ARM: entry: fix Thumb2 bug in iWMMXt exception handling
Subsystems (2)
PATCH 1/1 ARM: entry: fix Thumb2 bug in iWMMXt exception handling
The Thumb2 version of the FP exception handling entry code treats the register holding the CP number (R8) differently, resulting in the iWMMXT CP number check to be incorrect.
Fix this by unifying the ARM and Thumb2 code paths, by switching the order of the additions of the TI_USED_CP offset and the shifted CP index.
Cc <[email protected]>
Fixes b86040a59feb ("Thumb-2: Implementation of the unified start-up and exceptions code")
Signed-off-by Ard Biesheuvel <[email protected]>
--- arch/arm/kernel/entry-armv.S | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
Found through inspection, while I was looking at the entry code for the IRQ and vmap'ed stacks work. Not sure whether/how this affects the Thumb2 kernel running on PJ4 based systems.
arch/arm/kernel/entry-armv.S +3 -5
@@ -629,24 +629,22 @@ call_fpe: #endif tst r0, #0x08000000 @ only CDP/CPRT/LDC/STC have bit 27 tstne r0, #0x04000000 @ bit 26 set on both ARM and Thumb-2 reteq lr and r8, r0, #0x00000f00 @ mask out CP number - THUMB( lsr r8, r8, #8 ) mov r7, #1 - add r6, r10, #TI_USED_CP - ARM( strb r7, [r6, r8, lsr #8] ) @ set appropriate used_cp[] - THUMB( strb r7, [r6, r8] ) @ set appropriate used_cp[] + add r6, r10, r8, lsr #8 @ add used_cp[] array offset first + strb r7, [r6, #TI_USED_CP] @ set appropriate used_cp[] #ifdef CONFIG_IWMMXT @ Test if we need to give access to iWMMXt coprocessors ldr r5, [r10, #TI_FLAGS] rsbs r7, r8, #(1 << 8) @ CP 0 or 1 only movscs r7, r5, lsr #(TIF_USING_IWMMXT + 1) bcs iwmmxt_task_enable #endif ARM( add pc, pc, r8, lsr #6 ) - THUMB( lsl r8, r8, #2 ) + THUMB( lsr r8, r8, #6 ) THUMB( add pc, r8 ) nop ret.w lr @ CP#0 W(b) do_fpe @ CP#1 (FPE)
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2.30.2