Messages in this thread | | | Date | Tue, 31 Mar 2020 11:47:39 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH 10/12] powerpc/entry32: Blacklist exception entry points for kprobe. |
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Christophe Leroy wrote: > > > Le 30/03/2020 à 20:33, Christophe Leroy a écrit : >> >> >> Le 30/03/2020 à 19:08, Naveen N. Rao a écrit : >>> Christophe Leroy wrote: >>>> kprobe does not handle events happening in real mode. >>>> >>>> As exception entry points are running with MMU disabled, >>>> blacklist them. >>>> >>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> >>>> --- >>>> arch/powerpc/kernel/entry_32.S | 7 +++++++ >>>> 1 file changed, 7 insertions(+) >>>> >>>> diff --git a/arch/powerpc/kernel/entry_32.S >>>> b/arch/powerpc/kernel/entry_32.S >>>> index 94f78c03cb79..9a1a45d6038a 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 >>>> @@ -286,6 +291,8 @@ reenable_mmu: >>>> lwz r2, GPR2(r11) >>>> b fast_exception_return >>>> #endif >>>> +_ASM_NOKPROBE_SYMBOL(transfer_to_handler) >>>> +_ASM_NOKPROBE_SYMBOL(transfer_to_handler_cont) >>> >>> These are added after 'reenable_mmu', which is itself not blacklisted. >>> Is that intentional? >> >> Yes I put it as the complete end of the entry part, ie just before >> stack_ovf which is a function by itself. >> >> Note that reenable_mmu is inside an #ifdef CONFIG_TRACE_IRQFLAGS. >> >> I'm not completely sure where to put the _ASM_NOKPROBE_SYMBOL()s, that's >> the reason why I put it close to the symbol itself in my first series. >> >> Could you have a look at the code and tell me what looks the most >> appropriate as a location to you ? >> >> https://elixir.bootlin.com/linux/v5.6/source/arch/powerpc/kernel/entry_32.S#L230 > > Ok, thinking about it once more, I guess we have a problem as everything > after that reenable_mmu will be visible.
I see that we reach reenable_mmu through a 'rfi' with MSR_KERNEL, which seems safe to me. So, I figured it can be probed without issues?
- Naveen
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