sys_util: use MADV_DONTDUMP for new mmaps

The mmaps made through the sys_util API are usually for guest memory or
other large shared memory chunks that will pollute the file system with
huge dumps on crash. By using MADV_DONTDUMP, we save the file system
from storing these useless data segments when crosvm crashes.

TEST=./build_test
BUG=None

Change-Id: I2041523648cd7c150bbdbfceef589f42d3f9c2b9
Reviewed-on: https://chromium-review.googlesource.com/890279
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/sys_util/src/mmap.rs b/sys_util/src/mmap.rs
index 2813234..4ce72b6 100644
--- a/sys_util/src/mmap.rs
+++ b/sys_util/src/mmap.rs
@@ -69,6 +69,12 @@ impl MemoryMapping {
         if addr == libc::MAP_FAILED {
             return Err(Error::SystemCallFailed(errno::Error::last()));
         }
+        // This is safe because we call madvise with a valid address and size, and we check the
+        // return value. We only warn about an error because failure here is not fatal to the mmap.
+        if unsafe { libc::madvise(addr, size, libc::MADV_DONTDUMP) } == -1 {
+            warn!("failed madvise(MADV_DONTDUMP) on mmap: {:?}",
+                  errno::Error::last());
+        }
         Ok(MemoryMapping {
                addr: addr as *mut u8,
                size: size,
@@ -107,6 +113,12 @@ impl MemoryMapping {
         if addr == libc::MAP_FAILED {
             return Err(Error::SystemCallFailed(errno::Error::last()));
         }
+        // This is safe because we call madvise with a valid address and size, and we check the
+        // return value. We only warn about an error because failure here is not fatal to the mmap.
+        if unsafe { libc::madvise(addr, size, libc::MADV_DONTDUMP) } == -1 {
+            warn!("failed madvise(MADV_DONTDUMP) on mmap: {:?}",
+                  errno::Error::last());
+        }
         Ok(MemoryMapping {
                addr: addr as *mut u8,
                size: size,