[Linux] Retrieve modules from `/proc/<pid>/map_files` instead of `/proc/<pid>/maps` about libmem

[rdbo]

Tests (not 100% pair to pair, but anyways):

testing map_files
[*] enumerate modules with libmem
module: /proc/20824/root/dir/Repos/map-files-test/main 5577bd250000-5577bd255000
module: /proc/20824/root/usr/lib/libstdc++.so.6.0.32 7f2aa9000000-7f2aa9295000
module: /proc/20824/root/usr/lib/liblibmem.so 7f2aa9400000-7f2aa9d1e000
module: /proc/20824/root/usr/lib/libgcc_s.so.1 7f2aa9e26000-7f2aa9e4a000
module: /proc/20824/root/lib/ld-musl-x86_64.so.1 7f2aa9e4a000-7f2aa9eea000
[*] finished - time: 0.000405
[*] enumerate modules with /proc/<pid>/map_files
module: /dir/Repos/map-files-test/main 5577bd250000-5577bd255000
module: /usr/lib/libstdc++.so.6.0.32 7f2aa9000000-7f2aa9295000
module: /usr/lib/liblibmem.so 7f2aa9400000-7f2aa9d1e000
module: /usr/lib/libgcc_s.so.1 7f2aa9e26000-7f2aa9e4a000
module: /lib/ld-musl-x86_64.so.1 7f2aa9e4a000-7f2aa9eea000
[*] finished - time: 0.000287
[*] press enter to exit...

The map_files method takes slightly less time. This difference is way more noticeable on processes with huge /proc/<pid>/maps (contains both allocations and modules), which would take a long time to parse. Meanwhile, the map_files directory only contains modules, and should take a constant amount of time based on the amount of loaded modules.

Tests with a full-of-allocations /proc/<pid>/maps:

int main()
{
	clock_t start;
	clock_t end;
	size_t i;

	printf("doing useless random allocations to fill /proc/self/maps\n");
	for (i = 0; i < 10000; ++i) {
		int prot = random() & (PROT_EXEC | PROT_READ | PROT_WRITE);

		void *_alloc = mmap(NULL, sysconf(_SC_PAGESIZE), prot, MAP_PRIVATE | MAP_ANON, -1, 0);
	}
	
	printf("testing map_files\n");

	printf("[*] enumerate modules with libmem\n");
	start = clock();
	LM_EnumModules(lm_callback, NULL);
	end = clock();
	printf("[*] finished - time: %lf\n", (double)(end - start) / CLOCKS_PER_SEC);

	printf("[*] enumerate modules with /proc/<pid>/map_files\n");
	start = clock();
	enum_modules(callback);
	end = clock();
	printf("[*] finished - time: %lf\n", (double)(end - start) / CLOCKS_PER_SEC);

	printf("[*] press enter to exit...\n");
	scanf("%*c");
	
	return 0;
}

Output:

doing useless random allocations to fill /proc/self/maps
testing map_files
[*] enumerate modules with libmem
module: /proc/29048/root/dir/Repos/map-files-test/main 5592f409f000-5592f40a4000
module: /proc/29048/root/usr/lib/libstdc++.so.6.0.32 7fdd23e00000-7fdd24095000
module: /proc/29048/root/usr/lib/liblibmem.so 7fdd24200000-7fdd24b1e000
module: /proc/29048/root/usr/lib/libgcc_s.so.1 7fdd24b27000-7fdd24b4b000
module: /proc/29048/root/lib/ld-musl-x86_64.so.1 7fdd24b4b000-7fdd24beb000
[*] finished - time: 0.025560
[*] enumerate modules with /proc/<pid>/map_files
module: /dir/Repos/map-files-test/main 5592f409f000-5592f40a4000
module: /usr/lib/libstdc++.so.6.0.32 7fdd23e00000-7fdd24095000
module: /usr/lib/liblibmem.so 7fdd24200000-7fdd24b1e000
module: /usr/lib/libgcc_s.so.1 7fdd24b27000-7fdd24b4b000
module: /lib/ld-musl-x86_64.so.1 7fdd24b4b000-7fdd24beb000
[*] finished - time: 0.000923
[*] press enter to exit...

In this second test, with a /proc/<pid>/maps full of allocations, the map_files method performed the same task as LM_EnumModules in about 1 / 25 of the time. Which solidifies this method.
Again, the tests are not 100% equal. But the disparity between the methods is too big for it to be ignored.

[rdbo]

Full code: https://github.com/rdbo/linux-fast-modules-procfs/blob/master/main.c

[rdbo]

After 2153ed5:

doing useless random allocations to fill /proc/self/maps
testing map_files
[*] enumerate modules with libmem
module: /proc/27268/root/dir/Repos/map-files-test/main 55a8b1285000-55a8b128a000
module: /proc/27268/root/usr/lib/libstdc++.so.6.0.32 7f3b8ce00000-7f3b8d095000
module: /proc/27268/root/dir/Repos/map-files-test/liblibmem.so 7f3b8d200000-7f3b8db1e000
module: /proc/27268/root/usr/lib/libgcc_s.so.1 7f3b8db30000-7f3b8db54000
module: /proc/27268/root/lib/ld-musl-x86_64.so.1 7f3b8db54000-7f3b8dbf4000
[*] finished - time: 0.001146
[*] enumerate modules with /proc/<pid>/map_files
module: /dir/Repos/map-files-test/main 55a8b1285000-55a8b128a000
module: /usr/lib/libstdc++.so.6.0.32 7f3b8ce00000-7f3b8d095000
module: /dir/Repos/map-files-test/liblibmem.so 7f3b8d200000-7f3b8db1e000
module: /usr/lib/libgcc_s.so.1 7f3b8db30000-7f3b8db54000
module: /lib/ld-musl-x86_64.so.1 7f3b8db54000-7f3b8dbf4000
[*] finished - time: 0.000616
[*] press enter to exit...

Even with huge maps files, it no longer slows down.