When enabling gnu hash support, uClibc's build process errors out with

Rules.mak:585: *** Your binutils do not support --hash-style option, while you want to use it.  Stop.
make: *** [pregen-headers] Error 2

even though binutils does support the --hash-style option.

Looking into what happens, Rules.mak runs this command to determine if --hash-style is supported:

armv6j-blankpage-linux-gnueabi-ld --hash-style=gnu -o /dev/null -b binary /dev/null

This fails, but not because of --hash-style=gnu:

armv6j-blankpage-linux-gnueabi-ld: fatal error: /dev/null: mmap failed: Invalid argument

strace-ing ld shows:

open("/dev/null", O_RDONLY|0x80000)     = 3
fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0
mmap(NULL, 0, PROT_READ, MAP_PRIVATE, 3, 0) = -1 EINVAL (Invalid argument)

mmap with a size of 0 fails with EINVAL since Linux 2.6.12