Messages in this thread |  | | Date | Tue, 31 Mar 2020 22:35:22 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH v2 10/12] powerpc/entry32: Blacklist exception entry points for kprobe. |
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Christophe Leroy wrote: > kprobe does not handle events happening in real mode. > > As exception entry points are running with MMU disabled, > blacklist them. > > The handling of TLF_NAPPING and TLF_SLEEPING is moved before the > CONFIG_TRACE_IRQFLAGS which contains 'reenable_mmu' because from there > kprobe will be possible as the kernel will run with MMU enabled. > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> > --- > v2: Moved TLF_NAPPING and TLF_SLEEPING handling > --- > arch/powerpc/kernel/entry_32.S | 37 ++++++++++++++++++++-------------- > 1 file changed, 22 insertions(+), 15 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S > index 94f78c03cb79..215aa3a6d4f7 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -51,6 +51,7 @@ mcheck_transfer_to_handler: > mfspr r0,SPRN_DSRR1 > stw r0,_DSRR1(r11) > /* fall through */ > +_ASM_NOKPROBE_SYMBOL(mcheck_transfer_to_handler) > > .globl debug_transfer_to_handler > debug_transfer_to_handler: > @@ -59,6 +60,7 @@ debug_transfer_to_handler: > mfspr r0,SPRN_CSRR1 > stw r0,_CSRR1(r11) > /* fall through */ > +_ASM_NOKPROBE_SYMBOL(debug_transfer_to_handler) > > .globl crit_transfer_to_handler > crit_transfer_to_handler: > @@ -94,6 +96,7 @@ crit_transfer_to_handler: > rlwinm r0,r1,0,0,(31 - THREAD_SHIFT) > stw r0,KSP_LIMIT(r8) > /* fall through */ > +_ASM_NOKPROBE_SYMBOL(crit_transfer_to_handler) > #endif > > #ifdef CONFIG_40x > @@ -115,6 +118,7 @@ crit_transfer_to_handler: > rlwinm r0,r1,0,0,(31 - THREAD_SHIFT) > stw r0,KSP_LIMIT(r8) > /* fall through */ > +_ASM_NOKPROBE_SYMBOL(crit_transfer_to_handler) > #endif > > /* > @@ -127,6 +131,7 @@ crit_transfer_to_handler: > .globl transfer_to_handler_full > transfer_to_handler_full: > SAVE_NVGPRS(r11) > +_ASM_NOKPROBE_SYMBOL(transfer_to_handler_full) > /* fall through */ > > .globl transfer_to_handler > @@ -227,6 +232,23 @@ transfer_to_handler_cont: > SYNC > RFI /* jump to handler, enable MMU */ > > +#if defined (CONFIG_PPC_BOOK3S_32) || defined(CONFIG_E500) > +4: rlwinm r12,r12,0,~_TLF_NAPPING > + stw r12,TI_LOCAL_FLAGS(r2) > + b power_save_ppc32_restore > + > +7: rlwinm r12,r12,0,~_TLF_SLEEPING > + stw r12,TI_LOCAL_FLAGS(r2) > + lwz r9,_MSR(r11) /* if sleeping, clear MSR.EE */ > + rlwinm r9,r9,0,~MSR_EE > + lwz r12,_LINK(r11) /* and return to address in LR */ > + kuap_restore r11, r2, r3, r4, r5 > + lwz r2, GPR2(r11) > + b fast_exception_return > +#endif > +_ASM_NOKPROBE_SYMBOL(transfer_to_handler) > +_ASM_NOKPROBE_SYMBOL(transfer_to_handler_cont) > +
A very minor nit is that the above NOKPROBE annotation actually covers the block of code below between the label '1:' till 'reenable_mmu', but isn't obvious from the code. Splitting off 'reenable_mmu' would have made that clear.
You don't have to fix that though -- a kprobe still won't be allowed there and anyone interested should be able to look up this mail chain.
- Naveen
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