[PATCH 2/2] firmware_loader: builtin: fail build on empty firmware

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

If an empty firmware file is supplied via CONFIG_EXTRA_FIRMWARE, the
build currently succeeds but creates an empty section. While the
firmware loader will not return such sections it is better to avoid
adding them in the first place.

Add a compile-time size check to the filechk_fwbin macro to abort the
build early if a 0-size firmware is encountered.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/base/firmware_loader/builtin/Makefile | 32 +++++++++++--------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/drivers/base/firmware_loader/builtin/Makefile b/drivers/base/firmware_loader/builtin/Makefile
index 6c067dedc01e..af5b1bbb31e4 100644
--- a/drivers/base/firmware_loader/builtin/Makefile
+++ b/drivers/base/firmware_loader/builtin/Makefile
@@ -16,20 +16,24 @@ ASM_ALIGN = $(if $(CONFIG_64BIT),3,2)
 PROGBITS  = $(if $(CONFIG_ARM),%,@)progbits
 
 filechk_fwbin = \
-	echo "/* Generated by $(src)/Makefile */"		;\
-	echo "    .section .rodata"				;\
-	echo "    .p2align 4"					;\
-	echo "_fw_$(FWSTR)_bin:"				;\
-	echo "    .incbin \"$(fwdir)/$(FWNAME)\""		;\
-	echo "_fw_end:"						;\
-	echo "    .section .rodata.str,\"aMS\",$(PROGBITS),1"	;\
-	echo "    .p2align $(ASM_ALIGN)"			;\
-	echo "_fw_$(FWSTR)_name:"				;\
-	echo "    .string \"$(FWNAME)\""			;\
-	echo "    .section .builtin_fw,\"a\",$(PROGBITS)"	;\
-	echo "    .p2align $(ASM_ALIGN)"			;\
-	echo "    $(ASM_WORD) _fw_$(FWSTR)_name"		;\
-	echo "    $(ASM_WORD) _fw_$(FWSTR)_bin"			;\
+	if [ ! -s "$(fwdir)/$(FWNAME)" ]; then				 \
+		echo "error: empty firmware: $(fwdir)/$(FWNAME)" >&2	;\
+		exit							;\
+	fi								;\
+	echo "/* Generated by $(src)/Makefile */"			;\
+	echo "    .section .rodata"					;\
+	echo "    .p2align 4"						;\
+	echo "_fw_$(FWSTR)_bin:"					;\
+	echo "    .incbin \"$(fwdir)/$(FWNAME)\""			;\
+	echo "_fw_end:"							;\
+	echo "    .section .rodata.str,\"aMS\",$(PROGBITS),1"		;\
+	echo "    .p2align $(ASM_ALIGN)"				;\
+	echo "_fw_$(FWSTR)_name:"					;\
+	echo "    .string \"$(FWNAME)\""				;\
+	echo "    .section .builtin_fw,\"a\",$(PROGBITS)"		;\
+	echo "    .p2align $(ASM_ALIGN)"				;\
+	echo "    $(ASM_WORD) _fw_$(FWSTR)_name"			;\
+	echo "    $(ASM_WORD) _fw_$(FWSTR)_bin"				;\
 	echo "    $(ASM_WORD) _fw_end - _fw_$(FWSTR)_bin"
 
 $(obj)/%.gen.S: FORCE
-- 
2.54.0.545.g6539524ca2-goog