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Message-Id: <20180619192633.21846-2-ard.biesheuvel@linaro.org>
Date: Tue, 19 Jun 2018 21:26:32 +0200
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux@...linux.org.uk, linux@...ck-us.net, mark.rutland@....com,
arnd@...db.de, linux-kernel@...r.kernel.org,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH 1/2] ARM: avoid badr macro for switching to Thumb-2 mode
Switching to Thumb-2 mode can be done using a single 'sub' instruction
so use that instead of the badr macro in various places in the code.
This allows us to reimplement the macro in a way that does not allow
it to be used in ARM code sequences when building a Thumb2 kernel.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
arch/arm/common/mcpm_head.S | 5 ++---
arch/arm/kernel/head-nommu.S | 7 +++----
arch/arm/kernel/head.S | 15 +++++++--------
arch/arm/kernel/sleep.S | 7 +++----
4 files changed, 15 insertions(+), 19 deletions(-)
diff --git a/arch/arm/common/mcpm_head.S b/arch/arm/common/mcpm_head.S
index 08b3bb9bc6a2..4c72314e87a3 100644
--- a/arch/arm/common/mcpm_head.S
+++ b/arch/arm/common/mcpm_head.S
@@ -49,10 +49,9 @@
ENTRY(mcpm_entry_point)
ARM_BE8(setend be)
- THUMB( badr r12, 1f )
- THUMB( bx r12 )
+ THUMB( sub pc, pc, #3 )
THUMB( .thumb )
-1:
+
mrc p15, 0, r0, c0, c0, 5 @ MPIDR
ubfx r9, r0, #0, #8 @ r9 = cpu
ubfx r10, r0, #8, #8 @ r10 = cluster
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index dae8fa2f72c5..406dab0b773c 100644
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -47,10 +47,9 @@ ENTRY(stext)
.arm
ENTRY(stext)
- THUMB( badr r9, 1f ) @ Kernel is always entered in ARM.
- THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
- THUMB( .thumb ) @ switch to Thumb now.
- THUMB(1: )
+ THUMB( sub pc, pc, #3 ) @ Kernel is always entered in ARM.
+ THUMB( .thumb ) @ If this is a Thumb-2 kernel,
+ @ switch to Thumb now.
#endif
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 4b815821ec02..1e44ee9b2074 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -80,10 +80,9 @@
ENTRY(stext)
ARM_BE8(setend be ) @ ensure we are in BE8 mode
- THUMB( badr r9, 1f ) @ Kernel is always entered in ARM.
- THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
- THUMB( .thumb ) @ switch to Thumb now.
- THUMB(1: )
+ THUMB( sub pc, pc, #3 ) @ Kernel is always entered in ARM.
+ THUMB( .thumb ) @ If this is a Thumb-2 kernel,
+ @ switch to Thumb now.
#ifdef CONFIG_ARM_VIRT_EXT
bl __hyp_stub_install
@@ -363,10 +362,10 @@ __turn_mmu_on_loc:
.text
.arm
ENTRY(secondary_startup_arm)
- THUMB( badr r9, 1f ) @ Kernel is entered in ARM.
- THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
- THUMB( .thumb ) @ switch to Thumb now.
- THUMB(1: )
+ THUMB( sub pc, pc, #3 ) @ Kernel is entered in ARM.
+ THUMB( .thumb ) @ If this is a Thumb-2 kernel,
+ @ switch to Thumb now.
+
ENTRY(secondary_startup)
/*
* Common entry point for secondary CPUs.
diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index a8257fc9cf2a..76b3d7c1c8d0 100644
--- a/arch/arm/kernel/sleep.S
+++ b/arch/arm/kernel/sleep.S
@@ -123,10 +123,9 @@ ENDPROC(cpu_resume_after_mmu)
#ifdef CONFIG_MMU
.arm
ENTRY(cpu_resume_arm)
- THUMB( badr r9, 1f ) @ Kernel is entered in ARM.
- THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
- THUMB( .thumb ) @ switch to Thumb now.
- THUMB(1: )
+ THUMB( sub pc, pc, #3 ) @ Kernel is entered in ARM.
+ THUMB( .thumb ) @ If this is a Thumb-2 kernel,
+ @ switch to Thumb now.
#endif
ENTRY(cpu_resume)
--
2.17.1
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