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From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com,
	kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2 11/28] kbuild: lto: postpone objtool
Date: Tue, 8 Sep 2020 13:56:12 -0700
Message-ID: <20200908205612.GA1060586@google.com> (raw)
In-Reply-To: <202009031513.B558594FB9@keescook>

On Thu, Sep 03, 2020 at 03:19:43PM -0700, Kees Cook wrote:
> On Thu, Sep 03, 2020 at 01:30:36PM -0700, Sami Tolvanen wrote:
> > With LTO, LLVM bitcode won't be compiled into native code until
> > modpost_link, or modfinal for modules. This change postpones calls
> > to objtool until after these steps.
> > 
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> 
> For a "fail fast" style of building, it makes sense to have objtool run
> as early as possible, so it makes sense to keep the current behavior in
> non-LTO mode. I do wonder, though, if there is a real benefit to having
> "fail fast" case. I imagine a lot of automated builds are using
> --keep-going with make, and actually waiting until the end to do the
> validation means more code will get build-tested before objtool rejects
> the results. *shrug*
> 
> > ---
> >  arch/Kconfig              |  2 +-
> >  scripts/Makefile.build    |  2 ++
> >  scripts/Makefile.modfinal | 24 ++++++++++++++++++++++--
> >  scripts/link-vmlinux.sh   | 23 ++++++++++++++++++++++-
> >  4 files changed, 47 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 71392e4a8900..7a418907e686 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -599,7 +599,7 @@ config LTO_CLANG
> >  	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
> >  	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
> >  	depends on ARCH_SUPPORTS_LTO_CLANG
> > -	depends on !FTRACE_MCOUNT_RECORD
> > +	depends on HAVE_OBJTOOL_MCOUNT || !(X86_64 && DYNAMIC_FTRACE)
> >  	depends on !KASAN
> >  	depends on !GCOV_KERNEL
> >  	select LTO
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index c348e6d6b436..b8f1f0d65a73 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -218,6 +218,7 @@ cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),
> >  endif # USE_RECORDMCOUNT
> >  
> >  ifdef CONFIG_STACK_VALIDATION
> > +ifndef CONFIG_LTO_CLANG
> >  ifneq ($(SKIP_STACK_VALIDATION),1)
> >  
> >  __objtool_obj := $(objtree)/tools/objtool/objtool
> > @@ -253,6 +254,7 @@ objtool_obj = $(if $(patsubst y%,, \
> >  	$(__objtool_obj))
> >  
> >  endif # SKIP_STACK_VALIDATION
> > +endif # CONFIG_LTO_CLANG
> >  endif # CONFIG_STACK_VALIDATION
> >  
> >  # Rebuild all objects when objtool changes, or is enabled/disabled.
> > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> > index 1005b147abd0..909bd509edb4 100644
> > --- a/scripts/Makefile.modfinal
> > +++ b/scripts/Makefile.modfinal
> > @@ -34,10 +34,30 @@ ifdef CONFIG_LTO_CLANG
> >  # With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
> >  # avoid a second slow LTO link
> >  prelink-ext := .lto
> > -endif
> > +
> > +# ELF processing was skipped earlier because we didn't have native code,
> > +# so let's now process the prelinked binary before we link the module.
> > +
> > +ifdef CONFIG_STACK_VALIDATION
> > +ifneq ($(SKIP_STACK_VALIDATION),1)
> > +cmd_ld_ko_o +=								\
> > +	$(objtree)/tools/objtool/objtool				\
> > +		$(if $(CONFIG_UNWINDER_ORC),orc generate,check)		\
> > +		--module						\
> > +		$(if $(CONFIG_FRAME_POINTER),,--no-fp)			\
> > +		$(if $(CONFIG_GCOV_KERNEL),--no-unreachable,)		\
> > +		$(if $(CONFIG_RETPOLINE),--retpoline,)			\
> > +		$(if $(CONFIG_X86_SMAP),--uaccess,)			\
> > +		$(if $(USE_OBJTOOL_MCOUNT),--mcount,)			\
> > +		$(@:.ko=$(prelink-ext).o);
> > +
> > +endif # SKIP_STACK_VALIDATION
> > +endif # CONFIG_STACK_VALIDATION
> 
> I wonder if objtool_args could be reused here instead of having two
> places to keep in sync? It looks like that might mean moving things
> around a bit before this patch, since I can't quite see if
> Makefile.build's variables are visible to Makefile.modfinal?

