if (!x86_pmu.intel_cap.pebs_trap)
return 1;
+ /*
+ * No LBR entry, no basic block, no rewinding
+ */
if (!cpuc->lbr_stack.nr || !from || !to)
return 0;
- if (ip < to)
+ /*
+ * Basic blocks should never cross user/kernel boundaries
+ */
+ if (kernel_ip(ip) != kernel_ip(to))
+ return 0;
+
+ /*
+ * unsigned math, either ip is before the start (impossible) or
+ * the basic block is larger than 1 page (sanity)
+ */
+ if ((ip - to) > PAGE_SIZE)
return 0;
/*
old_to = to;
if (!kernel_ip(ip)) {
- int bytes, size = min_t(int, MAX_INSN_SIZE, ip - to);
+ int bytes, size = MAX_INSN_SIZE;
bytes = copy_from_user_nmi(buf, (void __user *)to, size);
if (bytes != size)
return 1;
}
+ /*
+ * Even though we decoded the basic block, the instruction stream
+ * never matched the given IP, either the TO or the IP got corrupted.
+ */
return 0;
}