From 6f84f14927460ade47c5e04836c79c17fa9fc42c Mon Sep 17 00:00:00 2001
From: Jim Newsome <jnewsome@torproject.org>
Date: Mon, 5 Oct 2020 09:18:44 -0500
Subject: Add wrapper for mremap

---
 src/sys/mman.rs | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'src/sys/mman.rs')

diff --git a/src/sys/mman.rs b/src/sys/mman.rs
index b2bed6e4..63a0779c 100644
--- a/src/sys/mman.rs
+++ b/src/sys/mman.rs
@@ -139,6 +139,17 @@ libc_bitflags!{
     }
 }
 
+#[cfg(target_os = "linux")]
+libc_bitflags!{
+    /// Options for `mremap()`.
+    pub struct MRemapFlags: c_int {
+        /// Permit the kernel to relocate the mapping to a new virtual address, if necessary.
+        MREMAP_MAYMOVE;
+        /// Place the mapping at exactly the address specified in `new_address`.
+        MREMAP_FIXED;
+    }
+}
+
 libc_enum!{
     /// Usage information for a range of memory to allow for performance optimizations by the kernel.
     ///
@@ -315,6 +326,30 @@ pub unsafe fn mmap(addr: *mut c_void, length: size_t, prot: ProtFlags, flags: Ma
     }
 }
 
+/// Expands (or shrinks) an existing memory mapping, potentially moving it at
+/// the same time.
+///
+/// # Safety
+///
+/// See the `mremap(2)` [man page](https://man7.org/linux/man-pages/man2/mremap.2.html) for
+/// detailed requirements.
+#[cfg(target_os = "linux")]
+pub unsafe fn mremap(
+    addr: *mut c_void,
+    old_size: size_t,
+    new_size: size_t,
+    flags: MRemapFlags,
+    new_address: Option<* mut c_void>,
+) -> Result<*mut c_void> {
+    let ret = libc::mremap(addr, old_size, new_size, flags.bits(), new_address.unwrap_or(std::ptr::null_mut()));
+
+    if ret == libc::MAP_FAILED {
+        Err(Error::Sys(Errno::last()))
+    } else {
+        Ok(ret)
+    }
+}
+
 /// remove a mapping
 ///
 /// # Safety
-- 
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