Commit:     cdc7dbdfe6edac177acb32e4ca56b525d0743fe7
Parent:     25d61578daae697c4a0eb817f42a868af9824f82
Author:     Anil S Keshavamurthy <[EMAIL PROTECTED]>
AuthorDate: Fri May 11 09:38:40 2007 -0700
Committer:  Tony Luck <[EMAIL PROTECTED]>
CommitDate: Fri May 11 09:38:40 2007 -0700

    [IA64] fix Kprobes reentrancy
    In case of reentrance i.e when a probe handler calls a functions which
    inturn has a probe, we save a previous kprobe information and just single
    step the reentrant probe without calling the actual probe handler.  During
    this reentracy period, if an interrupt occurs and if probe happens to
    trigger in the inturrupt path, then we were corrupting the previous kprobe(
    as we were overriding the previous kprobe info) info their by crashing the
    system.  This patch fixes this issues by having a an array of previous
    kprobe info struct(with the array size of 2).
    This similar technique is not needed on i386 and x86_64 because by default
    interrupts are turn off in the break/int3 exception handler.
    Signed-off-by: Anil S Keshavamurthy <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Tony Luck <[EMAIL PROTECTED]>
 arch/ia64/kernel/kprobes.c |   12 ++++++++----
 include/asm-ia64/kprobes.h |    4 +++-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 4f5fd09..72e593e 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -370,14 +370,18 @@ static int __kprobes valid_kprobe_addr(int template, int 
 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
-       kcb-> = kprobe_running();
-       kcb->prev_kprobe.status = kcb->kprobe_status;
+       unsigned int i;
+       i = atomic_add_return(1, &kcb->prev_kprobe_index);
+       kcb->prev_kprobe[i-1].kp = kprobe_running();
+       kcb->prev_kprobe[i-1].status = kcb->kprobe_status;
 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
-       __get_cpu_var(current_kprobe) = kcb->;
-       kcb->kprobe_status = kcb->prev_kprobe.status;
+       unsigned int i;
+       i = atomic_sub_return(1, &kcb->prev_kprobe_index);
+       __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i].kp;
+       kcb->kprobe_status = kcb->prev_kprobe[i].status;
 static void __kprobes set_current_kprobe(struct kprobe *p,
diff --git a/include/asm-ia64/kprobes.h b/include/asm-ia64/kprobes.h
index 828ae00..2abc98b 100644
--- a/include/asm-ia64/kprobes.h
+++ b/include/asm-ia64/kprobes.h
@@ -71,13 +71,15 @@ struct prev_kprobe {
 #define        MAX_PARAM_RSE_SIZE      (0x60+0x60/0x3f)
 /* per-cpu kprobe control block */
 struct kprobe_ctlblk {
        unsigned long kprobe_status;
        struct pt_regs jprobe_saved_regs;
        unsigned long jprobes_saved_stacked_regs[MAX_PARAM_RSE_SIZE];
        unsigned long *bsp;
        unsigned long cfm;
-       struct prev_kprobe prev_kprobe;
+       atomic_t prev_kprobe_index;
+       struct prev_kprobe prev_kprobe[ARCH_PREV_KPROBE_SZ];
 #define JPROBE_ENTRY(pentry)   (kprobe_opcode_t *)pentry
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