@ For 32-bit we have the following conventions - kernel is built with
.macro CALL_enter_from_user_mode
#ifdef CONFIG_CONTEXT_TRACKING
#ifdef HAVE_JUMP_LABEL
- STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
+ STATIC_BRANCH_JMP l_yes=.Lafter_call_\@, key=context_tracking_enabled, branch=1
#endif
call enter_from_user_mode
.Lafter_call_\@:
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 8c0de4282659..4606a7101f97 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -2,19 +2,6 @@
#ifndef _ASM_X86_JUMP_LABEL_H
#define _ASM_X86_JUMP_LABEL_H

-#ifndef HAVE_JUMP_LABEL
-/*
- * For better or for worse, if jump labels (the gcc extension) are missing,
- * then the entire static branch patching infrastructure is compiled out.
- * If that happens, the code in here will malfunction. Raise a compiler
- * error instead.
- *
- * In theory, jump labels and the static branch patching infrastructure
- * could be decoupled to fix this.
- */
-#error asm/jump_label.h included on a non-jump-label kernel
-#endif
-
#define JUMP_LABEL_NOP_SIZE 5

#ifdef CONFIG_X86_64
@@ -28,18 +15,27 @@

#ifndef __ASSEMBLY__

+#ifndef HAVE_JUMP_LABEL
+/*
+ * For better or for worse, if jump labels (the gcc extension) are missing,
+ * then the entire static branch patching infrastructure is compiled out.
+ * If that happens, the code in here will malfunction. Raise a compiler
+ * error instead.
+ *
+ * In theory, jump labels and the static branch patching infrastructure
+ * could be decoupled to fix this.
+ */
+#error asm/jump_label.h included on a non-jump-label kernel
+#endif
+
#include <linux/stringify.h>
#include <linux/types.h>

static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
- asm_volatile_goto("1:"
- ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
- ".pushsection __jump_table, \"aw\" \n\t"
- _ASM_ALIGN "\n\t"
- _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
- ".popsection \n\t"
- : : "i" (key), "i" (branch) : : l_yes);
+ asm_volatile_goto("STATIC_BRANCH_NOP l_yes=\"%l[l_yes]\" key=\"%c0\" "
+ "branch=\"%c1\""
+ : : "i" (key), "i" (branch) : : l_yes);

return false;
l_yes:
@@ -48,13 +44,8 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran

static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
- asm_volatile_goto("1:"
- ".byte 0xe9\n\t .long %l[l_yes] - 2f\n\t"
- "2:\n\t"
- ".pushsection __jump_table, \"aw\" \n\t"
- _ASM_ALIGN "\n\t"
- _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
- ".popsection \n\t"
+ asm_volatile_goto("STATIC_BRANCH_JMP l_yes=\"%l[l_yes]\" key=\"%c0\" "
+ "branch=\"%c1\""
: : "i" (key), "i" (branch) : : l_yes);

return false;
@@ -76,35 +67,23 @@ struct jump_entry {

#else /* __ASSEMBLY__ */

-.macro STATIC_JUMP_IF_TRUE target, key, def
-.Lstatic_jump_\@:
- .if \def
- /* Equivalent to "jmp.d32 \target" */
- .byte 0xe9
- .long \target - .Lstatic_jump_after_\@
-.Lstatic_jump_after_\@:
- .else
- .byte STATIC_KEY_INIT_NOP
- .endif
+.macro STATIC_BRANCH_NOP l_yes:req key:req branch:req
+1:
+ .byte STATIC_KEY_INIT_NOP
.pushsection __jump_table, "aw"
_ASM_ALIGN
- _ASM_PTR .Lstatic_jump_\@, \target, \key
+ _ASM_PTR 1b, \l_yes, \key + \branch
.popsection
.endm

-.macro STATIC_JUMP_IF_FALSE target, key, def
-.Lstatic_jump_\@:
- .if \def
- .byte STATIC_KEY_INIT_NOP
- .else
- /* Equivalent to "jmp.d32 \target" */
- .byte 0xe9
- .long \target - .Lstatic_jump_after_\@
-.Lstatic_jump_after_\@:
- .endif
+.macro STATIC_BRANCH_JMP l_yes:req key:req branch:req
+1:
+ .byte 0xe9
+ .long \l_yes - 2f
+2:
.pushsection __jump_table, "aw"
_ASM_ALIGN
- _ASM_PTR .Lstatic_jump_\@, \target, \key + 1
+ _ASM_PTR 1b, \l_yes, \key + \branch
.popsection
.endm

diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S
index bf8b9c93e255..161c95059044 100644
--- a/arch/x86/kernel/macros.S
+++ b/arch/x86/kernel/macros.S
@@ -13,3 +13,4 @@
#include <asm/paravirt.h>
#include <asm/asm.h>
#include <asm/cpufeature.h>
+#include <asm/jump_label.h>
--
2.17.1