linux-kernel - Re: [PATCH v4 00/45] x86: Kernel IBT

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Message-ID: <CAK7LNASOjsSRixifxxUBKiFdR_Q_pSoBu98zYU_u_z1rtUD=zA@mail.gmail.com>
Date:   Wed, 16 Mar 2022 01:26:25 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        X86 ML <x86@...nel.org>, joao@...rdrivepizza.com,
        "H . J . Lu" <hjl.tools@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Mark Rutland <mark.rutland@....com>, alyssa.milburn@...el.com,
        Miroslav Benes <mbenes@...e.cz>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v4 00/45] x86: Kernel IBT

On Mon, Mar 14, 2022 at 11:59 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Sun, Mar 13, 2022 at 09:52:14AM +0100, Peter Zijlstra wrote:
> > On Sat, Mar 12, 2022 at 05:33:39PM -0800, Alexei Starovoitov wrote:
> > > During the build with gcc 8.5 I see:
> > >
> > > arch/x86/crypto/crc32c-intel.o: warning: objtool: file already has
> > > .ibt_endbr_seal, skipping
> > > arch/x86/crypto/crc32c-intel.o: warning: objtool: file already has
> > > .orc_unwind section, skipping
> > >   LD [M]  crypto/async_tx/async_xor.ko
> > >   LD [M]  crypto/authenc.ko
> > > make[3]: *** [../scripts/Makefile.modfinal:61:
> > > arch/x86/crypto/crc32c-intel.ko] Error 255
> > > make[3]: *** Waiting for unfinished jobs....
> > >
> > > but make clean cures it.
> > > I suspect it's some missing makefile dependency.
> >
> > Yes, I recently ran into it; I've been trying to kick Makefile into
> > submission but have not had success yet. Will try again on Monday.
> >
> > Problem appears to be that it will re-link .ko even though .o hasn't
> > changed, resulting in duplicate objtool runs. I've been trying to have
> > makefile generate .o.objtool empty file to serve as dependency marker to
> > avoid doing second objtool run, but like said, no luck yet.
>
> Masahiro-san, I'm trying the below, but afaict it's not working because
> the rule for the .o file itself:
>
> $(multi-obj-m): FORCE
>         $(call if_changed,link_multi-m)
>
> will in fact update the timestamp of the .o file, even if if_changed
> nops out the cmd. Concequently all rules that try to use if_changed with
> this .o file as a dependency will find it newer and run anyway.
>
>
> remake -x output of a fs/f2fs/ module (re)build:
>
>      Prerequisite 'FORCE' of target 'fs/f2fs/f2fs.o' does not exist.
>     Must remake target 'fs/f2fs/f2fs.o'.
> ../scripts/Makefile.build:454: target 'fs/f2fs/f2fs.o' does not exist
> ##>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> :
> ##<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>     Successfully remade target file 'fs/f2fs/f2fs.o'.
>    Prerequisite 'fs/f2fs/f2fs.o' is newer than target 'fs/f2fs/f2fs.mod'.
>    Prerequisite 'FORCE' of target 'fs/f2fs/f2fs.mod' does not exist.
>   Must remake target 'fs/f2fs/f2fs.mod'.
> ../scripts/Makefile.build:281: update target 'fs/f2fs/f2fs.mod' due to: fs/f2fs/f2fs.o
> ##>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> set -e;   { echo  fs/f2fs/dir.o fs/f2fs/file.o fs/f2fs/inode.o fs/f2fs/namei.o fs/f2fs/hash.o fs/f2fs/super.o fs/f2fs/inline.o fs/f2fs/checkpoint.o fs/f2fs/gc.o fs/f2fs/data.o fs/f2fs/node.o fs/f2fs/segment.o fs/f2fs/recovery.o fs/f2fs/shrinker.o fs/f2fs/extent_cache.o fs/f2fs/sysfs.o fs/f2fs/debug.o fs/f2fs/xattr.o fs/f2fs/acl.o fs/f2fs/iostat.o;  echo; } > fs/f2fs/f2fs.mod; printf '%s\n' 'cmd_fs/f2fs/f2fs.mod := { echo  fs/f2fs/dir.o fs/f2fs/file.o fs/f2fs/inode.o fs/f2fs/namei.o fs/f2fs/hash.o fs/f2fs/super.o fs/f2fs/inline.o fs/f2fs/checkpoint.o fs/f2fs/gc.o fs/f2fs/data.o fs/f2fs/node.o fs/f2fs/segment.o fs/f2fs/recovery.o fs/f2fs/shrinker.o fs/f2fs/extent_cache.o fs/f2fs/sysfs.o fs/f2fs/debug.o fs/f2fs/xattr.o fs/f2fs/acl.o fs/f2fs/iostat.o;  echo; } > fs/f2fs/f2fs.mod' > fs/f2fs/.f2fs.mod.cmd
> ##<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>   Successfully remade target file 'fs/f2fs/f2fs.mod'.
>    Prerequisite 'fs/f2fs/f2fs.o' is newer than target 'fs/f2fs/f2fs.objtool'.
>    Prerequisite 'FORCE' of target 'fs/f2fs/f2fs.objtool' does not exist.
>   Must remake target 'fs/f2fs/f2fs.objtool'.
> ../scripts/Makefile.build:287: update target 'fs/f2fs/f2fs.objtool' due to: fs/f2fs/f2fs.o
> ##>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> set -e;   { echo fs/f2fs/f2fs.o  ; ./tools/objtool/objtool orc generate  --module  --lto --ibt  --no-fp    --uaccess   fs/f2fs/f2fs.o ; } > fs/f2fs/f2fs.objtool; printf '%s\n' 'cmd_fs/f2fs/f2fs.objtool := { echo fs/f2fs/f2fs.o  ; ./tools/objtool/objtool orc generate  --module  --lto --ibt  --no-fp    --uaccess   fs/f2fs/f2fs.o ; } > fs/f2fs/f2fs.objtool' > fs/f2fs/.f2fs.objtool.cmd
> ##<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> fs/f2fs/f2fs.o: warning: objtool: file already has .static_call_sites section, skipping
> fs/f2fs/f2fs.o: warning: objtool: file already has .ibt_endbr_seal, skipping
> fs/f2fs/f2fs.o: warning: objtool: file already has .orc_unwind section, skipping
> ../scripts/Makefile.build:286: *** [fs/f2fs/f2fs.objtool] error 255
>
>
> Where we can see that we don't re-generate f2fs.o (empty command), but
> then we do re-generate f2fs.mod because f2fs.o is newer and the same
> happens for the new f2fs.objtool.
>
> Help?


