From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Wed, 6 Jun 2018 20:51:05 +0200
Subject: ar71xx: lzma-loader: move padding workaround to gzip step

Some devices (TP-Link TL-WR1043ND v1) don't boot reliably when the
uncompressed loader is too small. This was workarounded in the loader by
adding 512KB of padding to the .data section of the loader binary.

This approach had two issues:

- The padding was only working when .data was non-empty (otherwise the
  section would become NOBITS, omitting it in the binary). .data was only
  empty when no CMDLINE was set, leading to further workarounds like
  fe594bf90d09 ("ath79: fix loader-okli, lzma-loader"), and this
  workaround was only effective because a missing "const" led to the kernel
  argv being stored in .data instead of .rodata
- The padding was not only added to the compressed .gz loader, but also
  uncompressed .bin and .elf loaders. The prevented embedding the kernel
  cmdline in the loader for non-gz loader types.

To fix both issues, move the creation of the padding from the linker script
to the gzip step.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

diff --git a/target/linux/ar71xx/image/lzma-loader/Makefile b/target/linux/ar71xx/image/lzma-loader/Makefile
index 9b81e87306f235d1e7284401828240b9b9787011..738093a958013624abb8f84a3874e1c795da349d 100644
--- a/target/linux/ar71xx/image/lzma-loader/Makefile
+++ b/target/linux/ar71xx/image/lzma-loader/Makefile
@@ -47,7 +47,11 @@ loader-compile: $(PKG_BUILD_DIR)/.prepared
 		clean all
 
 loader.gz: $(PKG_BUILD_DIR)/loader.bin
-	gzip -nc9 $< > $(LOADER_GZ)
+	# Workaround for buggy bootloaders: Some devices
+	# (TP-Link TL-WR1043ND v1) don't work correctly when
+	# the uncompressed loader is too small (probably a cache
+	# invalidation issue)
+	dd if=$< bs=512K conv=sync | gzip -nc9 > $(LOADER_GZ)
 
 loader.elf: $(PKG_BUILD_DIR)/loader.elf
 	$(CP) $< $(LOADER_ELF)
diff --git a/target/linux/ar71xx/image/lzma-loader/src/loader.lds b/target/linux/ar71xx/image/lzma-loader/src/loader.lds
index 80cc7ca3ecf53a747fc139560b89c233f4343293..01ff85236147dc62bae480b191a44005171b1561 100644
--- a/target/linux/ar71xx/image/lzma-loader/src/loader.lds
+++ b/target/linux/ar71xx/image/lzma-loader/src/loader.lds
@@ -13,7 +13,6 @@ SECTIONS {
 	.data : {
 		*(.data)
 		*(.data.*)
-		. = . + 524288;		/* workaround for buggy bootloaders */
 	}
 
 	. = ALIGN(32);