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Diffstat (limited to 'arch/x86_64/kernel/kprobes.c')
-rw-r--r--arch/x86_64/kernel/kprobes.c236
1 files changed, 66 insertions, 170 deletions
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 4e680f87a75..acd2a778ebe 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);
}