[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: 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, 89 insertions, 59 deletions

diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index ebfa2c9241ca..6cb40d133b7c 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -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;
         }
diff --git a/include/asm-x86_64/kprobes.h b/include/asm-x86_64/kprobes.h
index 6d6d883fdf6d..4dd7a7e148d4 100644
--- a/include/asm-x86_64/kprobes.h
+++ b/include/asm-x86_64/kprobes.h
@@ -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.
  */