brcm47xx: relocate the stack in loader

By default we are reusing the stack provided by CFE, like it is intended
by CFE. On my WRT54GS it is located at 0x8043BF30, so a big kernel image
could overwrite it. Relocate it to a different memory region which is
still under the 8MB RAM, but in the higher area. We only need this
memory region for the stack of the loader, Linux will set up this
for its own.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/brcm47xx/image/lzma-loader/src/Makefile

@@ -19,6 +19,7 @@
 
 TEXT_START	:= 0x80001000
 BZ_TEXT_START	:= 0x80600000
+BZ_STACK_START	:= 0x80700000
 
 OBJCOPY		:= $(CROSS_COMPILE)objcopy -O binary -R .reginfo -R .note -R .comment -R .mdebug -S
 
@@ -28,9 +29,9 @@ CFLAGS		= -D__KERNEL__ -Wall -Wstrict-prototypes -Wno-trigraphs -Os \
 		  -mabi=32 -march=mips32 -Wa,-32 -Wa,-march=mips32 -Wa,-mips32 -Wa,--trap
 CFLAGS		+= -DLOADADDR=$(TEXT_START) -D_LZMA_IN_CB
 
-ASFLAGS		= $(CFLAGS) -D__ASSEMBLY__ -DBZ_TEXT_START=$(BZ_TEXT_START)
+ASFLAGS		= $(CFLAGS) -D__ASSEMBLY__ -DBZ_TEXT_START=$(BZ_TEXT_START) -DBZ_STACK_START=$(BZ_STACK_START)
 
-SEDFLAGS	:= s/BZ_TEXT_START/$(BZ_TEXT_START)/;s/TEXT_START/$(TEXT_START)/
+SEDFLAGS	:= s/BZ_TEXT_START/$(BZ_TEXT_START)/;s/BZ_STACK_START/$(BZ_STACK_START)/;s/TEXT_START/$(TEXT_START)/
 
 OBJECTS		:= head.o data.o
 

target/linux/brcm47xx/image/lzma-loader/src/head.S

@@ -38,6 +38,7 @@
 	.text
 	LEAF(startup)
 	.set noreorder
+	li	sp, BZ_STACK_START
 	addi    sp, -48
 	sw      a0, 16(sp)
 	sw      a1, 20(sp)