21.07.2020 16:38, Russell King - ARM Linux admin пишет:

On Tue, Jul 21, 2020 at 04:37:09PM +0300, Dmitry Osipenko wrote:

quoted

27.05.2020 15:22, Linus Walleij пишет:

quoted

By using two BIC instructions we can replace the ARM/thumb
split instructions with something that works on either
and also save one instruction.

Based on code from proc-macros.S and an idea from Ard
Biesheuvel.

We need to include <linux/const.h> to expand the
THREAD_SIZE definition properly in the preprocessor.

Suggested-by: Russell King <linux@armlinux.org.uk>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Linus Walleij <redacted>
---
 arch/arm/include/asm/assembler.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 99929122dad7..f218e8cf7f88 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h

@@ -17,6 +17,7 @@
 #error "Only include this from assembly code"
 #endif
 
+#include <linux/const.h>
 #include <asm/ptrace.h>
 #include <asm/domain.h>
 #include <asm/opcodes-virt.h>

@@ -203,10 +204,8 @@
  * Get current thread_info.
  */
 	.macro	get_thread_info, rd
- ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)
- THUMB(	mov	\rd, sp			)
- THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)
-	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
+	bic	\rd, sp, #(THREAD_SIZE - 1) & ~63
+	bic	\rd, \rd, #63
 	.endm
 
 /*

Hello, Linus!

This patch was merged into a recent linux-next, unfortunately it breaks
CONFIG_THUMB2_KERNEL=y compilation:

arch/arm/kernel/entry-common.S: Assembler messages:
arch/arm/kernel/entry-common.S:159: Error: r13 not allowed here -- `bic
tsk,sp,#(((1<<12)<<1)-1)&~63'
arch/arm/kernel/entry-common.S:246: Error: r13 not allowed here -- `bic
tsk,sp,#(((1<<12)<<1)-1)&~63'
make[2]: *** [scripts/Makefile.build:361:
arch/arm/kernel/entry-common.o] Error 1

I've dropped it before you sent this email...

Hello, Russell!

Good to know, thank you!

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