leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

jump_label: s390: avoid pointless initial NOP patching

Browse Source 
Patching NOPs into other NOPs at boot time serves no purpose, so let's
use the same NOP encodings at compile time and runtime.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220615154142.1574619-2-ardb@kernel.org
This commit is contained in:
Ard Biesheuvel 2022-06-15 17:41:40 +02:00 committed by Peter Zijlstra
parent a111daf0c5
commit 0c3b61e00a
2 changed files with 7 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/s390/include/asm/jump_label.h
View File

@ -10,7 +10,6 @@
#include <linux/stringify.h>
#define JUMP_LABEL_NOP_SIZE 6
#define JUMP_LABEL_NOP_OFFSET 2
#ifdef CONFIG_CC_IS_CLANG
#define JUMP_LABEL_STATIC_KEY_CONSTRAINT "i"
@ -21,12 +20,12 @@
#endif
/*
* We use a brcl 0,2 instruction for jump labels at compile time so it
* We use a brcl 0,<offset> instruction for jump labels so it
* can be easily distinguished from a hotpatch generated instruction.
*/
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
asm_volatile_goto("0: brcl 0,%l[label]\n"
".pushsection __jump_table,\"aw\"\n"
".balign 8\n"
".long 0b-.,%l[label]-.\n"

23
arch/s390/kernel/jump_label.c
View File

@ -44,14 +44,8 @@ static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
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)
enum jump_label_type type)
{
void *code = (void *)jump_entry_code(entry);
struct insn old, new;
@ -63,27 +57,22 @@ static void jump_label_transform(struct jump_entry *entry,
jump_label_make_branch(entry, &old);
jump_label_make_nop(entry, &new);
}
if (init) {
if (memcmp(code, &orignop, sizeof(orignop)))
jump_label_bug(entry, &orignop, &new);
} else {
if (memcmp(code, &old, sizeof(old)))
jump_label_bug(entry, &old, &new);
}
if (memcmp(code, &old, sizeof(old)))
jump_label_bug(entry, &old, &new);
s390_kernel_write(code, &new, sizeof(new));
}
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
jump_label_transform(entry, type, 0);
jump_label_transform(entry, type);
text_poke_sync();
}
bool arch_jump_label_transform_queue(struct jump_entry *entry,
enum jump_label_type type)
{
jump_label_transform(entry, type, 0);
jump_label_transform(entry, type);
return true;
}
@ -95,6 +84,4 @@ void arch_jump_label_transform_apply(void)
void __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
jump_label_transform(entry, type, 1);
text_poke_sync();
}