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From: Sami Tolvanen <samitolvanen@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Jann Horn <jannh@google.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Will Deacon <will@kernel.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 <clang-built-linux@googlegroups.com>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-kbuild <linux-kbuild@vger.kernel.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps
Date: Wed, 21 Oct 2020 17:22:59 -0700
Message-ID: <CABCJKufL6=FiaeD8T0P+mK4JeR9J80hhjvJ6Z9S-m9UnCESxVA@mail.gmail.com> (raw)
In-Reply-To: <20201021085606.GZ2628@hirez.programming.kicks-ass.net>

On Wed, Oct 21, 2020 at 1:56 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Oct 20, 2020 at 12:24:37PM -0700, Sami Tolvanen wrote:
> > > > Building allyesconfig with this series and LTO enabled, I still see
> > > > the following objtool warnings for vmlinux.o, grouped by source file:
> > > >
> > > > arch/x86/entry/entry_64.S:
> > > > __switch_to_asm()+0x0: undefined stack state
> > > > .entry.text+0xffd: sibling call from callable instruction with
> > > > modified stack frame
> > > > .entry.text+0x48: stack state mismatch: cfa1=7-8 cfa2=-1+0
> > >
> > > Not sure what this one's about, there's no OBJECT_FILES_NON_STANDARD?
> >
> > Correct, because with LTO, we won't have an ELF binary to process
> > until we compile everything into vmlinux.o, and at that point we can
> > no longer skip individual object files.
>
> I think what Josh was trying to say is; this file is subject to objtool
> on a normal build and does not generate warnings. So why would it
> generate warnings when subject to objtool as result of a vmlinux run
> (due to LTO or otherwise).
>
> In fact, when I build a x86_64-defconfig and then run:
>
>   $ objtool check -barf defconfig-build/vmlinux.o

Note that I'm passing also --vmlinux and --duplicate to objtool when
processing vmlinux.o, and this series has a patch to split noinstr
validation from --vmlinux, so that's skipped.

> I do not see these in particular, although I do see a lot of:
>
>   "sibling call from callable instruction with modified stack frame"
>   "falls through to next function"
>
> that did not show up in the individual objtool runs during the build.

I'm able to reproduce these warnings with gcc 9.3 + allyesconfig, with
KASAN and GCOV_KERNEL disabled, as they are not enabled in LTO builds
either. This is without the LTO series applied, so we also have the
retpoline warnings:

$ ./tools/objtool/objtool check -arfld vmlinux.o 2>&1 | grep -vE
'(sibling|instr)'
vmlinux.o: warning: objtool: wakeup_long64()+0x61: indirect jump found
in RETPOLINE build
vmlinux.o: warning: objtool: .text+0x826308a: indirect jump found in
RETPOLINE build
vmlinux.o: warning: objtool: .text+0x82630c5: indirect jump found in
RETPOLINE build
vmlinux.o: warning: objtool: .head.text+0x748: indirect jump found in
RETPOLINE build
vmlinux.o: warning: objtool:
set_bringup_idt_handler.constprop.0()+0x0: undefined stack state
vmlinux.o: warning: objtool: .entry.text+0x1634: redundant CLD
vmlinux.o: warning: objtool: camellia_cbc_dec_32way()+0xb3: stack
state mismatch: cfa1=7+520 cfa2=7+8
vmlinux.o: warning: objtool: camellia_ctr_32way()+0x1a: stack state
mismatch: cfa1=7+520 cfa2=7+8
vmlinux.o: warning: objtool: aesni_gcm_init_avx_gen2()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_enc_update_avx_gen2()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_dec_update_avx_gen2()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_finalize_avx_gen2()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_init_avx_gen4()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_enc_update_avx_gen4()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_dec_update_avx_gen4()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: aesni_gcm_finalize_avx_gen4()+0x12:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: sha1_transform_avx2()+0xc: unsupported
stack pointer realignment
vmlinux.o: warning: objtool: sha1_ni_transform()+0x7: unsupported
stack pointer realignment
vmlinux.o: warning: objtool: sha256_transform_rorx()+0x13: unsupported
stack pointer realignment
vmlinux.o: warning: objtool: sha512_transform_ssse3()+0x14:
unsupported stack pointer realignment
vmlinux.o: warning: objtool: sha512_transform_avx()+0x14: unsupported
stack pointer realignment
vmlinux.o: warning: objtool: sha512_transform_rorx()+0x7: unsupported
stack pointer realignment
vmlinux.o: warning: objtool: __x86_retpoline_rdi()+0x10: return with
modified stack frame
vmlinux.o: warning: objtool: __x86_retpoline_rdi()+0x0: stack state
mismatch: cfa1=7+32 cfa2=7+8
vmlinux.o: warning: objtool: __x86_retpoline_rdi()+0x0: stack state
mismatch: cfa1=7+32 cfa2=-1+0
vmlinux.o: warning: objtool: reset_early_page_tables()+0x0: stack
state mismatch: cfa1=7+8 cfa2=-1+0
vmlinux.o: warning: objtool: .entry.text+0x48: stack state mismatch:
cfa1=7-8 cfa2=-1+0
vmlinux.o: warning: objtool: .entry.text+0x15fd: stack state mismatch:
cfa1=7-8 cfa2=-1+0
vmlinux.o: warning: objtool: .entry.text+0x168c: stack state mismatch:
cfa1=7-8 cfa2=-1+0

