Re: [PATCH] modpost: Optionally ignore secondary errors seen if a single module build fails

[Rusty Russell <rusty@rustcorp.com.au>]

Guenter Roeck <linux@roeck-us.net> writes:
> Commit ea4054a23 (modpost: handle huge numbers of modules) added
> support for building a large number of modules.

Wow, this is a lot of work for a trivial fix.

I was happy with any of the approaches, but I'll accept this.  I'm not
even going to bikeshed over the abuse of '-n' :)

Applied,
Rusty.

> Unfortunately, the commit changed the semantics of the makefile: Instead of
> passing only existing object files to modpost, make now passes all expected
> object files. If make was started with option -i, this results in a modpost
> error if a single file failed to build.
>
> Example with the current btrfs build falure on m68k:
>
> fs/btrfs/btrfs.o: No such file or directory
> make[1]: [__modpost] Error 1 (ignored)
>
> This error is followed by lots of errors such as:
>
> m68k-linux-gcc: error: arch/m68k/emu/nfcon.mod.c: No such file or directory
> m68k-linux-gcc: fatal error: no input files
> compilation terminated.
> make[1]: [arch/m68k/emu/nfcon.mod.o] Error 1 (ignored)
>
> This doesn't matter much for normal builds, but it is annoying for builds
> started with "make -i" due to the large number of secondary errors.
> Those errors unnececessarily clog any error log and make it difficult
> to find the real errors in the build.
>
> Fix the problem by adding a new parameter '-n' to modpost. If this parameter
> is specified, modpost reports but ignores missing object files.
>
> With this patch, error output from above problem is (with make -i):
>
> m68k-linux-ld: cannot find fs/btrfs/ioctl.o: No such file or directory
> make[2]: [fs/btrfs/btrfs.o] Error 1 (ignored)
> ...
> fs/btrfs/btrfs.o: No such file or directory (ignored)
>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael Marek <mmarek@suse.cz>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> Yet another attempt to fix this problem. I'll be happy to change the modpost
> flag to something else if so desired. Note that -i is already taken, though.
>
> I also did not change any of the existing object name filtering in
> Makefile.modpost. This is on purpose; I am concerned about introducing
> some other problem.
>
>  scripts/Makefile.modpost |    4 +++-
>  scripts/mod/modpost.c    |   13 ++++++++++++-
>  2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 8dcdca2..69f0a14 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -79,9 +79,11 @@ modpost = scripts/mod/modpost                    \
>   $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
>   $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
>  
> +MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS)))
> +
>  # We can go over command line length here, so be careful.
>  quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
> -      cmd_modpost = $(MODLISTCMD) | sed 's/\.ko$$/.o/' | $(modpost) -s -T -
> +      cmd_modpost = $(MODLISTCMD) | sed 's/\.ko$$/.o/' | $(modpost) $(MODPOST_OPT) -s -T -
>  
>  PHONY += __modpost
>  __modpost: $(modules:.ko=.o) FORCE
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 8247979..393706b 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -17,6 +17,7 @@
>  #include <string.h>
>  #include <limits.h>
>  #include <stdbool.h>
> +#include <errno.h>
>  #include "modpost.h"
>  #include "../../include/generated/autoconf.h"
>  #include "../../include/linux/license.h"
> @@ -37,6 +38,8 @@ static int warn_unresolved = 0;
>  /* How a symbol is exported */
>  static int sec_mismatch_count = 0;
>  static int sec_mismatch_verbose = 1;
> +/* ignore missing files */
> +static int ignore_missing_files;
>  
>  enum export {
>  	export_plain,      export_unused,     export_gpl,
> @@ -407,6 +410,11 @@ static int parse_elf(struct elf_info *info, const char *filename)
>  
>  	hdr = grab_file(filename, &info->size);
>  	if (!hdr) {
> +		if (ignore_missing_files) {
> +			fprintf(stderr, "%s: %s (ignored)\n", filename,
> +				strerror(errno));
> +			return 0;
> +		}
>  		perror(filename);
>  		exit(1);
>  	}
> @@ -2119,7 +2127,7 @@ int main(int argc, char **argv)
>  	struct ext_sym_list *extsym_iter;
>  	struct ext_sym_list *extsym_start = NULL;
>  
> -	while ((opt = getopt(argc, argv, "i:I:e:msST:o:awM:K:")) != -1) {
> +	while ((opt = getopt(argc, argv, "i:I:e:mnsST:o:awM:K:")) != -1) {
>  		switch (opt) {
>  		case 'i':
>  			kernel_read = optarg;
> @@ -2139,6 +2147,9 @@ int main(int argc, char **argv)
>  		case 'm':
>  			modversions = 1;
>  			break;
> +		case 'n':
> +			ignore_missing_files = 1;
> +			break;
>  		case 'o':
>  			dump_write = optarg;
>  			break;
> -- 
> 1.7.9.7