Hi all! I'm a participant in Googles Summer of Code Program, doing an entry level kernel project suggested by Fedora Core, "Getting and Setting Process Resource Limits out of Process Space".
Rationale: Currently resource usage limits (rlimits) can only be set inside a process space, or inherited from the parent process. It would be useful to allow adjusting resource limits for running processes, e.g. tuning the resource usage of daemon processes under changing workloads without restarting them. Implementation: This patch provides a new syscall getprlimit() for reading a given process resource limits for i386. Its implementation follows closely the getrlimit syscall. It is given a pid as an additional argument. If the given pid equals zero the current process rlimits are read and the behaviour resembles the behaviour of getrlimit. Otherwise some checking on the validity of the given pid is done and if the given process is found access is granted if - the calling process holds the CAP_SYS_RESOURCE capability or - the calling process uid equals the uid of the process whose rlimit is being read or - the calling process uid equals the suid of the process whose rlimit is being read or - the calling process euid equals the uid of the process whose rlimit is being read or - the calling process euid equals the suid of the process whose rlimit is being read See the followup for the writing syscall. Additionally a /proc/pid/rlimits interface for comfortable access is under construction. Simple programs for testing the syscalls can be found on http://stud4.tuwien.ac.at/~e8607062/studies/soc/patches/ Signed-off-by: Wieland Gmeiner <[EMAIL PROTECTED]> diff -uprN -X linux-2.6.13-rc6-vanilla/Documentation/dontdiff linux-2.6.13-rc6-vanilla/arch/i386/kernel/syscall_table.S linux-2.6.13-rc6-rlim/arch/i386/kernel/syscall_table.S --- linux-2.6.13-rc6-vanilla/arch/i386/kernel/syscall_table.S 2005-08-09 16:03:08.000000000 +0200 +++ linux-2.6.13-rc6-rlim/arch/i386/kernel/syscall_table.S 2005-08-09 15:06:54.000000000 +0200 @@ -294,3 +294,4 @@ ENTRY(sys_call_table) .long sys_inotify_init .long sys_inotify_add_watch .long sys_inotify_rm_watch + .long sys_getprlimit diff -uprN -X linux-2.6.13-rc6-vanilla/Documentation/dontdiff linux-2.6.13-rc6-vanilla/include/asm-i386/unistd.h linux-2.6.13-rc6-rlim/include/asm-i386/unistd.h --- linux-2.6.13-rc6-vanilla/include/asm-i386/unistd.h 2005-08-09 16:03:19.000000000 +0200 +++ linux-2.6.13-rc6-rlim/include/asm-i386/unistd.h 2005-08-09 15:07:46.000000000 +0200 @@ -299,8 +299,9 @@ #define __NR_inotify_init 291 #define __NR_inotify_add_watch 292 #define __NR_inotify_rm_watch 293 +#define __NR_getprlimit 294 -#define NR_syscalls 294 +#define NR_syscalls 295 /* * user-visible error numbers are in the range -1 - -128: see diff -uprN -X linux-2.6.13-rc6-vanilla/Documentation/dontdiff linux-2.6.13-rc6-vanilla/kernel/sys.c linux-2.6.13-rc6-rlim/kernel/sys.c --- linux-2.6.13-rc6-vanilla/kernel/sys.c 2005-08-09 16:03:21.000000000 +0200 +++ linux-2.6.13-rc6-rlim/kernel/sys.c 2005-08-09 15:10:32.000000000 +0200 @@ -1603,6 +1603,47 @@ asmlinkage long sys_setrlimit(unsigned i return 0; } +asmlinkage long sys_getprlimit(pid_t pid, unsigned int resource, struct rlimit __user *rlim) +{ + struct rlimit value; + task_t *p; + int retval = -EINVAL; + + if (resource >= RLIM_NLIMITS) + goto out_nounlock; + + if (pid < 0) + goto out_nounlock; + + retval = -ESRCH; + if (pid == 0) { + p = current; + } else { + read_lock(&tasklist_lock); + p = find_task_by_pid(pid); + } + if (p) { + retval = -EPERM; + if ((current->euid ^ p->suid) && (current->euid ^ p->uid) && + (current->uid ^ p->suid) && (current->uid ^ p->uid) && + !capable(CAP_SYS_RESOURCE)) + goto out_unlock; + + task_lock(p->group_leader); + value = p->signal->rlim[resource]; + task_unlock(p->group_leader); + retval = copy_to_user(rlim, &value, sizeof(*rlim)) ? -EFAULT : 0; + } + if (pid == 0) + goto out_nounlock; + +out_unlock: + read_unlock(&tasklist_lock); + +out_nounlock: + return retval; +} + /* * It would make sense to put struct rusage in the task_struct, * except that would make the task_struct be *really big*. After - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
