From: Ananth N Mavinakayanahalli Date: Fri, 11 Aug 2006 11:31:34 +0000 (+0530) Subject: [POWERPC] kprobes: Fix possible system crash during out-of-line single-stepping X-Git-Tag: v2.6.18-rc5~77^2~6 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=83db3dde2604d48e30a468c82da163dd1a8602b3;p=linux-2.6 [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 --- diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 9f0898c897..cd65c367b8 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;