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authorAnanth N Mavinakayanahalli <ananth@in.ibm.com>2005-06-27 18:17:01 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-27 18:23:52 -0400
commit9ec4b1f356b3bad928ae8e2aa9caebfa737d52df (patch)
tree24d27ffed66595a9d864448ec53200ca1745f62c /arch/x86_64/kernel/kprobes.c
parentd3b8a1a8496c83bc4a3cc76505c29255af15572c (diff)
[PATCH] kprobes: fix single-step out of line - take2
Now that PPC64 has no-execute support, here is a second try to fix the single step out of line during kprobe execution. Kprobes on x86_64 already solved this problem by allocating an executable page and using it as the scratch area for stepping out of line. Reuse that. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/x86_64/kernel/kprobes.c')
-rw-r--r--arch/x86_64/kernel/kprobes.c113
1 files changed, 1 insertions, 112 deletions
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 4e680f87a75..6a1c88376be 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -38,7 +38,7 @@
38#include <linux/string.h> 38#include <linux/string.h>
39#include <linux/slab.h> 39#include <linux/slab.h>
40#include <linux/preempt.h> 40#include <linux/preempt.h>
41#include <linux/moduleloader.h> 41
42#include <asm/cacheflush.h> 42#include <asm/cacheflush.h>
43#include <asm/pgtable.h> 43#include <asm/pgtable.h>
44#include <asm/kdebug.h> 44#include <asm/kdebug.h>
@@ -51,8 +51,6 @@ static struct kprobe *kprobe_prev;
51static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev; 51static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev;
52static struct pt_regs jprobe_saved_regs; 52static struct pt_regs jprobe_saved_regs;
53static long *jprobe_saved_rsp; 53static long *jprobe_saved_rsp;
54static kprobe_opcode_t *get_insn_slot(void);
55static void free_insn_slot(kprobe_opcode_t *slot);
56void jprobe_return_end(void); 54void jprobe_return_end(void);
57 55
58/* copy of the kernel stack at the probe fire time */ 56/* copy of the kernel stack at the probe fire time */
@@ -681,112 +679,3 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
681 } 679 }
682 return 0; 680 return 0;
683} 681}
684
685/*
686 * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped.
687 * By default on x86_64, pages we get from kmalloc or vmalloc are not
688 * executable. Single-stepping an instruction on such a page yields an
689 * oops. So instead of storing the instruction copies in their respective
690 * kprobe objects, we allocate a page, map it executable, and store all the
691 * instruction copies there. (We can allocate additional pages if somebody
692 * inserts a huge number of probes.) Each page can hold up to INSNS_PER_PAGE
693 * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t)
694 * bytes.
695 */
696#define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE*sizeof(kprobe_opcode_t)))
697struct kprobe_insn_page {
698 struct hlist_node hlist;
699 kprobe_opcode_t *insns; /* page of instruction slots */
700 char slot_used[INSNS_PER_PAGE];
701 int nused;
702};
703
704static struct hlist_head kprobe_insn_pages;
705
706/**
707 * get_insn_slot() - Find a slot on an executable page for an instruction.
708 * We allocate an executable page if there's no room on existing ones.
709 */
710static kprobe_opcode_t *get_insn_slot(void)
711{
712 struct kprobe_insn_page *kip;
713 struct hlist_node *pos;
714
715 hlist_for_each(pos, &kprobe_insn_pages) {
716 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
717 if (kip->nused < INSNS_PER_PAGE) {
718 int i;
719 for (i = 0; i < INSNS_PER_PAGE; i++) {
720 if (!kip->slot_used[i]) {
721 kip->slot_used[i] = 1;
722 kip->nused++;
723 return kip->insns + (i*MAX_INSN_SIZE);
724 }
725 }
726 /* Surprise! No unused slots. Fix kip->nused. */
727 kip->nused = INSNS_PER_PAGE;
728 }
729 }
730
731 /* All out of space. Need to allocate a new page. Use slot 0.*/
732 kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
733 if (!kip) {
734 return NULL;
735 }
736
737 /*
738 * For the %rip-relative displacement fixups to be doable, we
739 * need our instruction copy to be within +/- 2GB of any data it
740 * might access via %rip. That is, within 2GB of where the
741 * kernel image and loaded module images reside. So we allocate
742 * a page in the module loading area.
743 */
744 kip->insns = module_alloc(PAGE_SIZE);
745 if (!kip->insns) {
746 kfree(kip);
747 return NULL;
748 }
749 INIT_HLIST_NODE(&kip->hlist);
750 hlist_add_head(&kip->hlist, &kprobe_insn_pages);
751 memset(kip->slot_used, 0, INSNS_PER_PAGE);
752 kip->slot_used[0] = 1;
753 kip->nused = 1;
754 return kip->insns;
755}
756
757/**
758 * free_insn_slot() - Free instruction slot obtained from get_insn_slot().
759 */
760static void free_insn_slot(kprobe_opcode_t *slot)
761{
762 struct kprobe_insn_page *kip;
763 struct hlist_node *pos;
764
765 hlist_for_each(pos, &kprobe_insn_pages) {
766 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
767 if (kip->insns <= slot
768 && slot < kip->insns+(INSNS_PER_PAGE*MAX_INSN_SIZE)) {
769 int i = (slot - kip->insns) / MAX_INSN_SIZE;
770 kip->slot_used[i] = 0;
771 kip->nused--;
772 if (kip->nused == 0) {
773 /*
774 * Page is no longer in use. Free it unless
775 * it's the last one. We keep the last one
776 * so as not to have to set it up again the
777 * next time somebody inserts a probe.
778 */
779 hlist_del(&kip->hlist);
780 if (hlist_empty(&kprobe_insn_pages)) {
781 INIT_HLIST_NODE(&kip->hlist);
782 hlist_add_head(&kip->hlist,
783 &kprobe_insn_pages);
784 } else {
785 module_free(NULL, kip->insns);
786 kfree(kip);
787 }
788 }
789 return;
790 }
791 }
792}