1 files changed, 66 insertions, 170 deletions

diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 4e680f87a75f..acd2a778ebe6 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -38,7 +38,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/preempt.h>
-#include <linux/moduleloader.h>
+
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
@@ -51,8 +51,6 @@ static struct kprobe *kprobe_prev;
 static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev;
 static struct pt_regs jprobe_saved_regs;
 static long *jprobe_saved_rsp;
-static kprobe_opcode_t *get_insn_slot(void);
-static void free_insn_slot(kprobe_opcode_t *slot);
 void jprobe_return_end(void);
 
 /* copy of the kernel stack at the probe fire time */
@@ -274,48 +272,23 @@ static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
                 regs->rip = (unsigned long)p->ainsn.insn;
 }
 
-struct task_struct  *arch_get_kprobe_task(void *ptr)
-{
-        return ((struct thread_info *) (((unsigned long) ptr) &
-                                        (~(THREAD_SIZE -1))))->task;
-}
-
 void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
 {
         unsigned long *sara = (unsigned long *)regs->rsp;
-        struct kretprobe_instance *ri;
-        static void *orig_ret_addr;
+        struct kretprobe_instance *ri;
+
+        if ((ri = get_free_rp_inst(rp)) != NULL) {
+                ri->rp = rp;
+                ri->task = current;
+                ri->ret_addr = (kprobe_opcode_t *) *sara;
 
-        /*
-         * Save the return address when the return probe hits
-         * the first time, and use it to populate the (krprobe
-         * instance)->ret_addr for subsequent return probes at
-         * the same addrress since stack address would have
-         * the kretprobe_trampoline by then.
-         */
-        if (((void*) *sara) != kretprobe_trampoline)
-                orig_ret_addr = (void*) *sara;
-
-        if ((ri = get_free_rp_inst(rp)) != NULL) {
-                ri->rp = rp;
-                ri->stack_addr = sara;
-                ri->ret_addr = orig_ret_addr;
-                add_rp_inst(ri);
                 /* Replace the return addr with trampoline addr */
                 *sara = (unsigned long) &kretprobe_trampoline;
-        } else {
-                rp->nmissed++;
-        }
-}
 
-void arch_kprobe_flush_task(struct task_struct *tk)
-{
-        struct kretprobe_instance *ri;
-        while ((ri = get_rp_inst_tsk(tk)) != NULL) {
-                *((unsigned long *)(ri->stack_addr)) =
-                                        (unsigned long) ri->ret_addr;
-                recycle_rp_inst(ri);
-        }
+                add_rp_inst(ri);
+        } else {
+                rp->nmissed++;
+        }
 }
 
 /*
@@ -428,36 +401,59 @@ no_kprobe:
  */
 int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
-        struct task_struct *tsk;
-        struct kretprobe_instance *ri;
-        struct hlist_head *head;
-        struct hlist_node *node;
-        unsigned long *sara = (unsigned long *)regs->rsp - 1;
-
-        tsk = arch_get_kprobe_task(sara);
-        head = kretprobe_inst_table_head(tsk);
-
-        hlist_for_each_entry(ri, node, head, hlist) {
-                if (ri->stack_addr == sara && ri->rp) {
-                        if (ri->rp->handler)
-                                ri->rp->handler(ri, regs);
-                }
-        }
-        return 0;
-}
+        struct kretprobe_instance *ri = NULL;
+        struct hlist_head *head;
+        struct hlist_node *node, *tmp;
+        unsigned long orig_ret_address = 0;
+        unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 
-void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs,
-                                                unsigned long flags)
-{
-        struct kretprobe_instance *ri;
-        /* RA already popped */
-        unsigned long *sara = ((unsigned long *)regs->rsp) - 1;
+        head = kretprobe_inst_table_head(current);
 
-        while ((ri = get_rp_inst(sara))) {
-                regs->rip = (unsigned long)ri->ret_addr;
+        /*
+         * It is possible to have multiple instances associated with a given
+         * task either because an multiple functions in the call path
+         * have a return probe installed on them, and/or more then one return
+         * return probe was registered for a target function.
+         *
+         * We can handle this because:
+         *     - instances are always inserted at the head of the list
+         *     - when multiple return probes are registered for the same
+         *       function, the first instance's ret_addr will point to the
+         *       real return address, and all the rest will point to
+         *       kretprobe_trampoline
+         */
+        hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+                if (ri->task != current)
+                        /* another task is sharing our hash bucket */
+                        continue;
+
+                if (ri->rp && ri->rp->handler)
+                        ri->rp->handler(ri, regs);
+
+                orig_ret_address = (unsigned long)ri->ret_addr;
                 recycle_rp_inst(ri);
+
+                if (orig_ret_address != trampoline_address)
+                        /*
+                         * This is the real return address. Any other
+                         * instances associated with this task are for
+                         * other calls deeper on the call stack
+                         */
+                        break;
         }
-        regs->eflags &= ~TF_MASK;
+
+        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+        regs->rip = orig_ret_address;
+
+        unlock_kprobes();
+        preempt_enable_no_resched();
+
+        /*
+         * By returning a non-zero value, we are telling
+         * kprobe_handler() that we have handled unlocking
+         * and re-enabling preemption.
+         */
+        return 1;
 }
 
 /*
@@ -550,8 +546,7 @@ int post_kprobe_handler(struct pt_regs *regs)
                 current_kprobe->post_handler(current_kprobe, regs, 0);
         }
 
-        if (current_kprobe->post_handler != trampoline_post_handler)
-                resume_execution(current_kprobe, regs);
+        resume_execution(current_kprobe, regs);
         regs->eflags |= kprobe_saved_rflags;
 
         /* Restore the original saved kprobes variables and continue. */
@@ -682,111 +677,12 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
         return 0;
 }
 
-/*
- * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped.
- * By default on x86_64, pages we get from kmalloc or vmalloc are not
- * executable.  Single-stepping an instruction on such a page yields an
- * oops.  So instead of storing the instruction copies in their respective
- * kprobe objects, we allocate a page, map it executable, and store all the
- * instruction copies there.  (We can allocate additional pages if somebody
- * inserts a huge number of probes.)  Each page can hold up to INSNS_PER_PAGE
- * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t)
- * bytes.
- */
-#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 kprobe trampoline_p = {
+        .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+        .pre_handler = trampoline_probe_handler
 };
 
-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.
- */
-static 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;
-        }
-
-        /*
-         * For the %rip-relative displacement fixups to be doable, we
-         * need our instruction copy to be within +/- 2GB of any data it
-         * might access via %rip.  That is, within 2GB of where the
-         * kernel image and loaded module images reside.  So we allocate
-         * a page in the module loading area.
-         */
-        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;
-}
-
-/**
- * free_insn_slot() - Free instruction slot obtained from get_insn_slot().
- */
-static void free_insn_slot(kprobe_opcode_t *slot)
+int __init arch_init(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->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;
-                }
-        }
+        return register_kprobe(&trampoline_p);
 }