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-rw-r--r--arch/x86/kernel/jump_label.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
new file mode 100644
index 000000000..26d5a55a2
--- /dev/null
+++ b/arch/x86/kernel/jump_label.c
@@ -0,0 +1,144 @@
+/*
+ * jump label x86 support
+ *
+ * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
+ *
+ */
+#include <linux/jump_label.h>
+#include <linux/memory.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/jhash.h>
+#include <linux/cpu.h>
+#include <asm/kprobes.h>
+#include <asm/alternative.h>
+
+#ifdef HAVE_JUMP_LABEL
+
+union jump_code_union {
+ char code[JUMP_LABEL_NOP_SIZE];
+ struct {
+ char jump;
+ int offset;
+ } __attribute__((packed));
+};
+
+static void bug_at(unsigned char *ip, int line)
+{
+ /*
+ * The location is not an op that we were expecting.
+ * Something went wrong. Crash the box, as something could be
+ * corrupting the kernel.
+ */
+ pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
+ ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
+ BUG();
+}
+
+static void __jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type,
+ void *(*poker)(void *, const void *, size_t),
+ int init)
+{
+ union jump_code_union code;
+ const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
+ const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
+
+ if (type == JUMP_LABEL_ENABLE) {
+ if (init) {
+ /*
+ * Jump label is enabled for the first time.
+ * So we expect a default_nop...
+ */
+ if (unlikely(memcmp((void *)entry->code, default_nop, 5)
+ != 0))
+ bug_at((void *)entry->code, __LINE__);
+ } else {
+ /*
+ * ...otherwise expect an ideal_nop. Otherwise
+ * something went horribly wrong.
+ */
+ if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
+ != 0))
+ bug_at((void *)entry->code, __LINE__);
+ }
+
+ code.jump = 0xe9;
+ code.offset = entry->target -
+ (entry->code + JUMP_LABEL_NOP_SIZE);
+ } else {
+ /*
+ * We are disabling this jump label. If it is not what
+ * we think it is, then something must have gone wrong.
+ * If this is the first initialization call, then we
+ * are converting the default nop to the ideal nop.
+ */
+ if (init) {
+ if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ } else {
+ code.jump = 0xe9;
+ code.offset = entry->target -
+ (entry->code + JUMP_LABEL_NOP_SIZE);
+ if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ }
+ memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
+ }
+
+ /*
+ * Make text_poke_bp() a default fallback poker.
+ *
+ * At the time the change is being done, just ignore whether we
+ * are doing nop -> jump or jump -> nop transition, and assume
+ * always nop being the 'currently valid' instruction
+ *
+ */
+ if (poker)
+ (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+ else
+ text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
+ (void *)entry->code + JUMP_LABEL_NOP_SIZE);
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ get_online_cpus();
+ mutex_lock(&text_mutex);
+ __jump_label_transform(entry, type, NULL, 0);
+ mutex_unlock(&text_mutex);
+ put_online_cpus();
+}
+
+static enum {
+ JL_STATE_START,
+ JL_STATE_NO_UPDATE,
+ JL_STATE_UPDATE,
+} jlstate __initdata_or_module = JL_STATE_START;
+
+__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ /*
+ * This function is called at boot up and when modules are
+ * first loaded. Check if the default nop, the one that is
+ * inserted at compile time, is the ideal nop. If it is, then
+ * we do not need to update the nop, and we can leave it as is.
+ * If it is not, then we need to update the nop to the ideal nop.
+ */
+ if (jlstate == JL_STATE_START) {
+ const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
+ const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
+
+ if (memcmp(ideal_nop, default_nop, 5) != 0)
+ jlstate = JL_STATE_UPDATE;
+ else
+ jlstate = JL_STATE_NO_UPDATE;
+ }
+ if (jlstate == JL_STATE_UPDATE)
+ __jump_label_transform(entry, type, text_poke_early, 1);
+}
+
+#endif