xref: /xnu-8792.61.2/libkern/kmod/README (revision 42e220869062b56f8d7d0726fd4c88954f87902c)
1*42e22086SApple OSS Distributions#
2*42e22086SApple OSS Distributions# Subtle combination of files and libraries make up the C++ runtime system for
3*42e22086SApple OSS Distributions# kernel modules.  We are dependant on the KernelModule kmod.make and
4*42e22086SApple OSS Distributions# CreateKModInfo.perl scripts to be exactly instep with both this library
5*42e22086SApple OSS Distributions# module and the libkmod module as well.
6*42e22086SApple OSS Distributions#
7*42e22086SApple OSS Distributions# If you do any maintenance on any of the following files make sure great
8*42e22086SApple OSS Distributions# care is taken to keep them in Sync.
9*42e22086SApple OSS Distributions#    extenTools/KernelModule.bproj/kmod.make
10*42e22086SApple OSS Distributions#    extenTools/KernelModule.bproj/CreateKModInfo.perl
11*42e22086SApple OSS Distributions#    IOKitUser/kmodc++/pure.c
12*42e22086SApple OSS Distributions#    IOKitUser/kmodc++/cplus_start.c
13*42e22086SApple OSS Distributions#    IOKitUser/kmodc++/cplus_start.c
14*42e22086SApple OSS Distributions#    IOKitUser/kmodc/c_start.c
15*42e22086SApple OSS Distributions#    IOKitUser/kmodc/c_stop.c
16*42e22086SApple OSS Distributions#
17*42e22086SApple OSS Distributions# The trick is that the linkline links all of the developers modules.
18*42e22086SApple OSS Distributions# If any static constructors are used .constructors_used will be left as
19*42e22086SApple OSS Distributions# an undefined symbol.  This symbol is exported by the cplus_start.c routine
20*42e22086SApple OSS Distributions# which automatically brings in the appropriate C++ _start routine.  However
21*42e22086SApple OSS Distributions# the actual _start symbol is only required by the kmod_info structure that
22*42e22086SApple OSS Distributions# is created and initialized by the CreateKModInfo.perl script.  If no C++
23*42e22086SApple OSS Distributions# was used the _start will be an undefined symbol that is finally satisfied
24*42e22086SApple OSS Distributions# by the c_start module in the kmod library.
25*42e22086SApple OSS Distributions#
26*42e22086SApple OSS Distributions# The linkline must look like this.
27*42e22086SApple OSS Distributions#    *.o -lkmodc++ kmod_info.o -lkmod
28*42e22086SApple OSS Distributions#
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