[v9,06/16] kbuild: lto: add a default list of used symbols

Message ID	20201211184633.3213045-7-samitolvanen@google.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=gPQ1=FP=lists.openwall.com=kernel-hardening-return-20588-kernel-hardening=archiver.kernel.org@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16D4C23F37 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk Sender: "samitolvanen via sendgmr" <samitolvanen@samitolvanen1.mtv.corp.google.com> Date: Fri, 11 Dec 2020 10:46:23 -0800 In-Reply-To: <20201211184633.3213045-1-samitolvanen@google.com> Message-Id: <20201211184633.3213045-7-samitolvanen@google.com> Mime-Version: 1.0 References: <20201211184633.3213045-1-samitolvanen@google.com> Subject: [PATCH v9 06/16] kbuild: lto: add a default list of used symbols From: Sami Tolvanen <samitolvanen@google.com> To: Masahiro Yamada <masahiroy@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, Will Deacon <will@kernel.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "Paul E. McKenney" <paulmck@kernel.org>, Kees Cook <keescook@chromium.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, Sami Tolvanen <samitolvanen@google.com> Content-Type: text/plain; charset="UTF-8"
Series	Add support for Clang LTO \| expand [v9,00/16] Add support for Clang LTO [v9,01/16] tracing: move function tracer options to Kconfig [v9,02/16] kbuild: add support for Clang LTO [v9,03/16] kbuild: lto: fix module versioning [v9,04/16] kbuild: lto: limit inlining [v9,05/16] kbuild: lto: merge module sections [v9,06/16] kbuild: lto: add a default list of used symbols [v9,07/16] init: lto: ensure initcall ordering [v9,08/16] init: lto: fix PREL32 relocations [v9,09/16] PCI: Fix PREL32 relocations for LTO [v9,10/16] modpost: lto: strip .lto from module names [v9,11/16] scripts/mod: disable LTO for empty.c [v9,12/16] efi/libstub: disable LTO [v9,13/16] drivers/misc/lkdtm: disable LTO for rodata.o [v9,14/16] arm64: vdso: disable LTO [v9,15/16] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS [v9,16/16] arm64: allow LTO to be selected

Message ID

20201211184633.3213045-7-samitolvanen@google.com (mailing list archive)

State

New, archived

Headers

DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16D4C23F37
Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm
Precedence: bulk
Sender: "samitolvanen via sendgmr"
 <samitolvanen@samitolvanen1.mtv.corp.google.com>
Date: Fri, 11 Dec 2020 10:46:23 -0800
In-Reply-To: <20201211184633.3213045-1-samitolvanen@google.com>
Message-Id: <20201211184633.3213045-7-samitolvanen@google.com>
Mime-Version: 1.0
References: <20201211184633.3213045-1-samitolvanen@google.com>
Subject: [PATCH v9 06/16] kbuild: lto: add a default list of used symbols
From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
 Steven Rostedt <rostedt@goodmis.org>,
	Will Deacon <will@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
 Peter Zijlstra <peterz@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 "Paul E. McKenney" <paulmck@kernel.org>,
	Kees Cook <keescook@chromium.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, Sami Tolvanen <samitolvanen@google.com>
Content-Type: text/plain; charset="UTF-8"

Series

Add support for Clang LTO | expand

Commit Message

Sami Tolvanen Dec. 11, 2020, 6:46 p.m. UTC

With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a
binary when the .mod files are generated, which means they don't yet
contain references to certain symbols that will be present in the final
binaries. This includes intrinsic functions, such as memcpy, memmove,
and memset [1], and stack protector symbols [2]. This change adds a
default symbol list to use with CONFIG_TRIM_UNUSED_KSYMS when Clang's
LTO is used.

[1] https://llvm.org/docs/LangRef.html#standard-c-c-library-intrinsics
[2] https://llvm.org/docs/LangRef.html#llvm-stackprotector-intrinsic

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 init/Kconfig                | 1 +
 scripts/lto-used-symbollist | 5 +++++
 2 files changed, 6 insertions(+)
 create mode 100644 scripts/lto-used-symbollist

Comments

Kees Cook Dec. 11, 2020, 7:32 p.m. UTC | #1

On Fri, Dec 11, 2020 at 10:46:23AM -0800, Sami Tolvanen wrote:
> With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a
> binary when the .mod files are generated, which means they don't yet
> contain references to certain symbols that will be present in the final
> binaries. This includes intrinsic functions, such as memcpy, memmove,
> and memset [1], and stack protector symbols [2]. This change adds a
> default symbol list to use with CONFIG_TRIM_UNUSED_KSYMS when Clang's
> LTO is used.
> 
> [1] https://llvm.org/docs/LangRef.html#standard-c-c-library-intrinsics
> [2] https://llvm.org/docs/LangRef.html#llvm-stackprotector-intrinsic
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

