linux-kernel - [PATCH] xtensa: move coprocessor

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Message-Id: <20210226082219.8224-1-jcmvbkbc@gmail.com>
Date:   Fri, 26 Feb 2021 00:22:19 -0800
From:   Max Filippov <jcmvbkbc@...il.com>
To:     linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        Max Filippov <jcmvbkbc@...il.com>, stable@...r.kernel.org
Subject: [PATCH] xtensa: move coprocessor_flush to the .text section

coprocessor_flush is not a part of fast exception handlers, but it uses
parts of fast coprocessor handling code that's why it's in the same
source file. It uses call0 opcode to invoke those parts so there are no
limitations on their relative location, but the rest of the code calls
coprocessor_flush with call8 and that doesn't work when vectors are
placed in a different gigabyte-aligned area than the rest of the kernel.

Move coprocessor_flush from the .exception.text section to the .text so
that it's reachable from the rest of the kernel with call8.

Cc: stable@...r.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/kernel/coprocessor.S | 64 ++++++++++++++++----------------
 1 file changed, 33 insertions(+), 31 deletions(-)

diff --git a/arch/xtensa/kernel/coprocessor.S b/arch/xtensa/kernel/coprocessor.S
index c426b846beef..45cc0ae0af6f 100644
--- a/arch/xtensa/kernel/coprocessor.S
+++ b/arch/xtensa/kernel/coprocessor.S
@@ -99,37 +99,6 @@
 	LOAD_CP_REGS_TAB(6)
 	LOAD_CP_REGS_TAB(7)
 
-/*
- * coprocessor_flush(struct thread_info*, index)
- *                             a2        a3
- *
- * Save coprocessor registers for coprocessor 'index'.
- * The register values are saved to or loaded from the coprocessor area 
- * inside the task_info structure.
- *
- * Note that this function doesn't update the coprocessor_owner information!
- *
- */
-
-ENTRY(coprocessor_flush)
-
-	/* reserve 4 bytes on stack to save a0 */
-	abi_entry(4)
-
-	s32i	a0, a1, 0
-	movi	a0, .Lsave_cp_regs_jump_table
-	addx8	a3, a3, a0
-	l32i	a4, a3, 4
-	l32i	a3, a3, 0
-	add	a2, a2, a4
-	beqz	a3, 1f
-	callx0	a3
-1:	l32i	a0, a1, 0
-
-	abi_ret(4)
-
-ENDPROC(coprocessor_flush)
-
 /*
  * Entry condition:
  *
@@ -245,6 +214,39 @@ ENTRY(fast_coprocessor)
 
 ENDPROC(fast_coprocessor)
 
+	.text
+
+/*
+ * coprocessor_flush(struct thread_info*, index)
+ *                             a2        a3
+ *
+ * Save coprocessor registers for coprocessor 'index'.
+ * The register values are saved to or loaded from the coprocessor area
+ * inside the task_info structure.
+ *
+ * Note that this function doesn't update the coprocessor_owner information!
+ *
+ */
+
+ENTRY(coprocessor_flush)
+
+	/* reserve 4 bytes on stack to save a0 */
+	abi_entry(4)
+
+	s32i	a0, a1, 0
+	movi	a0, .Lsave_cp_regs_jump_table
+	addx8	a3, a3, a0
+	l32i	a4, a3, 4
+	l32i	a3, a3, 0
+	add	a2, a2, a4
+	beqz	a3, 1f
+	callx0	a3
+1:	l32i	a0, a1, 0
+
+	abi_ret(4)
+
+ENDPROC(coprocessor_flush)
+
 	.data
 
 ENTRY(coprocessor_owner)
-- 
2.20.1