Pusty program w C:
int main(){}
Kompiluję:
gcc wtf.c
Wywołuję:
strace ./a.out
Wypisuje mi od cholery zawołań systemowych:
execve("./a.out", ["./a.out"], [/* 56 vars */]) = 0
brk(NULL) = 0x10ed000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7850b46000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=140688, ...}) = 0
mmap(NULL, 140688, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7850b23000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\t\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1864888, ...}) = 0
mmap(NULL, 3967392, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f785055a000
mprotect(0x7f7850719000, 2097152, PROT_NONE) = 0
mmap(0x7f7850919000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1bf000) = 0x7f7850919000
mmap(0x7f785091f000, 14752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f785091f000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7850b22000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7850b21000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7850b20000
arch_prctl(ARCH_SET_FS, 0x7f7850b21700) = 0
mprotect(0x7f7850919000, 16384, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
mprotect(0x7f7850b48000, 4096, PROT_READ) = 0
munmap(0x7f7850b23000, 140688) = 0
exit_group(0) = ?
+++ exited with 0 +++
Po co to wszystko? Przecież to jest pusty program, nawet bez żadnych nagłówków. Czemu tam jest cokolwiek oprócz execve
i close
?