which kernel API does Linux cmd [ chattr ] call ?

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kernel

Hi:

Which kernel API does Linux cmd [ chattr ] call ?

Thanks!

Posted 24-Jun-13 20:35pm

Lucky_Girl

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3 solutions

Solution 2

The answer:

C#

int flags = 0;
ioctl(fd,FS_IOC_GETFLAGS,&flags);
flags |= FS_COMPR_FL;
flags &= ~FS_NOCOMP_FL;
ioctl(fd,FS_IOC_SETFLAGS,&flags);

C++

Thanks!

Posted 25-Jun-13 18:47pm

Lucky_Girl

Comments

Sergey Alexandrovich Kryukov 1-Jul-13 23:39pm

Not again.

Solution 1

Why not try looking for the man page[^] first?

Posted 24-Jun-13 21:06pm

Richard MacCutchan

Comments

Lucky_Girl 25-Jun-13 3:15am

I have tried .
It does not tell me which kernel Api calls.

Richard MacCutchan 25-Jun-13 3:22am

Follow the link to the source code.

Lucky_Girl 25-Jun-13 3:57am

I tried to [strace chattr +c main.cpp].

i can not find which Api i want is.
there are so many APIS
Thanks！
[biz@localhost TEST]$ strace chattr +c main.cpp

execve("/usr/bin/chattr", ["chattr", "+c", "main.cpp"], [/* 40 vars */]) = 0
brk(0) = 0xdac000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f07ee138000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=52661, ...}) = 0
mmap(NULL, 52661, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f07ee12b000
close(3) = 0
open("/lib64/libe2p.so.2", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\35@\3323\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=30552, ...}) = 0
mmap(0x33da400000, 2123888, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x33da400000
mprotect(0x33da406000, 2093056, PROT_NONE) = 0
mmap(0x33da605000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5000) = 0x33da605000
close(3) = 0
open("/lib64/libcom_err.so.2", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360\23\300\3443\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=17256, ...}) = 0
mmap(0x33e4c00000, 2109872, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x33e4c00000
mprotect(0x33e4c03000, 2093056, PROT_NONE) = 0
mmap(0x33e4e02000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x33e4e02000
close(3) = 0
open("/lib64/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360\355\201\3313\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1918016, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f07ee12a000
mmap(0x33d9800000, 3741864, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x33d9800000
mprotect(0x33d9989000, 2093056, PROT_NONE) = 0
mmap(0x33d9b88000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x188000) = 0x33d9b88000
mmap(0x33d9b8d000, 18600, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x33d9b8d000
close(3) = 0
open("/lib64/libpthread.so.0", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\\\300\3313\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=145720, ...}) = 0
mmap(0x33d9c00000, 2212768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x33d9c00000
mprotect(0x33d9c17000, 2097152, PROT_NONE) = 0
mmap(0x33d9e17000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x33d9e17000
mmap(0x33d9e19000, 13216, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x33d9e19000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f07ee129000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f07ee127000
arch_prctl(ARCH_SET_FS, 0x7f07ee127720) = 0
mprotect(0x601000, 4096, PROT_READ) = 0
mprotect(0x33da605000, 4096, PROT_READ) = 0
mprotect(0x33e4e02000, 4096, PROT_READ) = 0
mprotect(0x33d9b88000, 16384, PROT_READ) = 0
mprotect(0x33d9e17000, 4096, PROT_READ) = 0
mprotect(0x33d921f000, 4096, PROT_READ) = 0
munmap(0x7f07ee12b000, 52661) = 0
set_tid_address(0x7f07ee1279f0) = 6790
set_robust_list(0x7f07ee127a00, 0x18) = 0
futex(0x7fff425463cc, FUTEX_WAKE_PRIVATE, 1) = 0
futex(0x7fff425463cc, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1, NULL, 7f07ee127720) = -1 EAGAIN (Resource temporarily unavailable)
rt_sigaction(SIGRTMIN, {0x33d9c05ae0, [], SA_RESTORER|SA_SIGINFO, 0x33d9c0f500}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0x33d9c05b70, [], SA_RESTORER|SA_RESTART|SA_SIGINFO, 0x33d9c0f500}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NU

Lucky_Girl 25-Jun-13 4:01am

^ ^
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=10240*1024, rlim_max=RLIM_INFINITY}) = 0
brk(0) = 0xdac000
brk(0xdcd000) = 0xdcd000
open("/usr/lib/locale/locale-archive", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=99158576, ...}) = 0
mmap(NULL, 99158576, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f07e8296000
close(3) = 0
lstat("main.cpp", {st_mode=S_IFREG|0664, st_size=125, ...}) = 0
lstat("main.cpp", {st_mode=S_IFREG|0664, st_size=125, ...}) = 0
open("main.cpp", O_RDONLY|O_NONBLOCK) = 3
ioctl(3, EXT2_IOC_GETFLAGS, 0x7fff4254623c) = 0
close(3) = 0
lstat("main.cpp", {st_mode=S_IFREG|0664, st_size=125, ...}) = 0
open("main.cpp", O_RDONLY|O_NONBLOCK) = 3
ioctl(3, EXT2_IOC_SETFLAGS, 0x7fff4254623c) = 0
close(3) = 0
exit_group(0) = ?

Richard MacCutchan 25-Jun-13 4:32am

This looks like the one: ioctl(3, EXT2_IOC_SETFLAGS, 0x7fff4254623c) = 0.

Lucky_Girl 25-Jun-13 5:43am

Thank you! yes it is.
i found EXT2_IOC_SETFLAGS = FS_IOC_SETFLAGS
EXT2_IOC_SETFLAGS in #include<linux/ext2_fs.h>
FS_IOC_SETFLAGS in #include<linux/fs.h>
But i have another Problem
it output [ioctl: Bad address]
The code is here

/*#include <fcntl.h>
#include <sys ioctl.h="">
#include <linux/fs.h>
#include <errno.h>
#include <sys vfs.h="">
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;
*/
char* diskname="/home/biz/TEST/aa";

int main()
{
int fd = open(diskname,O_RDONLY);
if(-1 == fd)
{
perror("open");
return 0;
}
else
{
if(ioctl(fd,FS_IOC_SETFLAGS,0x7fff7af47e4c) >= 0) {
cout<<"succes"<<endl;
}
else {
perror("ioctl");
}
}

return 0;
}

Lucky_Girl 25-Jun-13 5:45am

I guess ---> ioctl(fd,FS_IOC_SETFLAGS,0x7fff7af47e4c)
the 3rd parameter is wrong?

Thanks！

Richard MacCutchan 25-Jun-13 5:49am

It's no good just copying this code and assuming that it does what you want. You need to go to the source code and/or documentation and check what the bit settings for this flag represent.

Lucky_Girl 26-Jun-13 0:46am

Thanks!
I have found the answer.
the code is below:

int flags = 0;
ioctl(fd,FS_IOC_GETFLAGS,&flags);
flags |= FS_COMPR_FL;
flags &= ~FS_NOCOMP_FL;
ioctl(fd,FS_IOC_SETFLAGS,&flags);
Thanks!

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Lucky_Girl · Accepted Answer · 2013-06-25T18:52:00

Solution 3

The answer:

C++

int flags = 0;
ioctl(fd,FS_IOC_GETFLAGS,&flags);
flags |= FS_COMPR_FL;
flags &= ~FS_NOCOMP_FL;
ioctl(fd,FS_IOC_SETFLAGS,&flags);

Thanks

Posted 25-Jun-13 18:52pm

Lucky_Girl

Comments

Sergey Alexandrovich Kryukov 1-Jul-13 23:38pm

How come it could be the answer?...
—SA