[PATCH] Kprobes IA64: arch_prepare_kprobes() cleanup

arch_prepare_kprobes() was doing lots of functionality
in just one single function. This patch
attempts to clean up arch_prepare_kprobes() by moving
specific sub task to the following (new)functions
1)valid_kprobe_addr() -->> validate the given kprobe address
2)get_kprobe_inst(slot..)->> Retrives the instruction for a given slot from the bundle
3)prepare_break_inst() -->> Prepares break instruction within the bundle
	3a)update_kprobe_inst_flag()-->>Updates the internal flags, required
			for proper emulation of the instruction at later
			point in time.

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>

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 98bef04d948459390f267d2bd98af318e230a494..5d53446815553892449e8d99bb8f249629996362 100644 (file)
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -81,90 +81,141 @@ static enum instruction_type bundle_encoding[32][3] = {
   { u, u, u },                         /* 1F */
 };
 
-int arch_prepare_kprobe(struct kprobe *p)
+/*
+ * In this function we check to see if the instruction
+ * is IP relative instruction and update the kprobe
+ * inst flag accordingly
+ */
+static void update_kprobe_inst_flag(uint template, uint  slot, uint major_opcode,
+       unsigned long kprobe_inst, struct kprobe *p)
 {
-       unsigned long addr = (unsigned long) p->addr;
-       unsigned long *bundle_addr = (unsigned long *)(addr & ~0xFULL);
-       unsigned long slot = addr & 0xf;
-       unsigned long template;
-       unsigned long major_opcode = 0;
-       unsigned long lx_type_inst = 0;
-       unsigned long kprobe_inst = 0;
-       bundle_t *bundle = &p->ainsn.insn.bundle;
-
-       memcpy(&p->opcode.bundle, bundle_addr, sizeof(bundle_t));
-       memcpy(&p->ainsn.insn.bundle, bundle_addr, sizeof(bundle_t));
-
        p->ainsn.inst_flag = 0;
        p->ainsn.target_br_reg = 0;
 
-       template = bundle->quad0.template;
+       if (bundle_encoding[template][slot] == B) {
+               switch (major_opcode) {
+                 case INDIRECT_CALL_OPCODE:
+                       p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
+                       p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
+                       break;
+                 case IP_RELATIVE_PREDICT_OPCODE:
+                 case IP_RELATIVE_BRANCH_OPCODE:
+                       p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
+                       break;
+                 case IP_RELATIVE_CALL_OPCODE:
+                       p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
+                       p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
+                       p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
+                       break;
+               }
+       } else if (bundle_encoding[template][slot] == X) {
+               switch (major_opcode) {
+                 case LONG_CALL_OPCODE:
+                       p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
+                       p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
+                 break;
+               }
+       }
+       return;
+}
 
-       if (((bundle_encoding[template][1] == L) && slot > 1) || (slot > 2)) {
-               printk(KERN_WARNING "Attempting to insert unaligned kprobe at 0x%lx\n",
-                               addr);
-               return -EINVAL;
+/*
+ * In this function we override the bundle with
+ * the break instruction at the given slot.
+ */
+static void prepare_break_inst(uint template, uint  slot, uint major_opcode,
+       unsigned long kprobe_inst, struct kprobe *p)
+{
+       unsigned long break_inst = BREAK_INST;
+       bundle_t *bundle = &p->ainsn.insn.bundle;
+
+       /*
+        * Copy the original kprobe_inst qualifying predicate(qp)
+        * to the break instruction
+        */
+       break_inst |= (0x3f & kprobe_inst);
+
+       switch (slot) {
+         case 0:
+               bundle->quad0.slot0 = break_inst;
+               break;
+         case 1:
+               bundle->quad0.slot1_p0 = break_inst;
+               bundle->quad1.slot1_p1 = break_inst >> (64-46);
+               break;
+         case 2:
+               bundle->quad1.slot2 = break_inst;
+               break;
        }
 
