Replace the a.out emulation of 'struct linker_set' with something
a little more flexible. <sys/linker_set.h> now provides macros for
accessing elements and completely hides the implementation.
The linker_set.h macros have been on the back burner in various
forms since 1998 and has ideas and code from Mike Smith (SET_FOREACH()),
John Polstra (ELF clue) and myself (cleaned up API and the conversion
of the rest of the kernel to use it).
The macros declare a strongly typed set. They return elements with the
type that you declare the set with, rather than a generic void *.
For ELF, we use the magic ld symbols (__start_<setname> and
__stop_<setname>). Thanks to Richard Henderson <rth@redhat.com> for the
trick about how to force ld to provide them for kld's.
For a.out, we use the old linker_set struct.
NOTE: the item lists are no longer null terminated. This is why
the code impact is high in certain areas.
The runtime linker has a new method to find the linker set
boundaries depending on which backend format is in use.
linker sets are still module/kld unfriendly and should never be used
for anything that may be modular one day.
Reviewed by: eivind
after the acquisition of any advisory locks. This fix corrects a case
in which a process tries to open a file with a non-blocking exclusive
lock. Even if it fails to get the lock it would still truncate the
file even though its open failed. With this change, the truncation
is done only after the lock is successfully acquired.
Obtained from: BSD/OS
version dependency system. This isn't quite finished, but it is at a
useful stage to do a functional checkpoint.
Highlights:
- version and dependency metadata is gathered via linker sets, so things
are handled the same for static kernels and code built to live in a kld.
- The dependencies are at module level (versus at file level).
- Dependencies determine kld symbol search order - this means that you
cannot link against symbols in another file unless you depend on it. This
is so that you cannot accidently unload the target out from underneath
the ones referencing it.
- It is flexible enough that we can put tags in #include files and macros
so that we can get decent hooks for enforcing recompiles on incompatable
ABI changes. eg: if we change struct proc, we could force a recompile
for all kld's that reference the proc struct.
- Tangled dependency references at boot time are sorted. Files are
relocated once all their dependencies are already relocated.
Caveats:
- Loader support is incomplete, but has been worked on seperately.
- Actual enforcement of the version number tags is not active yet - just
the module dependencies are live. The actual structure of versioning
hasn't been agreed on yet. (eg: major.minor, or whatever)
- There is some backwards compatability for old modules without metadata
but I'm not sure how good it is.
This is based on work originally done by Boris Popov (bp@freebsd.org),
but I'm not sure he'd recognize much of it now. Don't blame him. :-)
Also, ideas have been borrowed from Mike Smith.
* Report link errors to stdout with uprintf() so that the user can see
what went wrong (PR kern/9214).
* Add support code to allow module symbols to be loaded into GDB using
the debugger's "sharedlibrary" command.
- symbol_values checks that the symbol is indeed belonging to the
correct symbol and string table pairs before looking up. (since there
could be many pairs, and KLD/DDB need to find out).
- different ops for files versus preload modules - the unload mechanism
is different. (a preloaded module has to be deleted on unload since
the in-core image is tainted by relocation and variables used)
- Do not build an a.out kernel module if we're running on an elf
kernel. :-) Note that it should theoretically be possible to
mix a.out and elf KLD modules providing -mno-underscores was used
to compile it, or some other symbol conversion takes place.
- Support preload modules (even though /boot/loader doesn't yet)
- Search the module path when loading files.
respectively. Most of the longs should probably have been
u_longs, but this changes is just to prevent warnings about
casts between pointers and integers of different sizes, not
to fix poorly chosen types.
FreeBSD/alpha. The most significant item is to change the command
argument to ioctl functions from int to u_long. This change brings us
inline with various other BSD versions. Driver writers may like to
use (__FreeBSD_version == 300003) to detect this change.
The prototype FreeBSD/alpha machdep will follow in a couple of days
time.
the patches in freefall:/home/dfr/ld.diffs to your ld sources and set
BINFORMAT to aoutkld when linking the kernel.
Library changes and userland utilities will appear in a later commit.
