1 files changed, 120 insertions, 50 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 334f374..90c0e82 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -36,6 +36,7 @@
 #include <linux/hash.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/moduleloader.h>
 #include <asm/cacheflush.h>
 #include <asm/errno.h>
 #include <asm/kdebug.h>
@@ -50,6 +51,106 @@ unsigned int kprobe_cpu = NR_CPUS;
 static DEFINE_SPINLOCK(kprobe_lock);
 static struct kprobe *curr_kprobe;
 
+/*
+ * kprobe->ainsn.insn points to the copy of the instruction to be
+ * single-stepped. x86_64, POWER4 and above have no-exec support and
+ * stepping on the instruction on a vmalloced/kmalloced/data page
+ * is a recipe for disaster
+ */
+#define INSNS_PER_PAGE	(PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
+
+struct kprobe_insn_page {
+	struct hlist_node hlist;
+	kprobe_opcode_t *insns;		/* Page of instruction slots */
+	char slot_used[INSNS_PER_PAGE];
+	int nused;
+};
+
+static struct hlist_head kprobe_insn_pages;
+
+/**
+ * get_insn_slot() - Find a slot on an executable page for an instruction.
+ * We allocate an executable page if there's no room on existing ones.
+ */
+kprobe_opcode_t *get_insn_slot(void)
+{
+	struct kprobe_insn_page *kip;
+	struct hlist_node *pos;
+
+	hlist_for_each(pos, &kprobe_insn_pages) {
+		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
+		if (kip->nused < INSNS_PER_PAGE) {
+			int i;
+			for (i = 0; i < INSNS_PER_PAGE; i++) {
+				if (!kip->slot_used[i]) {
+					kip->slot_used[i] = 1;
+					kip->nused++;
+					return kip->insns + (i * MAX_INSN_SIZE);
+				}
+			}
+			/* Surprise!  No unused slots.  Fix kip->nused. */
+			kip->nused = INSNS_PER_PAGE;
+		}
+	}
+
+	/* All out of space.  Need to allocate a new page. Use slot 0.*/
+	kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
+	if (!kip) {
+		return NULL;
+	}
+
+	/*
+	 * Use module_alloc so this page is within +/- 2GB of where the
+	 * kernel image and loaded module images reside. This is required
+	 * so x86_64 can correctly handle the %rip-relative fixups.
+	 */
+	kip->insns = module_alloc(PAGE_SIZE);
+	if (!kip->insns) {
+		kfree(kip);
+		return NULL;
+	}
+	INIT_HLIST_NODE(&kip->hlist);
+	hlist_add_head(&kip->hlist, &kprobe_insn_pages);
+	memset(kip->slot_used, 0, INSNS_PER_PAGE);
+	kip->slot_used[0] = 1;
+	kip->nused = 1;
+	return kip->insns;
+}
+
+void free_insn_slot(kprobe_opcode_t *slot)
+{
+	struct kprobe_insn_page *kip;
+	struct hlist_node *pos;
+
+	hlist_for_each(pos, &kprobe_insn_pages) {
+		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
+		if (kip->insns <= slot &&
+		    slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
+			int i = (slot - kip->insns) / MAX_INSN_SIZE;
+			kip->slot_used[i] = 0;
+			kip->nused--;
+			if (kip->nused == 0) {
+				/*
+				 * Page is no longer in use.  Free it unless
+				 * it's the last one.  We keep the last one
+				 * so as not to have to set it up again the
+				 * next time somebody inserts a probe.
+				 */
+				hlist_del(&kip->hlist);
+				if (hlist_empty(&kprobe_insn_pages)) {
+					INIT_HLIST_NODE(&kip->hlist);
+					hlist_add_head(&kip->hlist,
+						&kprobe_insn_pages);
+				} else {
+					module_free(NULL, kip->insns);
+					kfree(kip);
+				}
+			}
+			return;
+		}
+	}
+}
+
 /* Locks kprobe: irqs must be disabled */
 void lock_kprobes(void)
 {
@@ -139,12 +240,6 @@ static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
 	return 0;
 }
 
-struct kprobe trampoline_p = {
-		.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
-		.pre_handler = trampoline_probe_handler,
-		.post_handler = trampoline_post_handler
-};
-
 struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp)
 {
 	struct hlist_node *node;
@@ -163,35 +258,18 @@ static struct kretprobe_instance *get_used_rp_inst(struct kretprobe *rp)
 	return NULL;
 }
 
-struct kretprobe_instance *get_rp_inst(void *sara)
-{
-	struct hlist_head *head;
-	struct hlist_node *node;
-	struct task_struct *tsk;
-	struct kretprobe_instance *ri;
-
-	tsk = arch_get_kprobe_task(sara);
-	head = &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
-	hlist_for_each_entry(ri, node, head, hlist) {
-		if (ri->stack_addr == sara)
-			return ri;
-	}
-	return NULL;
-}
-
 void add_rp_inst(struct kretprobe_instance *ri)
 {
-	struct task_struct *tsk;
 	/*
 	 * Remove rp inst off the free list -
 	 * Add it back when probed function returns
 	 */
 	hlist_del(&ri->uflist);
-	tsk = arch_get_kprobe_task(ri->stack_addr);
+
 	/* Add rp inst onto table */
 	INIT_HLIST_NODE(&ri->hlist);
 	hlist_add_head(&ri->hlist,
-			&kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)]);
+			&kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);
 
 	/* Also add this rp inst to the used list. */
 	INIT_HLIST_NODE(&ri->uflist);
@@ -218,34 +296,25 @@ struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk)
 	return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
 }
 
-struct kretprobe_instance *get_rp_inst_tsk(struct task_struct *tk)
-{
-	struct task_struct *tsk;
-	struct hlist_head *head;
-	struct hlist_node *node;
-	struct kretprobe_instance *ri;
-
-	head = &kretprobe_inst_table[hash_ptr(tk, KPROBE_HASH_BITS)];
-
-	hlist_for_each_entry(ri, node, head, hlist) {
-		tsk = arch_get_kprobe_task(ri->stack_addr);
-		if (tsk == tk)
-			return ri;
-	}
-	return NULL;
-}
-
 /*
- * This function is called from do_exit or do_execv when task tk's stack is
- * about to be recycled. Recycle any function-return probe instances
- * associated with this task. These represent probed functions that have
- * been called but may never return.
+ * This function is called from exit_thread or flush_thread when task tk's
+ * stack is being recycled so that we can recycle any function-return probe
+ * instances associated with this task. These left over instances represent
+ * probed functions that have been called but will never return.
  */
 void kprobe_flush_task(struct task_struct *tk)
 {
+        struct kretprobe_instance *ri;
+        struct hlist_head *head;
+	struct hlist_node *node, *tmp;
 	unsigned long flags = 0;
+
 	spin_lock_irqsave(&kprobe_lock, flags);
-	arch_kprobe_flush_task(tk);
+        head = kretprobe_inst_table_head(current);
+        hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+                if (ri->task == tk)
+                        recycle_rp_inst(ri);
+        }
 	spin_unlock_irqrestore(&kprobe_lock, flags);
 }
 
@@ -505,9 +574,10 @@ static int __init init_kprobes(void)
 		INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
 	}
 
-	err = register_die_notifier(&kprobe_exceptions_nb);
-	/* Register the trampoline probe for return probe */
-	register_kprobe(&trampoline_p);
+	err = arch_init();
+	if (!err)
+		err = register_die_notifier(&kprobe_exceptions_nb);
+
 	return err;
 }