diff options
| author | Stafford Horne <shorne@gmail.com> | 2018-07-01 14:17:36 +0900 |
|---|---|---|
| committer | Stafford Horne <shorne@gmail.com> | 2018-07-01 16:48:24 +0900 |
| commit | ae15a41a641449f536578b0d9ec0e4ade130deb5 (patch) | |
| tree | aeee6525fa9d315c05c4273bfc5d415e211baf36 /arch/openrisc/kernel/head.S | |
| parent | 560b423dd9af4272a1f3685c2d6b073fdc4af7c7 (diff) | |
openrisc: entry: Fix delay slot exception detection
Originally in patch e6d20c55a4 ("openrisc: entry: Fix delay slot
detection") I fixed delay slot detection, but only for QEMU. We missed
that hardware delay slot detection using delay slot exception flag (DSX)
was still broken. This was because QEMU set the DSX flag in both
pre-exception supervision register (ESR) and supervision register (SR)
register, but on real hardware the DSX flag is only set on the SR
register during exceptions.
Fix this by carrying the DSX flag into the SR register during exception.
We also update the DSX flag read locations to read the value from the SR
register not the pt_regs SR register which represents ESR. The ESR
should never have the DSX flag set.
In the process I updated/removed a few comments to match the current
state. Including removing a comment saying that the DSX detection logic
was inefficient and needed to be rewritten.
I have tested this on QEMU with a patch ensuring it matches the hardware
specification.
Link: https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg00000.html
Fixes: e6d20c55a4 ("openrisc: entry: Fix delay slot detection")
Signed-off-by: Stafford Horne <shorne@gmail.com>
Diffstat (limited to 'arch/openrisc/kernel/head.S')
| -rw-r--r-- | arch/openrisc/kernel/head.S | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S index fb02b2a1d6f2..9fc6b60140f0 100644 --- a/arch/openrisc/kernel/head.S +++ b/arch/openrisc/kernel/head.S @@ -210,8 +210,7 @@ * r4 - EEAR exception EA * r10 - current pointing to current_thread_info struct * r12 - syscall 0, since we didn't come from syscall - * r13 - temp it actually contains new SR, not needed anymore - * r31 - handler address of the handler we'll jump to + * r30 - handler address of the handler we'll jump to * * handler has to save remaining registers to the exception * ksp frame *before* tainting them! @@ -244,6 +243,7 @@ /* r1 is KSP, r30 is __pa(KSP) */ ;\ tophys (r30,r1) ;\ l.sw PT_GPR12(r30),r12 ;\ + /* r4 use for tmp before EA */ ;\ l.mfspr r12,r0,SPR_EPCR_BASE ;\ l.sw PT_PC(r30),r12 ;\ l.mfspr r12,r0,SPR_ESR_BASE ;\ @@ -263,7 +263,10 @@ /* r12 == 1 if we come from syscall */ ;\ CLEAR_GPR(r12) ;\ /* ----- turn on MMU ----- */ ;\ - l.ori r30,r0,(EXCEPTION_SR) ;\ + /* Carry DSX into exception SR */ ;\ + l.mfspr r30,r0,SPR_SR ;\ + l.andi r30,r30,SPR_SR_DSX ;\ + l.ori r30,r30,(EXCEPTION_SR) ;\ l.mtspr r0,r30,SPR_ESR_BASE ;\ /* r30: EA address of handler */ ;\ LOAD_SYMBOL_2_GPR(r30,handler) ;\ |