Quelle  jump_label.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
 * Jump label s390 support
 *
 * Copyright IBM Corp. 2011
 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
 */
#include <linux/uaccess.h>
#include <linux/jump_label.h>
#include <linux/module.h>
#include <asm/text-patching.h>
#include <asm/ipl.h>

struct insn {
 u16 opcode;
 s32 offset;
} __packed;

static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
{
 /* brcl 0,offset */
 insn->opcode = 0xc004;
 insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
}

static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
{
 /* brcl 15,offset */
 insn->opcode = 0xc0f4;
 insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
}

static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
      struct insn *new)
{
 unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
 unsigned char *ipe = (unsigned char *)expected;
 unsigned char *ipn = (unsigned char *)new;

 pr_emerg("Jump label code mismatch at %pS [%px]\n", ipc, ipc);
 pr_emerg("Found: %6ph\n", ipc);
 pr_emerg("Expected: %6ph\n", ipe);
 pr_emerg("New: %6ph\n", ipn);
 panic("Corrupted kernel text");
}

static void jump_label_transform(struct jump_entry *entry,
     enum jump_label_type type)
{
 void *code = (void *)jump_entry_code(entry);
 struct insn old, new;

 if (type == JUMP_LABEL_JMP) {
  jump_label_make_nop(entry, &old);
  jump_label_make_branch(entry, &new);
 } else {
  jump_label_make_branch(entry, &old);
  jump_label_make_nop(entry, &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);
 text_poke_sync();
}

bool arch_jump_label_transform_queue(struct jump_entry *entry,
         enum jump_label_type type)
{
 jump_label_transform(entry, type);
 return true;
}

void arch_jump_label_transform_apply(void)
{
 text_poke_sync();
}