[PATCH] Kprobes/IA64: support kprobe on branch/call instructions

This patch is required to support kprobe on branch/call instructions.

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, 116 insertions, 15 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 6683a44f419f..20a250e2e9b2 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -120,25 +120,75 @@ void arch_arm_kprobe(struct kprobe *p)
         unsigned long arm_addr = 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.inst_flag = 0;
+        p->ainsn.target_br_reg = 0;
+
         memcpy(&bundle, &p->ainsn.insn.bundle, sizeof(bundle_t));
+        template = bundle.quad0.template;
+        if (slot == 1 && bundle_encoding[template][1] == L) {
+                lx_type_inst = 1;
+                slot = 2;
+        }
+
 
-        template = bundle.quad0.template;
-        if (slot == 1 && bundle_encoding[template][1] == L)
-                slot = 2;
         switch (slot) {
         case 0:
+                major_opcode = (bundle.quad0.slot0 >> SLOT0_OPCODE_SHIFT);
+                kprobe_inst = bundle.quad0.slot0;
                 bundle.quad0.slot0 = BREAK_INST;
                 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;
                 bundle.quad1.slot1_p1 = (BREAK_INST >> (64-46));
                 break;
         case 2:
+                major_opcode = (bundle.quad1.slot2 >> SLOT2_OPCODE_SHIFT);
+                kprobe_inst = bundle.quad1.slot2;
                 bundle.quad1.slot2 = BREAK_INST;
                 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;
+                }
+        }
 
         /* Flush icache for the instruction at the emulated address */
         flush_icache_range((unsigned long)&p->ainsn.insn.bundle,
@@ -170,24 +220,75 @@ void arch_remove_kprobe(struct kprobe *p)
  * We are resuming execution after a single step fault, so the pt_regs
  * structure reflects the register state after we executed the instruction
  * located in the kprobe (p->ainsn.insn.bundle).  We still need to adjust
- * the ip to point back to the original stack address, and if we see that
- * the slot has incremented back to zero, then we need to point to the next
- * slot location.
+ * the ip to point back to the original stack address. To set the IP address
+ * to original stack address, handle the case where we need to fixup the
+ * relative IP address and/or fixup branch register.
  */
 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 {
-        unsigned long bundle = (unsigned long)p->addr & ~0xFULL;
+        unsigned long bundle_addr = ((unsigned long) (&p->ainsn.insn.bundle)) & ~0xFULL;
+        unsigned long resume_addr = (unsigned long)p->addr & ~0xFULL;
+        unsigned long template;
+        int slot = ((unsigned long)p->addr & 0xf);
 
-        /*
-         * TODO: Handle cases where kprobe was inserted on a branch instruction
-         */
+        template = p->opcode.bundle.quad0.template;
+
+        if (slot == 1 && bundle_encoding[template][1] == L)
+                slot = 2;
+
+        if (p->ainsn.inst_flag) {
 
-        if (!ia64_psr(regs)->ri)
-                regs->cr_iip = bundle + 0x10;
-        else
-                regs->cr_iip = bundle;
+                if (p->ainsn.inst_flag & INST_FLAG_FIX_RELATIVE_IP_ADDR) {
+                        /* Fix relative IP address */
+                        regs->cr_iip = (regs->cr_iip - bundle_addr) + resume_addr;
+                }
+
+                if (p->ainsn.inst_flag & INST_FLAG_FIX_BRANCH_REG) {
+                /*
+                 * Fix target branch register, software convention is
+                 * to use either b0 or b6 or b7, so just checking
+                 * only those registers
+                 */
+                        switch (p->ainsn.target_br_reg) {
+                        case 0:
+                                if ((regs->b0 == bundle_addr) ||
+                                        (regs->b0 == bundle_addr + 0x10)) {
+                                        regs->b0 = (regs->b0 - bundle_addr) +
+                                                resume_addr;
+                                }
+                                break;
+                        case 6:
+                                if ((regs->b6 == bundle_addr) ||
+                                        (regs->b6 == bundle_addr + 0x10)) {
+                                        regs->b6 = (regs->b6 - bundle_addr) +
+                                                resume_addr;
+                                }
+                                break;
+                        case 7:
+                                if ((regs->b7 == bundle_addr) ||
+                                        (regs->b7 == bundle_addr + 0x10)) {
+                                        regs->b7 = (regs->b7 - bundle_addr) +
+                                                resume_addr;
+                                }
+                                break;
+                        } /* end switch */
+                }
+                goto turn_ss_off;
+        }
 
-        ia64_psr(regs)->ss = 0;
+        if (slot == 2) {
+                if (regs->cr_iip == bundle_addr + 0x10) {
+                        regs->cr_iip = resume_addr + 0x10;
+                }
+        } else {
+                if (regs->cr_iip == bundle_addr) {
+                        regs->cr_iip = resume_addr;
+                }
+        }
+
+turn_ss_off:
+        /* Turn off Single Step bit */
+        ia64_psr(regs)->ss = 0;
 }
 
 static void prepare_ss(struct kprobe *p, struct pt_regs *regs)