linux-kernel - [PATCH v2 2/4] MIPS: microMIPS: Fix the judgment of mm_jr16_op and mm_jalr

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Message-Id: <1611207098-11381-3-git-send-email-hejinyang@loongson.cn>
Date:   Thu, 21 Jan 2021 13:31:36 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paul Burton <paulburton@...nel.org>,
        Jun-Ru Chang <jrjang@...ltek.com>
Subject: [PATCH v2 2/4] MIPS: microMIPS: Fix the judgment of mm_jr16_op and mm_jalr_op

mm16_r5_format.rt is 5 bits, so directly judge the value if equal or not.
mm_jalr_op requires 7th to 16th bits. These 10 which bits generated by
shifting u_format.uimmediate by 6 may be affected by sign extension.
Thus, take out the 10 bits for comparison.

Without this patch, errors may occur, such as these bits are all ones.

Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
---
 arch/mips/kernel/process.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index d737234..74d7fd8 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -292,8 +292,8 @@ static inline int is_jump_ins(union mips_instruction *ip)
 	 * microMIPS is kind of more fun...
 	 */
 	if (mm_insn_16bit(ip->word >> 16)) {
-		if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
-		    (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
+		if (ip->mm16_r5_format.opcode == mm_pool16c_op &&
+		    ip->mm16_r5_format.rt == mm_jr16_op)
 			return 1;
 		return 0;
 	}
@@ -305,7 +305,7 @@ static inline int is_jump_ins(union mips_instruction *ip)
 	if (ip->r_format.opcode != mm_pool32a_op ||
 			ip->r_format.func != mm_pool32axf_op)
 		return 0;
-	return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
+	return ((ip->u_format.uimmediate >> 6) & GENMASK(9, 0)) == mm_jalr_op;
 #else
 	if (ip->j_format.opcode == j_op)
 		return 1;
-- 
2.1.0