[RFC][PATCH] kprobes: kprobe-booster for ia64
From: Masami Hiramatsu
Date: Tue Feb 05 2008 - 17:57:29 EST
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Add kprobe-booster support on ia64.
On ia64, bundles which have B or X unit and which may cause an exception
(including break) are not boosted. And also, if several kprobes share a
bundle but are placed in different slots, only the hindmost kprobe is
boosted.
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
Kprobe-booster accelerates kprobes by skipping single stepping.
I ported it from x86.
Thank you
arch/ia64/kernel/kprobes.c | 133 ++++++++++++++++++++++++++++++++++++---------
include/asm-ia64/kprobes.h | 7 ++
2 files changed, 113 insertions(+), 27 deletions(-)
Index: linux-2.6/arch/ia64/kernel/kprobes.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/kprobes.c 2008-01-31 00:21:18.000000000 -0500
+++ linux-2.6/arch/ia64/kernel/kprobes.c 2008-01-31 00:44:28.000000000 -0500
@@ -78,6 +78,20 @@
{ u, u, u }, /* 1F */
};
+/* Insert a long branch code */
+static void __kprobes set_brl_inst(void *from, void *to)
+{
+ s64 rel = ((s64) to - (s64) from) >> 4;
+ bundle_t *brl;
+ brl = (bundle_t *) ((u64) from & ~0xf);
+ brl->quad0.template = 0x05; /* [MLX](stop) */
+ brl->quad0.slot0 = NOP_M_INST; /* nop.m 0x0 */
+ brl->quad0.slot1_p0 = ((rel >> 20) & 0x7fffffffff) << 2;
+ brl->quad1.slot1_p1 = (((rel >> 20) & 0x7fffffffff) << 2) >> (64 - 46);
+ /* brl.cond.sptk.many.clr rel<<4 (qp=0) */
+ brl->quad1.slot2 = BRL_INST(rel >> 59, rel & 0xfffff);
+}
+
/*
* In this function we check to see if the instruction
* is IP relative instruction and update the kprobe
@@ -496,6 +510,77 @@
regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
}
+/* Check the instruction in the slot is break */
+static int __kprobes __is_ia64_break_inst(bundle_t *bundle, uint slot)
+{
+ unsigned int major_opcode;
+ unsigned int template = bundle->quad0.template;
+ unsigned long kprobe_inst;
+
+ /* 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 probe instruction at given slot*/
+ get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode);
+
+ /* For break instruction,
+ * Bits 37:40 Major opcode to be zero
+ * Bits 27:32 X6 to be zero
+ * Bits 32:35 X3 to be zero
+ */
+ if (major_opcode || ((kprobe_inst >> 27) & 0x1FF)) {
+ /* Not a break instruction */
+ return 0;
+ }
+
+ /* Is a break instruction */
+ return 1;
+}
+
+/*
+ * In this function, we check whether the target bundle modifies IP or
+ * it triggers an exception. If so, it cannot be boostable.
+ */
+static int __kprobes can_boost(bundle_t *bundle, uint slot,
+ unsigned long bundle_addr)
+{
+ unsigned int template = bundle->quad0.template;
+
+ do {
+ if (search_exception_tables(bundle_addr + slot) ||
+ __is_ia64_break_inst(bundle, slot))
+ return 0; /* exception may occur in this bundle*/
+ } while ((++slot) < 3);
+ template &= 0x1e;
+ if (template >= 0x10 /* including B unit */ ||
+ template == 0x04 /* including X unit */ ||
+ template == 0x06) /* undefined */
+ return 0;
+
+ return 1;
+}
+
+/* Prepare long jump bundle and disables other boosters if need */
+static void __kprobes prepare_booster(struct kprobe *p)
+{
+ unsigned long addr = (unsigned long)p->addr & ~0xFULL;
+ unsigned int slot = addr & 0xf;
+ struct kprobe *other_kp;
+
+ if (can_boost(&p->ainsn.insn[0].bundle, slot, addr)) {
+ set_brl_inst(&p->ainsn.insn[1].bundle, (bundle_t *)addr + 1);
+ p->ainsn.inst_flag |= INST_FLAG_BOOSTABLE;
+ }
+
+ /* disables boosters in previous slots */
+ for (; addr < (unsigned long)p->addr; addr++) {
+ other_kp = get_kprobe((void *)addr);
+ if (other_kp)
+ other_kp->ainsn.inst_flag &= ~INST_FLAG_BOOSTABLE;
+ }
+}
+
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
unsigned long addr = (unsigned long) p->addr;
@@ -530,6 +615,8 @@
prepare_break_inst(template, slot, major_opcode, kprobe_inst, p, qp);
+ prepare_booster(p);
+
return 0;
}
@@ -543,7 +630,9 @@
src = &p->opcode.bundle;
flush_icache_range((unsigned long)p->ainsn.insn,
- (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
+ (unsigned long)p->ainsn.insn +
+ sizeof(kprobe_opcode_t) * MAX_INSN_SIZE);
+
switch (p->ainsn.slot) {
case 0:
dest->quad0.slot0 = src->quad0.slot0;
@@ -584,13 +673,13 @@
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
mutex_lock(&kprobe_mutex);
- free_insn_slot(p->ainsn.insn, 0);
+ free_insn_slot(p->ainsn.insn, p->ainsn.inst_flag & INST_FLAG_BOOSTABLE);
mutex_unlock(&kprobe_mutex);
}
/*
* 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
+ * located in the kprobe (p->ainsn.insn->bundle). We still need to adjust
* 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.
