diff options
authorAnanth N Mavinakayanahalli <>2006-08-11 17:01:34 +0530
committerPaul Mackerras <>2006-08-17 16:41:10 +1000
commit83db3dde2604d48e30a468c82da163dd1a8602b3 (patch)
parentb6f35b4966e0ae59cec45e5292b100698d12dc5f (diff)
[POWERPC] kprobes: Fix possible system crash during out-of-line single-stepping
- On archs that have no-exec support, we vmalloc() a executable scratch area of PAGE_SIZE and divide it up into an array of slots of maximum instruction size for that arch - On a kprobe registration, the original instruction is copied to the first available free slot, so if multiple kprobes are registered, chances are, they get contiguous slots - On POWER4, due to not having coherent icaches, we could hit a situation where a probe that is registered on one processor, is hit immediately on another. This second processor could have fetched the stream of text from the out-of-line single-stepping area *before* the probe registration completed, possibly due to an earlier (and a different) kprobe hit and hence would see stale data at the slot. Executing such an arbitrary instruction lead to a problem as reported in LTC bugzilla 23555. The correct solution is to call flush_icache_range() as soon as the instruction is copied for out-of-line single-stepping, so the correct instruction is seen on all processors. Thanks to Will Schmidt who tracked this down. Signed-off-by: Ananth N Mavinakayanahalli <> Acked-by: Will Schmidt <> Signed-off-by: Paul Mackerras <>
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 9f0898c89759..cd65c367b8b6 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -61,6 +61,8 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
if (!ret) {
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
+ flush_icache_range((unsigned long)p->ainsn.insn,
+ (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
return ret;