Re: 'getgroups' syscall does not work with kernel 2.6.34

----- Original Nachricht ----
Von:     Indan Zupancic <[email protected]>
An:      [email protected]
Datum:   19.05.2010 13:14
Betreff: Re: 'getgroups' syscall does not work with kernel 2.6.34

> Hello,
> 
> On Wed, May 19, 2010 11:12, [email protected] wrote:
> > Hi,
> >
> > I've just updated to the new linux kernel 2.6.34 and I've noticed that
> > there is a problem with the system call 'getgroups()': it returns a -1
> > and 'errno' is set to 38.
> > Here is a simple test program:
> >
> > #include <unistd.h>
> > #include <errno.h>
> >
> > int main(int argc, char *argv[])
> > {
> > 	int res;
> >
> > 	res = getgroups(0,NULL);
> >
> > 	if(res < 0)
> > 		return errno;
> >
> > 	return 0;
> > };
> >
> > # ./test
> > # echo $?
> > 38
> > #
> >
> > The same test program works as expected when linked against the glibc.
> > I've run the test on both an i386 and an arm platform with the same
> results.
> 
> 38 is ENOSYS, meaning that somewhere somehow the wrong syscall number is
> used.
> Dietlibc 0.35 works for me with linux 2.6.34-rc6.
> 
> What Dietlibc version are you using?
> 
> Also look at the strace output of your test program. I get:
> 
> $ strace ./t
> execve("./t", ["./t"], [/* 49 vars */]) = 0
> open("/dev/urandom", O_RDONLY)          = 3
> read(3, "\212\n\302J", 4)               = 4
> close(3)                                = 0
> set_thread_area({entry_number:-1 -> 6, base_addr:0x8049254, limit:1048575,
> seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1,
> seg_not_present:0, useable:1}) = 0
> getgroups(0, NULL)                      = 2
> _exit(2)                                = ?
> 
> (I changed it to return ret.)
> 
> Greetings,
> 
> Indan
> 
> 
Hi,

I'm using the cvs repository.

strace is actually a good idea... :-)

Here is the strace for the dietlibc test version:
root [ /tmp ]# strace ./test
execve("./test", ["./test"], [/* 31 vars */]) = 0
set_thread_area({entry_number:-1 -> 6, base_addr:0xbff2c3b0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
getgroups(0, NULL)                      = -1 ENOSYS (Function not implemented)
_exit(38)                               = ?

and here the glibc 2.11.1 version:
execve("./test", ["./test"], [/* 31 vars */]) = 0
brk(0)                                  = 0x86cc000
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb783a000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=71959, ...}) = 0
mmap2(NULL, 71959, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7828000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\0m\1\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1724047, ...}) = 0
mmap2(NULL, 1489160, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb76bc000
mmap2(0xb7822000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x166) = 0xb7822000
mmap2(0xb7825000, 10504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7825000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb76bb000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb76bb6c0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7822000, 8192, PROT_READ)   = 0
mprotect(0xb785b000, 4096, PROT_READ)   = 0
munmap(0xb7828000, 71959)               = 0
getgroups32(0, NULL)                    = 1
exit_group(0)                           = ?


glibc calls actually 'getgroups32()', dietlibc calls 'getgroups()'.

I verified that if I force dietlibc to call 'getgroups32()' instead of 'getgroups()' than it works.

The problem is now I've done this test with kind of a hack; just modifying the source file:

<dietlibc>/syscalls.s/getgroups.S

to:
#include "syscalls.h"

syscall(getgroups32,getgroups)

Maybe Felix knows here the correct patch.

giorgio


Giorgio, [email protected]