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Re: [PATCH 2/2] xen: Add CONFIG_GC_SECTIONS
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Wed, 10 Dec 2025 11:57:32 -0500
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- Cc: Victor Lira <victorm.lira@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Timothy Pearson <tpearson@xxxxxxxxxxxxxxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Bob Eshleman <bobbyeshleman@xxxxxxxxx>, "Connor Davis" <connojdavis@xxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Grygorii Strashko <grygorii_strashko@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 10 Dec 2025 16:57:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-12-10 03:17, Jan Beulich wrote:
On 09.12.2025 22:47, Jason Andryuk wrote:
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -469,10 +469,13 @@ all-symbols-$(CONFIG_FAST_SYMBOL_LOOKUP) += --sort-by-name
include $(srctree)/arch/$(SRCARCH)/arch.mk
+XEN_FINAL_LDFLAGS-$(CONFIG_GC_SECTIONS) := --gc-sections
+
# define new variables to avoid the ones defined in Config.mk
export XEN_CFLAGS := $(CFLAGS)
export XEN_AFLAGS := $(AFLAGS)
export XEN_LDFLAGS := $(LDFLAGS)
+export XEN_FINAL_LDFLAGS := $(LDFLAGS) $(XEN_FINAL_LDFLAGS-y)
export CFLAGS_UBSAN
Imo the introduction of XEN_FINAL_LDFLAGS would best be a separate, prereq
change. That could then also go in already while the KEEP() issue is still
being sorted.
The appending of --gc-sections should then also be truly appending, so make
sure that e.g. anything set by arch/$(SRCARCH)/arch.mk wouldn't be purged
again. IOW I think ahead of that include we want
XEN_FINAL_LDFLAGS-y :=
This all sounds fine, though with Anthony's response the variable name
may change.
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -680,4 +680,13 @@ config PM_STATS
Enable collection of performance management statistics to aid in
analyzing and tuning power/performance characteristics of the system
+config GC_SECTIONS
+ bool "Garbage Collect Sections"
+ select CC_SPLIT_SECTIONS
+ help
+ During final linking, garbage collect unused sections. This will
+ reduce the size of the final Xen binary
+
+ Only supported for ELF/Multiboot xen/xen.gz, not EFI xen.efi.
This last sentence is x86-centric, which it shouldn't be here (or it should
say that this is an x86-only aspect).
I also wonder whether this wouldn't better live next to CC_SPLIT_SECTIONS.
If I put it immediately after CC_SPLIT_SECTIONS, menuconfig puts it as a
top level option:
│ │ [*] Garbage Collect Sections
│ │ Architecture Features --->
│ │ Common Features --->
I thought Common Features was a better place for it.
Also, I think it should probably gain " if EXPERT" as well.
Thanks,
Jason
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