boot/syslinux: fix gcc-10.x compile

Add two patches ([1], [2]) taken from the fedora syslinux package ([3]) to fix
compile/linking with gcc-10.x compiler.

[1] https://src.fedoraproject.org/rpms/syslinux/raw/rawhide/f/0005-Workaround-multiple-definition-of-symbol-errors.patch
[2] https://src.fedoraproject.org/rpms/syslinux/raw/rawhide/f/0006-Replace-builtin-strlen-that-appears-to-get-optimized.patch
[3] https://src.fedoraproject.org/rpms/syslinux/tree/rawhide

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

boot/syslinux/0016-Workaround-multiple-definition-of-symbol-errors.patch

@@ -0,0 +1,126 @@
+From 16f293d67eace501c98494976030f4319778ebf5 Mon Sep 17 00:00:00 2001
+From: Merlin Mathesius <mmathesi@redhat.com>
+Date: Wed, 13 May 2020 08:02:27 -0500
+Subject: [PATCH] Workaround multiple definition of symbol errors
+
+[From https://src.fedoraproject.org/rpms/syslinux/raw/rawhide/f/0005-Workaround-multiple-definition-of-symbol-errors.patch
+ plus adding '-z muldefs' for gpxe]
+Signed-off-by: Peter Seiderer <ps.report@gmx.net>
+---
+ com32/cmenu/Makefile           | 2 +-
+ com32/elflink/ldlinux/Makefile | 2 +-
+ com32/gpllib/Makefile          | 2 +-
+ com32/hdt/Makefile             | 2 +-
+ core/Makefile                  | 2 +-
+ dos/Makefile                   | 2 +-
+ efi/Makefile                   | 2 +-
+ gpxe/src/arch/i386/Makefile    | 2 +-
+ 8 files changed, 8 insertions(+), 8 deletions(-)
+
+diff --git a/com32/cmenu/Makefile b/com32/cmenu/Makefile
+index 6bb52316..66cdd649 100644
+--- a/com32/cmenu/Makefile
++++ b/com32/cmenu/Makefile
+@@ -49,7 +49,7 @@ makeoutputdirs:
+ 	@mkdir -p $(OBJ)/libmenu
+ 
+ libmenu/libmenu.elf: $(LIBMENU)
+-	$(LD) -shared $(LDFLAGS) -soname $(patsubst %.elf,%.c32,$(@F)) \
++	$(LD) -shared $(LDFLAGS) -z muldefs -soname $(patsubst %.elf,%.c32,$(@F)) \
+ 		-o $@ $^
+ 
+ tidy dist:
+diff --git a/com32/elflink/ldlinux/Makefile b/com32/elflink/ldlinux/Makefile
+index d948da43..67434a1f 100644
+--- a/com32/elflink/ldlinux/Makefile
++++ b/com32/elflink/ldlinux/Makefile
+@@ -33,7 +33,7 @@ endif
+ all: $(BTARGET) ldlinux_lnx.a
+ 
+ ldlinux.elf : $(OBJS)
+-	$(LD) $(LDFLAGS) -soname $(SONAME) -o $@ $^ $(LIBS)
++	$(LD) $(LDFLAGS) -z muldefs -soname $(SONAME) -o $@ $^ $(LIBS)
+ 
+ LNXCFLAGS += -D__export='__attribute__((visibility("default")))'
+ LNXLIBOBJS = get_key.lo
+diff --git a/com32/gpllib/Makefile b/com32/gpllib/Makefile
+index e3e30d76..17520a1e 100644
+--- a/com32/gpllib/Makefile
++++ b/com32/gpllib/Makefile
+@@ -24,7 +24,7 @@ makeoutputdirs:
+ 		$(addprefix $(OBJ),$(sort $(dir $(LIBOBJS)))),$(b))
+ 
+ libgpl.elf : $(LIBOBJS)
+-	$(LD) -shared $(LDFLAGS) -soname $(patsubst %.elf,%.c32,$(@F)) -o $@ $^
++	$(LD) -shared $(LDFLAGS) -z muldefs -soname $(patsubst %.elf,%.c32,$(@F)) -o $@ $^
+ 
+ tidy dist clean:
+ 	find . \( -name \*.o -o -name .\*.d -o -name \*.tmp \) -print0 | \
+diff --git a/com32/hdt/Makefile b/com32/hdt/Makefile
+index 80f2d0a0..8509cd96 100644
+--- a/com32/hdt/Makefile
++++ b/com32/hdt/Makefile
+@@ -52,7 +52,7 @@ QEMU			?= qemu-kvm
+ all: $(MODULES) $(TESTFILES)
+ 
+ hdt.elf : $(OBJS) $(LIBS) $(C_LIBS)
+-	$(LD) $(LDFLAGS) -o $@ $^
++	$(LD) $(LDFLAGS) -z muldefs -o $@ $^
+ 
+ memtest:
+ 	-[ ! -f $(FLOPPY_DIR)/$(MEMTEST) ] && $(WGET) $(MEMTEST_URL) -O $(FLOPPY_DIR)/$(MEMTEST)
+diff --git a/core/Makefile b/core/Makefile
+index ad0acb5a..3bee4dc9 100644
+--- a/core/Makefile
++++ b/core/Makefile
+@@ -164,7 +164,7 @@ AUXLIBS = libisolinux.a libisolinux-debug.a libldlinux.a \
+ LDSCRIPT = $(SRC)/$(ARCH)/syslinux.ld
+ 
+ %.elf: %.o $(LIBDEP) $(LDSCRIPT) $(AUXLIBS)
+-	$(LD) $(LDFLAGS) -Bsymbolic $(LD_PIE) -E --hash-style=gnu -T $(LDSCRIPT) -M -o $@ $< \
++	$(LD) $(LDFLAGS) -z muldefs -Bsymbolic $(LD_PIE) -E --hash-style=gnu -T $(LDSCRIPT) -M -o $@ $< \
+ 		--start-group $(LIBS) $(subst $(*F).elf,lib$(*F).a,$@) --end-group \
+ 		> $(@:.elf=.map)
+ 	$(OBJDUMP) -h $@ > $(@:.elf=.sec)
+diff --git a/dos/Makefile b/dos/Makefile
+index b9c337d5..2af87346 100644
+--- a/dos/Makefile
++++ b/dos/Makefile
+@@ -19,7 +19,7 @@ include $(MAKEDIR)/embedded.mk
+ CFLAGS	+= -D__MSDOS__ -mregparm=3 -DREGPARM=3
+ # CFLAGS  += -DDEBUG
+ 
+-LDFLAGS	 = -T $(SRC)/dosexe.ld
++LDFLAGS	 = -T $(SRC)/dosexe.ld -z muldefs
+ OPTFLAGS = -g
+ INCLUDES = -include code16.h -nostdinc -iwithprefix include \
+ 	   -I$(SRC) -I$(SRC)/.. -I$(SRC)/../libfat \
+diff --git a/efi/Makefile b/efi/Makefile
+index d24d16db..7c714ebf 100644
+--- a/efi/Makefile
++++ b/efi/Makefile
+@@ -70,7 +70,7 @@ $(OBJS): subdirs
+ BTARGET  = syslinux.efi
+ 
+ syslinux.so: $(OBJS) $(CORE_OBJS) $(LIB_OBJS)
+-	$(LD) $(LDFLAGS) --strip-debug -o $@ $^ -lgnuefi -lefi
++	$(LD) $(LDFLAGS) -z muldefs --strip-debug -o $@ $^ -lgnuefi -lefi
+ 
+ # We need to rename the .hash section because the EFI firmware
+ # linker really doesn't like it.
+diff --git a/gpxe/src/arch/i386/Makefile b/gpxe/src/arch/i386/Makefile
+index dd8da802..be1d00ff 100644
+--- a/gpxe/src/arch/i386/Makefile
++++ b/gpxe/src/arch/i386/Makefile
+@@ -55,7 +55,7 @@ ASFLAGS		+= --32
+ ifeq ($(HOST_OS),FreeBSD)
+ LDFLAGS		+= -m elf_i386_fbsd
+ else
+-LDFLAGS		+= -m elf_i386
++LDFLAGS		+= -z muldefs -m elf_i386
+ endif
+ 
+ # EFI requires -fshort-wchar, and nothing else currently uses wchar_t
+-- 
+2.30.1
+

