lualoader: Create a module blacklist, add DRM modules to it

This is a step in the process of easing migration into the new world order
of DRM drivers. Strongly encourage users towards loading DRM modules via
rc.conf(5) instead of loader.conf(5) by failing the load from loader(8).
Users so inclined may wipe out the blacklist via module_blacklist="" in
loader.conf(5), and it is expected that these modules will eventually be
removed from the blacklist. They may still be loaded as dependencies of
other modules or explicitly via the loader prompt, but this should not be a
major problem.

Approved by:	re (rgrimes)
Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D16914

UPDATING

@@ -31,6 +31,13 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 12.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20181006:
+	The legacy DRM modules and drivers have now been added to the loader's
+	module blacklist, in favor of loading them with kld_list in rc.conf(5).
+	The module blacklist may be overridden with the loader.conf(5)
+	'module_blacklist' variable, but loading them via rc.conf(5) is strongly
+	encouraged.
+
 20181002:
 	The cam(4) based nda(4) driver will be used over nvd(4) by default on
 	powerpc64. You may set 'options NVME_USE_NVD=1' in your kernel conf or

stand/defaults/loader.conf

@@ -97,6 +97,7 @@ efi_max_resolution="1x1"	# Set the max resolution for EFI loader to use:
 #console="vidconsole"		# A comma separated list of console(s)
 #currdev="disk1s1a"		# Set the current device
 module_path="/boot/modules;/boot/dtb;/boot/dtb/overlays"	# Set the module search path
+module_blacklist="drm drm2 radeonkms i915kms amdgpu"	# Loader module blacklist
 #prompt="\\${interpret}"	# Set the command prompt
 #root_disk_unit="0"		# Force the root disk unit number
 #rootdev="disk1s1a"		# Set the root filesystem

stand/defaults/loader.conf.5

@@ -23,7 +23,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
-.Dd August 28, 2018
+.Dd October 6, 2018
 .Dt LOADER.CONF 5
 .Os
 .Sh NAME
@@ -147,6 +147,15 @@ If a password is set, the user must provide specified password to boot.
 If set to
 .Dq YES ,
 module names will be displayed as they are loaded.
+.It Ar module_blacklist
+Blacklist of modules.
+Modules specified in the blacklist may not be loaded automatically with a
+.Ar *_load
+directive, but they may be loaded directly at the
+.Xr loader 8
+prompt.
+Blacklisted modules may still be loaded indirectly as dependencies of other
+moduled.
 .It Ar *_load
 If set to
 .Dq YES ,

stand/lua/config.lua

@@ -54,6 +54,7 @@ local MSG_XENKERNFAIL = "Failed to load Xen kernel '%s'"
 local MSG_XENKERNLOADING = "Loading Xen kernel..."
 local MSG_KERNLOADING = "Loading kernel..."
 local MSG_MODLOADING = "Loading configured modules..."
+local MSG_MODBLACKLIST = "Not loading blacklisted module '%s'"
 local MSG_MODLOADFAIL = "Could not load one or more modules!"
 
 local MODULEEXPR = '([%w-_]+)'
@@ -265,20 +266,37 @@ local function isValidComment(line)
 	return true
 end
 
+local function getBlacklist()
+	local blacklist_str = loader.getenv('module_blacklist')
+	if blacklist_str == nil then
+		return nil
+	end
+
+	local blacklist = {}
+	for mod in blacklist_str:gmatch("[;, ]?([%w-_]+)[;, ]?") do
+		blacklist[mod] = true
+	end
+	return blacklist
+end
+
 local function loadModule(mod, silent)
 	local status = true
+	local blacklist = getBlacklist()
 	local pstatus
 	for k, v in pairs(mod) do
 		if v.load ~= nil and v.load:lower() == "yes" then
+			local module_name = v.name or k
+			if blacklist[module_name] ~= nil then
+				if not silent then
+					print(MSG_MODBLACKLIST:format(module_name))
+				end
+				goto continue
+			end
 			local str = "load "
 			if v.type ~= nil then
 				str = str .. "-t " .. v.type .. " "
 			end
-			if v.name ~= nil then
-				str = str .. v.name
-			else
-				str = str .. k
-			end
+			str = str .. module_name
 			if v.flags ~= nil then
 				str = str .. " " .. v.flags
 			end
@@ -309,6 +327,7 @@ local function loadModule(mod, silent)
 			end
 
 		end
+		::continue::
 	end
 
 	return status