[PATCH 3/9] Kprobes: Track kprobe on a per_cpu basis - i386 changes

From: Ananth N Mavinakayanahalli
Date: Mon Oct 10 2005 - 09:42:46 EST

From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>

I386 changes to track kprobe execution on a per-cpu basis. We now track
the kprobe state machine independently on each cpu, using an arch specific
kprobe control block.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
---

arch/i386/kernel/kprobes.c | 126 ++++++++++++++++++++++++---------------------
include/asm-i386/kprobes.h | 17 ++++++
2 files changed, 86 insertions(+), 57 deletions(-)

Index: linux-2.6.14-rc3/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc3.orig/arch/i386/kernel/kprobes.c 2005-10-05 15:22:37.000000000 -0400
+++ linux-2.6.14-rc3/arch/i386/kernel/kprobes.c 2005-10-05 15:27:19.000000000 -0400
@@ -37,16 +37,11 @@
#include <asm/kdebug.h>
#include <asm/desc.h>

-static struct kprobe *current_kprobe;
-static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
-static struct kprobe *kprobe_prev;
-static unsigned long kprobe_status_prev, kprobe_old_eflags_prev, kprobe_saved_eflags_prev;
-static struct pt_regs jprobe_saved_regs;
-static long *jprobe_saved_esp;
-/* copy of the kernel stack at the probe fire time */
-static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
void jprobe_return_end(void);

+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.
*/
@@ -91,29 +86,30 @@ void __kprobes arch_remove_kprobe(struct
{
}

-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_eflags_prev = kprobe_old_eflags;
- kprobe_saved_eflags_prev = kprobe_saved_eflags;
+ kcb->prev_kprobe.kp = kprobe_running();
+ kcb->prev_kprobe.status = kcb->kprobe_status;
+ kcb->prev_kprobe.old_eflags = kcb->kprobe_old_eflags;
+ kcb->prev_kprobe.saved_eflags = kcb->kprobe_saved_eflags;
}

-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_eflags = kprobe_old_eflags_prev;
- kprobe_saved_eflags = kprobe_saved_eflags_prev;
+ __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
+ kcb->kprobe_status = kcb->prev_kprobe.status;
+ kcb->kprobe_old_eflags = kcb->prev_kprobe.old_eflags;
+ kcb->kprobe_saved_eflags = kcb->prev_kprobe.saved_eflags;
}

-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_eflags = kprobe_old_eflags
+ __get_cpu_var(current_kprobe) = p;
+ kcb->kprobe_saved_eflags = kcb->kprobe_old_eflags
= (regs->eflags & (TF_MASK | IF_MASK));
if (is_IF_modifier(p->opcode))
- kprobe_saved_eflags &= ~IF_MASK;
+ kcb->kprobe_saved_eflags &= ~IF_MASK;
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -157,6 +153,7 @@ static int __kprobes kprobe_handler(stru
int ret = 0;
kprobe_opcode_t *addr = NULL;
unsigned long *lp;
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

/* Check if the application is using LDT entry for its code segment and
* calculate the address by reading the base address from the LDT entry.
@@ -175,10 +172,10 @@ static int __kprobes kprobe_handler(stru
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_eflags;
+ regs->eflags |= kcb->kprobe_saved_eflags;
unlock_kprobes();
goto no_kprobe;
}
@@ -188,14 +185,14 @@ static int __kprobes kprobe_handler(stru
* just single step on the instruction 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;
}
@@ -235,8 +232,8 @@ static int __kprobes kprobe_handler(stru
* 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 */
@@ -244,7 +241,7 @@ static int __kprobes kprobe_handler(stru

ss_probe:
prepare_singlestep(p, regs);
- kprobe_status = KPROBE_HIT_SS;
+ kcb->kprobe_status = KPROBE_HIT_SS;
return 1;

no_kprobe:
@@ -312,6 +309,7 @@ int __kprobes trampoline_probe_handler(s
BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
regs->eip = orig_ret_address;

+ reset_current_kprobe();
unlock_kprobes();
preempt_enable_no_resched();

