Add helper functions to copy strings into struct image_args.

Given a zeroed struct image_args with an allocated buf member,
exec_args_add_fname() must be called to install a file name (or NULL).
Then zero or more calls to exec_args_add_env() followed by zero or
more calls to exec_args_add_env(). exec_args_adjust_args() may be
called after args and/or env to allow an interpreter to be prepended to
the argument list.

To allow code reuse when adding arg and env variables, begin_envv
should be accessed with the accessor exec_args_get_begin_envv()
which handles the case when no environment entries have been added.

Use these functions to simplify exec_copyin_args() and
freebsd32_exec_copyin_args().

Reviewed by:	kib
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D15468

3 files changed, 13 insertions, 37 deletions

diff --git a/sys/compat/cloudabi32/cloudabi32_module.c b/sys/compat/cloudabi32/cloudabi32_module.c
index 001c673a7d7a..51beae7519ac 100644
--- a/sys/compat/cloudabi32/cloudabi32_module.c
+++ b/sys/compat/cloudabi32/cloudabi32_module.c
@@ -54,7 +54,7 @@ cloudabi32_copyout_strings(struct image_params *imgp)
 
 	/* Copy out program arguments. */
 	args = imgp->args;
-	len = args->begin_envv - args->begin_argv;
+	len = exec_args_get_begin_envv(args) - args->begin_argv;
 	begin = rounddown2(imgp->sysent->sv_usrstack - len, sizeof(register_t));
 	copyout(args->begin_argv, (void *)begin, len);
 	return ((register_t *)begin);
@@ -109,7 +109,8 @@ cloudabi32_fixup(register_t **stack_base, struct image_params *imgp)
 	 * exec_copyin_data_fds(). Undo this by reducing the length.
 	 */
 	args = (Elf32_Auxargs *)imgp->auxargs;
-	argdatalen = imgp->args->begin_envv - imgp->args->begin_argv;
+	argdatalen = exec_args_get_begin_envv(imgp->args) -
+	    imgp->args->begin_argv;
 	if (argdatalen > 0)
 		--argdatalen;
 
diff --git a/sys/compat/cloudabi64/cloudabi64_module.c b/sys/compat/cloudabi64/cloudabi64_module.c
index 9c71b87b08f4..fd0be086aac3 100644
--- a/sys/compat/cloudabi64/cloudabi64_module.c
+++ b/sys/compat/cloudabi64/cloudabi64_module.c
@@ -54,7 +54,7 @@ cloudabi64_copyout_strings(struct image_params *imgp)
 
 	/* Copy out program arguments. */
 	args = imgp->args;
-	len = args->begin_envv - args->begin_argv;
+	len = exec_args_get_begin_envv(args) - args->begin_argv;
 	begin = rounddown2(imgp->sysent->sv_usrstack - len, sizeof(register_t));
 	copyout(args->begin_argv, (void *)begin, len);
 	return ((register_t *)begin);
@@ -109,7 +109,8 @@ cloudabi64_fixup(register_t **stack_base, struct image_params *imgp)
 	 * exec_copyin_data_fds(). Undo this by reducing the length.
 	 */
 	args = (Elf64_Auxargs *)imgp->auxargs;
-	argdatalen = imgp->args->begin_envv - imgp->args->begin_argv;
+	argdatalen = exec_args_get_begin_envv(imgp->args) -
+	    imgp->args->begin_argv;
 	if (argdatalen > 0)
 		--argdatalen;
 
diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c
index 3c2cdec819b0..d596eb4d6acf 100644
--- a/sys/compat/freebsd32/freebsd32_misc.c
+++ b/sys/compat/freebsd32/freebsd32_misc.c
@@ -337,7 +337,6 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
 {
 	char *argp, *envp;
 	u_int32_t *p32, arg;
-	size_t length;
 	int error;
 
 	bzero(args, sizeof(*args));
@@ -355,19 +354,9 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
 	/*
 	 * Copy the file name.
 	 */
-	if (fname != NULL) {
-		args->fname = args->buf;
-		error = (segflg == UIO_SYSSPACE) ?
-		    copystr(fname, args->fname, PATH_MAX, &length) :
-		    copyinstr(fname, args->fname, PATH_MAX, &length);
-		if (error != 0)
-			goto err_exit;
-	} else
-		length = 0;
-
-	args->begin_argv = args->buf + length;
-	args->endp = args->begin_argv;
-	args->stringspace = ARG_MAX;
+	error = exec_args_add_fname(args, fname, segflg);
+	if (error != 0)
+		goto err_exit;
 
 	/*
 	 * extract arguments first
@@ -380,19 +369,11 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
 		if (arg == 0)
 			break;
 		argp = PTRIN(arg);
-		error = copyinstr(argp, args->endp, args->stringspace, &length);
-		if (error) {
-			if (error == ENAMETOOLONG)
-				error = E2BIG;
+		error = exec_args_add_arg(args, argp, UIO_USERSPACE);
+		if (error != 0)
 			goto err_exit;
-		}
-		args->stringspace -= length;
-		args->endp += length;
-		args->argc++;
 	}
 			
-	args->begin_envv = args->endp;
-
 	/*
 	 * extract environment strings
 	 */
@@ -405,16 +386,9 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
 			if (arg == 0)
 				break;
 			envp = PTRIN(arg);
-			error = copyinstr(envp, args->endp, args->stringspace,
-			    &length);
-			if (error) {
-				if (error == ENAMETOOLONG)
-					error = E2BIG;
+			error = exec_args_add_env(args, envp, UIO_USERSPACE);
+			if (error != 0)
 				goto err_exit;
-			}
-			args->stringspace -= length;
-			args->endp += length;
-			args->envc++;
 		}
 	}