linux-kernel - Re: [PATCH 2/4] x86/srso: Rename fam17 SRSO infrastructure to srso_fam17

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Date:   Wed, 13 Sep 2023 15:15:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andrew Cooper <andrew.cooper3@...rix.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Babu Moger <babu.moger@....com>, David.Kaplan@....com,
        Nikolay Borisov <nik.borisov@...e.com>,
        gregkh@...uxfoundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/4] x86/srso: Rename fam17 SRSO infrastructure to
 srso_fam17_*()

On Mon, Aug 21, 2023 at 12:27:21PM +0100, Andrew Cooper wrote:
> The naming is inconsistent.  Rename it to fam17 to state the microarchitecture
> it is applicable to, and to mirror the srso_fam19_*() change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@...rix.com>
> ---
> CC: x86@...nel.org
> CC: linux-kernel@...r.kernel.org
> CC: Borislav Petkov <bp@...en8.de>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Josh Poimboeuf <jpoimboe@...nel.org>
> CC: Babu Moger <babu.moger@....com>
> CC: David.Kaplan@....com
> CC: Nikolay Borisov <nik.borisov@...e.com>
> CC: gregkh@...uxfoundation.org
> CC: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/include/asm/nospec-branch.h |  4 ++--
>  arch/x86/kernel/cpu/bugs.c           |  2 +-
>  arch/x86/kernel/vmlinux.lds.S        |  2 +-
>  arch/x86/lib/retpoline.S             | 32 ++++++++++++++--------------
>  4 files changed, 20 insertions(+), 20 deletions(-)
> 

Re your objtool woes:

> -SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
> +	.skip 64 - (srso_fam17_safe_ret - srso_fam17_untrain_ret), 0xcc
> +SYM_START(srso_fam17_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
>  	ANNOTATE_NOENDBR
>  	.byte 0x48, 0xb8
>  
>  /*
>   * This forces the function return instruction to speculate into a trap
> - * (UD2 in srso_return_thunk() below).  This RET will then mispredict
> + * (UD2 in srso_fam17_return_thunk() below).  This RET will then mispredict
>   * and execution will continue at the return site read from the top of
>   * the stack.
>   */
> -SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
> +SYM_INNER_LABEL(srso_fam17_safe_ret, SYM_L_GLOBAL)

Note that there is a mention of 'srso_safe_ret' in
tools/objtool/arch/x86/decode.c:arch_is_embedded_insn() which you
'forgot' to update.

>  	lea 8(%_ASM_SP), %_ASM_SP
>  	ret
>  	int3
>  	int3
>  	/* end of movabs */
>  	lfence
> -	call srso_safe_ret
> +	call srso_fam17_safe_ret
>  	ud2
> -SYM_CODE_END(srso_safe_ret)
> -SYM_FUNC_END(srso_untrain_ret)
> -__EXPORT_THUNK(srso_untrain_ret)
> +SYM_CODE_END(srso_fam17_safe_ret)
> +SYM_FUNC_END(srso_fam17_untrain_ret)
> +__EXPORT_THUNK(srso_fam17_untrain_ret)