mirrors/yosys
3
0
Fork 0
mirror of https://github.com/YosysHQ/yosys synced 2025-06-06 14:13:23 +00:00
Code Activity

write_cxxrtl: avoid undefined behavior on out-of-bounds memory access.

Browse source 
After this commit, if NDEBUG is not defined, out-of-bounds accesses
cause assertion failures for reads and writes. If NDEBUG is defined,
out-of-bounds reads return zeroes, and out-of-bounds writes are
ignored.

This commit also adds support for memories that start with a non-zero
index (`Memory::start_offset` in RTLIL).
This commit is contained in:
whitequark 2020-04-04 22:53:46 +00:00
parent 5157691f0e
commit 3376dcf37c
2 changed files with 78 additions and 46 deletions
Download patch file Download diff file Expand all files Collapse all files

21
backends/cxxrtl/cxxrtl.h
View file

@ -23,6 +23,7 @@
#include <cstddef>
#include <cstdint>
#include <cassert>
#include <limits>
#include <type_traits>
#include <tuple>
@ -614,7 +615,6 @@ struct memory {
template<size_t... InitSize>
explicit memory(size_t depth, const init<InitSize> &...init) : data(depth) {
// FIXME: assert(init.size() <= depth);
data.resize(depth);
// This utterly reprehensible construct is the most reasonable way to apply a function to every element
// of a parameter pack, if the elements all have different types and so cannot be cast to an initializer list.
@ -622,15 +622,9 @@ struct memory {
}
Elem &operator [](size_t index) {
// FIXME: assert(index < data.size());
assert(index < data.size());
return data[index];
}
template<size_t AddrBits>
Elem &operator [](const value<AddrBits> &addr) {
static_assert(value<AddrBits>::chunks <= 1, "memory indexing with unreasonably large address is not supported");
return (*this)[addr.data[0]];
}
};
template<size_t Width>
@ -1103,6 +1097,17 @@ value<BitsY> mod_ss(const value<BitsA> &a, const value<BitsB> &b) {
return divmod_ss<BitsY>(a, b).second;
}
// Memory helper
template<size_t BitsAddr>
std::pair<bool, size_t> memory_index(const value<BitsAddr> &addr, size_t offset, size_t depth) {
static_assert(value<BitsAddr>::chunks <= 1, "memory address is too wide");
size_t offset_index = addr.data[0];
bool valid = (offset_index >= offset && offset_index < offset + depth);
size_t index = offset_index - offset;
return std::make_pair(valid, index);
}
} // namespace cxxrtl_yosys
#endif