[PATCHv2] ldnoexec: Add script to remove ET_EXEC flag from intermediate build objects

[Kevin O'Connor]

Add a script to remove the ET_EXEC flag from the 16bit and "32bit
segmented" intermediate objects.  This avoids build failures with some
linkers that will not allow linking these objects again.

Signed-off-by: Kevin O'Connor 
--

v2: Use python instead of python2 in the script header

---
 Makefile            |  9 +++++----
 scripts/ldnoexec.py | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100755 scripts/ldnoexec.py

diff --git a/Makefile b/Makefile
index c20be15..3d8943e 100644
--- a/Makefile
+++ b/Makefile
@@ -127,9 +127,10 @@ $(Q)printf '$(foreach i,$2,#include "$i"\n)' > $3.tmp.c
 $(Q)$(CC) -I. $1 $(CFLAGSWHOLE) -c $3.tmp.c -o $3
 endef

-%.strip.o: %.o
+%.noexec.o: %.o
    @echo "  Stripping $@"
-	$(Q)$(STRIP) $< -o $@
+	$(Q)$(STRIP) $< -o $<.strip.o
+	$(Q)$(PYTHON) ./scripts/ldnoexec.py $<.strip.o $@

$(OUT)%.s: %.c
    @echo "  Compiling to assembler $@"
@@ -185,9 +186,9 @@ $(OUT)rom32seg.o: $(OUT)code32seg.o $(OUT)romlayout32seg.lds
    @echo "  Linking $@"
    $(Q)$(LD) -T $(OUT)romlayout32seg.lds $< -o $@

-$(OUT)rom.o: $(OUT)rom16.strip.o $(OUT)rom32seg.strip.o $(OUT)code32flat.o $(OUT)romlayout32flat.lds
+$(OUT)rom.o: $(OUT)rom16.noexec.o $(OUT)rom32seg.noexec.o $(OUT)code32flat.o $(OUT)romlayout32flat.lds
    @echo "  Linking $@"
-	$(Q)$(LD) -N -T $(OUT)romlayout32flat.lds $(OUT)rom16.strip.o $(OUT)rom32seg.strip.o $(OUT)code32flat.o -o $@
+	$(Q)$(LD) -N -T $(OUT)romlayout32flat.lds $(OUT)rom16.noexec.o $(OUT)rom32seg.noexec.o $(OUT)code32flat.o -o $@

$(OUT)bios.bin.prep: $(OUT)rom.o scripts/checkrom.py
    @echo "  Prepping $@"
diff --git a/scripts/ldnoexec.py b/scripts/ldnoexec.py
new file mode 100755
index 0000000..6d4e14b
--- /dev/null
+++ b/scripts/ldnoexec.py
@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+# Script to remove EXEC flag from an ELF file
+#
+# Copyright (C) 2020  Kevin O'Connor 
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import os, optparse, sys
+
+FLAG_OFFSET = 16
+
+def main():
+    # Parse command-line arguments
+    usage = "%prog <input_file> <output_file>"
+    opts = optparse.OptionParser(usage)
+    options, args = opts.parse_args()
+    if len(args) != 2:
+        opts.error("Incorrect number of arguments")
+    infilename, outfilename = args
+    # Read input
+    f = open(infilename, "rb")
+    srcdata = f.read()
+    f.close()
+    # Update
+    outdata = bytearray(srcdata)
+    outdata[FLAG_OFFSET] = 0x01 # change ET_EXEC to ET_REL
+    # Write output
+    f = open(outfilename, "wb")
+    f.write(outdata)
+    f.close()
+
+if __name__ == '__main__':
+    main()