sys_util: replace sysconf(_SC_PAGESIZE) with a safe wrapper

There were a few places that used this to get the page size inside of an
unsafe block, For convenience, this adds a safe wrapper in sys_util and
replaces all extant usage of sysconf with the wrapper version.

BUG=chromium:800626
TEST=./build_test

Change-Id: Ic65bf72aea90eabd4158fbdcdbe25c3f13ca93ac
Reviewed-on: https://chromium-review.googlesource.com/857907
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/sys_util/src/lib.rs b/sys_util/src/lib.rs
index dea290a..7f9f034 100644
--- a/sys_util/src/lib.rs
+++ b/sys_util/src/lib.rs
@@ -55,10 +55,18 @@ pub use signalfd::Error as SignalFdError;
 use std::ffi::CStr;
 use std::ptr;
 
-use libc::{kill, syscall, waitpid, c_long, pid_t, uid_t, gid_t, SIGKILL, WNOHANG};
+use libc::{kill, syscall, sysconf, waitpid, c_long, pid_t, uid_t, gid_t, _SC_PAGESIZE,
+           SIGKILL, WNOHANG};
 
 use syscall_defines::linux::LinuxSyscall::SYS_getpid;
 
+/// Safe wrapper for `sysconf(_SC_PAGESIZE)`.
+#[inline(always)]
+pub fn pagesize() -> usize {
+    // Trivially safe
+    unsafe { sysconf(_SC_PAGESIZE) as usize }
+}
+
 /// This bypasses `libc`'s caching `getpid(2)` wrapper which can be invalid if a raw clone was used
 /// elsewhere.
 #[inline(always)]