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[PATCH 3/7] xen: remove -N from the linker command line

To: xen-devel@xxxxxxxxxxxxxxxxxxxx
From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
Date: Tue, 18 Mar 2025 18:35:43 +0100
Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Bob Eshleman <bobbyeshleman@xxxxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Delivery-date: Tue, 18 Mar 2025 17:36:21 +0000
List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

It's unclear why -N is being used in the first place.  It was added by
commit 40828c657dd0c back in 2004 without any justification.

When building a PE image it's actually detrimental to forcefully set the
.text section as writable.  The GNU LD man page contains the following
warning regarding the -N option:

> Note: Although a writable text section is allowed for PE-COFF targets, it
> does not conform to the format specification published by Microsoft.

Remove the usage of -N uniformly on all architectures, assuming that the
addition was simply done as a copy and paste of the original x86 linking
rune.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/arm/Makefile   |  6 +++---
 xen/arch/ppc/Makefile   |  6 +++---
 xen/arch/riscv/Makefile |  6 +++---
 xen/arch/x86/Makefile   | 12 ++++++------
 4 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 4837ad467a06..129a109d6ec5 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -97,19 +97,19 @@ ifeq ($(CONFIG_ARM_64),y)
 endif
 
 $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(objtree)/common/symbols-dummy.o -o $(dot-target).0
        $(NM) -pa --format=sysv $(dot-target).0 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).0.S
        $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(dot-target).0.o -o $(dot-target).1
        $(NM) -pa --format=sysv $(dot-target).1 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).1.S
        $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(dot-target).1.o -o $@
        $(NM) -pa --format=sysv $@ \
                | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
diff --git a/xen/arch/ppc/Makefile b/xen/arch/ppc/Makefile
index 655d212f6687..cf27bcebb25a 100644
--- a/xen/arch/ppc/Makefile
+++ b/xen/arch/ppc/Makefile
@@ -12,19 +12,19 @@ $(TARGET): $(TARGET)-syms
        cp -f $< $@
 
 $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(objtree)/common/symbols-dummy.o -o $(dot-target).0
        $(NM) -pa --format=sysv $(dot-target).0 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).0.S
        $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(dot-target).0.o -o $(dot-target).1
        $(NM) -pa --format=sysv $(dot-target).1 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).1.S
        $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(dot-target).1.o -o $@
        $(NM) -pa --format=sysv $@ \
                | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index b0c8270a9947..516f5d505ca8 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -16,19 +16,19 @@ $(TARGET): $(TARGET)-syms
        $(OBJCOPY) -O binary -S $< $@
 
 $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(objtree)/common/symbols-dummy.o -o $(dot-target).0
        $(NM) -pa --format=sysv $(dot-target).0 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).0.S
        $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< \
            $(dot-target).0.o -o $(dot-target).1
        $(NM) -pa --format=sysv $(dot-target).1 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).1.S
        $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(dot-target).1.o -o $@
        $(NM) -pa --format=sysv $@ \
                | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index f59c9665fdd0..c2f1dcf301d6 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -139,19 +139,19 @@ $(TARGET): $(TARGET)-syms $(efi-y) $(obj)/boot/mkelf32
 CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_EFI
 
 $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(objtree)/common/symbols-dummy.o -o $(dot-target).0
        $(NM) -pa --format=sysv $(dot-target).0 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).0.S
        $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(dot-target).0.o -o $(dot-target).1
        $(NM) -pa --format=sysv $(dot-target).1 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort 
$(syms-warn-dup-y) \
                > $(dot-target).1.S
        $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds -N $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
            $(orphan-handling-y) $(dot-target).1.o -o $@
        $(NM) -pa --format=sysv $@ \
                | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
@@ -212,7 +212,7 @@ ifeq ($(CONFIG_DEBUG_INFO),y)
        $(if $(filter --strip-debug,$(EFI_LDFLAGS)),echo,:) "Will strip debug 
info from $(@F)"
 endif
        $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
-                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds -N $< 
$(relocs-dummy) \
+                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $< 
$(relocs-dummy) \
                        $(objtree)/common/symbols-dummy.o $(note_file_option) \
                        -o $(dot-target).$(base).0 &&) :
        $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).0) \
@@ -222,7 +222,7 @@ endif
                > $(dot-target).0s.S
        $(MAKE) $(build)=$(@D) .$(@F).0r.o .$(@F).0s.o
        $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
-                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds -N $< \
+                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $< \
                        $(dot-target).0r.o $(dot-target).0s.o 
$(note_file_option) \
                        -o $(dot-target).$(base).1 &&) :
        $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).1) \
@@ -231,7 +231,7 @@ endif
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).1s.S
        $(MAKE) $(build)=$(@D) .$(@F).1r.o .$(@F).1s.o
-       $(LD) $(call EFI_LDFLAGS,$(VIRT_BASE)) -T $(obj)/efi.lds -N $< \
+       $(LD) $(call EFI_LDFLAGS,$(VIRT_BASE)) -T $(obj)/efi.lds $< \
              $(dot-target).1r.o $(dot-target).1s.o $(orphan-handling-y) \
              $(note_file_option) -o $@
        $(NM) -pa --format=sysv $@ \
-- 
2.48.1

Follow-Ups:
- Re: [PATCH 3/7] xen: remove -N from the linker command line
  - From: Oleksii Kurochko
- Re: [PATCH 3/7] xen: remove -N from the linker command line
  - From: Jan Beulich
- Re: [PATCH 3/7] xen: remove -N from the linker command line
  - From: Andrew Cooper

References:
- [PATCH 0/7] x86: generate xen.efi image with no write-execute sections
  - From: Roger Pau Monne

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