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

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@in.ibm.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 86 insertions, 57 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index fd35039859e6..99565a66915d 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -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 kprobe *p)
 {
 }
 
-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(struct pt_regs *regs)
         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(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_eflags;
+                                regs->eflags |= kcb->kprobe_saved_eflags;
                                 unlock_kprobes();
                                 goto no_kprobe;
                         }
@@ -188,14 +185,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
                          * 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(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 */
@@ -244,7 +241,7 @@ static 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:
@@ -312,6 +309,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
         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(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->esp;
         unsigned long next_eip = 0;
@@ -355,7 +354,7 @@ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
         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(struct kprobe *p, struct pt_regs *regs)
  */
 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 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_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 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->eip = (unsigned long)(jp->entry);
         return 1;
@@ -504,34 +512,38 @@ 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 ("       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;
         }
diff --git a/include/asm-i386/kprobes.h b/include/asm-i386/kprobes.h
index 8b6d3a90cd78..ca916a892877 100644
--- a/include/asm-i386/kprobes.h
+++ b/include/asm-i386/kprobes.h
@@ -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.