linux-kernel - [PATCH 5.15 024/136] riscv: lib: uaccess: fold fixups into body

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Date:   Mon, 29 Aug 2022 12:58:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jisheng Zhang <jszhang@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 024/136] riscv: lib: uaccess: fold fixups into body

From: Jisheng Zhang <jszhang@...nel.org>

[ Upstream commit 9d504f9aa5c1b76673018da9503e76b351a24b8c ]

uaccess functions such __asm_copy_to_user(),  __arch_copy_from_user()
and __clear_user() place their exception fixups in the `.fixup` section
without any clear association with themselves. If we backtrace the
fixup code, it will be symbolized as an offset from the nearest prior
symbol.

Similar as arm64 does, we must move fixups into the body of the
functions themselves, after the usual fast-path returns.

Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/riscv/lib/uaccess.S | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index 63bc691cff91b..ac34f0026adcd 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -173,6 +173,13 @@ ENTRY(__asm_copy_from_user)
 	csrc CSR_STATUS, t6
 	li	a0, 0
 	ret
+
+	/* Exception fixup code */
+10:
+	/* Disable access to user memory */
+	csrs CSR_STATUS, t6
+	mv a0, t5
+	ret
 ENDPROC(__asm_copy_to_user)
 ENDPROC(__asm_copy_from_user)
 EXPORT_SYMBOL(__asm_copy_to_user)
@@ -218,19 +225,12 @@ ENTRY(__clear_user)
 	addi a0, a0, 1
 	bltu a0, a3, 5b
 	j 3b
-ENDPROC(__clear_user)
-EXPORT_SYMBOL(__clear_user)
 
-	.section .fixup,"ax"
-	.balign 4
-	/* Fixup code for __copy_user(10) and __clear_user(11) */
-10:
-	/* Disable access to user memory */
-	csrs CSR_STATUS, t6
-	mv a0, t5
-	ret
+	/* Exception fixup code */
 11:
+	/* Disable access to user memory */
 	csrs CSR_STATUS, t6
 	mv a0, a1
 	ret
-	.previous
+ENDPROC(__clear_user)
+EXPORT_SYMBOL(__clear_user)
-- 
2.35.1