Index: usr.sbin/config/config.h
===================================================================
--- usr.sbin/config/config.h
+++ usr.sbin/config/config.h
@@ -140,6 +140,14 @@
 
 SLIST_HEAD(, opt_list) otab;
 
+struct envvar {
+	char	*env_key;
+	char	*env_val;
+	STAILQ_ENTRY(envvar) envvar_next;
+};
+
+STAILQ_HEAD(envvar_head, envvar) envvars;
+
 struct hint {
 	char	*hint_name;
 	STAILQ_ENTRY(hint) hint_next;
Index: usr.sbin/config/config.5
===================================================================
--- usr.sbin/config/config.5
+++ usr.sbin/config/config.5
@@ -23,7 +23,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 21, 2016
+.Dd June 22, 2018
 .Dt CONFIG 5
 .Os
 .Sh NAME
@@ -124,6 +124,20 @@
 This directive is useful for setting kernel tunables in
 embedded environments that do not start from
 .Xr loader 8 .
+.\" -------- ENVVAR --------
+.Pp
+.It Ic envvar Ar setting
+Specifies an individual environment setting to be added to the kernel's
+compiled-in environment.
+.Ar setting
+must be of the form
+.Dq Va name=value
+without any quotes included in the value or the right hand side of the setting.
+All environment variables specified with
+.Ic envvar
+will be set after any
+.Ic env
+files are included.
 .\" -------- FILES --------
 .Pp
 .It Ic files Ar filename
Index: usr.sbin/config/config.y
===================================================================
--- usr.sbin/config/config.y
+++ usr.sbin/config/config.y
@@ -12,6 +12,7 @@
 %token	DEVICE
 %token	NODEVICE
 %token	ENV
+%token	ENVVAR
 %token	EQUALS
 %token	PLUSEQUALS
 %token	HINTS
@@ -193,6 +194,16 @@
 		env = $2;
 		envmode = 1;
 		} |
+	ENVVAR ID EQUALS ID {
+		struct envvar *envvar;
+
+		envvar = (struct envvar *)calloc(1, sizeof (struct envvar));
+		if (envvar == NULL)
+			err(EXIT_FAILURE, "calloc");
+		envvar->env_key = $2;
+		envvar->env_val = $4;
+		STAILQ_INSERT_TAIL(&envvars, envvar, envvar_next);
+	        } |
 	HINTS ID {
 		struct hint *hint;
 
Index: usr.sbin/config/lang.l
===================================================================
--- usr.sbin/config/lang.l
+++ usr.sbin/config/lang.l
@@ -70,6 +70,7 @@
 	{ "nodevice",	NODEVICE },
 	{ "nodevices",	NODEVICE },
 	{ "env",	ENV },
+	{ "envvar",	ENVVAR },
 	{ "hints",	HINTS },
 	{ "ident",	IDENT },
 	{ "machine",	ARCH }, /* MACHINE is defined in /sys/param.h */
Index: usr.sbin/config/main.c
===================================================================
--- usr.sbin/config/main.c
+++ usr.sbin/config/main.c
@@ -204,6 +204,7 @@
 	STAILQ_INIT(&fntab);
 	STAILQ_INIT(&ftab);
 	STAILQ_INIT(&hints);
+	STAILQ_INIT(&envvars);
 	if (yyparse())
 		exit(3);
 
Index: usr.sbin/config/mkmakefile.c
===================================================================
--- usr.sbin/config/mkmakefile.c
+++ usr.sbin/config/mkmakefile.c
@@ -46,6 +46,7 @@
 #include <ctype.h>
 #include <err.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/param.h>
@@ -238,6 +239,63 @@
 	moveifchanged(path("hints.c.new"), path("hints.c"));
 }
 
+static void
+sanitize_envline(char *result, const char *src)
+{
+	const char *eq;
+	char c, *dst;
+	bool leading;
+
+	/* If there is no '=' it's not a well-formed name=value line. */
+	if ((eq = strchr(src, '=')) == NULL) {
+		*result = 0;
+		return;
+	}
+	dst = result;
+
+	/* Copy chars before the '=', skipping any leading spaces/quotes. */
+	leading = true;
+	while (src < eq) {
+		c = *src++;
+		if (leading && (isspace(c) || c == '"'))
+			continue;
+		*dst++ = c;
+		leading = false;
+	}
+
+	/* If it was all leading space, we don't have a well-formed line. */
+	if (leading) {
+		*result = 0;
+		return;
+	}
+
+	/* Trim spaces/quotes immediately before the '=', then copy the '='. */
+	while (isspace(dst[-1]) || dst[-1] == '"')
+		--dst;
+	*dst++ = *src++;
+
+	/* Copy chars after the '=', skipping any leading whitespace. */
+	leading = true;
+	while ((c = *src++) != 0) {
+		if (leading && (isspace(c) || c == '"'))
+			continue;
+		*dst++ = c;
+		leading = false;
+	}
+
+	/* If it was all leading space, it's a valid 'var=' (nil value). */
+	if (leading) {
+		*dst = 0;
+		return;
+	}
+
+	/* Trim trailing whitespace and quotes. */
+	while (isspace(dst[-1]) || dst[-1] == '"')
+		--dst;
+
+	*dst = 0;
+}
+
 /*
  * Build env.c from the skeleton
  */
@@ -245,8 +303,9 @@
 makeenv(void)
 {
 	FILE *ifp, *ofp;
-	char line[BUFSIZ];
-	char *s;
+	char line[BUFSIZ], result[BUFSIZ], *linep;
+	int linesz;
+	struct envvar *envvar;
 
 	if (env) {
 		ifp = fopen(env, "r");
@@ -265,35 +324,23 @@
 	fprintf(ofp, "char static_env[] = {\n");
 	if (ifp) {
 		while (fgets(line, BUFSIZ, ifp) != NULL) {
-			/* zap trailing CR and/or LF */
-			while ((s = strrchr(line, '\n')) != NULL)
-				*s = '\0';
-			while ((s = strrchr(line, '\r')) != NULL)
-				*s = '\0';
-			/* remove # comments */
-			s = strchr(line, '#');
-			if (s)
-				*s = '\0';
-			/* remove any whitespace and " characters */
-			s = line;
-			while (*s) {
-				if (*s == ' ' || *s == '\t' || *s == '"') {
-					while (*s) {
-						s[0] = s[1];
-						s++;
-					}
-					/* start over */
-					s = line;
-					continue;
-				}
-				s++;
-			}
+			sanitize_envline(result, line);
 			/* anything left? */
-			if (*line == '\0')
+			if (*result == '\0')
 				continue;
-			fprintf(ofp, "\"%s\\0\"\n", line);
+			fprintf(ofp, "\"%s\\0\"\n", result);
 		}
 	}
+	STAILQ_FOREACH(envvar, &envvars, envvar_next) {
+		linesz = strlen(envvar->env_key) + strlen(envvar->env_val) + 2;
+		linep = malloc(linesz);
+		sprintf(linep, "%s=%s", envvar->env_key, envvar->env_val);
+		linep[linesz - 1] = '\0';
+		sanitize_envline(result, linep);
+		if (*result == '\0')
+			continue;
+		fprintf(ofp, "\"%s\\0\"\n", result);
+	}
 	fprintf(ofp, "\"\\0\"\n};\n");
 	if (ifp)
 		fclose(ifp);