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Commit e7a510f9 authored by Ananth N Mavinakayanahalli's avatar Ananth N Mavinakayanahalli Committed by Linus Torvalds
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[PATCH] Kprobes: Track kprobe on a per_cpu basis - x86_64 changes 



x86_64 changes to track kprobe execution on a per-cpu basis.  We now track the
kprobe state machine independently on each cpu using a arch specific kprobe
control block.

Signed-off-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: default avatarAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f215d985

arch/x86_64/kernel/kprobes.c

+70 −59
Original line number Diff line number Diff line
@@ -44,17 +44,10 @@ 
#include <asm/kdebug.h>



static DECLARE_MUTEX(kprobe_mutex);



static struct kprobe *current_kprobe;

static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags;

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;

void jprobe_return_end(void);



/* copy of the kernel stack at the probe fire time */

static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];

DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;

DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);



/*

 * returns non-zero if opcode modifies the interrupt flag.
@@ -236,29 +229,30 @@ void __kprobes arch_remove_kprobe(struct kprobe *p) 
	up(&kprobe_mutex);

}



static inline void save_previous_kprobe(void)

static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)

{

	kprobe_prev = current_kprobe;

	kprobe_status_prev = kprobe_status;

	kprobe_old_rflags_prev = kprobe_old_rflags;

	kprobe_saved_rflags_prev = kprobe_saved_rflags;

	kcb->prev_kprobe.kp = kprobe_running();

	kcb->prev_kprobe.status = kcb->kprobe_status;

	kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;

	kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;

}



static inline void restore_previous_kprobe(void)

static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)

{

	current_kprobe = kprobe_prev;

	kprobe_status = kprobe_status_prev;

	kprobe_old_rflags = kprobe_old_rflags_prev;

	kprobe_saved_rflags = kprobe_saved_rflags_prev;

	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;

	kcb->kprobe_status = kcb->prev_kprobe.status;

	kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;

	kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;

}



static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)

static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,

				struct kprobe_ctlblk *kcb)

{

	current_kprobe = p;

	kprobe_saved_rflags = kprobe_old_rflags

	__get_cpu_var(current_kprobe) = p;

	kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags

		= (regs->eflags & (TF_MASK | IF_MASK));

	if (is_IF_modifier(p->ainsn.insn))

		kprobe_saved_rflags &= ~IF_MASK;

		kcb->kprobe_saved_rflags &= ~IF_MASK;

}



static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -301,6 +295,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
	struct kprobe *p;

	int ret = 0;

	kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	/* Check we're not actually recursing */

	if (kprobe_running()) {
@@ -308,13 +303,13 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
		   Disarm the probe we just hit, and ignore it. */

		p = get_kprobe(addr);

		if (p) {

			if (kprobe_status == KPROBE_HIT_SS &&

			if (kcb->kprobe_status == KPROBE_HIT_SS &&

				*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {

				regs->eflags &= ~TF_MASK;

				regs->eflags |= kprobe_saved_rflags;

				regs->eflags |= kcb->kprobe_saved_rflags;

				unlock_kprobes();

				goto no_kprobe;

			} else if (kprobe_status == KPROBE_HIT_SSDONE) {

			} else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {

				/* TODO: Provide re-entrancy from

				 * post_kprobes_handler() and avoid exception

				 * stack corruption while single-stepping on
@@ -322,6 +317,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
				 */

				arch_disarm_kprobe(p);

				regs->rip = (unsigned long)p->addr;

				reset_current_kprobe();

				ret = 1;

			} else {

				/* We have reentered the kprobe_handler(), since
@@ -331,15 +327,15 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
				 * of the new probe without calling any user

				 * handlers.

				 */

				save_previous_kprobe();

				set_current_kprobe(p, regs);

				save_previous_kprobe(kcb);

				set_current_kprobe(p, regs, kcb);

				p->nmissed++;

				prepare_singlestep(p, regs);

				kprobe_status = KPROBE_REENTER;

				kcb->kprobe_status = KPROBE_REENTER;

				return 1;

			}

		} else {

			p = current_kprobe;

			p = __get_cpu_var(current_kprobe);

			if (p->break_handler && p->break_handler(p, regs)) {

				goto ss_probe;

			}
@@ -374,8 +370,8 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
	 * in post_kprobe_handler()

	 */

	preempt_disable();

	kprobe_status = KPROBE_HIT_ACTIVE;

	set_current_kprobe(p, regs);

	set_current_kprobe(p, regs, kcb);

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;



	if (p->pre_handler && p->pre_handler(p, regs))

		/* handler has already set things up, so skip ss setup */
@@ -383,7 +379,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 


ss_probe:

	prepare_singlestep(p, regs);

	kprobe_status = KPROBE_HIT_SS;

	kcb->kprobe_status = KPROBE_HIT_SS;

	return 1;



no_kprobe:
@@ -451,6 +447,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 
	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));

	regs->rip = orig_ret_address;



	reset_current_kprobe();

	unlock_kprobes();

	preempt_enable_no_resched();
@@ -484,7 +481,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 
 * that is atop the stack is the address following the copied instruction.

 * We need to make it the address following the original instruction.

