Re: [PATCH for-4.22] xen/x86: Always strip xen.efi

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Jun 08, 2026 at 06:31:08PM +0100, Andrew Cooper wrote:
> From: Frediano Ziglio <frediano.ziglio@citrix.com>
> 
> xen.efi with debugging symbols is ~45MB, down to ~9.3MB when stripped.
> Multiple firmwares (as seen by QubesOS, Trenchboot, and XenServer) are unable
> to boot xen.efi when debugging symbols are included.
> 
> Either way, having debug symbols by default is abnormal and contrary to how
> the non-EFI path works.
> 
> Produce xen-syms.efi unconditionally, just like xen-syms.  If
> CONFIG_DEBUG_INFO is enabled, these will contain debug symbols, and if not,
> then not.  When xen-syms is processed by mkelf32, the debug symbols are simply
> discarded.  For xen-syms.efi, call $(STRIP) to produce xen.efi.
> 
> Some old versions of binutils ld managed to produce efi files which the
> matching version of strip couldn't process.  This includes Binutils 2.26
> included in Ubuntu 16.04.  Delete the workaround for this bug, and require a
> less broken toolchain.

We should then bump the minimum required GNU binutils version in the
README, as strip is also part of the binutils suite itself?

> 
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Jan Beulich <jbeulich@suse.com>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: Teddy Astie <teddy.astie@vates.tech>
> CC: Frediano Ziglio <frediano.ziglio@citrix.com>
> CC: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> CC: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> CC: Daniel P. Smith <dpsmith@apertussolutions.com>
> 
> For 4.22.  This was posted previously as
> 
>   https://lore.kernel.org/xen-devel/20251208133945.61375-1-frediano.ziglio@citrix.com/T/#u
> 
> but merged the two patches and rewritten the commit message to make it clear
> that failing to strip xen.efi is causing boot failures.
> 
> Previously xen.efi.elf was produced but it's unclear why, and unnecessaerily
> different, so I've dropped it.
> 
> While this does want backporting, it can't be.  Xen 4.21 and older still build
> test with Ubuntu 16.04 and choke
> ---
>  .gitignore            |  1 +
>  CHANGELOG.md          |  3 +++
>  docs/misc/efi.pandoc  |  8 +-------
>  xen/Kconfig.debug     |  9 ++-------
>  xen/Makefile          | 19 -------------------
>  xen/arch/x86/Makefile | 11 ++++-------
>  xen/arch/x86/arch.mk  |  7 -------
>  7 files changed, 11 insertions(+), 47 deletions(-)
> 
> diff --git a/.gitignore b/.gitignore
> index bfc7bdf043c3..49e2c6961768 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -224,6 +224,7 @@ tools/flask/policy/xenpolicy-*
>  xen/xen
>  xen/suppression-list.txt
>  xen/xen-syms
> +xen/xen-syms.efi
>  xen/xen-syms.map
>  xen/xen.*
>  
> diff --git a/CHANGELOG.md b/CHANGELOG.md
> index 5cf19372a361..71d1e9ab8c69 100644
> --- a/CHANGELOG.md
> +++ b/CHANGELOG.md
> @@ -14,6 +14,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
>   - On x86:
>     - Enable pf-fixup option by default for PVH dom0.
>     - The libxenguest bzImage loader now uses the system liblz4 library.
> +   - The install-time environment variable INSTALL_EFI_STRIP no longer exists.
> +     xen.efi is always stripped, while the symbols remain available in
> +     xen-syms.efi.

This is not x86-only, AFAICT ARM also seems to have a rune to generate
a xen.efi image, which will be affected by the removal of
INSTALL_EFI_STRIP?

