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From: Deepak Gupta <debug@rivosinc.com>
To: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev
Cc: paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, nathan@kernel.org,
	ndesaulniers@google.com, morbo@google.com,
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	falcon@tinylab.org, viro@zeniv.linux.org.uk, bhe@redhat.com,
	chenjiahao16@huawei.com, hca@linux.ibm.com, arnd@arndb.de,
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	paulmck@kernel.org, broonie@kernel.org,
	rick.p.edgecombe@intel.com
Subject: [RFC PATCH 05/12] riscv: fix certain indirect jumps for kernel cfi
Date: Mon,  8 Apr 2024 23:10:36 -0700	[thread overview]
Message-ID: <20240409061043.3269676-6-debug@rivosinc.com> (raw)
In-Reply-To: <20240409061043.3269676-1-debug@rivosinc.com>

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@rivosinc.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


  parent reply	other threads:[~2024-04-09  6:12 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-09  6:10 [RFC PATCH v1] riscv kernel control flow integrity Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 01/12] riscv: zicfiss / zicfilp extension csr and bit definitions Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 02/12] riscv: add landing pad for asm routines Deepak Gupta
2024-04-11 17:15   ` Sami Tolvanen
2024-04-11 17:53     ` Deepak Gupta
2024-04-11 18:33       ` Sami Tolvanen
2024-04-09  6:10 ` [RFC PATCH 03/12] riscv: after saving expected landing pad (elp), clear elp state Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 04/12] riscv: update asm call sites with label setup Deepak Gupta
2024-04-09  6:10 ` Deepak Gupta [this message]
2024-04-09  6:10 ` [RFC PATCH 06/12] scs: place init shadow stack in .shadowstack section Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 07/12] riscv/mm: prepare shadow stack for init task for kernel cfi Deepak Gupta
2024-05-12 20:12   ` Alexandre Ghiti
2024-05-13 18:59     ` Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 08/12] riscv: dynamic (zicfiss) shadow call stack support Deepak Gupta
2024-04-11 17:05   ` Sami Tolvanen
2024-04-11 17:30     ` Deepak Gupta
2024-04-11 17:47       ` Sami Tolvanen
2024-04-09  6:10 ` [RFC PATCH 09/12] scs: kernel shadow stack with hardware assistance Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 10/12] riscv/traps: Introduce software check exception Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 11/12] riscv: Kconfig & Makefile for riscv kernel control flow integrity Deepak Gupta
2024-04-09  6:10 ` [RFC PATCH 12/12] riscv: enable kernel shadow stack and landing pad enforcement Deepak Gupta

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