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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	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: Fri, 13 Nov 2020 16:34:12 -0600	[thread overview]
Message-ID: <20201113223412.inono2ekrs7ky7rm@treble> (raw)
In-Reply-To: <CABCJKufA-aOcsOqb1NiMQeBGm9Q-JxjoPjsuNpHh0kL4LzfO0w@mail.gmail.com>

On Fri, Nov 13, 2020 at 12:24:32PM -0800, Sami Tolvanen wrote:
> > I still don't see this warning for some reason.
> 
> Do you have CONFIG_XEN enabled? I can reproduce this on ToT master as follows:
> 
> $ git rev-parse HEAD
> 585e5b17b92dead8a3aca4e3c9876fbca5f7e0ba
> $ make defconfig && \
> ./scripts/config -e HYPERVISOR_GUEST -e PARAVIRT -e XEN && \
> make olddefconfig && \
> make -j110
> ...
> $ ./tools/objtool/objtool check -arfld vmlinux.o 2>&1 | grep secondary
> vmlinux.o: warning: objtool: __startup_secondary_64()+0x2: return with
> modified stack frame
> 
> > Is it fixed by adding cpu_bringup_and_idle() to global_noreturns[] in
> > tools/objtool/check.c?
> 
> No, that didn't fix the warning. Here's what I tested:

I think this fixes it:

From: Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH] x86/xen: Fix objtool vmlinux.o validation of xen hypercalls

Objtool vmlinux.o validation is showing warnings like the following:

  # tools/objtool/objtool check -barfld vmlinux.o
  vmlinux.o: warning: objtool: __startup_secondary_64()+0x2: return with modified stack frame
  vmlinux.o: warning: objtool:   xen_hypercall_set_trap_table()+0x0: <=== (sym)

Objtool falls through all the empty hypercall text and gets confused
when it encounters the first real function afterwards.  The empty unwind
hints in the hypercalls aren't working for some reason.  Replace them
with a more straightforward use of STACK_FRAME_NON_STANDARD.

Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/xen/xen-head.S | 9 ++++-----
 include/linux/objtool.h | 8 ++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 2d7c8f34f56c..3c538b1ff4a6 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -6,6 +6,7 @@
 
 #include <linux/elfnote.h>
 #include <linux/init.h>
+#include <linux/objtool.h>
 
 #include <asm/boot.h>
 #include <asm/asm.h>
@@ -67,14 +68,12 @@ SYM_CODE_END(asm_cpu_bringup_and_idle)
 .pushsection .text
 	.balign PAGE_SIZE
 SYM_CODE_START(hypercall_page)
-	.rept (PAGE_SIZE / 32)
-		UNWIND_HINT_EMPTY
-		.skip 32
-	.endr
+	.skip PAGE_SIZE
 
 #define HYPERCALL(n) \
 	.equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \
-	.type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32
+	.type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32; \
+	STACK_FRAME_NON_STANDARD xen_hypercall_##n
 #include <asm/xen-hypercalls.h>
 #undef HYPERCALL
 SYM_CODE_END(hypercall_page)
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 577f51436cf9..746617265236 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -109,6 +109,12 @@ struct unwind_hint {
 	.popsection
 .endm
 
+.macro STACK_FRAME_NON_STANDARD func:req
+	.pushsection .discard.func_stack_frame_non_standard
+		.long \func - .
+	.popsection
+.endm
+
 #endif /* __ASSEMBLY__ */
 
 #else /* !CONFIG_STACK_VALIDATION */
@@ -123,6 +129,8 @@ struct unwind_hint {
 .macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
 .endm
 #endif
+.macro STACK_FRAME_NON_STANDARD func:req
+.endm
 
 #endif /* CONFIG_STACK_VALIDATION */
 
-- 
2.25.4


  parent reply	other threads:[~2020-11-13 22:34 UTC|newest]

Thread overview: 73+ 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
2020-12-03 17:59     ` Masahiro Yamada
2020-12-03 18:47       ` Sami Tolvanen
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
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 [this message]
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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