spl: add overall SPL size check

This adds a size check for SPL that can dynamically check generated
SPL binaries (including devicetree) for a size limit that ensures
this image plus global data, heap and stack fit in initial SRAM.

Since some of these sizes are not available to make, a new host tool
'spl_size_limit' is added that dumps the resulting maximum size for
an SPL binary to stdout. This tool is used in toplevel Makefile to
implement the size check on SPL binaries.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>

Kconfig

@@ -173,14 +173,6 @@ config TPL_SYS_MALLOC_F_LEN
 	  particular needs this to operate, so that it can allocate the
 	  initial serial device and any others that are needed.
 
-config SPL_SIZE_LIMIT
-	int "Maximum size of SPL image"
-	depends on SPL
-	default 0
-	help
-	  Specifies the maximum length of the U-Boot SPL image.
-	  If this value is zero, it is ignored.
-
 menuconfig EXPERT
 	bool "Configure standard U-Boot features (expert users)"
 	default y

Makefile

@@ -797,7 +797,7 @@ BOARD_SIZE_CHECK =
 endif
 
 ifneq ($(CONFIG_SPL_SIZE_LIMIT),0)
-SPL_SIZE_CHECK = @$(call size_check,$@,$(CONFIG_SPL_SIZE_LIMIT))
+SPL_SIZE_CHECK = @$(call size_check,$@,$$(tools/spl_size_limit))
 else
 SPL_SIZE_CHECK =
 endif
@@ -1782,6 +1782,7 @@ checkarmreloc: u-boot
 envtools: scripts_basic $(version_h) $(timestamp_h)
 	$(Q)$(MAKE) $(build)=tools/env
 
+tools-only: export TOOLS_ONLY=y
 tools-only: scripts_basic $(version_h) $(timestamp_h)
 	$(Q)$(MAKE) $(build)=tools
 

common/spl/Kconfig

@@ -25,6 +25,42 @@ config SPL_FRAMEWORK
 	  supports MMC, NAND and YMODEM and other methods loading of U-Boot
 	  and the Linux Kernel.  If unsure, say Y.
 
+config SPL_SIZE_LIMIT
+	hex "Maximum size of SPL image"
+	depends on SPL
+	default 0
+	help
+	  Specifies the maximum length of the U-Boot SPL image.
+	  If this value is zero, it is ignored.
+
+config SPL_SIZE_LIMIT_SUBTRACT_GD
+	bool "SPL image size check: provide space for global data"
+	depends on SPL_SIZE_LIMIT > 0
+	help
+	  If enabled, aligned size of global data is reserved in
+	  SPL_SIZE_LIMIT check to ensure such an image does not overflow SRAM
+	  if SPL_SIZE_LIMIT describes the size of SRAM available for SPL when
+	  pre-reloc global data is put into this SRAM, too.
+
+config SPL_SIZE_LIMIT_SUBTRACT_MALLOC
+	bool "SPL image size check: provide space for malloc() pool before relocation"
+	depends on SPL_SIZE_LIMIT > 0
+	help
+	  If enabled, SPL_SYS_MALLOC_F_LEN is reserved in SPL_SIZE_LIMIT check
+	  to ensure such an image does not overflow SRAM if SPL_SIZE_LIMIT
+	  describes the size of SRAM available for SPL when pre-reloc malloc
+	  pool is put into this SRAM, too.
+
+config SPL_SIZE_LIMIT_PROVIDE_STACK
+	hex "SPL image size check: provide stack space before relocation"
+	depends on SPL_SIZE_LIMIT > 0
+	default 0
+	help
+	  If set, this size is reserved in SPL_SIZE_LIMIT check to ensure such
+	  an image does not overflow SRAM if SPL_SIZE_LIMIT describes the size
+	  of SRAM available for SPL when the stack required before reolcation
+	  uses this SRAM, too.
+
 config HANDOFF
 	bool "Pass hand-off information from SPL to U-Boot proper"
 	depends on BLOBLIST

tools/Makefile

@@ -199,6 +199,10 @@ hostprogs-$(CONFIG_RISCV) += prelink-riscv
 hostprogs-y += fdtgrep
 fdtgrep-objs += $(LIBFDT_OBJS) fdtgrep.o
 
+ifneq ($(TOOLS_ONLY),y)
+hostprogs-y += spl_size_limit
+endif
+
 hostprogs-$(CONFIG_MIPS) += mips-relocs
 
 # We build some files with extra pedantic flags to try to minimize things

tools/spl_size_limit.c

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2019, Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
+ *
+ * This tool helps to return the size available for SPL image during build
+ */
+
+#include <generated/autoconf.h>
+#include <generated/generic-asm-offsets.h>
+
+int main(int argc, char *argv[])
+{
+	int spl_size_limit = 0;
+
+#ifdef CONFIG_SPL_SIZE_LIMIT
+	spl_size_limit = CONFIG_SPL_SIZE_LIMIT;
+#ifdef CONFIG_SPL_SIZE_LIMIT_SUBTRACT_GD
+	spl_size_limit -= GENERATED_GBL_DATA_SIZE;
+#endif
+#ifdef CONFIG_SPL_SIZE_LIMIT_SUBTRACT_MALLOC
+	spl_size_limit -= CONFIG_SPL_SYS_MALLOC_F_LEN;
+#endif
+#ifdef CONFIG_SPL_SIZE_LIMIT_PROVIDE_STACK
+	spl_size_limit -= CONFIG_SPL_SIZE_LIMIT_PROVIDE_STACK;
+#endif
+#endif
+
+	printf("%d", spl_size_limit);
+	return 0;
+}