"Christopher M. Riedl" <c...@codefail.de> writes: > The idle entry/exit code saves/restores GPRs in the stack "red zone" > (Protected Zone according to PowerPC64 ELF ABI v2). However, the offset > used for the first GPR is incorrect and overwrites the back chain - the > Protected Zone actually starts below the current SP. In practice this is > probably not an issue, but it's still incorrect so fix it.
Nice catch. Corrupting the back chain means you can't backtrace from there, which could be confusing for debugging one day. It does make me wonder why we don't just create a stack frame and use the normal macros? It would use a bit more stack space, but we shouldn't be short of stack space when going idle. Nick, was there a particular reason for using the red zone? cheers > diff --git a/arch/powerpc/kernel/idle_book3s.S > b/arch/powerpc/kernel/idle_book3s.S > index 22f249b6f58d..80cf35183e9d 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -53,27 +53,27 @@ _GLOBAL(isa300_idle_stop_mayloss) > mflr r4 > mfcr r5 > /* use stack red zone rather than a new frame for saving regs */ > - std r2,-8*0(r1) > - std r14,-8*1(r1) > - std r15,-8*2(r1) > - std r16,-8*3(r1) > - std r17,-8*4(r1) > - std r18,-8*5(r1) > - std r19,-8*6(r1) > - std r20,-8*7(r1) > - std r21,-8*8(r1) > - std r22,-8*9(r1) > - std r23,-8*10(r1) > - std r24,-8*11(r1) > - std r25,-8*12(r1) > - std r26,-8*13(r1) > - std r27,-8*14(r1) > - std r28,-8*15(r1) > - std r29,-8*16(r1) > - std r30,-8*17(r1) > - std r31,-8*18(r1) > - std r4,-8*19(r1) > - std r5,-8*20(r1) > + std r2,-8*1(r1) > + std r14,-8*2(r1) > + std r15,-8*3(r1) > + std r16,-8*4(r1) > + std r17,-8*5(r1) > + std r18,-8*6(r1) > + std r19,-8*7(r1) > + std r20,-8*8(r1) > + std r21,-8*9(r1) > + std r22,-8*10(r1) > + std r23,-8*11(r1) > + std r24,-8*12(r1) > + std r25,-8*13(r1) > + std r26,-8*14(r1) > + std r27,-8*15(r1) > + std r28,-8*16(r1) > + std r29,-8*17(r1) > + std r30,-8*18(r1) > + std r31,-8*19(r1) > + std r4,-8*20(r1) > + std r5,-8*21(r1) > /* 168 bytes */ > PPC_STOP > b . /* catch bugs */ > @@ -89,8 +89,8 @@ _GLOBAL(isa300_idle_stop_mayloss) > */ > _GLOBAL(idle_return_gpr_loss) > ld r1,PACAR1(r13) > - ld r4,-8*19(r1) > - ld r5,-8*20(r1) > + ld r4,-8*20(r1) > + ld r5,-8*21(r1) > mtlr r4 > mtcr r5 > /* > @@ -98,25 +98,25 @@ _GLOBAL(idle_return_gpr_loss) > * from PACATOC. This could be avoided for that less common case > * if KVM saved its r2. > */ > - ld r2,-8*0(r1) > - ld r14,-8*1(r1) > - ld r15,-8*2(r1) > - ld r16,-8*3(r1) > - ld r17,-8*4(r1) > - ld r18,-8*5(r1) > - ld r19,-8*6(r1) > - ld r20,-8*7(r1) > - ld r21,-8*8(r1) > - ld r22,-8*9(r1) > - ld r23,-8*10(r1) > - ld r24,-8*11(r1) > - ld r25,-8*12(r1) > - ld r26,-8*13(r1) > - ld r27,-8*14(r1) > - ld r28,-8*15(r1) > - ld r29,-8*16(r1) > - ld r30,-8*17(r1) > - ld r31,-8*18(r1) > + ld r2,-8*1(r1) > + ld r14,-8*2(r1) > + ld r15,-8*3(r1) > + ld r16,-8*4(r1) > + ld r17,-8*5(r1) > + ld r18,-8*6(r1) > + ld r19,-8*7(r1) > + ld r20,-8*8(r1) > + ld r21,-8*9(r1) > + ld r22,-8*10(r1) > + ld r23,-8*11(r1) > + ld r24,-8*12(r1) > + ld r25,-8*13(r1) > + ld r26,-8*14(r1) > + ld r27,-8*15(r1) > + ld r28,-8*16(r1) > + ld r29,-8*17(r1) > + ld r30,-8*18(r1) > + ld r31,-8*19(r1) > blr > > /* > @@ -155,27 +155,27 @@ _GLOBAL(isa206_idle_insn_mayloss) > mflr r4 > mfcr r5 > /* use stack red zone rather than a new frame for saving regs */ > - std r2,-8*0(r1) > - std r14,-8*1(r1) > - std r15,-8*2(r1) > - std r16,-8*3(r1) > - std r17,-8*4(r1) > - std r18,-8*5(r1) > - std r19,-8*6(r1) > - std r20,-8*7(r1) > - std r21,-8*8(r1) > - std r22,-8*9(r1) > - std r23,-8*10(r1) > - std r24,-8*11(r1) > - std r25,-8*12(r1) > - std r26,-8*13(r1) > - std r27,-8*14(r1) > - std r28,-8*15(r1) > - std r29,-8*16(r1) > - std r30,-8*17(r1) > - std r31,-8*18(r1) > - std r4,-8*19(r1) > - std r5,-8*20(r1) > + std r2,-8*1(r1) > + std r14,-8*2(r1) > + std r15,-8*3(r1) > + std r16,-8*4(r1) > + std r17,-8*5(r1) > + std r18,-8*6(r1) > + std r19,-8*7(r1) > + std r20,-8*8(r1) > + std r21,-8*9(r1) > + std r22,-8*10(r1) > + std r23,-8*11(r1) > + std r24,-8*12(r1) > + std r25,-8*13(r1) > + std r26,-8*14(r1) > + std r27,-8*15(r1) > + std r28,-8*16(r1) > + std r29,-8*17(r1) > + std r30,-8*18(r1) > + std r31,-8*19(r1) > + std r4,-8*20(r1) > + std r5,-8*21(r1) > cmpwi r3,PNV_THREAD_NAP > bne 1f > IDLE_STATE_ENTER_SEQ_NORET(PPC_NAP) > -- > 2.26.1
