# HG changeset patch
# User Timothy M. Jones <[email protected]>
# Date 1255004954 -3600
# Node ID 0569f32a43a12eaa170b8d9a804e78ad9bef6de4
# Parent 0c3f1856877bc570e3c853ff6a79fab71bcd6f95
Zero out memory that already exists during the brk system call.
Glibc often assumes that memory it receives from the kernel after a brk
system call will contain only zeros. This is important during a calloc,
because it won't clear the new memory itself. In the simulator, if the
new page exists, it will be cleared using this patch, to mimic the kernel's
functionality.
diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -144,6 +144,25 @@
if (!p->pTable->translate(gen.addr()))
p->pTable->allocate(roundDown(gen.addr(), VMPageSize),
VMPageSize);
+
+ // if the address is already there, zero it out
+ else {
+ uint8_t zero[VMPageSize];
+ memset(zero, 0, VMPageSize);
+ TranslatingPort *tp = tc->getMemPort();
+
+ // split non-page aligned accesses
+ Addr next_page = roundUp(gen.addr(), VMPageSize);
+ uint32_t size_needed = next_page - gen.addr();
+ tp->writeBlob(gen.addr(), zero, size_needed);
+ if (gen.addr() + VMPageSize > next_page &&
+ next_page < new_brk &&
+ p->pTable->translate(next_page))
+ {
+ size_needed = VMPageSize - size_needed;
+ tp->writeBlob(next_page, zero, size_needed);
+ }
+ }
}
}
--
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