From cd06bcf4ec2443eb719410e7e496e3d9d4d479c9 Mon Sep 17 00:00:00 2001 From: Alec Roelke Date: Tue, 21 Mar 2017 12:53:29 -0400 Subject: [PATCH] riscv: fix error on memory op address overflow Previously, if a memory operation referenced an address that caused the data to wrap around to the beginning of the memory (such as -1 or 0xFFFFFFFFFFFFFFFF), an assert would fail during address translation and gem5 would crash. This patch fixes that by checking for such a case in RISC-V's TLB code and returning a fault from translateData if that would happen. Because RISC-V does support unaligned memory accesses, no checking is performed to make sure that an access doesn't cross a cache line. [Update creation of page table fault to use make_shared.] [Add comment explaining the change and assertion that the memory request isn't zero size.] Change-Id: I7b8ef9a5838f30184dbdbd0c7c1655e1c04a9410 Reviewed-on: https://gem5-review.googlesource.com/2345 Maintainer: Alec Roelke Reviewed-by: Brandon Potter Reviewed-by: Jason Lowe-Power --- src/arch/riscv/tlb.cc | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/src/arch/riscv/tlb.cc b/src/arch/riscv/tlb.cc index 841be2488..c47260e76 100644 --- a/src/arch/riscv/tlb.cc +++ b/src/arch/riscv/tlb.cc @@ -303,6 +303,17 @@ TLB::translateData(RequestPtr req, ThreadContext *tc, bool write) if (FullSystem) panic("translateData not implemented in RISC-V.\n"); + // In the O3 CPU model, sometimes a memory access will be speculatively + // executed along a branch that will end up not being taken where the + // address is invalid. In that case, return a fault rather than trying + // to translate it (which will cause a panic). Since RISC-V allows + // unaligned memory accesses, this should only happen if the request's + // length is long enough to wrap around from the end of the memory to the + // start. + assert(req->getSize() > 0); + if (req->getVaddr() + req->getSize() - 1 < req->getVaddr()) + return make_shared(req->getVaddr()); + Process * p = tc->getProcessPtr(); Fault fault = p->pTable->translate(req); -- 2.30.2