> ---
>  init/Kconfig                | 1 +
>  scripts/lto-used-symbollist | 5 +++++
>  2 files changed, 6 insertions(+)
>  create mode 100644 scripts/lto-used-symbollist
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 0872a5a2e759..e88c919c1bf1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -2297,6 +2297,7 @@ config TRIM_UNUSED_KSYMS
>  config UNUSED_KSYMS_WHITELIST
>  	string "Whitelist of symbols to keep in ksymtab"
>  	depends on TRIM_UNUSED_KSYMS
> +	default "scripts/lto-used-symbollist" if LTO_CLANG
>  	help
>  	  By default, all unused exported symbols will be un-exported from the
>  	  build when TRIM_UNUSED_KSYMS is selected.
> diff --git a/scripts/lto-used-symbollist b/scripts/lto-used-symbollist
> new file mode 100644
> index 000000000000..38e7bb9ebaae
> --- /dev/null
> +++ b/scripts/lto-used-symbollist
> @@ -0,0 +1,5 @@
> +memcpy
> +memmove
> +memset
> +__stack_chk_fail
> +__stack_chk_guard
> -- 
> 2.29.2.576.ga3fc446d84-goog
> 

bikeshed: Should this filename use some kind of extension, like
lto-user-symbols.txt or .list, to make it more human-friendly?

Sami Tolvanen Dec. 11, 2020, 7:40 p.m. UTC | #2

On Fri, Dec 11, 2020 at 11:32 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Fri, Dec 11, 2020 at 10:46:23AM -0800, Sami Tolvanen wrote:
> > With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a
> > binary when the .mod files are generated, which means they don't yet
> > contain references to certain symbols that will be present in the final
> > binaries. This includes intrinsic functions, such as memcpy, memmove,
> > and memset [1], and stack protector symbols [2]. This change adds a
> > default symbol list to use with CONFIG_TRIM_UNUSED_KSYMS when Clang's
> > LTO is used.
> >
> > [1] https://llvm.org/docs/LangRef.html#standard-c-c-library-intrinsics
> > [2] https://llvm.org/docs/LangRef.html#llvm-stackprotector-intrinsic
> >
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> > ---
> >  init/Kconfig                | 1 +
> >  scripts/lto-used-symbollist | 5 +++++
> >  2 files changed, 6 insertions(+)
> >  create mode 100644 scripts/lto-used-symbollist
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 0872a5a2e759..e88c919c1bf1 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -2297,6 +2297,7 @@ config TRIM_UNUSED_KSYMS
> >  config UNUSED_KSYMS_WHITELIST
> >       string "Whitelist of symbols to keep in ksymtab"
> >       depends on TRIM_UNUSED_KSYMS
> > +     default "scripts/lto-used-symbollist" if LTO_CLANG
> >       help
> >         By default, all unused exported symbols will be un-exported from the
> >         build when TRIM_UNUSED_KSYMS is selected.
> > diff --git a/scripts/lto-used-symbollist b/scripts/lto-used-symbollist
> > new file mode 100644
> > index 000000000000..38e7bb9ebaae
> > --- /dev/null
> > +++ b/scripts/lto-used-symbollist
> > @@ -0,0 +1,5 @@
> > +memcpy
> > +memmove
> > +memset
> > +__stack_chk_fail
> > +__stack_chk_guard
> > --
> > 2.29.2.576.ga3fc446d84-goog
> >
>
> bikeshed: Should this filename use some kind of extension, like
> lto-user-symbols.txt or .list, to make it more human-friendly?

Sure, I can rename this in the next version. Does anyone have strong
opinions about the name and/or extension?

Sami

Nick Desaulniers Dec. 11, 2020, 7:45 p.m. UTC | #3

On Fri, Dec 11, 2020 at 11:40 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> On Fri, Dec 11, 2020 at 11:32 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Fri, Dec 11, 2020 at 10:46:23AM -0800, Sami Tolvanen wrote:
> > > --- /dev/null
> > > +++ b/scripts/lto-used-symbollist
> > > @@ -0,0 +1,5 @@
> > > +memcpy
> > > +memmove
> > > +memset
> > > +__stack_chk_fail
> > > +__stack_chk_guard
> > > --
> > > 2.29.2.576.ga3fc446d84-goog
> > >
> >
> > bikeshed: Should this filename use some kind of extension, like
> > lto-user-symbols.txt or .list, to make it more human-friendly?
>
> Sure, I can rename this in the next version. Does anyone have strong
> opinions about the name and/or extension?

.txt extension would be fine.

diff --git a/init/Kconfig b/init/Kconfig
index 0872a5a2e759..e88c919c1bf1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2297,6 +2297,7 @@  config TRIM_UNUSED_KSYMS
 config UNUSED_KSYMS_WHITELIST
 	string "Whitelist of symbols to keep in ksymtab"
 	depends on TRIM_UNUSED_KSYMS
+	default "scripts/lto-used-symbollist" if LTO_CLANG
 	help
 	  By default, all unused exported symbols will be un-exported from the
 	  build when TRIM_UNUSED_KSYMS is selected.
diff --git a/scripts/lto-used-symbollist b/scripts/lto-used-symbollist
new file mode 100644
index 000000000000..38e7bb9ebaae
--- /dev/null
+++ b/scripts/lto-used-symbollist
@@ -0,0 +1,5 @@ 
+memcpy
+memmove
+memset
+__stack_chk_fail
+__stack_chk_guard

[v9,06/16] kbuild: lto: add a default list of used symbols

Commit Message

Comments

Patch