Date: Sun, 7 Dec 2008 19:42:20 +0000 (UTC) From: Luigi Rizzo <luigi@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r185746 - head/sys/boot/forth Message-ID: <200812071942.mB7JgK94034137@svn.freebsd.org>
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Author: luigi Date: Sun Dec 7 19:42:20 2008 New Revision: 185746 URL: http://svn.freebsd.org/changeset/base/185746 Log: PROBLEM: putting in a loader config file a line of the form loader_conf_files="foo bar baz" should cause loading the files listed, and then resume with the remaining config files (from previous values of the variable). Unfortunately, sometimes the line was ignored -- actually even modifying the line in /boot/default/loader.conf sometimes doesn't work. ANALYSIS: After much investigation, turned out to be a bug in the logic. The existing code detected a new assignment by looking at the address of the the variable containing the string. This only worked by pure chance, i.e. if the new string is longer than the previous value then the memory allocator may return a different address to store the string hence triggering the detection. SOLUTION: This commit contains a minimal change to fix the problem, without altering too much the existing structure of the code. However, as a step towards improving the quality and reliability of this code, I have introduced a handful of one-line functions (strget, strset, strfree, string= ) that could be used in dozens of places in the existing code. HOWEVER: There is a much bigger problem here. Even though I am no Forth expert (as most fellow src committers) I can tell that much of the forth code (in support.4th at least) is in severe need of a review/refactoring: + pieces of code are replicated multiple times instead of writing functions (see e.g. set_module_*); + a lot of stale code (e.g. "structure" definitions for preloaded_files, kernel_module, pnp stuff) which is not used or at least belongs elsewhere. The code bload is extremely bad as the loader runs with very small memory constraints, and we already hit the limit once (see http://svn.freebsd.org/viewvc/base?view=revision&revision=185132 Reducing the footprint of the forth files is critical. + two different styles of coding, one using pure stack functions (maybe beautiful but surely highly unreadable), one using high level mechanisms to give names to arguments and local variables (which leads to readable code). Note that this code is used by default by all FreeBSD installations, so the fragility and the code bloat are extremely damaging. I will try to work fixing the three items above, but if others have time, please have a look at these issues. MFC after: 4 weeks Modified: head/sys/boot/forth/support.4th Modified: head/sys/boot/forth/support.4th ============================================================================== --- head/sys/boot/forth/support.4th Sun Dec 7 19:29:11 2008 (r185745) +++ head/sys/boot/forth/support.4th Sun Dec 7 19:42:20 2008 (r185746) @@ -288,6 +288,17 @@ only forth also support-functions defini : free-memory free if free_error throw then ; +: strget { var -- addr len } var .addr @ var .len @ ; + +\ assign addr len to variable. +: strset { addr len var -- } addr var .addr ! len var .len ! ; + +\ free memory and reset fields +: strfree { var -- } var .addr @ ?dup if free-memory 0 0 var strset then ; + +\ free old content, make a copy of the string and assign to variable +: string= { addr len var -- } var strfree addr len strdup var strset ; + \ Assignment data temporary storage string name_buffer @@ -712,19 +723,6 @@ only forth also support-functions also f module_loaderror_suffix suffix_type? ; -: set_conf_files - conf_files .addr @ ?dup if - free-memory - then - value_buffer .addr @ c@ [char] " = if - value_buffer .addr @ char+ value_buffer .len @ 2 chars - - else - value_buffer .addr @ value_buffer .len @ - then - strdup - conf_files .len ! conf_files .addr ! -; - : set_nextboot_conf nextboot_conf_file .addr @ ?dup if free-memory @@ -888,6 +886,11 @@ only forth also support-functions also f then ; +: set_conf_files + set_environment_variable + s" loader_conf_files" getenv conf_files string= +; + : set_nextboot_flag yes_value? to nextboot? ; @@ -1045,7 +1048,6 @@ only forth also support-functions defini \ Variables used for processing multiple conf files string current_file_name -variable current_conf_files \ Indicates if any conf file was succesfully read @@ -1053,16 +1055,8 @@ variable current_conf_files \ loader_conf_files processing support functions -: set_current_conf_files - conf_files .addr @ current_conf_files ! -; - -: get_conf_files - conf_files .addr @ conf_files .len @ strdup -; - -: recurse_on_conf_files? - current_conf_files @ conf_files .addr @ <> +: get_conf_files ( -- addr len ) \ put addr/len on stack, reset var + conf_files strget 0 0 conf_files strset ; : skip_leading_spaces { addr len pos -- addr len pos' } @@ -1133,7 +1127,6 @@ variable current_conf_files \ Interface to loader_conf_files processing : include_conf_files - set_current_conf_files get_conf_files 0 begin get_next_file ?dup @@ -1141,7 +1134,7 @@ variable current_conf_files set_current_file_name ['] load_conf catch process_conf_errors - recurse_on_conf_files? if recurse then + conf_files .addr @ if recurse then repeat ;
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