diff --git a/libc-test/Cargo.toml b/libc-test/Cargo.toml
index 721ccc90932dc..e86f704a49221 100644
--- a/libc-test/Cargo.toml
+++ b/libc-test/Cargo.toml
@@ -90,3 +90,8 @@ harness = false
 name = "primitive_types"
 path = "test/primitive_types.rs"
 harness = true
+
+[[test]]
+name = "syslog"
+path = "test/syslog.rs"
+harness = true
diff --git a/libc-test/build.rs b/libc-test/build.rs
index b7608eedb5fc5..e8610d8f81659 100644
--- a/libc-test/build.rs
+++ b/libc-test/build.rs
@@ -34,6 +34,8 @@ fn do_cc() {
         {
             cc::Build::new().file("src/makedev.c").compile("makedev");
         }
+
+        cc::Build::new().file("src/syslog.c").compile("syslog");
     }
     if target.contains("android") || target.contains("linux") {
         cc::Build::new().file("src/errqueue.c").compile("errqueue");
diff --git a/libc-test/semver/unix.txt b/libc-test/semver/unix.txt
index 052c24178dfcc..73262de39a2e7 100644
--- a/libc-test/semver/unix.txt
+++ b/libc-test/semver/unix.txt
@@ -210,6 +210,7 @@ LOG_LOCAL6
 LOG_LOCAL7
 LOG_LPR
 LOG_MAIL
+LOG_MASK
 LOG_NDELAY
 LOG_NEWS
 LOG_NOTICE
@@ -218,6 +219,7 @@ LOG_ODELAY
 LOG_PID
 LOG_PRIMASK
 LOG_SYSLOG
+LOG_UPTO
 LOG_USER
 LOG_UUCP
 LOG_WARNING
diff --git a/libc-test/src/syslog.c b/libc-test/src/syslog.c
new file mode 100644
index 0000000000000..0aed13c6018eb
--- /dev/null
+++ b/libc-test/src/syslog.c
@@ -0,0 +1,14 @@
+#include <sys/syslog.h>
+
+// Since the syslog(3) macros are macros instead of functions, they aren't
+// available to FFI.  libc must reimplement them, which is error-prone.  This
+// file provides FFI access to the actual macros so they can be tested against
+// the Rust reimplementations.
+
+int LOG_MASK_ffi(int priority) {
+    return LOG_MASK(priority);
+}
+
+int LOG_UPTO_ffi(int priority) {
+    return LOG_UPTO(priority);
+}
diff --git a/libc-test/test/syslog.rs b/libc-test/test/syslog.rs
new file mode 100644
index 0000000000000..e295027bc26ba
--- /dev/null
+++ b/libc-test/test/syslog.rs
@@ -0,0 +1,55 @@
+#[cfg(unix)]
+mod t {
+    use libc::c_int;
+
+    use libc::LOG_ALERT;
+    use libc::LOG_CRIT;
+    use libc::LOG_DEBUG;
+    use libc::LOG_EMERG;
+    use libc::LOG_ERR;
+    use libc::LOG_INFO;
+    use libc::LOG_NOTICE;
+    use libc::LOG_WARNING;
+
+    use libc::LOG_MASK;
+    use libc::LOG_UPTO;
+
+    extern "C" {
+        pub fn LOG_MASK_ffi(priority: c_int) -> c_int;
+        pub fn LOG_UPTO_ffi(priority: c_int) -> c_int;
+    }
+
+    #[test]
+    fn test_log_mask() {
+        // Ensure our Rust impl returns the same value as the C macros
+
+        // *_ffi interfaces are unsafe
+        unsafe {
+            assert_eq!(LOG_MASK(LOG_EMERG), LOG_MASK_ffi(LOG_EMERG));
+            assert_eq!(LOG_MASK(LOG_ALERT), LOG_MASK_ffi(LOG_ALERT));
+            assert_eq!(LOG_MASK(LOG_CRIT), LOG_MASK_ffi(LOG_CRIT));
+            assert_eq!(LOG_MASK(LOG_ERR), LOG_MASK_ffi(LOG_ERR));
+            assert_eq!(LOG_MASK(LOG_WARNING), LOG_MASK_ffi(LOG_WARNING));
+            assert_eq!(LOG_MASK(LOG_NOTICE), LOG_MASK_ffi(LOG_NOTICE));
+            assert_eq!(LOG_MASK(LOG_INFO), LOG_MASK_ffi(LOG_INFO));
+            assert_eq!(LOG_MASK(LOG_DEBUG), LOG_MASK_ffi(LOG_DEBUG));
+        }
+    }
+
+    #[test]
+    fn test_log_upto() {
+        // Ensure our Rust impl returns the same value as the C macros
+
+        // *_ffi interfaces are unsafe
+        unsafe {
+            assert_eq!(LOG_UPTO(LOG_EMERG), LOG_UPTO_ffi(LOG_EMERG));
+            assert_eq!(LOG_UPTO(LOG_ALERT), LOG_UPTO_ffi(LOG_ALERT));
+            assert_eq!(LOG_UPTO(LOG_CRIT), LOG_UPTO_ffi(LOG_CRIT));
+            assert_eq!(LOG_UPTO(LOG_ERR), LOG_UPTO_ffi(LOG_ERR));
+            assert_eq!(LOG_UPTO(LOG_WARNING), LOG_UPTO_ffi(LOG_WARNING));
+            assert_eq!(LOG_UPTO(LOG_NOTICE), LOG_UPTO_ffi(LOG_NOTICE));
+            assert_eq!(LOG_UPTO(LOG_INFO), LOG_UPTO_ffi(LOG_INFO));
+            assert_eq!(LOG_UPTO(LOG_DEBUG), LOG_UPTO_ffi(LOG_DEBUG));
+        }
+    }
+}
diff --git a/src/unix/mod.rs b/src/unix/mod.rs
index 84298804c594f..938e96687c6ed 100644
--- a/src/unix/mod.rs
+++ b/src/unix/mod.rs
@@ -1514,6 +1514,14 @@ safe_f! {
     pub {const} fn ntohs(netshort: u16) -> u16 {
         u16::from_be(netshort)
     }
+
+    pub {const} fn LOG_MASK(priority: c_int) -> c_int {
+        1 << priority
+    }
+
+    pub {const} fn LOG_UPTO(priority: c_int) -> c_int {
+        (1 << ((priority) + 1)) - 1
+    }
 }
 
 cfg_if! {