[PATCH v4 01/12] ARM: vfp: Pass thread_info pointer to vfp_support_entry

From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH v4 01/12] ARM: vfp: Pass thread_info pointer to vfp_support_entry
Date: Mon, 20 Mar 2023 14:18:34 +0100	[thread overview]
Message-ID: <20230320131845.3138015-2-ardb@kernel.org> (raw)
In-Reply-To: <20230320131845.3138015-1-ardb@kernel.org>

Instead of dereferencing thread_info in do_vfp, pass the thread_info
pointer to vfp_support_entry via R1. That way, we only use a single
caller save register, which makes it easier to convert do_vfp to C code
in a subsequent patch.

Note that, unlike the CPU number, which can change due to preemption,
passing the thread_info pointer can safely be done with preemption
enabled.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
---
 arch/arm/vfp/entry.S |  5 +----
 arch/arm/vfp/vfphw.S | 10 +++++++---
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S
index 9a89264cdcc0b46e..cfedc2a3dbd68f1c 100644
--- a/arch/arm/vfp/entry.S
+++ b/arch/arm/vfp/entry.S
@@ -22,15 +22,12 @@
 @  IRQs enabled.
 @
 ENTRY(do_vfp)
-	local_bh_disable r10, r4
+	mov	r1, r10
  	ldr	r4, .LCvfp
-	ldr	r11, [r10, #TI_CPU]	@ CPU number
-	add	r10, r10, #TI_VFPSTATE	@ r10 = workspace
 	ldr	pc, [r4]		@ call VFP entry point
 ENDPROC(do_vfp)
 
 ENTRY(vfp_null_entry)
-	local_bh_enable_ti r10, r4
 	ret	lr
 ENDPROC(vfp_null_entry)
 
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index 26c4f61ecfa39638..6d056d810e4868c2 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -6,9 +6,9 @@
  *  Written by Deep Blue Solutions Limited.
  *
  * This code is called from the kernel's undefined instruction trap.
+ * r1 holds the thread_info pointer
  * r9 holds the return address for successful handling.
  * lr holds the return address for unrecognised instructions.
- * r10 points at the start of the private FP workspace in the thread structure
  * sp points to a struct pt_regs (as defined in include/asm/proc/ptrace.h)
  */
 #include <linux/init.h>
@@ -69,13 +69,17 @@
 @ VFP hardware support entry point.
 @
 @  r0  = instruction opcode (32-bit ARM or two 16-bit Thumb)
+@  r1  = thread_info pointer
 @  r2  = PC value to resume execution after successful emulation
 @  r9  = normal "successful" return address
-@  r10 = vfp_state union
-@  r11 = CPU number
 @  lr  = unrecognised instruction return address
 @  IRQs enabled.
 ENTRY(vfp_support_entry)
+	local_bh_disable r1, r4
+
+	ldr	r11, [r1, #TI_CPU]	@ CPU number
+	add	r10, r1, #TI_VFPSTATE	@ r10 = workspace
+
 	DBGSTR3	"instr %08x pc %08x state %p", r0, r2, r10
 
 	.fpu	vfpv2
-- 
2.39.2


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