Check pages are readable after mprotect for SEGV_ACCERR diagnosis
We have a suspected mprotect issue where we see seg faults after pages
are mprotected with PROT_READ|PROT_WRITE with the SS collector on
host. This change attempts to see if earlier reads would cause faults
similarly.
Bug: 19894268
Change-Id: I041a663c6b55b747120915f73a0db5f566744ed8
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index 18c52e4..c908b39 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -877,4 +877,22 @@
return os;
}
+void MemMap::TryReadable() {
+ if (base_begin_ == nullptr && base_size_ == 0) {
+ return;
+ }
+ CHECK_NE(prot_ & PROT_READ, 0);
+ volatile uint8_t* begin = reinterpret_cast<volatile uint8_t*>(base_begin_);
+ volatile uint8_t* end = begin + base_size_;
+ DCHECK(IsAligned<kPageSize>(begin));
+ DCHECK(IsAligned<kPageSize>(end));
+ // Read the first byte of each page. Use volatile to prevent the compiler from optimizing away the
+ // reads.
+ for (volatile uint8_t* ptr = begin; ptr < end; ptr += kPageSize) {
+ // This read could fault if protection wasn't set correctly.
+ uint8_t value = *ptr;
+ UNUSED(value);
+ }
+}
+
} // namespace art