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From: "Jürgen Groß" <jgross@suse.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>, x86@kernel.org
Cc: 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 06:24:10 +0100	[thread overview]
Message-ID: <12afb52c-f555-656e-d544-c2965a616bdc@suse.com> (raw)
In-Reply-To: <adfa2afe5ddc831017222db9f48ad0fbff17c807.1610652862.git.jpoimboe@redhat.com>


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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.


Juergen

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  parent reply	other threads:[~2021-01-15  5:25 UTC|newest]

Thread overview: 58+ 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
2021-01-15  8:49   ` [PATCH " kernel test robot
2021-01-15 14:09   ` kernel test robot
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
2021-01-15 11:07   ` [PATCH " kernel test robot
2021-01-15 17:31   ` kernel test robot
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 [this message]
2021-01-15 15:08     ` Josh Poimboeuf
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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