Re: [PATCH 5.15 5.10 5.4 v2] kbuild: fix Build ID if CONFIG_MODVERSIONS

[Tom Saeger <tom.saeger@oracle.com>]

On Thu, Jan 12, 2023 at 01:00:57PM +0100, Greg Kroah-Hartman wrote:
> On Mon, Jan 09, 2023 at 12:36:15PM -0600, Tom Saeger wrote:
> > On Thu, Dec 22, 2022 at 07:01:11AM +0100, Greg Kroah-Hartman wrote:
> > > On Wed, Dec 21, 2022 at 02:52:10PM -0600, Tom Saeger wrote:
> > > > On Wed, Dec 21, 2022 at 05:31:51PM +0100, Greg Kroah-Hartman wrote:
> > > > > On Thu, Dec 15, 2022 at 04:18:18PM -0700, Tom Saeger wrote:
> > > > > > Backport of:
> > > > > > commit 0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments")
> > > > > > breaks arm64 Build ID when CONFIG_MODVERSIONS=y for all kernels
> > > > > > from: commit e4484a495586 ("Merge tag 'kbuild-fixes-v5.0' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
> > > > > > until: commit df202b452fe6 ("Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
> > > > > > 
> > > > > > Linus's tree doesn't have this issue since 0d362be5b142 was merged
> > > > > > after df202b452fe6 which included:
> > > > > > commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS")
> > > > > 
> > > > > Why can't we add this one instead of a custom change?
> > > > 
> > > > I quickly abandoned that route - there are too many dependencies.
> > > 
> > > How many?  Why?  Whenever we add a "this is not upstream" patch, 90% of
> > > the time it is incorrect and causes problems (merge issues included.)
> > > So please please please let's try to keep in sync with what is in
> > > Linus's tree.
> > > 
> > > thanks,
> > > 
> > > greg k-h
> > 
> > Ok - I spent some time on this.
> > 
> > The haystack I searched:
> > 
> >   git rev-list --grep="masahiroy/linux-kbuild" v5.15..v5.19-rc1 | while read -r CID ; do git rev-list "${CID}^-" ; done | wc -l
> >   182
> > 
> > I have 54 of those 182 applied to 5.15.85, and this works in my
> > limited build testing (x86_64 gcc, arm64 gcc, arm64 clang).
> > 
> > Specifically:
> > 
> > 
> > cbfc9bf3223f genksyms: adjust the output format to modpost
> > e7c9c2630e59 kbuild: stop merging *.symversions
> > 1d788aa800c7 kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS
> > 8a01c770955b modpost: extract symbol versions from *.cmd files
> > a8ade6b33772 modpost: add sym_find_with_module() helper
> > a9639fe6b516 modpost: change the license of EXPORT_SYMBOL to bool type
> > 04804878f631 modpost: remove left-over cross_compile declaration
> > 3388b8af9698 kbuild: record symbol versions in *.cmd files
> > 4ff3946463a0 kbuild: generate a list of objects in vmlinux
> > 074617e2ad6a modpost: move *.mod.c generation to write_mod_c_files()
> > 81b78cb6e821 modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header
> > 9df4f00b53b4 modpost: split new_symbol() to symbol allocation and hash table addition
> > 85728bcbc500 modpost: make sym_add_exported() always allocate a new symbol
> > 82aa2b4d30af modpost: make multiple export error
> > 6cc962f0a175 modpost: dump Module.symvers in the same order of modules.order
> > 39db82cea373 modpost: traverse the namespace_list in order
> > 45dc7b236dcb modpost: use doubly linked list for dump_lists
> > 2a322506403a modpost: traverse unresolved symbols in order
> > a85718443348 modpost: add sym_add_unresolved() helper
> > 5c44b0f89c82 modpost: traverse modules in order
> > a0b68f6655f2 modpost: import include/linux/list.h
> > ce9f4d32be4e modpost: change mod->gpl_compatible to bool type
