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

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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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.

While I see Ubuntu 16.04 dropped, how is the "require a less broken
toolchain" addressed? By implicitly disabling xen.efi build on broken
toolchain? Maybe README should have a note about needing newer Binutils
for xen.efi? Currently it says just Binutils 2.25. There is a section
about optional build deps, maybe add there something like "GNU Binutils
X.Y (required for building xen.efi)", if the version is known, or at
least "GNU Binutils capable of producing non-broken PE files (required
for building xen.efi)" if the version is not known.

> 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.
>  
>  ### 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 $@
>  ifeq ($(CONFIG_XEN_IBT),y)
>  	$(SHELL) $(srctree)/tools/check-endbr.sh $@
>  endif
> diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
> index cd0602a79aaf..199adc1a0967 100644
> --- a/xen/arch/x86/arch.mk
> +++ b/xen/arch/x86/arch.mk
> @@ -95,13 +95,6 @@ EFI_LDFLAGS := $(patsubst -m%,-mi386pep,$(LDFLAGS)) --subsystem=10 --enable-long
>  LD_PE_check_cmd = $(call ld-option,$(EFI_LDFLAGS) --image-base=0x100000000 -o $(efi-check).efi $(efi-check).o)
>  XEN_BUILD_PE := $(LD_PE_check_cmd)
>  
> -# If the above failed, it may be merely because of the linker not dealing well
> -# with debug info. Try again with stripping it.
> -ifeq ($(CONFIG_DEBUG_INFO)-$(XEN_BUILD_PE),y-n)
> -EFI_LDFLAGS += --strip-debug
> -XEN_BUILD_PE := $(LD_PE_check_cmd)
> -endif
> -
>  ifeq ($(XEN_BUILD_PE),y)
>  
>  # Check if the linker produces fixups in PE by default
> 
> base-commit: 37df17d2f903503c619713eb01e488f2cb1a257f
> -- 
> 2.39.5
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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