Help?

I had never noticed this thread before because
you did not CC me or kbuild ML.


Looking at the build system changes:
https://lore.kernel.org/all/20220308154319.528181453@infradead.org/
https://lore.kernel.org/all/20220308154319.822545231@infradead.org/

Both patches are wrong.
So is the fix-up you appended lator in this thread.

Apparently, you were screwing up Kbuild in a brown paper bag.
So scared.







>
> ---
> Index: linux-2.6/scripts/Makefile.build
> ===================================================================
> --- linux-2.6.orig/scripts/Makefile.build
> +++ linux-2.6/scripts/Makefile.build
> @@ -92,6 +92,10 @@ ifdef CONFIG_LTO_CLANG
>  targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
>  endif
>
> +ifdef CONFIG_X86_KERNEL_IBT
> +targets-for-modules += $(patsubst %.o, %.objtool, $(filter %.o, $(obj-m)))
> +endif
> +
>  ifdef need-modorder
>  targets-for-modules += $(obj)/modules.order
>  endif
> @@ -276,6 +280,12 @@ cmd_mod = { \
>  $(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
>         $(call if_changed,mod)
>
> +cmd_objtool_mod =                                                      \
> +       { echo $< $(cmd_objtool) ; } > $@
> +
> +$(obj)/%.objtool: $(obj)/%$(mod-prelink-ext).o FORCE
> +       $(call if_changed,objtool_mod)
> +
>  quiet_cmd_cc_lst_c = MKLST   $@
>        cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
>                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
> Index: linux-2.6/scripts/Makefile.lib
> ===================================================================
> --- linux-2.6.orig/scripts/Makefile.lib
> +++ linux-2.6/scripts/Makefile.lib
> @@ -552,9 +552,8 @@ objtool_args =                                                              \
>         $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)             \
>         $(if $(CONFIG_SLS), --sls)
>
> -cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
> -cmd_objtool_mod = $(if $(objtool-enabled), $(objtool) $(objtool_args) $(@:.ko=.o) ; )
> -cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
> +cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $(@:.objtool=.o))
> +cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$(@:.objtool=.o): $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
>
>  endif # CONFIG_STACK_VALIDATION
>
> @@ -575,8 +574,8 @@ $(obj)/%.o: objtool-enabled :=
>
>  # instead run objtool on the module as a whole, right before
>  # the final link pass with the linker script.
> -%.ko: objtool-enabled = y
> -%.ko: part-of-module := y
> +$(obj)/%.objtool: objtool-enabled = y
> +$(obj)/%.objtool: part-of-module := y
>
>  else
>
> Index: linux-2.6/scripts/Makefile.modfinal
> ===================================================================
> --- linux-2.6.orig/scripts/Makefile.modfinal
> +++ linux-2.6/scripts/Makefile.modfinal
> @@ -32,7 +32,6 @@ ARCH_POSTLINK := $(wildcard $(srctree)/a
>
>  quiet_cmd_ld_ko_o = LD [M]  $@
>        cmd_ld_ko_o +=                                                   \
> -       $(cmd_objtool_mod)                                              \
>         $(LD) -r $(KBUILD_LDFLAGS)                                      \
>                 $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)              \
>                 -T scripts/module.lds -o $@ $(filter %.o, $^);          \



-- 
Best Regards
Masahiro Yamada