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Date: Sat, 22 Sep 2012 14:14:48 +0200 (CEST)
From: Jens <jensl@...s.mine.nu>
To: musl@...ts.openwall.com
Subject: Re: semtcl for x86_64
This is dependent on kernel config option ARCH_WANT_IPC_PARSE_VERSION.
Looks like it is not set for x86_64.
select ARCH_WANT_IPC_PARSE_VERSION if X86_32
Looking at the code:
#ifndef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
/* On IA-64, we always use the "64-bit version" of the IPC structures.
*/
# define ipc_parse_version(cmd) IPC_64
#else
int ipc_parse_version (int *cmd);
#endif
SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
{
int err = -EINVAL;
int version;
struct ipc_namespace *ns;
if (semid < 0)
return -EINVAL;
version = ipc_parse_version(&cmd);
...
switch(cmd) {
...
case SETVAL:
case SETALL:
err = semctl_main(ns,semid,semnum,cmd,version,arg);
return err;
...
default:
return -EINVAL;
}
}
So IPC_64 will not be cleared from cmd since parse_version do not remove
the bit since its only a macro that returns IPC_64.
Hence EINVAL.
Regards,
Jens
On Sat, 22 Sep 2012, Jens wrote:
>
> Hello I have some trouble getting semctl working:
>
> Tried in both musl and uclibc to compare.
> See below.
>
> The only difference I can see is the IPC_64 flag.
>
> (I haven't tried 32-bit).
>
> Regards,
> Jens
>
> program:
> bash-4.1# cat t.c
> #include <sys/types.h>
> #include <sys/ipc.h>
> #include <sys/sem.h>
>
> main() {
> int sem;
> // semget(IPC_PRIVATE, 1, IPC_CREAT|0600) = 131076
> sem = semget(IPC_PRIVATE, 1, IPC_CREAT);
> semctl(sem, 0, SETVAL, 0x1);
>
> }
>
> musl:
>
> bash-4.1# /bin64/strace ./m
> execve("./m", ["./m"], [/* 19 vars */]) = 0
> semget(IPC_PRIVATE, 1, IPC_CREAT|0) = 327688
> semctl(327688, 0, IPC_64|SETVAL, 0x1) = -1 EINVAL (Invalid argument)
> exit_group(-1) = ?
> bash-4.1#
>
>
> uclibc:
>
> semget(IPC_PRIVATE, 1, IPC_CREAT|0) = 262150
> semctl(262150, 0, SETVAL, 0x1) = 0
> _exit(0) = ?
> bash-4.1#
>
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