It doesn't look like they are. I suppose we could move objtool_args to
Makefile.lib. Masahiro, any thoughts?

Sami

  reply index

Thread overview: 207+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 20:31 [PATCH 00/22] add support for Clang LTO Sami Tolvanen
2020-06-24 20:31 ` [PATCH 01/22] objtool: use sh_info to find the base for .rela sections Sami Tolvanen
2020-06-24 20:31 ` [PATCH 02/22] kbuild: add support for Clang LTO Sami Tolvanen
2020-06-24 20:53   ` Nick Desaulniers
2020-06-24 21:29     ` Sami Tolvanen
2020-06-25  2:26   ` Nathan Chancellor
2020-06-25 16:13     ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 03/22] kbuild: lto: fix module versioning Sami Tolvanen
2020-06-24 20:31 ` [PATCH 04/22] kbuild: lto: fix recordmcount Sami Tolvanen
2020-06-24 21:27   ` Peter Zijlstra
2020-06-24 21:45     ` Sami Tolvanen
2020-06-25  7:45       ` Peter Zijlstra
2020-06-25 16:15         ` Sami Tolvanen
2020-06-25 20:02           ` [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool Peter Zijlstra
2020-06-25 20:54             ` Nick Desaulniers
2020-06-25 22:40             ` Sami Tolvanen
2020-06-26 11:29               ` Peter Zijlstra
2020-06-26 11:42                 ` Peter Zijlstra
2020-07-17 17:28                 ` Sami Tolvanen
2020-07-17 17:36                   ` Steven Rostedt
2020-07-17 17:47                     ` Sami Tolvanen
2020-07-17 18:05                       ` Steven Rostedt
2020-07-20 16:52                         ` Sami Tolvanen
2020-07-22 17:58                           ` Steven Rostedt
2020-07-22 18:07                             ` Sami Tolvanen
2020-07-22 17:55                 ` Steven Rostedt
2020-07-22 18:41                   ` Peter Zijlstra
2020-07-22 19:09                     ` Steven Rostedt
2020-07-22 20:03                       ` Sami Tolvanen
2020-07-22 23:56                       ` Peter Zijlstra
2020-07-23  0:06                         ` Steven Rostedt
2020-08-06 22:09                           ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 05/22] kbuild: lto: postpone objtool Sami Tolvanen
2020-06-24 21:19   ` Peter Zijlstra
2020-06-24 21:49     ` Sami Tolvanen
2020-06-25  7:47       ` Peter Zijlstra
2020-06-25 16:22         ` Sami Tolvanen
2020-06-25 18:33           ` Peter Zijlstra
2020-06-25 19:32             ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 06/22] kbuild: lto: limit inlining Sami Tolvanen
2020-06-24 21:20   ` Peter Zijlstra
2020-06-24 23:37     ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 07/22] kbuild: lto: merge module sections Sami Tolvanen
2020-06-24 21:01   ` Nick Desaulniers
2020-06-24 21:31     ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 08/22] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-06-24 21:13   ` Nick Desaulniers
2020-06-24 20:31 ` [PATCH 09/22] init: lto: ensure initcall ordering Sami Tolvanen
2020-06-24 20:31 ` [PATCH 10/22] init: lto: fix PREL32 relocations Sami Tolvanen
2020-06-24 20:31 ` [PATCH 11/22] pci: " Sami Tolvanen
2020-07-17 20:26   ` Bjorn Helgaas
2020-07-22 18:15     ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 12/22] modpost: lto: strip .lto from module names Sami Tolvanen
2020-06-24 22:05   ` Nick Desaulniers
2020-06-24 20:31 ` [PATCH 13/22] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-06-24 20:57   ` Nick Desaulniers
2020-06-24 20:31 ` [PATCH 14/22] efi/libstub: disable LTO Sami Tolvanen
2020-06-24 20:31 ` [PATCH 15/22] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-06-24 20:31 ` [PATCH 16/22] arm64: export CC_USING_PATCHABLE_FUNCTION_ENTRY Sami Tolvanen
2020-06-24 20:31 ` [PATCH 17/22] arm64: vdso: disable LTO Sami Tolvanen
2020-06-24 20:58   ` Nick Desaulniers
2020-06-24 21:09     ` Nick Desaulniers
2020-06-24 23:51       ` Andi Kleen
2020-06-24 21:52     ` Sami Tolvanen
2020-06-24 23:05       ` Nick Desaulniers
2020-06-24 23:39         ` Sami Tolvanen
