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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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