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Add getrlimit(2) and setrlimit(2) #364

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2 changes: 2 additions & 0 deletions src/sys/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@ pub mod memfd;
#[cfg(not(any(target_os = "ios", target_os = "freebsd", target_os = "dragonfly")))]
pub mod ioctl;

pub mod resource;

#[cfg(any(target_os = "linux", target_os = "android"))]
pub mod sendfile;

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54 changes: 54 additions & 0 deletions src/sys/resource.rs
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@@ -0,0 +1,54 @@
use std::mem;

use libc::{self, c_int};
pub use libc::{rlimit, RLIM_INFINITY};
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I think these should be reexported, but I'm not sure if we are consistently doing that.

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What about RLIM_SAVED_CUR and RLIM_SAVED_MAX?

Why don't we wrap rlimit and provide proper accessor methods? I admit that it would be purely cosmetic in this case, as far as I can see.

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forgotten! fixed.

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What about the rlimit wrapper?

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oh I was deciding not to do that since we aren't doing anything with the type. I wanted it to be easy to specify inline, eg

setrlimit(RLIMIT_STACK, rlimit { rlim_cur: 1024*1024, rlim_max: RLIM_INFINITY }).unwrap()

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What about ResourceLimit::new(1024 * 1024, RLIM_INFINITY) ?

#[cfg(any(target_os = "linux",
target_os = "openbsd",
target_os = "netbsd",
target_os = "bitrig"))]
pub use libc::{RLIM_SAVED_CUR, RLIM_SAVED_MAX};

use {Errno, Result};

#[repr(i32)]
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Using the type i32 here is dangerous. Who says that the constants are represented by 32bit integers on all (current and future) platforms?

I got around that in my pull request by using the default (isize) and casting the constants to isize in the enumeration, for example: RLIMIT_CORE = libc::RLIMIT_CORE as isize.

I would prefer to write #[repr(libc::c_int)] or whatever type is used for these constants at the moment in libc. But even that can differ from platform to platform.

Is there a way to conditionalize the repr line on platforms? We certainly can conditionalise the whole enumeration definition on the platform, but that is a lot of repetition, though that certainly can be dealt with using macros.

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Is there a way to conditionalize the repr line on platforms?

This should work:

#[cfg_attr(target_os = "linux", repr(i32))]
#[cfg_attr(target_os = "some_other", repr(i16))]
pub enum Resource {
    ...
}

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@kamalmarhubi kamalmarhubi Apr 30, 2016 •
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Also I kind of answered this in #362 (comment) before seeing the question.

pub enum Resource {
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should this be Resource or Rlimit / RLimit?

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@fiveop thoughts? since you added the convention on enums...

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I would prefer Resource, because it very clearly expresses what it stands for.

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Resource as a name still feels a little off give the values in the enum. You are not really getting the rlimit of a resource, you are getting the value of a specific resource limit in the system (one "resource" may have multiple related limits).

I'm not completely sold on this, but I could see naming the enum ResourceLimit and allowing get/set on the limit. E.g.

let limit =  ResourceLimit::RLIMIT_STACK.get().unwrap();
ResourceLimit::RLIMIT_STACK.set(limit).unwrap();

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yeah I thought of this kind of approach but I don't know yet how I feel about going so far from the C API.

In related news: I just created https://github.com/nix-rust/rfcs and will create RFC 0000 soon (probably tomorrow) to bootstrap the process. Then we'll have a good place to discuss stuff like this.

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If we add the get and set methods to the type, the name ResourceLimit does make more sense. However, if we don't do that, the variants of the enum actually represent the Resource, whose limit is set/get by the methods setrlimit, getrlimit.

The more I think about it, the more I like @posborne's proposal.

// POSIX
RLIMIT_CORE = libc::RLIMIT_CORE,
RLIMIT_CPU = libc::RLIMIT_CPU,
RLIMIT_DATA = libc::RLIMIT_DATA,
RLIMIT_FSIZE = libc::RLIMIT_FSIZE,
RLIMIT_NOFILE = libc::RLIMIT_NOFILE,
RLIMIT_STACK = libc::RLIMIT_STACK,
RLIMIT_AS = libc::RLIMIT_AS,
// BSDs and Linux
#[cfg(all(unix, not(target_os = "solaris")))]
RLIMIT_MEMLOCK = libc::RLIMIT_MEMLOCK,
#[cfg(all(unix, not(target_os = "solaris")))]
RLIMIT_NPROC = libc::RLIMIT_NPROC,
#[cfg(all(unix, not(target_os = "solaris")))]
RLIMIT_RSS = libc::RLIMIT_RSS,
// Linux-only
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_LOCKS = libc::RLIMIT_LOCKS,
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_MSGQUEUE = libc::RLIMIT_MSGQUEUE,
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_NICE = libc::RLIMIT_NICE,
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_RTPRIO = libc::RLIMIT_RTPRIO,
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_RTTIME = libc::RLIMIT_RTTIME,
#[cfg(any(target_os = "linux", target_os = "android"))]
RLIMIT_SIGPENDING = libc::RLIMIT_SIGPENDING,
}

pub fn getrlimit(resource: Resource) -> Result<rlimit> {
let mut rlim = unsafe { mem::uninitialized() };
let res = unsafe { libc::getrlimit(resource as c_int, &mut rlim as *mut _) };
Errno::result(res).map(|_| rlim)
}

pub fn setrlimit(resource: Resource, rlim: rlimit) -> Result<()> {
let res = unsafe { libc::setrlimit(resource as c_int, &rlim as *const _) };
Errno::result(res).map(drop)
}
1 change: 1 addition & 0 deletions test/test.rs
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Expand Up @@ -11,6 +11,7 @@ mod sys;
mod test_fcntl;
mod test_net;
mod test_nix_path;
mod test_resource;
#[cfg(any(target_os = "linux", target_os = "android"))]
mod test_sendfile;
mod test_stat;
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22 changes: 22 additions & 0 deletions test/test_resource.rs
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use nix::sys::resource::{Resource, getrlimit, setrlimit};

#[test]
pub fn test_resource_limits() {
let mut limit = getrlimit(Resource::RLIMIT_STACK).unwrap();
assert!(limit.rlim_cur != limit.rlim_max);

let orig_limit = limit;

limit.rlim_cur = limit.rlim_max;
setrlimit(Resource::RLIMIT_STACK, limit).unwrap();

let limit2 = getrlimit(Resource::RLIMIT_STACK).unwrap();
assert_eq!(limit.rlim_cur, limit2.rlim_cur);
assert_eq!(limit.rlim_max, limit2.rlim_max);

setrlimit(Resource::RLIMIT_STACK, orig_limit).unwrap();

let final_limit = getrlimit(Resource::RLIMIT_STACK).unwrap();
assert_eq!(orig_limit.rlim_cur, final_limit.rlim_cur);
assert_eq!(orig_limit.rlim_max, final_limit.rlim_max);
}