On 2025-12-08 03:56, Jan Beulich wrote:
On 05.12.2025 23:28, Jason Andryuk wrote:
When linking to create xen-syms, add --gc-sections to garbage collect
unused stuff.
What about xen.efi?
I tried briefly and it fails to link. The GCC manual says it is
considered experimental for PE and COFF.
I just added into EFI_LDFLAGS:
CC .xen.efi.0s.o
ld -mi386pep --no-warn-rwx-segments --subsystem=10
--enable-long-section-names --disable-high-entropy-va --dynamicbase
--image-base=0xffff82d040000000 --stack=0,0 --heap=0,0
--section-alignment=0x200000 --file-alignment=0x20
--major-image-version=4 --minor-image-version=22 --major-os-version=2
--minor-os-version=0 --major-subsystem-version=2
--minor-subsystem-version=0 --gc-sections --print-gc-sections
--build-id=sha1 -T arch/x86/efi.lds prelink.o ./.xen.efi.0s.o -b
pe-x86-64 arch/x86/efi/buildid.o -o ./.xen.efi.0xffff82d040000000.0 && :
ld: kexec_reloc is too large
ld: kexec_reloc is too large
ld:
prelink.o:/home/jandryuk/xen/xen/arch/x86/boot/head.S:60:(.text.header+0x48):
undefined reference to `start'
Relies on CONFIG_CC_SPLIT_SECTIONS
Yet still ...
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -137,18 +137,21 @@ $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
$(objtree)/tools/symbols $(all_symbols) --empty > $(dot-target).0.S
$(MAKE) $(build)=$(@D) $(dot-target).0.o
$(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
+ --gc-sections \
... you pass the option unconditionally. Which may be fine from a functional
perspective (little if anything will be saved), but besides being a little
inconsistent with the description I also wonder whether the option won't have
unwanted side effects (longer linking time, bigger working set).
$(dot-target).0.o -o $(dot-target).0
$(NM) -pa --format=sysv $(dot-target).0 \
| $(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 $< $(build_id_linker) \
+ --gc-sections \
$(dot-target).1.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).2.S
$(MAKE) $(build)=$(@D) $(dot-target).2.o
$(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
+ --gc-sections \
$(orphan-handling-y) $(dot-target).2.o -o $@
$(NM) -pa --format=sysv $@ \
Rather than having to alter three locations (plus another three for xen.efi,
plus another three for every other architecture that would want to follow
suit), should we perhaps introduce $(XEN_FINAL_LDFLAGS) or some such? That
could then have --gc-sections conditionally upon CONFIG_CC_SPLIT_SECTIONS.
Yes, I thought something like thiat would be better after posting.
I further wonder whether the use of the option wouldn't want gating by its
own Kconfig control (dependent upon CC_SPLIT_SECTIONS). If nothing else than
to have an easy workaround if either we had a usage bug (e.g. a missing
KEEP() somewhere in a linker script) or there was a related bug in the
linker that we end up being affected by.
Makes sense.
Thanks,
Jason