> > f9fe36a515ca modpost: use bool type where appropriate
> > 46f6334d7055 modpost: move struct namespace_list to modpost.c
> > afa24c45af49 modpost: retrieve the module dependency and CRCs in check_exports()
> > a8f687dc3ac2 modpost: add a separate error for exported symbols without definition
> > f97f0e32b230 modpost: remove stale comment about sym_add_exported()
> > 0af2ad9d11c3 modpost: do not write out any file when error occurred
> > 09eac5681c02 modpost: use snprintf() instead of sprintf() for safety
> > ee07380110f2 kbuild: read *.mod to get objects passed to $(LD) or $(AR)
> > 97976e5c6d55 kbuild: make *.mod not depend on *.o
> > 0d4368c8da07 kbuild: get rid of duplication in *.mod files
> > 55f602f00903 kbuild: split the second line of *.mod into *.usyms
> > ea9730eb0788 kbuild: reuse real-search to simplify cmd_mod
> > 1eacf71f885a kbuild: make multi_depend work with targets in subdirectory
> > 19c2b5b6f769 kbuild: reuse suffix-search to refactor multi_depend
> > 75df07a9133d kbuild: refactor cmd_modversions_S
> > 53257fbea174 kbuild: refactor cmd_modversions_c
> > b6e50682c261 modpost: remove annoying namespace_from_kstrtabns()
> > 1002d8f060b0 modpost: remove redundant initializes for static variables
> > 921fbb7ab714 modpost: move export_from_secname() call to more relevant place
> > f49c0989e01b modpost: remove useless export_from_sec()
> > 7a98501a77db kbuild: do not remove empty *.symtypes explicitly
> > 500f1b31c16f kbuild: factor out genksyms command from cmd_gensymtypes_{c,S}
> > e04fcad29aa3 kallsyms: ignore all local labels prefixed by '.L'
> > 9e01f7ef15d2 kbuild: drop $(size_append) from cmd_zstd
> > 054133567480 kbuild: do not include include/config/auto.conf from shell scripts
> > 34d14831eecb kbuild: stop using config_filename in scripts/Makefile.modsign
> > 75155bda5498 kbuild: use more subdir- for visiting subdirectories while cleaning
> > 1a3f00cd3be8 kbuild: reuse $(cmd_objtool) for cmd_cc_lto_link_modules
> > 47704d10e997 kbuild: detect objtool update without using .SECONDEXPANSION
> > 7a89d034ccc6 kbuild: factor out OBJECT_FILES_NON_STANDARD check into a macro
> > 3cbbf4b9d188 kbuild: store the objtool command in *.cmd files
> > 467f0d0aa6b4 kbuild: rename __objtool_obj and reuse it for cmd_cc_lto_link_modules
> > 
> > There may be a few more patches post v5.19-rc1 for Fixes.
> > I haven't tried minimizing the 54.
> > 
> > Greg - is 54 too many?
> 
> Yes.
> 
> How about we just revert the original problem commit here to solve this
> mess?  Wouldn't that be easier overall?
> 
> thanks,
> 
> greg k-h

What about a partial revert like:

diff --git a/Makefile b/Makefile
index 9f5d2e87150e..aa0f7578653d 100644
--- a/Makefile
+++ b/Makefile
@@ -1083,7 +1083,9 @@ KBUILD_CFLAGS   += $(KCFLAGS)
 KBUILD_LDFLAGS_MODULE += --build-id=sha1
 LDFLAGS_vmlinux += --build-id=sha1

+ifneq ($(ARCH),$(filter $(ARCH),arm64))
 KBUILD_LDFLAGS += -z noexecstack
+endif
 ifeq ($(CONFIG_LD_IS_BFD),y)
 KBUILD_LDFLAGS += $(call ld-option,--no-warn-rwx-segments)
 endif


Only arm64 gcc/ld builds would need to change (with the option of adding
other architectures if anyone reports same issue).

With a full revert we lose --no-warn-rwx-segments and warnings show-up
with later versions of ld.


I did open a bug against 'ld' as Nick requested:
https://sourceware.org/bugzilla/show_bug.cgi?id=29994

If this is this is a better way to go - I can form up a v3 patch.

--Tom