boot/syslinux/0017-Replace-builtin-strlen-that-appears-to-get-optimized.patch

@@ -0,0 +1,42 @@
+From 698a6ce88524b727d265b204d648e78d8acb485c Mon Sep 17 00:00:00 2001
+From: Merlin Mathesius <mmathesi@redhat.com>
+Date: Wed, 13 May 2020 11:58:37 -0500
+Subject: [PATCH] Replace builtin strlen that appears to get optimized away
+
+[From https://src.fedoraproject.org/rpms/syslinux/raw/rawhide/f/0006-Replace-builtin-strlen-that-appears-to-get-optimized.patch]
+Signed-off-by: Peter Seiderer <ps.report@gmx.net>
+---
+ dos/string.h | 12 +++++++++++-
+ 1 file changed, 11 insertions(+), 1 deletion(-)
+
+diff --git a/dos/string.h b/dos/string.h
+index f648de2d..407d0233 100644
+--- a/dos/string.h
++++ b/dos/string.h
+@@ -5,12 +5,22 @@
+ #ifndef _STRING_H
+ #define _STRING_H
+ 
++#include <stddef.h>
++
+ /* Standard routines */
+ #define memcpy(a,b,c)	__builtin_memcpy(a,b,c)
+ #define memmove(a,b,c)	__builtin_memmove(a,b,c)
+ #define memset(a,b,c)	__builtin_memset(a,b,c)
+ #define strcpy(a,b)	__builtin_strcpy(a,b)
+-#define strlen(a)	__builtin_strlen(a)
++#define strlen(a)	inline_strlen(a)
++
++/* replacement for builtin strlen that appears to get optimized away */
++static inline size_t inline_strlen(const char *str)
++{
++    size_t l;
++    for (l = 0; *str++; l++);
++    return l;
++}
+ 
+ /* This only returns true or false */
+ static inline int memcmp(const void *__m1, const void *__m2, unsigned int __n)
+-- 
+2.30.1
+