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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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19
arch/s390/kernel/jump_label.c
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@@ -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));
}