From: Peter Zijlstra <peterz@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
linux-kernel@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
Ashok Raj <ashok.raj@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg KH <gregkh@linuxfoundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Jason Baron <jbaron@akamai.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH 08/24] x86,sme: Annotate indirect call
Date: Wed, 31 Jan 2018 10:29:21 +0100 [thread overview]
Message-ID: <20180131092921.GI2269@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1516963050.30244.188.camel@infradead.org>
On Fri, Jan 26, 2018 at 10:37:30AM +0000, David Woodhouse wrote:
> On Tue, 2018-01-23 at 16:25 +0100, Peter Zijlstra wrote:
> > This is boot code, we run this _way_ before userspace comes along to
> > poison our branch predictor.
>
> Hm, objtool knows about sections, doesn't it? Why it is whining about
> indirect jumps in inittext anyway?
>
> In fact, why are we even *doing* retpolines in inittext? Not that we
> are; since we flipped the ALTERNATIVE logic around, at that point we
> still have the 'oldinstr' which is a bare jmp anyway. We might as well
> do this:
>
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -37,10 +37,15 @@
> * as gcc otherwise puts the data into the bss section and not into the init
> * section.
> */
> +#if defined(RETPOLINE) && !defined(MODULE)
> +#define __noretpoline __attribute__((indirect_branch("keep")))
> +#else
> +#define __noretpoline
> +#endif
>
> /* These are for everybody (although not all archs will actually
> discard it in modules) */
> -#define __init __section(.init.text) __cold __inittrace __latent_entropy
> +#define __init __section(.init.text) __cold __inittrace __latent_entropy __noretpoline
> #define __initdata __section(.init.data)
> #define __initconst __section(.init.rodata)
> #define __exitdata __section(.exit.data)
Something like so then?
---
Subject: objtool: Add module specific retpoline rules
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Jan 31 10:18:28 CET 2018
David wanted to not use retpolines in .init.text but that will trip up
objtool retpoline validation, fix that.
Requested-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
scripts/Makefile.build | 2 ++
tools/objtool/builtin-check.c | 3 ++-
tools/objtool/builtin.h | 2 +-
tools/objtool/check.c | 9 +++++++++
4 files changed, 14 insertions(+), 2 deletions(-)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -256,6 +256,8 @@ __objtool_obj := $(objtree)/tools/objtoo
objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
+objtool_args += $(if $(part-of-module), --module,)
+
ifndef CONFIG_FRAME_POINTER
objtool_args += --no-fp
endif
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -29,7 +29,7 @@
#include "builtin.h"
#include "check.h"
-bool no_fp, no_unreachable, retpoline;
+bool no_fp, no_unreachable, retpoline, module;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -40,6 +40,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('f', "no-fp", &no_fp, "Skip frame pointer validation"),
OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"),
OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"),
+ OPT_BOOLEAN('m', "module", &module, "Indicates the object will be part of a kernel module"),
OPT_END(),
};
--- a/tools/objtool/builtin.h
+++ b/tools/objtool/builtin.h
@@ -20,7 +20,7 @@
#include <subcmd/parse-options.h>
extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline;
+extern bool no_fp, no_unreachable, retpoline, module;
extern int cmd_check(int argc, const char **argv);
extern int cmd_orc(int argc, const char **argv);
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1920,6 +1920,15 @@ static int validate_retpoline(struct obj
if (insn->retpoline_safe)
continue;
+ /*
+ * .init.text code is ran before userspace and thus doesn't
+ * strictly need retpolines, except for modules which are
+ * loaded late, they very much do need retpoline in their
+ * .init.text
+ */
+ if (!strcmp(insn->sec->name, ".init.text") && !module)
+ continue;
+
WARN_FUNC("indirect %s found in RETPOLINE build",
insn->sec, insn->offset,
insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
next prev parent reply other threads:[~2018-01-31 9:29 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 15:25 [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 01/24] objtool: Use existing global variables for options Peter Zijlstra
2018-01-23 15:25 ` [PATCH 02/24] objtool: Add retpoline validation Peter Zijlstra
2018-01-23 18:21 ` Borislav Petkov
2018-01-26 9:54 ` David Woodhouse
2018-01-23 15:25 ` [PATCH 03/24] x86/paravirt: Annotate indirect calls Peter Zijlstra
2018-01-25 10:02 ` David Woodhouse
2018-01-25 10:22 ` Peter Zijlstra
2018-01-25 10:26 ` Juergen Gross
2018-01-25 10:52 ` David Woodhouse
2018-01-25 11:35 ` Peter Zijlstra
2018-01-26 9:57 ` David Woodhouse
2018-01-29 17:58 ` Josh Poimboeuf
2018-01-29 18:09 ` David Woodhouse
2018-01-29 18:17 ` Peter Zijlstra
2018-01-29 18:38 ` Josh Poimboeuf
2018-01-29 19:21 ` Peter Zijlstra
2018-01-30 16:02 ` Josh Poimboeuf
2018-01-31 4:13 ` [PATCH] x86/paravirt: Remove 'noreplace-paravirt' cmdline option Josh Poimboeuf
2018-01-31 5:59 ` Juergen Gross
2018-01-31 9:42 ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-23 15:25 ` [PATCH 04/24] x86,nospec: Annotate indirect calls/jumps Peter Zijlstra
2018-01-26 10:19 ` David Woodhouse
2018-01-29 17:44 ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 05/24] x86: Annotate indirect jump in head_64.S Peter Zijlstra
2018-01-26 10:24 ` David Woodhouse
2018-01-23 15:25 ` [PATCH 06/24] x86,kvm: Fix indirect calls in emulator Peter Zijlstra
2018-01-23 20:28 ` Borislav Petkov
2018-01-23 20:48 ` David Woodhouse
2018-01-24 10:35 ` Peter Zijlstra
2018-01-24 10:43 ` Paolo Bonzini
2018-01-25 9:34 ` Peter Zijlstra
2018-01-25 9:49 ` David Woodhouse
2018-01-26 10:57 ` Paolo Bonzini
2018-01-23 15:25 ` [PATCH 07/24] x86,vmx: Fix indirect call Peter Zijlstra
2018-01-25 9:36 ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 08/24] x86,sme: Annotate " Peter Zijlstra
2018-01-26 10:37 ` David Woodhouse
2018-01-29 17:49 ` Peter Zijlstra
2018-01-29 17:50 ` Peter Zijlstra
2018-01-31 9:29 ` Peter Zijlstra [this message]
2018-01-31 15:04 ` Josh Poimboeuf
2018-01-31 16:00 ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 09/24] jump_label: Add branch hints to static_branch_{un,}likely() Peter Zijlstra
2018-01-24 18:46 ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 10/24] sched: Optimize ttwu_stat() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 11/24] x86: Reindent _static_cpu_has Peter Zijlstra
2018-01-23 15:25 ` [PATCH 12/24] x86: Update _static_cpu_has to use all named variables Peter Zijlstra
2018-01-25 19:31 ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 13/24] objtool: Implement base jump_assert support Peter Zijlstra
2018-01-26 10:45 ` David Woodhouse
2018-01-23 15:25 ` [PATCH 14/24] x86: Add a type field to alt_instr Peter Zijlstra
2018-01-23 15:25 ` [PATCH 15/24] x86: Annotate static_cpu_has alternative Peter Zijlstra
2018-01-23 15:25 ` [PATCH 16/24] objtool: Implement jump_assert for _static_cpu_has() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 17/24] objtool: Introduce special_type Peter Zijlstra
2018-01-23 15:25 ` [PATCH 18/24] objtool: More complex static jump implementation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 19/24] objtool: Even more complex static block checks Peter Zijlstra
2018-01-23 15:25 ` [PATCH 20/24] objtool: Another static block fail Peter Zijlstra
2018-01-29 22:52 ` Josh Poimboeuf
2018-01-30 9:56 ` Peter Zijlstra
2018-01-31 3:12 ` Josh Poimboeuf
2018-01-31 10:01 ` Peter Zijlstra
2018-01-31 10:07 ` David Woodhouse
2018-01-31 10:27 ` Peter Zijlstra
2018-01-23 15:26 ` [PATCH 21/24] objtool: Skip static assert when KCOV/KASAN Peter Zijlstra
2018-01-23 15:26 ` [PATCH 22/24] x86/jump_label: Implement arch_static_assert() Peter Zijlstra
2018-01-23 15:26 ` [PATCH 23/24] x86: Force asm-goto Peter Zijlstra
2018-01-23 15:26 ` [PATCH 24/24] x86: Remove FAST_FEATURE_TESTS Peter Zijlstra
2018-01-23 15:42 ` [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:57 ` David Woodhouse
2018-01-23 16:03 ` Peter Zijlstra
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