There are a couple of differences, like the first "undefined stack
state" warning pointing to set_bringup_idt_handler.constprop.0()
instead of __switch_to_asm(). I tried running this with --backtrace,
but objtool segfaults at the first .entry.text warning:

$ ./tools/objtool/objtool check -barfld vmlinux.o
...
vmlinux.o: warning: objtool:
set_bringup_idt_handler.constprop.0()+0x0: undefined stack state
vmlinux.o: warning: objtool:   xen_hypercall_set_trap_table()+0x0: <=== (sym)
...
vmlinux.o: warning: objtool: .entry.text+0xffd: sibling call from
callable instruction with modified stack frame
vmlinux.o: warning: objtool:   .entry.text+0xfcb: (branch)
Segmentation fault

Going back to the allyesconfig+LTO vmlinux.o, the "undefined stack
state" warning looks quite similar:

$ ./tools/objtool/objtool check -barlfd vmlinux.o
vmlinux.o: warning: objtool: __switch_to_asm()+0x0: undefined stack state
vmlinux.o: warning: objtool:   xen_hypercall_set_trap_table()+0x0: <=== (sym)
vmlinux.o: warning: objtool: .entry.text+0xffd: sibling call from
callable instruction with modified stack frame
vmlinux.o: warning: objtool:   .entry.text+0xfcb: (branch)
Segmentation fault

Sami

  parent reply index

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-13  0:31 [PATCH v6 00/25] Add support for Clang LTO Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 01/25] kbuild: preprocess module linker script Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 02/25] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-14 16:50   ` Ingo Molnar
2020-10-14 18:21     ` Peter Zijlstra
2020-10-15 20:10       ` Josh Poimboeuf
2020-10-13  0:31 ` [PATCH v6 03/25] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 04/25] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 05/25] tracing: add support for objtool mcount Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 06/25] x86, build: use " Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 07/25] treewide: remove DISABLE_LTO Sami Tolvanen
2020-10-14 22:43   ` Kees Cook
2020-10-17  1:46     ` Masahiro Yamada
2020-10-13  0:31 ` [PATCH v6 08/25] kbuild: add support for Clang LTO Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 09/25] kbuild: lto: fix module versioning Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 10/25] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 11/25] kbuild: lto: postpone objtool Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 12/25] kbuild: lto: limit inlining Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 13/25] kbuild: lto: merge module sections Sami Tolvanen
2020-10-14 22:49   ` Kees Cook
2020-10-20 16:42     ` Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 14/25] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-10-14 22:50   ` Kees Cook
2020-10-13  0:31 ` [PATCH v6 15/25] init: lto: ensure initcall ordering Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 16/25] init: lto: fix PREL32 relocations Sami Tolvanen
2020-10-14 22:53   ` Kees Cook
2020-10-15  0:12   ` Jann Horn
2020-10-13  0:31 ` [PATCH v6 17/25] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-10-14 22:58   ` Kees Cook
2020-10-13  0:31 ` [PATCH v6 18/25] modpost: lto: strip .lto from module names Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 19/25] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 20/25] efi/libstub: disable LTO Sami Tolvanen
2020-10-13  0:31 ` [PATCH v6 21/25] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-10-13  0:32 ` [PATCH v6 22/25] x86/asm: annotate indirect jumps Sami Tolvanen
2020-10-14 22:46   ` Kees Cook
2020-10-14 23:23   ` Jann Horn
2020-10-15 10:22     ` Peter Zijlstra
2020-10-15 20:39       ` Josh Poimboeuf
2020-10-20 16:45         ` Sami Tolvanen
2020-10-20 18:52           ` Josh Poimboeuf
2020-10-20 19:24             ` Sami Tolvanen
2020-10-21  8:56               ` Peter Zijlstra
2020-10-21  9:08                 ` Peter Zijlstra
2020-10-21  9:32                 ` Peter Zijlstra
2020-10-21 21:27                   ` Josh Poimboeuf
2020-10-22  7:25                     ` Peter Zijlstra
2020-10-23 17:48                       ` Sami Tolvanen
2020-10-23 18:04                         ` Nick Desaulniers
2020-10-21 15:01                 ` Sami Tolvanen
2020-10-22  0:22                 ` Sami Tolvanen [this message]
2020-10-23 17:36                   ` Sami Tolvanen
2020-11-09 23:11                     ` Sami Tolvanen
2020-11-10  2:29                       ` Josh Poimboeuf
2020-11-10  3:18                         ` Nick Desaulniers
2020-11-10  4:48                         ` Sami Tolvanen
2020-11-10 16:11                           ` Josh Poimboeuf
2020-11-10 17:46                         ` Josh Poimboeuf
2020-11-10 18:59                           ` Sami Tolvanen
2020-11-13 19:54                             ` Josh Poimboeuf
2020-11-13 20:24                               ` Sami Tolvanen
2020-11-13 20:52                                 ` Josh Poimboeuf
2020-11-13 22:34                                 ` Josh Poimboeuf
2020-11-13 22:54                                   ` Sami Tolvanen
2020-11-13 22:56                                     ` Josh Poimboeuf
2020-11-13 23:31                                   ` Sami Tolvanen
2020-11-14  0:49                                     ` Josh Poimboeuf
2020-10-21  9:51             ` Peter Zijlstra
2020-10-21 18:30               ` Josh Poimboeuf
2020-10-13  0:32 ` [PATCH v6 23/25] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-10-13  0:32 ` [PATCH v6 24/25] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-10-13  0:32 ` [PATCH v6 25/25] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen

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