2020-06-24 20:31 ` [PATCH 18/22] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-06-24 20:31 ` [PATCH 19/22] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-06-24 20:31 ` [PATCH 20/22] x86, ftrace: disable recordmcount for ftrace_make_nop Sami Tolvanen
2020-06-24 20:31 ` [PATCH 21/22] x86, relocs: Ignore L4_PAGE_OFFSET relocations Sami Tolvanen
2020-06-24 20:32 ` [PATCH 22/22] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-06-24 21:15 ` [PATCH 00/22] add support for Clang LTO Peter Zijlstra
2020-06-24 21:30   ` Sami Tolvanen
2020-06-25  8:27     ` Will Deacon
2020-06-24 21:31   ` Nick Desaulniers
2020-06-25  8:03     ` Peter Zijlstra
2020-06-25  8:24       ` Peter Zijlstra
2020-06-25  8:57         ` Peter Zijlstra
2020-06-30 19:19           ` Marco Elver
2020-06-30 20:12             ` Peter Zijlstra
2020-06-30 20:30               ` Paul E. McKenney
2020-07-01  9:10                 ` Peter Zijlstra
2020-07-01 14:20                   ` David Laight
2020-07-01 16:06                     ` Paul E. McKenney
2020-07-02  9:37                       ` David Laight
2020-07-02 18:00                         ` Paul E. McKenney
2020-07-01  9:41                 ` Marco Elver
2020-07-01 10:03                   ` Will Deacon
2020-07-01 11:40                   ` Peter Zijlstra
2020-07-01 14:06                     ` Paul E. McKenney
2020-07-01 15:05                       ` Peter Zijlstra
2020-07-01 16:03                         ` Paul E. McKenney
2020-07-02  8:20                           ` Peter Zijlstra
2020-07-02 17:59                             ` Paul E. McKenney
2020-07-03 13:13                               ` Peter Zijlstra
2020-07-03 13:25                                 ` Peter Zijlstra
2020-07-03 14:51                                   ` Paul E. McKenney
2020-07-03 14:42                                 ` Paul E. McKenney
2020-07-06 16:26                                   ` Paul E. McKenney
2020-07-06 18:29                                     ` Peter Zijlstra
2020-07-06 18:39                                       ` Paul E. McKenney
2020-07-06 19:40                                         ` Peter Zijlstra
2020-07-06 23:41                                           ` Paul E. McKenney
2020-06-28 16:56 ` Masahiro Yamada
2020-06-29 23:20   ` Sami Tolvanen
2020-07-07 15:51     ` Sami Tolvanen
2020-07-07 16:05       ` Sami Tolvanen
2020-07-07 16:56         ` Jakub Kicinski
2020-07-07 17:17           ` Nick Desaulniers
2020-07-07 17:30             ` Jakub Kicinski
2020-07-11 16:32 ` Paul Menzel
2020-07-12  8:59   ` Sedat Dilek
2020-07-12 18:40     ` Nathan Chancellor
2020-07-14  9:44       ` Sedat Dilek
2020-07-14 17:54         ` Nick Desaulniers
2020-07-12 23:34   ` Sami Tolvanen
2020-07-14 12:16     ` Paul Menzel
2020-07-14 12:35       ` Sedat Dilek
2020-09-03 20:30 ` [PATCH v2 00/28] Add " Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 01/28] x86/boot/compressed: Disable relocation relaxation Sami Tolvanen
2020-09-03 21:44     ` Kees Cook
2020-09-03 23:42       ` Arvind Sankar
2020-09-04  7:14         ` Nathan Chancellor
2020-09-03 20:30   ` [PATCH v2 02/28] x86/asm: Replace __force_order with memory clobber Sami Tolvanen
2020-09-03 21:45     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 03/28] lib/string.c: implement stpcpy Sami Tolvanen
2020-09-03 21:47     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 04/28] RAS/CEC: Fix cec_init() prototype Sami Tolvanen
2020-09-03 21:50     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 05/28] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-09-03 21:51     ` Kees Cook
2020-09-03 22:03       ` Sami Tolvanen
2020-09-04  9:31         ` peterz
2020-09-10 18:29           ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 06/28] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-09-03 21:52     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 07/28] kbuild: add support for objtool mcount Sami Tolvanen
