From: Josh Poimboeuf <jpoimboe@redhat.com>
To: "Jürgen Groß" <jgross@suse.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Sami Tolvanen <samitolvanen@google.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Kees Cook <keescook@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux@googlegroups.com,
Miroslav Benes <mbenes@suse.cz>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH 15/21] x86/xen/pvh: Convert indirect jump to retpoline
Date: Fri, 15 Jan 2021 09:08:11 -0600 [thread overview]
Message-ID: <20210115150811.abom3lkutyrwetpi@treble> (raw)
In-Reply-To: <12afb52c-f555-656e-d544-c2965a616bdc@suse.com>
On Fri, Jan 15, 2021 at 06:24:10AM +0100, Jürgen Groß wrote:
> On 14.01.21 20:40, Josh Poimboeuf wrote:
> > It's kernel policy to not have (unannotated) indirect jumps because of
> > Spectre v2. This one's probably harmless, but better safe than sorry.
> > Convert it to a retpoline.
> >
> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Cc: Juergen Gross <jgross@suse.com>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > ---
> > arch/x86/platform/pvh/head.S | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
> > index 43b4d864817e..d87cebd08d32 100644
> > --- a/arch/x86/platform/pvh/head.S
> > +++ b/arch/x86/platform/pvh/head.S
> > @@ -16,6 +16,7 @@
> > #include <asm/boot.h>
> > #include <asm/processor-flags.h>
> > #include <asm/msr.h>
> > +#include <asm/nospec-branch.h>
> > #include <xen/interface/elfnote.h>
> > __HEAD
> > @@ -105,7 +106,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
> > /* startup_64 expects boot_params in %rsi. */
> > mov $_pa(pvh_bootparams), %rsi
> > mov $_pa(startup_64), %rax
> > - jmp *%rax
> > + JMP_NOSPEC rax
>
> I'd rather have it annotated only.
>
> Using ALTERNATIVE in very early boot code is just adding needless
> clutter, as the retpoline variant won't ever be active.
Yeah, Andy pointed out something similar. I'll be changing this to an
annotation.
--
Josh
next prev parent reply other threads:[~2021-01-15 15:10 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 19:39 [PATCH 00/21] objtool: vmlinux.o and CLANG LTO support Josh Poimboeuf
2021-01-14 19:39 ` [PATCH 01/21] objtool: Fix seg fault in BT_FUNC() with fake jump Josh Poimboeuf
2021-01-14 20:04 ` Josh Poimboeuf
2021-01-14 19:39 ` [PATCH 02/21] objtool: Fix error handling for STD/CLD warnings Josh Poimboeuf
2021-01-14 19:39 ` [PATCH 03/21] objtool: Fix retpoline detection in asm code Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 04/21] objtool: Fix ".cold" section suffix check for newer versions of GCC Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 05/21] objtool: Support retpoline jump detection for vmlinux.o Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 06/21] x86/ftrace: Add UNWIND_HINT_FUNC annotation for ftrace_stub Josh Poimboeuf
2021-01-14 20:42 ` Steven Rostedt
2021-01-14 19:40 ` [PATCH 07/21] objtool: Assume only ELF functions do sibling calls Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 08/21] objtool: Add asm version of STACK_FRAME_NON_STANDARD Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 09/21] objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 10/21] objtool: Add xen_start_kernel() to noreturn list Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 11/21] objtool: Move unsuffixed symbol conversion to a helper function Josh Poimboeuf
2021-01-14 20:55 ` [PATCH v1.1 " Josh Poimboeuf
2021-01-14 21:30 ` Sedat Dilek
2021-01-14 19:40 ` [PATCH 12/21] objtool: Add CONFIG_CFI_CLANG support Josh Poimboeuf
2021-01-14 20:49 ` Sami Tolvanen
2021-01-14 20:52 ` Josh Poimboeuf
2021-01-14 20:56 ` [PATCH v1.1 " Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 13/21] x86/xen: Support objtool validation in xen-asm.S Josh Poimboeuf
2021-01-15 0:31 ` boris.ostrovsky
2021-01-14 19:40 ` [PATCH 14/21] x86/xen: Support objtool vmlinux.o validation in xen-head.S Josh Poimboeuf
2021-01-15 0:32 ` boris.ostrovsky
2021-01-15 5:17 ` Jürgen Groß
2021-01-15 19:46 ` Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 15/21] x86/xen/pvh: Convert indirect jump to retpoline Josh Poimboeuf
2021-01-15 0:33 ` boris.ostrovsky
2021-01-15 5:24 ` Jürgen Groß
2021-01-15 15:08 ` Josh Poimboeuf [this message]
2021-01-14 19:40 ` [PATCH 16/21] x86/ftrace: Support objtool vmlinux.o validation in ftrace_64.S Josh Poimboeuf
2021-01-14 20:42 ` Steven Rostedt
2021-01-14 19:40 ` [PATCH 17/21] x86/acpi: Convert indirect jump to retpoline Josh Poimboeuf
2021-01-14 22:59 ` Andrew Cooper
2021-01-14 23:47 ` Josh Poimboeuf
2021-01-15 0:54 ` Andrew Cooper
2021-01-14 19:40 ` [PATCH 18/21] x86/acpi: Support objtool validation in wakeup_64.S Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 19/21] x86/power: Convert indirect jumps to retpolines Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 20/21] x86/power: Move restore_registers() to top of the file Josh Poimboeuf
2021-01-14 19:40 ` [PATCH 21/21] x86/power: Support objtool validation in hibernate_asm_64.S Josh Poimboeuf
2021-01-15 0:41 ` [PATCH 00/21] objtool: vmlinux.o and CLANG LTO support Sami Tolvanen
2021-01-15 0:49 ` Nick Desaulniers
2021-01-15 19:52 ` Josh Poimboeuf
2021-01-15 20:19 ` Sedat Dilek
2021-01-15 20:59 ` Josh Poimboeuf
2021-01-15 21:01 ` Sedat Dilek
2021-01-18 17:22 ` Josh Poimboeuf
2021-01-19 21:29 ` Nick Desaulniers
2021-01-20 15:37 ` Josh Poimboeuf
2021-01-15 4:51 ` Sedat Dilek
2021-01-15 5:18 ` Sedat Dilek
2021-01-15 15:30 ` Sedat Dilek
2021-01-15 18:54 ` Sedat Dilek
2021-01-15 19:28 ` Josh Poimboeuf
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