Bad check for return value of mmap()

In
./roms/skiboot/extract-gcov.c
there is this code:

        addr = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        assert(addr != NULL);

This check is wrong, mmap never returns NULL, on errors it returns MAP_FAILED (or -1). (Also sidenote: asserts usually shouldn't be used for error checking.)

In
roms/skiboot/libstb/print-container.c
there's a similar issue:

        payload = mmap(NULL, payload_st.st_size - SECURE_BOOT_HEADERS_SIZE,
                        PROT_READ, MAP_PRIVATE, fdin, SECURE_BOOT_HEADERS_SIZE);
        if (!payload)

This if should be (payload == MAP_FAILED).

Another one is in
./roms/skiboot/libstb/create-container.c

And in
./roms/u-boot/tools/aisimage.c
there's an mmap call that does not check the return value at all.