linux-kernel - [RFC PATCH 05/12] riscv: fix certain indirect jumps for kernel cfi

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]

Date: Mon,  8 Apr 2024 23:10:36 -0700
From: Deepak Gupta <debug@...osinc.com>
To: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Cc: paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	nathan@...nel.org,
	ndesaulniers@...gle.com,
	morbo@...gle.com,
	justinstitt@...gle.com,
	andy.chiu@...ive.com,
	debug@...osinc.com,
	hankuan.chen@...ive.com,
	guoren@...nel.org,
	greentime.hu@...ive.com,
	samitolvanen@...gle.com,
	cleger@...osinc.com,
	apatel@...tanamicro.com,
	ajones@...tanamicro.com,
	conor.dooley@...rochip.com,
	mchitale@...tanamicro.com,
	dbarboza@...tanamicro.com,
	waylingii@...il.com,
	sameo@...osinc.com,
	alexghiti@...osinc.com,
	akpm@...ux-foundation.org,
	shikemeng@...weicloud.com,
	rppt@...nel.org,
	charlie@...osinc.com,
	xiao.w.wang@...el.com,
	willy@...radead.org,
	jszhang@...nel.org,
	leobras@...hat.com,
	songshuaishuai@...ylab.org,
	haxel@....de,
	samuel.holland@...ive.com,
	namcaov@...il.com,
	bjorn@...osinc.com,
	cuiyunhui@...edance.com,
	wangkefeng.wang@...wei.com,
	falcon@...ylab.org,
	viro@...iv.linux.org.uk,
	bhe@...hat.com,
	chenjiahao16@...wei.com,
	hca@...ux.ibm.com,
	arnd@...db.de,
	kent.overstreet@...ux.dev,
	boqun.feng@...il.com,
	oleg@...hat.com,
	paulmck@...nel.org,
	broonie@...nel.org,
	rick.p.edgecombe@...el.com
Subject: [RFC PATCH 05/12] riscv: fix certain indirect jumps for kernel cfi

Handwritten `__memset` asm routine performs certain 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>
---
 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 35f358e70bdb..e129ebf66986 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)
-- 
2.43.2