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Subject[RFC][PATCH 1/3]Djprobe (Direct Jump Probe) for 2.6.14-rc5-mm1
Hi,

This patch enables get_insn_slot() to handle slots that have
different size.
The djprobe requires this patch to work it on the machines which
support "NX bit".
---
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: hiramatu@sdl.hitachi.co.jp
Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>

include/linux/kprobes.h | 5 ++++
kernel/kprobes.c | 58 +++++++++++++++++++++++++++++++-----------------
2 files changed, 43 insertions(+), 20 deletions(-)
diff -Narup linux-2.6.14-rc5-mm1/include/linux/kprobes.h linux-2.6.14-rc5-mm1.djp.1/include/linux/kprobes.h
--- linux-2.6.14-rc5-mm1/include/linux/kprobes.h 2005-10-25 11:29:02.000000000 +0900
+++ linux-2.6.14-rc5-mm1.djp.1/include/linux/kprobes.h 2005-10-25 13:11:26.000000000 +0900
@@ -147,6 +147,11 @@ struct kretprobe_instance {
struct task_struct *task;
};

+struct kprobe_insn_page_list {
+ struct hlist_head list;
+ int insn_size; /* size of an instruction slot */
+};
+
#ifdef CONFIG_KPROBES
extern spinlock_t kretprobe_lock;
extern int arch_prepare_kprobe(struct kprobe *p);
diff -Narup linux-2.6.14-rc5-mm1/kernel/kprobes.c linux-2.6.14-rc5-mm1.djp.1/kernel/kprobes.c
--- linux-2.6.14-rc5-mm1/kernel/kprobes.c 2005-10-25 11:29:02.000000000 +0900
+++ linux-2.6.14-rc5-mm1.djp.1/kernel/kprobes.c 2005-10-25 13:13:58.000000000 +0900
@@ -58,44 +58,50 @@ static DEFINE_PER_CPU(struct kprobe *, k
* 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)))
+#define INSNS_PER_PAGE(size) (PAGE_SIZE/(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;
+ char slot_used[1];
};

-static struct hlist_head kprobe_insn_pages;
+static struct kprobe_insn_page_list kprobe_insn_pages = {
+ HLIST_HEAD_INIT, MAX_INSN_SIZE
+};

/**
- * get_insn_slot() - Find a slot on an executable page for an instruction.
+ * __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 __kprobes *get_insn_slot(void)
+kprobe_opcode_t
+ __kprobes * __get_insn_slot(struct kprobe_insn_page_list *pages)
{
struct kprobe_insn_page *kip;
struct hlist_node *pos;
+ int ninsns = INSNS_PER_PAGE(pages->insn_size);

- hlist_for_each(pos, &kprobe_insn_pages) {
+ hlist_for_each(pos, &pages->list) {
kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
- if (kip->nused < INSNS_PER_PAGE) {
+ if (kip->nused < ninsns) {
int i;
- for (i = 0; i < INSNS_PER_PAGE; i++) {
+ for (i = 0; i < ninsns; i++) {
if (!kip->slot_used[i]) {
kip->slot_used[i] = 1;
kip->nused++;
- return kip->insns + (i * MAX_INSN_SIZE);
+ return kip->insns +
+ (i * pages->insn_size);
}
}
/* Surprise! No unused slots. Fix kip->nused. */
- kip->nused = INSNS_PER_PAGE;
+ kip->nused = ninsns;
}
}

- /* All out of space. Need to allocate a new page. Use slot 0.*/
- kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
+ /* All out of space. Need to allocate a new page. Use slot 0. */
+ kip = kmalloc(sizeof(struct kprobe_insn_page) +
+ sizeof(char) * (ninsns - 1), GFP_ATOMIC);
if (!kip) {
return NULL;
}
@@ -111,23 +117,25 @@ kprobe_opcode_t __kprobes *get_insn_slot
return NULL;
}
INIT_HLIST_NODE(&kip->hlist);
- hlist_add_head(&kip->hlist, &kprobe_insn_pages);
- memset(kip->slot_used, 0, INSNS_PER_PAGE);
+ hlist_add_head(&kip->hlist, &pages->list);
+ memset(kip->slot_used, 0, ninsns);
kip->slot_used[0] = 1;
kip->nused = 1;
return kip->insns;
}

-void __kprobes free_insn_slot(kprobe_opcode_t *slot)
+void __kprobes __free_insn_slot(struct kprobe_insn_page_list *pages,
+ kprobe_opcode_t * slot)
{
struct kprobe_insn_page *kip;
struct hlist_node *pos;
+ int ninsns = INSNS_PER_PAGE(pages->insn_size);

- hlist_for_each(pos, &kprobe_insn_pages) {
+ hlist_for_each(pos, &pages->list) {
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;
+ slot < kip->insns + (ninsns * pages->insn_size)) {
+ int i = (slot - kip->insns) / pages->insn_size;
kip->slot_used[i] = 0;
kip->nused--;
if (kip->nused == 0) {
@@ -138,10 +146,10 @@ void __kprobes free_insn_slot(kprobe_opc
* next time somebody inserts a probe.
*/
hlist_del(&kip->hlist);
- if (hlist_empty(&kprobe_insn_pages)) {
+ if (hlist_empty(&pages->list)) {
INIT_HLIST_NODE(&kip->hlist);
hlist_add_head(&kip->hlist,
- &kprobe_insn_pages);
+ &pages->list);
} else {
module_free(NULL, kip->insns);
kfree(kip);
@@ -152,6 +160,16 @@ void __kprobes free_insn_slot(kprobe_opc
}
}

+kprobe_opcode_t __kprobes *get_insn_slot(void)
+{
+ return __get_insn_slot(&kprobe_insn_pages);
+}
+
+void __kprobes free_insn_slot(kprobe_opcode_t * slot)
+{
+ __free_insn_slot(&kprobe_insn_pages, slot);
+}
+
/* We have preemption disabled.. so it is safe to use __ versions */
static inline void set_kprobe_instance(struct kprobe *kp)
{
-
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