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-rw-r--r--Documentation/arm/Booting5
-rw-r--r--arch/arm/boot/compressed/head.S3
-rw-r--r--arch/arm/kernel/head-nommu.S8
-rw-r--r--arch/arm/kernel/head.S8
4 files changed, 23 insertions, 1 deletions
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting
index 4e686a2ed91e..a341d87d276e 100644
--- a/Documentation/arm/Booting
+++ b/Documentation/arm/Booting
@@ -164,3 +164,8 @@ In either case, the following conditions must be met:
- The boot loader is expected to call the kernel image by jumping
directly to the first instruction of the kernel image.
+ On CPUs supporting the ARM instruction set, the entry must be
+ made in ARM state, even for a Thumb-2 kernel.
+
+ On CPUs supporting only the Thumb instruction set such as
+ Cortex-M class CPUs, the entry must be made in Thumb state.
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index f9da41921c52..51af7091d84d 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -353,7 +353,8 @@ not_relocated: mov r0, #0
mov r0, #0 @ must be zero
mov r1, r7 @ restore architecture number
mov r2, r8 @ restore atags pointer
- mov pc, r4 @ call kernel
+ ARM( mov pc, r4 ) @ call kernel
+ THUMB( bx r4 ) @ entry point is always ARM
.align 2
.type LC0, #object
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index 6b1e0ad9ec3b..d46f25968bec 100644
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -32,8 +32,16 @@
* numbers for r1.
*
*/
+ .arm
+
__HEAD
ENTRY(stext)
+
+ THUMB( adr r9, BSYM(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: )
+
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
@ and irqs disabled
#ifndef CONFIG_CPU_CP15
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 278c1b0ebb2e..742b6108a001 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -71,8 +71,16 @@
* crap here - that's what the boot loader (or in extreme, well justified
* circumstances, zImage) is for.
*/
+ .arm
+
__HEAD
ENTRY(stext)
+
+ THUMB( adr r9, BSYM(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: )
+
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
@ and irqs disabled
mrc p15, 0, r9, c0, c0 @ get processor id