diff options
author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2015-01-29 14:10:22 +0100 |
---|---|---|
committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2015-01-29 16:33:34 +0100 |
commit | d5caa4dbf9bd2ad8cd7f6be0ca76722be947182b (patch) | |
tree | 6d58cdd140333e17c881667e9691b17f7dcd6e4d /arch/s390 | |
parent | 5c6497c50f8d809eac6d01512c291a1f67382abd (diff) | |
download | op-kernel-dev-d5caa4dbf9bd2ad8cd7f6be0ca76722be947182b.zip op-kernel-dev-d5caa4dbf9bd2ad8cd7f6be0ca76722be947182b.tar.gz |
s390/jump label: use different nop instruction
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>
Diffstat (limited to 'arch/s390')
-rw-r--r-- | arch/s390/include/asm/jump_label.h | 7 | ||||
-rw-r--r-- | arch/s390/kernel/jump_label.c | 19 |
2 files changed, 19 insertions, 7 deletions
diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h index 346b1c8..58642fd 100644 --- a/arch/s390/include/asm/jump_label.h +++ b/arch/s390/include/asm/jump_label.h @@ -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" diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c index 25aef40..cb2d51e 100644 --- a/arch/s390/kernel/jump_label.c +++ b/arch/s390/kernel/jump_label.c @@ -49,6 +49,11 @@ static void jump_label_bug(struct jump_entry *entry, struct insn *insn) panic("Corrupted kernel text"); } +static struct insn orignop = { + .opcode = 0xc004, + .offset = JUMP_LABEL_NOP_OFFSET >> 1, +}; + static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, int init) @@ -59,14 +64,16 @@ static void __jump_label_transform(struct jump_entry *entry, jump_label_make_nop(entry, &old); jump_label_make_branch(entry, &new); } else { - if (init) - jump_label_make_nop(entry, &old); - else - jump_label_make_branch(entry, &old); + jump_label_make_branch(entry, &old); jump_label_make_nop(entry, &new); } - if (memcmp((void *)entry->code, &old, sizeof(old))) - jump_label_bug(entry, &old); + if (init) { + if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) + jump_label_bug(entry, &old); + } else { + if (memcmp((void *)entry->code, &old, sizeof(old))) + jump_label_bug(entry, &old); + } probe_kernel_write((void *)entry->code, &new, sizeof(new)); } |