2020-09-03 21:56     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 08/28] x86, build: use " Sami Tolvanen
2020-09-03 21:58     ` Kees Cook
2020-09-03 22:11       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 09/28] kbuild: add support for Clang LTO Sami Tolvanen
2020-09-03 22:08     ` Kees Cook
2020-09-08 17:02       ` Sami Tolvanen
2020-09-05 19:36     ` Masahiro Yamada
2020-09-08 17:10       ` Sami Tolvanen
2020-09-05 20:17     ` Masahiro Yamada
2020-09-08 17:14       ` Sami Tolvanen
2020-09-07 15:30     ` Masahiro Yamada
2020-09-08 17:30       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 10/28] kbuild: lto: fix module versioning Sami Tolvanen
2020-09-03 22:11     ` Kees Cook
2020-09-08 18:23       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 11/28] kbuild: lto: postpone objtool Sami Tolvanen
2020-09-03 22:19     ` Kees Cook
2020-09-08 20:56       ` Sami Tolvanen [this message]
2020-09-03 20:30   ` [PATCH v2 12/28] kbuild: lto: limit inlining Sami Tolvanen
2020-09-03 22:20     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 13/28] kbuild: lto: merge module sections Sami Tolvanen
2020-09-03 22:23     ` Kees Cook
2020-09-07 15:25     ` Masahiro Yamada
2020-09-08 21:07       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 14/28] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-09-03 22:29     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 15/28] init: lto: ensure initcall ordering Sami Tolvanen
2020-09-03 22:40     ` Kees Cook
2020-09-08 21:16       ` Sami Tolvanen
2020-09-10  9:25     ` David Woodhouse
2020-09-10 15:07       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 16/28] init: lto: fix PREL32 relocations Sami Tolvanen
2020-09-03 22:41     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 17/28] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-09-03 22:42     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 18/28] modpost: lto: strip .lto from module names Sami Tolvanen
2020-09-03 22:42     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 19/28] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-09-03 22:43     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 20/28] efi/libstub: disable LTO Sami Tolvanen
2020-09-03 22:43     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 21/28] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 22/28] arm64: export CC_USING_PATCHABLE_FUNCTION_ENTRY Sami Tolvanen
2020-09-03 22:44     ` Kees Cook
2020-09-08 21:23       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 23/28] arm64: vdso: disable LTO Sami Tolvanen
2020-09-03 22:45     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 24/28] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
2020-09-03 22:45     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 25/28] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-09-03 22:45     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 26/28] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-09-03 22:46     ` Kees Cook
2020-09-03 20:30   ` [PATCH v2 27/28] x86, relocs: Ignore L4_PAGE_OFFSET relocations Sami Tolvanen
2020-09-03 22:47     ` Kees Cook
2020-09-08 23:28       ` Sami Tolvanen
2020-09-03 20:30   ` [PATCH v2 28/28] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-09-03 22:48     ` Kees Cook
2020-09-03 23:34   ` [PATCH v2 00/28] Add support for Clang LTO Kees Cook
2020-09-04  4:45     ` Nathan Chancellor
2020-09-03 23:38   ` Kees Cook
2020-09-04  7:53   ` Sedat Dilek
2020-09-04  8:55   ` peterz
2020-09-04  9:08     ` Sedat Dilek
2020-09-06  0:24   ` Masahiro Yamada
2020-09-08 23:46     ` Sami Tolvanen
2020-09-10  1:18       ` Masahiro Yamada
2020-09-10 15:17         ` Sami Tolvanen
2020-09-10 18:18         ` Kees Cook

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