to file specifications. The prefixes are arranged in a stack, and
nest, so that file, object, and include specifications are normalized,
and all end up relative to the kernel compile directory.
For example, in the kernel config file:
# Pull in config fragments for kernel crypto
prefix ../crypto-us/sys # push it
cinclude "conf/files.crypto-us" # include it if it's there
prefix # pop it
and in files.crypto-us:
file netinet6/esp_core.c ipsec & ipsec_esp
file netinet6/esp_output.c ipsec & ipsec_esp
file netinet6/esp_input.c ipsec & ipsec_esp
...generates the following in the kernel Makefile:
$S/../crypto-us/sys/netinet6/esp_core.c \
$S/../crypto-us/sys/netinet6/esp_output.c \
$S/../crypto-us/sys/netinet6/esp_input.c \
By placing this all in the kernel config file, all the magic involved in
reaching into non-standard kernel source directories is placed into a file
that the user is expected to edit anyway, and reasonable examples (and
sane defaults, for typical source checkouts) can be provided.
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