[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>
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 4e680f8..6a1c883 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 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 */
@@ -681,112 +679,3 @@
}
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 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)
-{
- 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;
- }
- }
-}