[enhance] memory: Add FreeBSD support in the memory.c.

build/myocamlbuild_prefix.ml

@@ -541,9 +541,12 @@ let _ = dispatch begin function
         let file = dir / "lib" ^ name -.- !Options.ext_lib in
         dep ["ocaml"; tag] [file];
         flag ["ocaml"; "byte"; "link"; tag] (S[A"-ccopt";A("-L"^dir);A"-cclib";A("-l"^name);A"-custom"]);
-        flag ["ocaml"; "native"; "link"; tag] (S[A"-ccopt";A("-L"^dir);A"-cclib";A("-l"^name)])
+        flag ["ocaml"; "native"; "link"; tag] (S[A"-ccopt";A("-L"^dir);A"-cclib";A("-l"^name)]);
       in
 
+      (* In the memory.c in FreeBSD part that uses kvm_getprocs() required link with -lkvm. *)
+      if is_fbsd then
+        flag ["use_stubs"; "link"] (S[A "-cclib";A "-lkvm"]);
 
 (* -- Don't forget that the rest of the "mlstate build stdlib" is in --
    -- myocamlbuild_suffix.ml. The rest comes from the build_rules*.ml in each repo -- *)

libbase/memory.c

@@ -38,7 +38,36 @@ int get_mem (unsigned int *rss)
     return 0;
 }
 
-#else /* not MAC */
+#elif (defined(__FreeBSD__) || defined(__FreeBSD_kernel__)) /* FreeBSD */
+
+#include <kvm.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#include <sys/user.h>
+
+int get_mem (unsigned int *rss)
+{
+    kvm_t *kv;
+    int cnt,pagesize,pid;
+
+    pagesize = getpagesize();
+    pid = getpid();
+    kv = kvm_open(NULL, "/dev/null", NULL, O_RDONLY, NULL);
+
+    if (kv != NULL) {
+        struct kinfo_proc *kproc;
+        kproc = kvm_getprocs(kv, KERN_PROC_PID, pid, &cnt);
+        if (kproc && cnt > 0)
+            *rss = kproc->ki_rssize * pagesize;
+        else *rss = 0;
+        kvm_close(kv);
+        return 0;
+    } else return -1;
+}
+
+#else /* not MAC and FreeBSD */
 
 #include <stdio.h>
 #include <unistd.h>