[patch 4/4] Kprobes support for IA64

Anil S Keshavamurthy
2005-05-23T15:56:05Z

[-- Attachment #1: kprobes-branch-support.patch --]
[-- Type: text/plain, Size: 7083 bytes --]

This patch is required to support kprobe on branch/call instructions.
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
=====================================================================
arch/ia64/kernel/kprobes.c | 131 +++++++++++++++++++++++++++++++++++++++------
include/asm-ia64/kprobes.h | 17 +++++
2 files changed, 132 insertions(+), 16 deletions(-)

Index: linux-2.6.12-rc4/arch/ia64/kernel/kprobes.c
===================================================================
--- linux-2.6.12-rc4.orig/arch/ia64/kernel/kprobes.c 2005-05-23 07:57:22.848550199 -0700
+++ linux-2.6.12-rc4/arch/ia64/kernel/kprobes.c 2005-05-23 07:57:24.205972057 -0700
@@ -120,25 +120,75 @@
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 @@
* 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 (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 (!ia64_psr(regs)->ri)
- regs->cr_iip = bundle + 0x10;
- else
- regs->cr_iip = bundle;
+ 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)
Index: linux-2.6.12-rc4/include/asm-ia64/kprobes.h
===================================================================
--- linux-2.6.12-rc4.orig/include/asm-ia64/kprobes.h 2005-05-23 07:57:22.851479886 -0700
+++ linux-2.6.12-rc4/include/asm-ia64/kprobes.h 2005-05-23 07:57:24.207925182 -0700
@@ -42,6 +42,17 @@
} quad1;
} __attribute__((__aligned__(16))) bundle_t;

+#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;
@@ -53,8 +64,12 @@

/* 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 */

--