-       if (slot == 1 && bundle_encoding[template][1] == L) {
-               lx_type_inst = 1;
-               slot = 2;
-       }
+       /*
+        * Update the instruction flag, so that we can
+        * emulate the instruction properly after we
+        * single step on original instruction
+        */
+       update_kprobe_inst_flag(template, slot, major_opcode, kprobe_inst, p);
+}
+
+static inline void get_kprobe_inst(bundle_t *bundle, uint slot,
+               unsigned long *kprobe_inst, uint *major_opcode)
+{
+       unsigned long kprobe_inst_p0, kprobe_inst_p1;
+       unsigned int template;
+
+       template = bundle->quad0.template;
 
        switch (slot) {
-       case 0:
-               major_opcode = (bundle->quad0.slot0 >> SLOT0_OPCODE_SHIFT);
-               kprobe_inst = bundle->quad0.slot0;
-               bundle->quad0.slot0 = BREAK_INST | (0x3f & kprobe_inst);
+         case 0:
+               *major_opcode = (bundle->quad0.slot0 >> SLOT0_OPCODE_SHIFT);
+               *kprobe_inst = bundle->quad0.slot0;
                break;
-       case 1:
-               major_opcode = (bundle->quad1.slot1_p1 >> SLOT1_p1_OPCODE_SHIFT);
-               kprobe_inst = (bundle->quad0.slot1_p0 |
-                               (bundle->quad1.slot1_p1 << (64-46)));
-               bundle->quad0.slot1_p0 = BREAK_INST | (0x3f & kprobe_inst);
-               bundle->quad1.slot1_p1 = (BREAK_INST >> (64-46));
+         case 1:
+               *major_opcode = (bundle->quad1.slot1_p1 >> SLOT1_p1_OPCODE_SHIFT);
+               kprobe_inst_p0 = bundle->quad0.slot1_p0;
+               kprobe_inst_p1 = bundle->quad1.slot1_p1;
+               *kprobe_inst = kprobe_inst_p0 | (kprobe_inst_p1 << (64-46));
                break;
-       case 2:
-               major_opcode = (bundle->quad1.slot2 >> SLOT2_OPCODE_SHIFT);
-               kprobe_inst = bundle->quad1.slot2;
-               bundle->quad1.slot2 = BREAK_INST | (0x3f & kprobe_inst);
+         case 2:
+               *major_opcode = (bundle->quad1.slot2 >> SLOT2_OPCODE_SHIFT);
+               *kprobe_inst = bundle->quad1.slot2;
                break;
        }
+}
 
-       /*
-        * Look for IP relative Branches, IP relative call or
-        * IP relative predicate instructions
-        */
-       if (bundle_encoding[template][slot] == B) {
-               switch (major_opcode) {
-                       case INDIRECT_CALL_OPCODE:
-                               p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
-                               p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
-                               break;
-                       case IP_RELATIVE_PREDICT_OPCODE:
-                       case IP_RELATIVE_BRANCH_OPCODE:
-                               p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
-                               break;
-                       case IP_RELATIVE_CALL_OPCODE:
-                               p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
-                               p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
-                               p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
-                               break;
-                       default:
-                               /* Do nothing */
-                               break;
-               }
-       } else if (lx_type_inst) {
-               switch (major_opcode) {
-                       case LONG_CALL_OPCODE:
-                               p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
-                               p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
-                               break;
-                       default:
-                               /* Do nothing */
-                               break;
-               }
+static int valid_kprobe_addr(int template, int slot, unsigned long addr)
+{
+       if ((slot > 2) || ((bundle_encoding[template][1] == L) && slot > 1)) {
+               printk(KERN_WARNING "Attempting to insert unaligned kprobe at 0x%lx\n",
+                               addr);
+               return -EINVAL;
        }
+       return 0;
+}
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+       unsigned long addr = (unsigned long) p->addr;
+       unsigned long *kprobe_addr = (unsigned long *)(addr & ~0xFULL);
+       unsigned long kprobe_inst=0;
+       unsigned int slot = addr & 0xf, template, major_opcode = 0;
+       bundle_t *bundle = &p->ainsn.insn.bundle;
+
+       memcpy(&p->opcode.bundle, kprobe_addr, sizeof(bundle_t));
+       memcpy(&p->ainsn.insn.bundle, kprobe_addr, sizeof(bundle_t));
+
+       template = bundle->quad0.template;
+
+       if(valid_kprobe_addr(template, slot, addr))
+               return -EINVAL;
+
+       /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */
+       if (slot == 1 && bundle_encoding[template][1] == L)
+               slot++;
+
+       /* Get kprobe_inst and major_opcode from the bundle */
+       get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode);
+
+       prepare_break_inst(template, slot, major_opcode, kprobe_inst, p);
 
        return 0;
 }
@@ -260,7 +311,7 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs)
                if (regs->cr_iip == bundle_addr) {
                        regs->cr_iip = resume_addr;
                }
-       }
+       }
 
 turn_ss_off:
        /* Turn off Single Step bit */