>  
>  ### Added
>   - Support for per-domain Xenstore quota in C xenstored (includes
> diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
> index 8198a7f063cf..0a3fd67076fc 100644
> --- a/docs/misc/efi.pandoc
> +++ b/docs/misc/efi.pandoc
> @@ -20,13 +20,7 @@ Xen to load the configuration file even if multiboot modules are found.
>  Once built, `make install-xen` will place the resulting binary directly into
>  the EFI boot partition, provided `EFI_VENDOR` is set in the environment (and
>  `EFI_MOUNTPOINT` is overridden as needed, should the default of `/boot/efi` not
> -match your system). When built with debug info, the binary can be quite large.
> -Setting `INSTALL_EFI_STRIP=1` in the environment will cause it to be stripped
> -of debug info in the process of installing. `INSTALL_EFI_STRIP` can also be set
> -to any combination of options suitable to pass to `strip`, in case the default
> -ones don't do. The xen.efi binary will also be installed in `/usr/lib64/efi/`,
> -unless `EFI_DIR` is set in the environment to override this default. This
> -binary will not be stripped in the process.
> +match your system).
>  
>  The binary itself will require a configuration file (names with the `.efi`
>  extension of the binary's name replaced by `.cfg`, and - until an existing
> diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
> index d900d926c555..fcd3fc3d36cf 100644
> --- a/xen/Kconfig.debug
> +++ b/xen/Kconfig.debug
> @@ -147,12 +147,7 @@ config DEBUG_INFO
>  	  Say Y here if you want to build Xen with debug information. This
>  	  information is needed e.g. for doing crash dump analysis of the
>  	  hypervisor via the "crash" tool.
> -	  Saying Y will increase the size of the xen-syms and xen.efi
> -	  binaries. In case the space on the EFI boot partition is rather
> -	  limited, you may want to install a stripped variant of xen.efi in
> -	  the EFI boot partition (look for "INSTALL_EFI_STRIP" in
> -	  docs/misc/efi.pandoc for more information - when not using
> -	  "make install-xen" for installing xen.efi, stripping needs to be
> -	  done outside the Xen build environment).
> +	  Saying Y will increase the size of the xen-syms and xen-syms.efi
> +	  binaries.
>  
>  endmenu
> diff --git a/xen/Makefile b/xen/Makefile
> index 1f11610b5f68..0f9b56fc399d 100644
> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -493,22 +493,6 @@ endif
>  .PHONY: _build
>  _build: $(TARGET)$(CONFIG_XEN_INSTALL_SUFFIX)
>  
> -# Strip
> -#
> -# INSTALL_EFI_STRIP, if defined, will cause xen.efi to be stripped before it
> -# is installed. If INSTALL_EFI_STRIP is '1', then the default option(s) below
> -# will be used. Otherwise, INSTALL_EFI_STRIP value will be used as the
> -# option(s) to the strip command.
> -ifdef INSTALL_EFI_STRIP
> -
> -ifeq ($(INSTALL_EFI_STRIP),1)
> -efi-strip-opt := --strip-debug --keep-file-symbols
> -else
> -efi-strip-opt := $(INSTALL_EFI_STRIP)
> -endif
> -
> -endif
> -
>  .PHONY: _install
>  _install: D=$(DESTDIR)
>  _install: T=$(notdir $(TARGET))
> @@ -535,9 +519,6 @@ _install: $(TARGET)$(CONFIG_XEN_INSTALL_SUFFIX)
>  		ln -sf $(T)-$(XEN_FULLVERSION).efi $(D)$(EFI_DIR)/$(T)-$(XEN_VERSION).efi; \
>  		ln -sf $(T)-$(XEN_FULLVERSION).efi $(D)$(EFI_DIR)/$(T).efi; \
>  		if [ -n '$(EFI_MOUNTPOINT)' -a -n '$(EFI_VENDOR)' ]; then \
> -			$(if $(efi-strip-opt), \
> -			     $(STRIP) $(efi-strip-opt) -p -o $(TARGET).efi.stripped $(TARGET).efi && \
> -			     $(INSTALL_DATA) $(TARGET).efi.stripped $(D)$(EFI_MOUNTPOINT)/efi/$(EFI_VENDOR)/$(T)-$(XEN_FULLVERSION).efi ||) \
>  			$(INSTALL_DATA) $(TARGET).efi $(D)$(EFI_MOUNTPOINT)/efi/$(EFI_VENDOR)/$(T)-$(XEN_FULLVERSION).efi; \
>  		elif [ "$(D)" = "$(patsubst $(shell cd $(XEN_ROOT) && pwd)/%,%,$(D))" ]; then \
>  			echo 'EFI installation only partially done (EFI_VENDOR not set)' >&2; \
> diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> index 47dd6c50fe88..01ed7302202e 100644
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -196,10 +196,7 @@ note_file_option ?= $(note_file)
>  
>  extra-$(XEN_BUILD_PE) += efi.lds
>  ifeq ($(XEN_BUILD_PE),y)
> -$(TARGET).efi: $(objtree)/prelink.o $(note_file) $(obj)/efi.lds $(obj)/efi/relocs-dummy.o $(obj)/efi/mkreloc
> -ifeq ($(CONFIG_DEBUG_INFO),y)
> -	$(if $(filter --strip-debug,$(EFI_LDFLAGS)),echo,:) "Will strip debug info from $(@F)"
> -endif
> +$(TARGET)-syms.efi: $(objtree)/prelink.o $(note_file) $(obj)/efi.lds $(obj)/efi/relocs-dummy.o $(obj)/efi/mkreloc
>  	$(objtree)/tools/symbols $(all_symbols) --source-name=$(@F).S --empty \
>  		> $(dot-target).0s.S
>  	$(MAKE) $(build)=$(@D) .$(@F).0s.o
> @@ -233,10 +230,10 @@ endif
>  	$(NM) -pa --format=sysv $@ \
>  		| $(objtree)/tools/symbols --all-symbols --xensyms --sysv --sort \
>  		> $@.map
> -ifeq ($(CONFIG_DEBUG_INFO),y)
> -	$(if $(filter --strip-debug,$(EFI_LDFLAGS)),:$(space))$(OBJCOPY) -O elf64-x86-64 $@ $@.elf
> -endif
>  	rm -f $(dot-target).[0-9]* $(@D)/..$(@F).[0-9]*
> +
> +$(TARGET).efi: $(TARGET)-syms.efi
> +	$(STRIP) $< -o $@

I'm not that good with Makefiles, but don't we need a similar
adjustment to strip the .efi generated for ARM?

Thanks, Roger.