====== New kernel configuration system ======
//Wojciech A. Koszek// \\
''%%wkoszek@FreeBSD.org%%'' \\
Current kernel configuration system has its roots in
old BSD days. It's similar to ''%%sysinstall%%'' -- it does
the job, but the %%FreeBSD%% world would be a bit better
with having different/better ''%%config(8)%%''.
The goal of the page is to list config(8) limitations
and problems hitting us in %%FreeBSD%%-9 times. This may be
a root of "config(8) suck less" project.
This page contains some ideas about config(8) in random
order. Some are outdated, but later ones are relatively
new. Keep that in mind while studying this page.
===== New version of config(8): requirements =====
Current implementation of kernel configuration tool has a lot of problems and shortcomings
that make a life of typical %%FreeBSD%% user much hard. Below I try to address them:
* build all .c files just once, and use object files to create the kernel and modules
* right now we actually compile kernel twice--for the %%%%kernel //and %%%%modules// separately
* support dependencies -- right now when some option is missing, you'll get link time error
* try to keep nice structure of ''%%conf/files%%'', since it's relatively easy to insert file there
* this is stricly related with entry above
* **do NOT block advanced users from providing their own .o (custom) files if they want it** (Peter)
* support out-of-tree module build
* or at least be smart enough to let us to remove (or limit) src/sys/modules; stay away from empty ''%%opt_*.h%%'' recreation.
* support "kernel will accept this KLD for sure and won't panic":
* compile the kernel against particular kernel -- if the kernel has INVARIANTS, KLD should be compiled with INVARIANTS as well.
* DSL implemented:
* instead of ''%%nooption nosomething%%'' or ''%%enable disable%%'' I want "if (something) { static mydriver; }". Not 1st priority requirement, but would be nice to have.
* be able to configure cross-arch kernels
* include whole ''%%src/sys%%'' stuff :-) (''%%imp@%%'')
* include only .c files, from which kernel has been built (''%%des@%%'')
* ''%%INCLUDE_CONFIG_FILE%%'' should include comments in the generated output
----
Proposed syntax for the new kernel configurator a.k.a config2:
==== src/sys/conf/files ====
component kernel {
files {
kern_main.c,
kern_exec.c,
[...]
};
};
component md {
files {
md.c
};
};
component mii {
files {
mii.c
};
};
component acphy {
files {
dev/mii/acphy.c
};
depends {
mii
};
};
component amphy {
files {
dev/mii/amphy.c
};
depends {
mii
};
};
component miibus {
embed {
mii, amphy, acphy
};
};
component em {
compile_with "${NORMAL_C} -I$S/dev/e1000"; // compile_with can take block or a string
files {
dev/e1000/if_em.c
dev/e1000/if_lem.c
dev/e1000/if_igb.c
dev/e1000/e1000_80003es2lan.c
dev/e1000/e1000_82540.c
[...]
};
};
component ipwibssfw {
compile_with { // compile_with as a block + possibility of line breaking
${AWK} -f $S/tools/fw_stub.awk ipw_ibss.fw:ipw_ibss:130
-lintel_ipw -mipw_ibss -c${.TARGET}
};
clean "ipwibssfw.c"; // I think we could either accept {} block or a string for single statements
no_implicit_rule;
before_depend;
local
};
%%=%%=== Seriously ponder =====
Lua's syntax is almost perfect for explaining this datastructure. (it looks almost the same)...
----
Keyword **component** would define what functionality is provided.
Keyword **files** would be used to start a block with //c// files enlisted.
Keyword **embed** just picks the content of previous blocks and merges them in a current block.
Keyword **compile_with** sets the generation command
Keywords **no_implicit_rule**, **before_depend**, **local** stay as they were.
==== src/sys//conf/GENERIC ====
static kernel; // This could eventually be implicit
// From DEFAULTS we would be picking architecture name.
// So for 'i386' there would be component i386 { ...}
// also included as either 'static i386' (easiest, the best for me)
// or we could just make 'machine' keyword be an implicit 'static i386'
static md; // Instead of 'device md' you'd just device if it's staticly in the kernel
makeoptions "DEBUG=-g" // This stays. Not much harm.
options SCHED_ULE # Some options would stay. I want my 1st work *NOT* address
options PREEMPTION # the eventual problems with '''options'''; but the suggestions
options INET # are always welcome.
options INET6 #
options NFSCL # Some options COULD probably be just
options NFSD # included as "static nfscl"
options NFSLOCKD # Why would NFS be included as an "options?"
With "components" and dependencies, //src/sys/modules// could go away, so modules would be built 'for free'.
And kernel configuration would only enlist things necessary for components that we want to link staticly.
==== Parsing ====
In my view, we should use the same parsing for //src/sys/conf/files' and// src/sys/%%<%%arch>/conf/KERNCONF//, so that//
cat src/sys/conf/files src/sys/amd64/conf/KERNCONF > kconf
config2 -f kconf
is possible. The reason is that for development, I'd like to have kern_something.c included from my KERNCONF
and the whole case with parsing would just be simplified.
The idea which Peter prototyped already in the past was to use //config(8)// to dump
configuration data in the form of easily parseable tables, which would later get
consumed by scripts.
It would be scripts that generate Makefiles and other metadata files necessary by
a boot process.
----
Study once again conversations from 2007-05-16-