@@ -607,7 +696,7 @@
if (slot == 1 && bundle_encoding[template][1] == L)
slot = 2;
- if (p->ainsn.inst_flag) {
+ if (p->ainsn.inst_flag & ~INST_FLAG_BOOSTABLE) {
if (p->ainsn.inst_flag & INST_FLAG_FIX_RELATIVE_IP_ADDR) {
/* Fix relative IP address */
@@ -686,33 +775,12 @@
static int __kprobes is_ia64_break_inst(struct pt_regs *regs)
{
unsigned int slot = ia64_psr(regs)->ri;
- unsigned int template, major_opcode;
- unsigned long kprobe_inst;
unsigned long *kprobe_addr = (unsigned long *)regs->cr_iip;
bundle_t bundle;
memcpy(&bundle, kprobe_addr, sizeof(bundle_t));
- template = bundle.quad0.template;
-
- /* 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 probe instruction at given slot*/
- get_kprobe_inst(&bundle, slot, &kprobe_inst, &major_opcode);
-
- /* For break instruction,
- * Bits 37:40 Major opcode to be zero
- * Bits 27:32 X6 to be zero
- * Bits 32:35 X3 to be zero
- */
- if (major_opcode || ((kprobe_inst >> 27) & 0x1FF) ) {
- /* Not a break instruction */
- return 0;
- }
- /* Is a break instruction */
- return 1;
+ return __is_ia64_break_inst(&bundle, slot);
}
static int __kprobes pre_kprobes_handler(struct die_args *args)
@@ -802,6 +870,19 @@
return 1;
ss_probe:
+#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
+ if (p->ainsn.inst_flag == INST_FLAG_BOOSTABLE && !p->post_handler) {
+ /* Boost up -- we can execute copied instructions directly */
+ ia64_psr(regs)->ri = p->ainsn.slot;
+ regs->cr_iip = (unsigned long)&p->ainsn.insn->bundle & ~0xFULL;
+ /* turn single stepping off */
+ ia64_psr(regs)->ss = 0;
+
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ return 1;
+ }
+#endif
prepare_ss(p, regs);
kcb->kprobe_status = KPROBE_HIT_SS;
return 1;
Index: linux-2.6/include/asm-ia64/kprobes.h
===================================================================
--- linux-2.6.orig/include/asm-ia64/kprobes.h 2008-01-31 00:21:18.000000000 -0500
+++ linux-2.6/include/asm-ia64/kprobes.h 2008-01-31 00:45:07.000000000 -0500
@@ -30,8 +30,12 @@
#include <asm/break.h>
#define __ARCH_WANT_KPROBES_INSN_SLOT
-#define MAX_INSN_SIZE 1
+#define MAX_INSN_SIZE 2 /* last half is for kprobe-booster */
#define BREAK_INST (long)(__IA64_BREAK_KPROBE << 6)
+#define NOP_M_INST (long)(1<<27)
+#define BRL_INST(i1, i2) ((long)((0xcL << 37) | /* brl */ \
+ (0x1L << 12) | /* many */ \
+ (((i1) & 1) << 36) | ((i2) << 13))) /* imm */
typedef union cmp_inst {
struct {
@@ -113,6 +117,7 @@
#define INST_FLAG_FIX_RELATIVE_IP_ADDR 1
#define INST_FLAG_FIX_BRANCH_REG 2
#define INST_FLAG_BREAK_INST 4
+ #define INST_FLAG_BOOSTABLE 8
unsigned long inst_flag;
unsigned short target_br_reg;
unsigned short slot;
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@xxxxxxxxxx
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