arch: Add explicit linker script for u-boot-elf

Commit f4dc714aaa ("arm64: Turn u-boot.bin back into an ELF file after
relocate-rela")
introduce REMAKE_ELF option to recreate u-boot.elf from u-boot ->
u-boot.bin + DT -> u-boot.elf.

The best is to ilustrate it from make V=1 output
  cat u-boot-nodtb.bin dts/dt.dtb > u-boot-dtb.bin
  cp u-boot-dtb.bin u-boot.bin
aarch64-linux-gnu-objcopy -I binary -B aarch64 -O elf64-littleaarch64  u-boot.bin u-boot-elf.o
  aarch64-linux-gnu-ld.bfd u-boot-elf.o -o u-boot.elf --defsym="_start"=0x8000000 -Ttext=0x8000000

Last command has no explicit linker script passed that's why toolchain
internal linker script is used.
In Binutils 2.32 case it contains SIZEOF_HEADERS symbol which has changed
behavior by commit
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=64029e93683a266c38d19789e780f3748bd6a188
which result in situation that program headers has changed from
(xilinx_zynqmp_mini_defconfig)

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000010000 0x00000000fffc0000 0x00000000fffc0000
                 0x0000000000018918 0x0000000000018918  RW     0x10000

to

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x00000000fffb0000 0x00000000fffb0000
                 0x0000000000028918 0x0000000000028918  RW     0x10000

Xilinx tools like XSDB or Bootgen are using program headers for loading ELF
to the right location and by above binutils change ELF is loaded to
incorrect location.

The patch is explicitly use u-boot-elf.lds (just cat now) for u-boot.elf
recreation which is called when REMAKE_ELF is setup.
By purpose u-boot-elf.lds doesn't contain OUTPUT_FORMAT/OUTPUT_ARCH to be
able to use by all archs.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Tested-By: Álvaro Fernández Rojas <noltari@gmail.com>

Kconfig

@@ -299,6 +299,11 @@ config ERR_PTR_OFFSET
 	  pointer values - up to 'MAX_ERRNO' bytes below this value must be
 	  unused/invalid addresses.
 
+config PLATFORM_ELFENTRY
+	string
+	default "__start" if MIPS
+	default "_start"
+
 endmenu		# General setup
 
 menu "Boot images"

Makefile

@@ -1647,18 +1647,17 @@ OBJCOPYFLAGS_u-boot-img-spl-at-end.bin := -I binary -O binary \
 u-boot-img-spl-at-end.bin: u-boot.img spl/u-boot-spl.bin FORCE
 	$(call if_changed,pad_cat)
 
-# Create a new ELF from a raw binary file.
-ifndef PLATFORM_ELFENTRY
-  PLATFORM_ELFENTRY = "_start"
-endif
 quiet_cmd_u-boot-elf ?= LD      $@
 	cmd_u-boot-elf ?= $(LD) u-boot-elf.o -o $@ \
-	--defsym=$(PLATFORM_ELFENTRY)=$(CONFIG_SYS_TEXT_BASE) \
+	-T u-boot-elf.lds --defsym=$(CONFIG_PLATFORM_ELFENTRY)=$(CONFIG_SYS_TEXT_BASE) \
 	-Ttext=$(CONFIG_SYS_TEXT_BASE)
-u-boot.elf: u-boot.bin
+u-boot.elf: u-boot.bin u-boot-elf.lds
 	$(Q)$(OBJCOPY) -I binary $(PLATFORM_ELFFLAGS) $< u-boot-elf.o
 	$(call if_changed,u-boot-elf)
 
+u-boot-elf.lds: arch/u-boot-elf.lds prepare FORCE
+	$(call if_changed_dep,cpp_lds)
+
 # MediaTek's ARM-based u-boot needs a header to contains its load address
 # which is parsed by the BootROM.
 # If the SPL build is enabled, the header will be added to the spl binary,

arch/mips/config.mk

@@ -36,7 +36,6 @@ CONFIG_STANDALONE_LOAD_ADDR	?= 0xffffffff80200000
 endif
 
 PLATFORM_CPPFLAGS += -D__MIPS__
-PLATFORM_ELFENTRY = "__start"
 PLATFORM_ELFFLAGS += -B mips $(OBJCOPYFLAGS)
 
 #

arch/u-boot-elf.lds

@@ -0,0 +1,9 @@
+ENTRY(CONFIG_PLATFORM_ELFENTRY)
+SECTIONS
+{
+	. = CONFIG_PLATFORM_ELFENTRY;
+
+	.data : {
+		*(.data*)
+	}
+}