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[PATCH] kprobes: fix single-step out of line - take2

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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>
This commit is contained in:
Ananth N Mavinakayanahalli 2005-06-27 15:17:01 -07:00 committed by Linus Torvalds
parent d3b8a1a849
commit 9ec4b1f356
6 changed files with 128 additions and 117 deletions
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26
arch/ppc64/kernel/kprobes.c
View File

@ -36,6 +36,8 @@
#include <asm/kdebug.h>
#include <asm/sstep.h>
static DECLARE_MUTEX(kprobe_mutex);
static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_saved_msr;
static struct kprobe *kprobe_prev;
@ -54,6 +56,15 @@ int arch_prepare_kprobe(struct kprobe *p)
printk("Cannot register a kprobe on rfid or mtmsrd\n");
ret = -EINVAL;
}
/* insn must be on a special executable page on ppc64 */
if (!ret) {
up(&kprobe_mutex);
p->ainsn.insn = get_insn_slot();
down(&kprobe_mutex);
if (!p->ainsn.insn)
ret = -ENOMEM;
}
return ret;
}
@ -79,16 +90,22 @@ void arch_disarm_kprobe(struct kprobe *p)
void arch_remove_kprobe(struct kprobe *p)
{
up(&kprobe_mutex);
free_insn_slot(p->ainsn.insn);
down(&kprobe_mutex);
}
static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = *p->ainsn.insn;
regs->msr |= MSR_SE;
/*single step inline if it a breakpoint instruction*/
if (p->opcode == BREAKPOINT_INSTRUCTION)
/* single step inline if it is a trap variant */
if (IS_TW(insn) || IS_TD(insn) || IS_TWI(insn) || IS_TDI(insn))
regs->nip = (unsigned long)p->addr;
else
regs->nip = (unsigned long)&p->ainsn.insn;
regs->nip = (unsigned long)p->ainsn.insn;
}
static inline void save_previous_kprobe(void)
@ -205,9 +222,10 @@ static inline int kprobe_handler(struct pt_regs *regs)
static void resume_execution(struct kprobe *p, struct pt_regs *regs)
{
int ret;
unsigned int insn = *p->ainsn.insn;
regs->nip = (unsigned long)p->addr;
ret = emulate_step(regs, p->ainsn.insn[0]);
ret = emulate_step(regs, insn);
if (ret == 0)
regs->nip = (unsigned long)p->addr + 4;
}

113
arch/x86_64/kernel/kprobes.c
View File

@ -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 */
@ -681,112 +679,3 @@ 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 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;
}
}
}

1
include/asm-ia64/kprobes.h
View File

@ -28,6 +28,7 @@
#include <linux/ptrace.h>
#include <asm/break.h>
#define MAX_INSN_SIZE 16
#define BREAK_INST (long)(__IA64_BREAK_KPROBE << 6)
typedef union cmp_inst {

2
include/asm-ppc64/kprobes.h
View File

@ -45,7 +45,7 @@ typedef unsigned int kprobe_opcode_t;
/* Architecture specific copy of original instruction */
struct arch_specific_insn {
/* copy of original instruction */
kprobe_opcode_t insn[MAX_INSN_SIZE];
kprobe_opcode_t *insn;
};
#ifdef CONFIG_KPROBES

2
include/linux/kprobes.h
View File

@ -177,6 +177,8 @@ extern void arch_arm_kprobe(struct kprobe *p);
extern void arch_disarm_kprobe(struct kprobe *p);
extern void arch_remove_kprobe(struct kprobe *p);
extern void show_registers(struct pt_regs *regs);
extern kprobe_opcode_t *get_insn_slot(void);
extern void free_insn_slot(kprobe_opcode_t *slot);
/* Get the kprobe at this addr (if any). Must have called lock_kprobes */
struct kprobe *get_kprobe(void *addr);

101
kernel/kprobes.c
View File

@ -36,6 +36,7 @@
#include <linux/hash.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
#include <asm/errno.h>
#include <asm/kdebug.h>
@ -50,6 +51,106 @@ unsigned int kprobe_cpu = NR_CPUS;
static DEFINE_SPINLOCK(kprobe_lock);
static struct kprobe *curr_kprobe;
/*
* kprobe->ainsn.insn points to the copy of the instruction to be
* single-stepped. x86_64, POWER4 and above have no-exec support and
* 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)))
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.
*/
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;
}
/*
* Use module_alloc so this page is within +/- 2GB of where the
* kernel image and loaded module images reside. This is required
* so x86_64 can correctly handle the %rip-relative fixups.
*/
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;
}
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;
}
}
}
/* Locks kprobe: irqs must be disabled */
void lock_kprobes(void)
{