@@ -345,7 +343,8 @@ int __kprobes trampoline_probe_handler(s
* 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->esp;
unsigned long next_eip = 0;
@@ -355,7 +354,7 @@ static void __kprobes resume_execution(s
switch (p->ainsn.insn[0]) {
case 0x9c: /* pushfl */
*tos &= ~(TF_MASK | IF_MASK);
- *tos |= kprobe_old_eflags;
+ *tos |= kcb->kprobe_old_eflags;
break;
case 0xc3: /* ret/lret */
case 0xcb:
@@ -400,22 +399,26 @@ static void __kprobes resume_execution(s
*/
static inline int 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_eflags;
+ resume_execution(cur, regs, kcb);
+ regs->eflags |= kcb->kprobe_saved_eflags;

/*Restore back 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;
}
+ reset_current_kprobe();
unlock_kprobes();
out:
preempt_enable_no_resched();
@@ -434,14 +437,17 @@ out:
/* Interrupts disabled, kprobe_lock held. */
static inline int 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_eflags;
+ if (kcb->kprobe_status & KPROBE_HIT_SS) {
+ resume_execution(cur, regs, kcb);
+ regs->eflags |= kcb->kprobe_old_eflags;

+ reset_current_kprobe();
unlock_kprobes();
preempt_enable_no_resched();
}
@@ -484,10 +490,11 @@ int __kprobes setjmp_pre_handler(struct
{
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_esp = &regs->esp;
- addr = (unsigned long)jprobe_saved_esp;
+ kcb->jprobe_saved_regs = *regs;
+ kcb->jprobe_saved_esp = &regs->esp;
+ addr = (unsigned long)(kcb->jprobe_saved_esp);

/*
* TBD: As Linus pointed out, gcc assumes that the callee
@@ -496,7 +503,8 @@ int __kprobes setjmp_pre_handler(struct
* 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->eip = (unsigned long)(jp->entry);
return 1;
@@ -504,34 +512,38 @@ int __kprobes setjmp_pre_handler(struct

void __kprobes jprobe_return(void)
{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
asm volatile (" xchgl %%ebx,%%esp \n"
" int3 \n"
" .globl jprobe_return_end \n"
" jprobe_return_end: \n"
" nop \n"::"b"
- (jprobe_saved_esp):"memory");
+ (kcb->jprobe_saved_esp):"memory");
}

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
u8 *addr = (u8 *) (regs->eip - 1);
- unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
+ unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_esp);
struct jprobe *jp = container_of(p, struct jprobe, kp);

if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
- if (&regs->esp != jprobe_saved_esp) {
+ if (&regs->esp != kcb->jprobe_saved_esp) {
struct pt_regs *saved_regs =
- container_of(jprobe_saved_esp, struct pt_regs, esp);
+ container_of(kcb->jprobe_saved_esp,
+ struct pt_regs, esp);
printk("current esp %p does not match saved esp %p\n",
- &regs->esp, jprobe_saved_esp);
+ &regs->esp, kcb->jprobe_saved_esp);
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;
}
Index: linux-2.6.14-rc3/include/asm-i386/kprobes.h
===================================================================
--- linux-2.6.14-rc3.orig/include/asm-i386/kprobes.h 2005-09-30 17:17:35.000000000 -0400
+++ linux-2.6.14-rc3/include/asm-i386/kprobes.h 2005-10-05 15:26:29.000000000 -0400
@@ -49,6 +49,23 @@ struct arch_specific_insn {
kprobe_opcode_t insn[MAX_INSN_SIZE];
};

+struct prev_kprobe {
+ struct kprobe *kp;
+ unsigned long status;
+ unsigned long old_eflags;
+ unsigned long saved_eflags;
+};
+
+/* per-cpu kprobe control block */
+struct kprobe_ctlblk {
+ unsigned long kprobe_status;
+ unsigned long kprobe_old_eflags;
+ unsigned long kprobe_saved_eflags;
+ long *jprobe_saved_esp;
+ 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.
-
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