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Subject[PATCH]kprobes fix bug when probed on task and isr functions
	This patch fixes a race condition where in system used to hang
or sometime crash within minutes when kprobes are inserted on
ISR routine and a task routine.

The fix has been stress tested on i386, ia64, pp64 and on x86_64.
To reproduce the problem insert kprobes on schedule() and do_IRQ() functions and
you should see hang or system crash.

This patch should apply cleanly on 2.6.13-mm1 kernel.

Please apply.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>


=====================================================
arch/i386/kernel/kprobes.c | 3 ++-
arch/ia64/kernel/kprobes.c | 22 +++++++++++++++++++---
arch/ppc64/kernel/kprobes.c | 11 ++++++-----
arch/x86_64/kernel/kprobes.c | 3 ++-
include/asm-ia64/kprobes.h | 1 +
include/asm-ppc64/kprobes.h | 3 +++
kernel/kprobes.c | 8 ++++++++
7 files changed, 41 insertions(+), 10 deletions(-)
Index: linux-2.6.13-mm1/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.13-mm1.orig/arch/i386/kernel/kprobes.c
+++ linux-2.6.13-mm1/arch/i386/kernel/kprobes.c
@@ -190,7 +190,8 @@ static int __kprobes kprobe_handler(stru
Disarm the probe we just hit, and ignore it. */
p = get_kprobe(addr);
if (p) {
- if (kprobe_status == KPROBE_HIT_SS) {
+ if (kprobe_status == KPROBE_HIT_SS &&
+ *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
regs->eflags &= ~TF_MASK;
regs->eflags |= kprobe_saved_eflags;
unlock_kprobes();
Index: linux-2.6.13-mm1/arch/ia64/kernel/kprobes.c
===================================================================
--- linux-2.6.13-mm1.orig/arch/ia64/kernel/kprobes.c
+++ linux-2.6.13-mm1/arch/ia64/kernel/kprobes.c
@@ -95,6 +95,17 @@ static void __kprobes update_kprobe_inst
p->ainsn.inst_flag = 0;
p->ainsn.target_br_reg = 0;

+ /* Check 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)) ) {
+ /* is a break instruction */
+ p->ainsn.inst_flag |= INST_FLAG_BREAK_INST;
+ return;
+ }
+
if (bundle_encoding[template][slot] == B) {
switch (major_opcode) {
case INDIRECT_CALL_OPCODE:
@@ -542,8 +553,11 @@ static void __kprobes prepare_ss(struct
unsigned long bundle_addr = (unsigned long) &p->opcode.bundle;
unsigned long slot = (unsigned long)p->addr & 0xf;

- /* Update instruction pointer (IIP) and slot number (IPSR.ri) */
- regs->cr_iip = bundle_addr & ~0xFULL;
+ /* single step inline if break instruction */
+ if (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)
+ regs->cr_iip = (unsigned long)p->addr & ~0xFULL;
+ else
+ regs->cr_iip = bundle_addr & ~0xFULL;

if (slot > 2)
slot = 0;
@@ -599,7 +613,9 @@ static int __kprobes pre_kprobes_handler
if (kprobe_running()) {
p = get_kprobe(addr);
if (p) {
- if (kprobe_status == KPROBE_HIT_SS) {
+ if ( (kprobe_status == KPROBE_HIT_SS) &&
+ (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) {
+ ia64_psr(regs)->ss = 0;
unlock_kprobes();
goto no_kprobe;
}
Index: linux-2.6.13-mm1/arch/ppc64/kernel/kprobes.c
===================================================================
--- linux-2.6.13-mm1.orig/arch/ppc64/kernel/kprobes.c
+++ linux-2.6.13-mm1/arch/ppc64/kernel/kprobes.c
@@ -102,7 +102,7 @@ static inline void prepare_singlestep(st
regs->msr |= MSR_SE;

