In this case, pvPortMalloc and friends is what Espressif SDK provides in their binaries; it doesn't provide sources. So we can't just extend existing allocator,

In this case, pvPortMalloc and friends is what Espressif SDK provides in their binaries; it doesn't provide sources. So we can't just extend existing allocator, without actually replacing functions with our implementations by objdump. We could replace them with whatever, but umm_malloc is still the most efficient allocator for memory-constrained devices that I'm aware of.