Direct exec of /usr/bin/ld fails with "mmap of entire address space failed: Cannot allocate memory"

If I try direct exec ld via rtld, I get the following failure:

# /libexec/ld-elf.so.1 /usr/bin/ld
ld-elf.so.1: /usr/bin/ld: mmap of entire address space failed: Cannot
allocate memory

Is there some sysctl limit I need to bump up to get around this?  I
presume that the binary is just too large given that I can direct exec
smaller binaries like /bin/cat.