diff options
| author | Vladimir Murzin <vladimir.murzin@arm.com> | 2019-01-25 15:18:37 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2019-02-01 21:44:19 +0000 |
| commit | 72cd4064fccaae15ab84d40d4be23667402df4ed (patch) | |
| tree | dbd4813fa104ed4e0359e5a546acee47fb5ef613 /arch/arm/mm | |
| parent | eb7ff9023e4f2998d527b37bffe794759800332a (diff) | |
ARM: 8830/1: NOMMU: Toggle only bits in EXC_RETURN we are really care of
ARMv8M introduces support for Security extension to M class, among
other things it affects exception handling, especially, encoding of
EXC_RETURN.
The new bits have been added:
Bit [6] Secure or Non-secure stack
Bit [5] Default callee register stacking
Bit [0] Exception Secure
which conflicts with hard-coded value of EXC_RETURN:
In fact, we only care of few bits:
Bit [3] Mode (0 - Handler, 1 - Thread)
Bit [2] Stack pointer selection (0 - Main, 1 - Process)
We can toggle only those bits and left other bits as they were on
exception entry.
It is basically, what patch does - saves EXC_RETURN when we do
transition form Thread to Handler mode (it is first svc), so later
saved value is used instead of EXC_RET_THREADMODE_PROCESSSTACK.
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/mm')
| -rw-r--r-- | arch/arm/mm/proc-v7m.S | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/arm/mm/proc-v7m.S b/arch/arm/mm/proc-v7m.S index 47a5acc64433..92e84181933a 100644 --- a/arch/arm/mm/proc-v7m.S +++ b/arch/arm/mm/proc-v7m.S @@ -139,6 +139,9 @@ __v7m_setup_cont: cpsie i svc #0 1: cpsid i + ldr r0, =exc_ret + orr lr, lr, #EXC_RET_THREADMODE_PROCESSSTACK + str lr, [r0] ldmia sp, {r0-r3, r12} str r5, [r12, #11 * 4] @ restore the original SVC vector entry mov lr, r6 @ restore LR |