diff --git a/dev/ncpu/ncpu.c b/dev/ncpu/ncpu.c
index 62f9fde79..cdc91eb33 100644
--- a/dev/ncpu/ncpu.c
+++ b/dev/ncpu/ncpu.c
@@ -1,11 +1,16 @@
 #define _GNU_SOURCE
+#include <limits.h>
 #include <sched.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 // gcc -fPIC -shared -O2 -o ncpu{.so,.c}
 // NCPU=16 LD_PRELOAD=$PWD/ncpu.so command args...
 
+static char prog_full_path[PATH_MAX];
+
 /* return a cpu_set having the first $NCPU set */
 int sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask)
 {
@@ -30,3 +35,85 @@ int sched_setaffinity(pid_t pid, size_t cpusetsize, const cpu_set_t *mask)
 {
 	return 0;
 }
+
+void usage(const char *argv0)
+{
+	fprintf(stderr,
+		"Usage: %s [-n ncpu] [cmd [args...]]\n"
+		"       Will install itself in LD_PRELOAD before calling <cmd> with args.\n"
+		"       The number of CPUs may also come from variable NCPU or default to %d.\n"
+		"\n"
+		"",
+		argv0, CPU_SETSIZE);
+	exit(1);
+}
+
+/* Called in wrapper mode, no longer supported on recent glibc */
+int main(int argc, char **argv)
+{
+	const char *argv0 = argv[0];
+	char *preload;
+	int plen;
+
+	prog_full_path[0] = 0;
+	plen = readlink("/proc/self/exe", prog_full_path, sizeof(prog_full_path) - 1);
+	if (plen != -1)
+		prog_full_path[plen] = 0;
+	else
+		plen = snprintf(prog_full_path, sizeof(prog_full_path), "%s", argv[0]);
+
+	while (1) {
+		argc--;
+		argv++;
+
+		if (argc < 1)
+			usage(argv0);
+
+		if (strcmp(argv[0], "--") == 0) {
+			argc--;
+			argv++;
+			break;
+		}
+		else if (strcmp(argv[0], "-n") == 0) {
+			if (argc < 2)
+				usage(argv0);
+
+			if (setenv("NCPU", argv[1], 1) != 0)
+				usage(argv0);
+			argc--;
+			argv++;
+		}
+		else {
+			/* unknown arg, that's the command */
+			break;
+		}
+	}
+
+	/* here the only args left start with the cmd name */
+
+	/* now we'll concatenate ourselves at the end of the LD_PRELOAD variable */
+	preload = getenv("LD_PRELOAD");
+	if (preload) {
+		int olen = strlen(preload);
+		preload = realloc(preload, olen + 1 + plen + 1);
+		if (!preload) {
+			perror("realloc");
+			exit(2);
+		}
+		preload[olen] = ' ';
+		memcpy(preload + olen + 1, prog_full_path, plen);
+		preload[olen + 1 + plen] = 0;
+	}
+	else {
+		preload = prog_full_path;
+	}
+
+	if (setenv("LD_PRELOAD", preload, 1) < 0) {
+		perror("setenv");
+		exit(2);
+	}
+
+	execvp(*argv, argv);
+	perror("execve");
+	exit(2);
+}