 */

static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)

static void __kprobes resume_execution(struct kprobe *p,

		struct pt_regs *regs, struct kprobe_ctlblk *kcb)

{

	unsigned long *tos = (unsigned long *)regs->rsp;

	unsigned long next_rip = 0;
@@ -499,7 +497,7 @@ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs) 
	switch (*insn) {

	case 0x9c:		/* pushfl */

		*tos &= ~(TF_MASK | IF_MASK);

		*tos |= kprobe_old_rflags;

		*tos |= kcb->kprobe_old_rflags;

		break;

	case 0xc3:		/* ret/lret */

	case 0xcb:
@@ -544,24 +542,28 @@ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs) 
 */

int __kprobes post_kprobe_handler(struct pt_regs *regs)

{

	if (!kprobe_running())

	struct kprobe *cur = kprobe_running();

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	if (!cur)

		return 0;



	if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {

		kprobe_status = KPROBE_HIT_SSDONE;

		current_kprobe->post_handler(current_kprobe, regs, 0);

	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {

		kcb->kprobe_status = KPROBE_HIT_SSDONE;

		cur->post_handler(cur, regs, 0);

	}



	resume_execution(current_kprobe, regs);

	regs->eflags |= kprobe_saved_rflags;

	resume_execution(cur, regs, kcb);

	regs->eflags |= kcb->kprobe_saved_rflags;



	/* Restore the original saved kprobes variables and continue. */

	if (kprobe_status == KPROBE_REENTER) {

		restore_previous_kprobe();

	if (kcb->kprobe_status == KPROBE_REENTER) {

		restore_previous_kprobe(kcb);

		goto out;

	} else {

		unlock_kprobes();

	}

	reset_current_kprobe();

out:

	preempt_enable_no_resched();
@@ -579,14 +581,17 @@ out: 
/* Interrupts disabled, kprobe_lock held. */

int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)

{

	if (current_kprobe->fault_handler

	    && current_kprobe->fault_handler(current_kprobe, regs, trapnr))

	struct kprobe *cur = kprobe_running();

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))

		return 1;



	if (kprobe_status & KPROBE_HIT_SS) {

		resume_execution(current_kprobe, regs);

		regs->eflags |= kprobe_old_rflags;

	if (kcb->kprobe_status & KPROBE_HIT_SS) {

		resume_execution(cur, regs, kcb);

		regs->eflags |= kcb->kprobe_old_rflags;



		reset_current_kprobe();

		unlock_kprobes();

		preempt_enable_no_resched();

	}
@@ -629,10 +634,11 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) 
{

	struct jprobe *jp = container_of(p, struct jprobe, kp);

	unsigned long addr;

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	jprobe_saved_regs = *regs;

	jprobe_saved_rsp = (long *) regs->rsp;

	addr = (unsigned long)jprobe_saved_rsp;

	kcb->jprobe_saved_regs = *regs;

	kcb->jprobe_saved_rsp = (long *) regs->rsp;

	addr = (unsigned long)(kcb->jprobe_saved_rsp);

	/*

	 * As Linus pointed out, gcc assumes that the callee

	 * owns the argument space and could overwrite it, e.g.
@@ -640,7 +646,8 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) 
	 * we also save and restore enough stack bytes to cover

	 * the argument area.

	 */

	memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));

	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,

			MIN_STACK_SIZE(addr));

	regs->eflags &= ~IF_MASK;

	regs->rip = (unsigned long)(jp->entry);

	return 1;
@@ -648,34 +655,38 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) 


void __kprobes jprobe_return(void)

{

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	asm volatile ("       xchg   %%rbx,%%rsp     \n"

		      "       int3			\n"

		      "       .globl jprobe_return_end	\n"

		      "       jprobe_return_end:	\n"

		      "       nop			\n"::"b"

		      (jprobe_saved_rsp):"memory");

		      (kcb->jprobe_saved_rsp):"memory");

}



int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)

{

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	u8 *addr = (u8 *) (regs->rip - 1);

	unsigned long stack_addr = (unsigned long)jprobe_saved_rsp;

	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);

	struct jprobe *jp = container_of(p, struct jprobe, kp);



	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {

		if ((long *)regs->rsp != jprobe_saved_rsp) {

		if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {

			struct pt_regs *saved_regs =

			    container_of(jprobe_saved_rsp, struct pt_regs, rsp);

			    container_of(kcb->jprobe_saved_rsp,

					    struct pt_regs, rsp);

			printk("current rsp %p does not match saved rsp %p\n",

			       (long *)regs->rsp, jprobe_saved_rsp);

			       (long *)regs->rsp, kcb->jprobe_saved_rsp);

			printk("Saved registers for jprobe %p\n", jp);

			show_registers(saved_regs);

			printk("Current registers\n");

			show_registers(regs);

			BUG();

		}

		*regs = jprobe_saved_regs;

		memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,

		*regs = kcb->jprobe_saved_regs;

		memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,

		       MIN_STACK_SIZE(stack_addr));

		return 1;

	}

include/asm-x86_64/kprobes.h

+19 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
 */

#include <linux/types.h>

#include <linux/ptrace.h>

#include <linux/percpu.h>



struct pt_regs;
@@ -48,6 +49,24 @@ struct arch_specific_insn { 
	kprobe_opcode_t *insn;

};



struct prev_kprobe {

	struct kprobe *kp;

	unsigned long status;

	unsigned long old_rflags;

	unsigned long saved_rflags;

};



/* per-cpu kprobe control block */

struct kprobe_ctlblk {

	unsigned long kprobe_status;

	unsigned long kprobe_old_rflags;

	unsigned long kprobe_saved_rflags;

	long *jprobe_saved_rsp;

	struct pt_regs jprobe_saved_regs;

	kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];

	struct prev_kprobe prev_kprobe;

};



/* trap3/1 are intr gates for kprobes.  So, restore the status of IF,

 * if necessary, before executing the original int3/1 (trap) handler.

 */