[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>

1 files changed, 121 insertions, 70 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 98bef04d9484..5d5344681555 100644
--- 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 */