linux-kernel - Re: [PATCH 03/11] riscv: indirect jmp in asm that's static in nature to use sw guarded jump

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0532c555-1876-449b-89cb-36ce5394433f@canonical.com>
Date: Fri, 25 Jul 2025 08:26:39 +0200
From: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To: Deepak Gupta <debug@...osinc.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Masahiro Yamada <masahiroy@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nicolas Schier <nicolas.schier@...ux.dev>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Monk Chiang <monk.chiang@...ive.com>,
 Kito Cheng <kito.cheng@...ive.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-kbuild@...r.kernel.org, linux-mm@...ck.org, llvm@...ts.linux.dev,
 rick.p.edgecombe@...el.com, broonie@...nel.org, cleger@...osinc.com,
 samitolvanen@...gle.com, apatel@...tanamicro.com, ajones@...tanamicro.com,
 conor.dooley@...rochip.com, charlie@...osinc.com, samuel.holland@...ive.com,
 bjorn@...osinc.com, fweimer@...hat.com, jeffreyalaw@...il.com,
 andrew@...ive.com, ved@...osinc.com
Subject: Re: [PATCH 03/11] riscv: indirect jmp in asm that's static in nature
 to use sw guarded jump

On 25.07.25 01:36, Deepak Gupta wrote:
> Handwritten `__memset` asm routine perform static jumps within
> function and uses `a5` to do that. This would require a landing pad
> instruction at the target. Since its static jump and no memory load is
> involved, use `t2` instead which is exempt from requiring a landing pad.
> 
> Signed-off-by: Deepak Gupta <debug@...osinc.com>

Acked-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>

> ---
>   arch/riscv/lib/memset.S | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S
> index da23b8347e2d..c4a318d8eef3 100644
> --- a/arch/riscv/lib/memset.S
> +++ b/arch/riscv/lib/memset.S
> @@ -56,12 +56,12 @@ SYM_FUNC_START(__memset)
>   
>   	/* Jump into loop body */
>   	/* Assumes 32-bit instruction lengths */
> -	la a5, 3f
> +	la t2, 3f
>   #ifdef CONFIG_64BIT
>   	srli a4, a4, 1
>   #endif
> -	add a5, a5, a4
> -	jr a5
> +	add t2, t2, a4
> +	jr t2
>   3:
>   	REG_S a1,        0(t0)
>   	REG_S a1,    SZREG(t0)
>