On Fri, 6 Nov 2015, Andy Lutomirski wrote:
> Unfortunately, these only work if HAVE_JUMP_LABEL. In principle, we
> could do some serious surgery on the core jump label infrastructure
> to keep the patch infrastructure available on x86 on all builds, but
> that's probably not worth it.
No, but we can be smarter about it. There is nothing which that asm
entry code needs from linux/jump_label.h and asm/jump_label.h execpt
STATIC_KEY_INIT_NOP. Something like the patch below should do the
trick.
Thanks,
tglx
Index: tip/arch/x86/entry/calling.h
===================================================================
--- tip.orig/arch/x86/entry/calling.h
+++ tip/arch/x86/entry/calling.h
@@ -232,3 +232,22 @@ For 32-bit we have the following convent
#endif /* CONFIG_X86_64 */
+/* ASM jump label support */
+#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
+#include <asm/jump_label.h>
+
+ .macro STATIC_CALL_IF_ENABLED fun, key
+ 1:
+ jmp.d32 2f
+ call fun
+ .pushsection __jump_table, "aw"
+ _ASM_ALIGN
+ _ASM_PTR 1b, 2f, \key
+ .popsection
+ 2:
+ .endm
+#else
+ .macro STATIC_CALL_IF_ENABLED fun, key
+ call fun
+ .endm
+#endif
Index: tip/arch/x86/entry/entry_64.S
===================================================================
--- tip.orig/arch/x86/entry/entry_64.S
+++ tip/arch/x86/entry/entry_64.S
@@ -510,7 +510,7 @@ END(irq_entries_start)
*/
SWAPGS
#ifdef CONFIG_CONTEXT_TRACKING
- call enter_from_user_mode
+ STATIC_CALL_IF_ENABLED enter_from_user_mode, context_tracking_enabled
#endif
1:
@@ -1050,7 +1050,7 @@ ENTRY(error_entry)
.Lerror_entry_from_usermode_after_swapgs:
#ifdef CONFIG_CONTEXT_TRACKING
- call enter_from_user_mode
+ STATIC_CALL_IF_ENABLED enter_from_user_mode, context_tracking_enabled
#endif
.Lerror_entry_done:
Index: tip/arch/x86/include/asm/jump_label.h
===================================================================
--- tip.orig/arch/x86/include/asm/jump_label.h
+++ tip/arch/x86/include/asm/jump_label.h
@@ -1,10 +1,6 @@
#ifndef _ASM_X86_JUMP_LABEL_H
#define _ASM_X86_JUMP_LABEL_H
-#ifndef __ASSEMBLY__
-
-#include <linux/stringify.h>
-#include <linux/types.h>
#include <asm/nops.h>
#include <asm/asm.h>
@@ -16,6 +12,11 @@
# define STATIC_KEY_INIT_NOP GENERIC_NOP5_ATOMIC
#endif
+#ifndef __ASSEMBLY__
+
+#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:"
--
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