kmod/libkmod
Lucas De Marchi 09c9f8c5df libkmod: Use kernel decompression when available
With the recent changes to bypass loading the file it's possible to
reduce the work in userspace and delegating it to the kernel. Without
any compression to illustrate:

Before:
	read(3, "\177ELF\2\1", 6)               = 6
	lseek(3, 0, SEEK_SET)                   = 0
	newfstatat(3, "", {st_mode=S_IFREG|0644, st_size=238592, ...}, AT_EMPTY_PATH) = 0
	mmap(NULL, 238592, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fd85cbd1000
	finit_module(3, "", 0)                  = 0
	munmap(0x7fd85cbd1000, 238592)          = 0
	close(3)                                = 0

After:
	read(3, "\177ELF\2\1", 6)               = 6
	lseek(3, 0, SEEK_SET)                   = 0
	finit_module(3, "", 0)                  = 0
	close(3)                                = 0

When using kernel compression now it's also possible to direct libkmod
to take the finit_module() path, avoiding the decompression in userspace
and just delegating it to the kernel.

Before:
	read(3, "(\265/\375\244\0", 6)          = 6
	lseek(3, 0, SEEK_SET)                   = 0
	read(3, "(\265/\375\244", 5)            = 5
	mmap(NULL, 135168, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f3fa431e000
	read(3, "\0\244\3\0\\y\6", 7)           = 7
	mmap(NULL, 372736, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f3fa414f000
	brk(0x55944c6a1000)                     = 0x55944c6a1000
	read(3, "\356|\6G\27U\20 \312\260s\211\335\333\263\326\330\336\273O\211\356\306K\360Z\341\374U6\342\221"..., 53038) = 53038
	mremap(0x7f3fa431e000, 135168, 266240, MREMAP_MAYMOVE) = 0x7f3fa410e000
	read(3, ",;\3\nqf\311\362\325\211\7\341\375A\355\221\371L\\\5\7\375 \32\246<(\258=K\304"..., 20851) = 20851
	mremap(0x7f3fa410e000, 266240, 397312, MREMAP_MAYMOVE) = 0x7f3fa40ad000
	read(3, ")\36\250\213", 4)              = 4
	read(3, "", 4)                          = 0
	munmap(0x7f3fa414f000, 372736)          = 0
	init_module(0x7f3fa40ad010, 238592, "") = 0
	munmap(0x7f3fa40ad000, 397312)          = 0
	close(3)                                = 0

After:
	read(3, "(\265/\375\244P", 6)           = 6
	lseek(3, 0, SEEK_SET)                   = 0
	finit_module(3, "", 0x4 /* MODULE_INIT_??? */) = 0
	close(3)                                = 0

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
2023-06-20 14:39:25 -07:00
..
2015-01-02 13:11:39 -02:00
2011-11-21 14:35:35 -02:00
2011-12-12 18:24:35 -02:00
2014-12-25 23:41:34 -02:00
2013-07-17 02:31:27 -03:00

libkmod - linux kernel module handling library

ABSTRACT
========

libkmod was created to allow programs to easily insert, remove and
list modules, also checking its properties, dependencies and aliases.

there is no shared/global context information and it can be used by
multiple sites on a single program, also being able to be used from
threads, although it's not thread safe (you must lock explicitly).


OVERVIEW
========

Every user should create and manage it's own library context with:

   struct kmod_ctx *ctx = kmod_new(kernel_dirname);
   kmod_unref(ctx);


Modules can be created by various means:

   struct kmod_module *mod;
   int err;

   err = kmod_module_new_from_path(ctx, path, &mod);
   if (err < 0) {
      /* code */
   } else {
      /* code */
      kmod_module_unref(mod);
   }

   err = kmod_module_new_from_name(ctx, name, &mod);
   if (err < 0) {
      /* code */
   } else {
      /* code */
      kmod_module_unref(mod);
   }


Or could be resolved from a known alias to a list of alternatives:

   struct kmod_list *list, *itr;
   int err;
   err = kmod_module_new_from_lookup(ctx, alias, &list);
   if (err < 0) {
      /* code */
   } else {
      kmod_list_foreach(itr, list) {
         struct kmod_module *mod = kmod_module_get_module(itr);
         /* code */
      }
   }