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s390/jump label: use different nop instruction

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Use a brcl 0,2 instruction for jump label nops during compile time,
so we don't mix up the different nops during mcount/hotpatch call
site detection.
The initial jump label code instruction replacement will exchange
these instructions with either a branch or a brcl 0,0 instruction.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens
2015-01-29 14:10:22 +01:00
committed by Martin Schwidefsky
parent 5c6497c50f
commit d5caa4dbf9
2 changed files with 19 additions and 7 deletions
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7
arch/s390/include/asm/jump_label.h
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@@ -4,6 +4,7 @@
#include <linux/types.h>
#define JUMP_LABEL_NOP_SIZE 6
#define JUMP_LABEL_NOP_OFFSET 2
#ifdef CONFIG_64BIT
#define ASM_PTR ".quad"
@@ -13,9 +14,13 @@
#define ASM_ALIGN ".balign 4"
#endif
/*
* We use a brcl 0,2 instruction for jump labels at compile time so it
* can be easily distinguished from a hotpatch generated instruction.
*/
static __always_inline bool arch_static_branch(struct static_key *key)
{
asm_volatile_goto("0: brcl 0,0\n"
asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
".pushsection __jump_table, \"aw\"\n"
ASM_ALIGN "\n"
ASM_PTR " 0b, %l[label], %0\n"