[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>

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 6683a44..20a250e 100644 (file)
--- 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)

diff --git a/include/asm-ia64/kprobes.h b/include/asm-ia64/kprobes.h
index fec3506..d30af77 100644 (file)
--- a/include/asm-ia64/kprobes.h
+++ b/include/asm-ia64/kprobes.h
@@ -44,6 +44,17 @@ typedef struct _bundle {
 
 #define JPROBE_ENTRY(pentry)   (kprobe_opcode_t *)pentry
 
+#define SLOT0_OPCODE_SHIFT     (37)
+#define SLOT1_p1_OPCODE_SHIFT  (37 - (64-46))
+#define SLOT2_OPCODE_SHIFT     (37)
+
+#define INDIRECT_CALL_OPCODE           (1)
+#define IP_RELATIVE_CALL_OPCODE                (5)
+#define IP_RELATIVE_BRANCH_OPCODE      (4)
+#define IP_RELATIVE_PREDICT_OPCODE     (7)
+#define LONG_BRANCH_OPCODE             (0xC)
+#define LONG_CALL_OPCODE               (0xD)
+
 typedef struct kprobe_opcode {
        bundle_t bundle;
 } kprobe_opcode_t;
@@ -55,8 +66,12 @@ struct fnptr {
 
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {
-       /* copy of the original instruction */
+       /* copy of the instruction to be emulated */
        kprobe_opcode_t insn;
+ #define INST_FLAG_FIX_RELATIVE_IP_ADDR                1
+ #define INST_FLAG_FIX_BRANCH_REG              2
+       unsigned long inst_flag;
+       unsigned short target_br_reg;
 };
 
 /* ia64 does not need this */