/* single step inline if it is a trap variant */
- if (IS_TW(insn) || IS_TD(insn) || IS_TWI(insn) || IS_TDI(insn))
+ if (is_trap(insn))
regs->nip = (unsigned long)p->addr;
else
regs->nip = (unsigned long)p->ainsn.insn;
@@ -152,7 +152,9 @@ static inline int kprobe_handler(struct
Disarm the probe we just hit, and ignore it. */
p = get_kprobe(addr);
if (p) {
- if (kprobe_status == KPROBE_HIT_SS) {
+ kprobe_opcode_t insn = *p->ainsn.insn;
+ if (kprobe_status == KPROBE_HIT_SS &&
+ is_trap(insn)) {
regs->msr &= ~MSR_SE;
regs->msr |= kprobe_saved_msr;
unlock_kprobes();
@@ -192,8 +194,7 @@ static inline int kprobe_handler(struct
* trap variant, it could belong to someone else
*/
kprobe_opcode_t cur_insn = *addr;
- if (IS_TW(cur_insn) || IS_TD(cur_insn) ||
- IS_TWI(cur_insn) || IS_TDI(cur_insn))
+ if (is_trap(cur_insn))
goto no_kprobe;
/*
* The breakpoint instruction was removed right
@@ -403,7 +404,7 @@ int __kprobes kprobe_exceptions_notify(s
default:
break;
}
- preempt_enable();
+ preempt_enable_no_resched();
return ret;
}

Index: linux-2.6.13-mm1/arch/x86_64/kernel/kprobes.c
===================================================================
--- linux-2.6.13-mm1.orig/arch/x86_64/kernel/kprobes.c
+++ linux-2.6.13-mm1/arch/x86_64/kernel/kprobes.c
@@ -311,7 +311,8 @@ int __kprobes kprobe_handler(struct pt_r
Disarm the probe we just hit, and ignore it. */
p = get_kprobe(addr);
if (p) {
- if (kprobe_status == KPROBE_HIT_SS) {
+ if (kprobe_status == KPROBE_HIT_SS &&
+ *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
regs->eflags &= ~TF_MASK;
regs->eflags |= kprobe_saved_rflags;
unlock_kprobes();
Index: linux-2.6.13-mm1/include/asm-ia64/kprobes.h
===================================================================
--- linux-2.6.13-mm1.orig/include/asm-ia64/kprobes.h
+++ linux-2.6.13-mm1/include/asm-ia64/kprobes.h
@@ -92,6 +92,7 @@ struct arch_specific_insn {
kprobe_opcode_t insn;
#define INST_FLAG_FIX_RELATIVE_IP_ADDR 1
#define INST_FLAG_FIX_BRANCH_REG 2
+ #define INST_FLAG_BREAK_INST 4
unsigned long inst_flag;
unsigned short target_br_reg;
};
Index: linux-2.6.13-mm1/include/asm-ppc64/kprobes.h
===================================================================
--- linux-2.6.13-mm1.orig/include/asm-ppc64/kprobes.h
+++ linux-2.6.13-mm1/include/asm-ppc64/kprobes.h
@@ -42,6 +42,9 @@ typedef unsigned int kprobe_opcode_t;

#define JPROBE_ENTRY(pentry) (kprobe_opcode_t *)((func_descr_t *)pentry)

+#define is_trap(instr) (IS_TW(instr) || IS_TD(instr) || \
+ IS_TWI(instr) || IS_TDI(instr))
+
#define ARCH_SUPPORTS_KRETPROBES
void kretprobe_trampoline(void);

Index: linux-2.6.13-mm1/kernel/kprobes.c
===================================================================
--- linux-2.6.13-mm1.orig/kernel/kprobes.c
+++ linux-2.6.13-mm1/kernel/kprobes.c
@@ -155,14 +155,22 @@ void __kprobes free_insn_slot(kprobe_opc
/* Locks kprobe: irqs must be disabled */
void __kprobes lock_kprobes(void)
{
+ unsigned long flags = 0;
+
+ local_irq_save(flags);
spin_lock(&kprobe_lock);
kprobe_cpu = smp_processor_id();
+ local_irq_restore(flags);
}

void __kprobes unlock_kprobes(void)
{
+ unsigned long flags = 0;
+
+ local_irq_save(flags);
kprobe_cpu = NR_CPUS;
spin_unlock(&kprobe_lock);
+ local_irq_restore(flags);
}

/* You have to be holding the kprobe_lock */
-
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