| Message ID | aea027844b12fcbc29ea78d26c5848a6794d1688.1585474724.git.christophe.leroy@c-s.fr (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [01/12] powerpc/52xx: Blacklist functions running with MMU disabled for kprobe | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (c6624071c338732402e8c726df6a4074473eaa0e) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 43 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
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? - Naveen
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 Thanks Christophe
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. So I'll respin Christophe
Christophe Leroy wrote: > > > 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. Ok, I see what you mean. 'reenable_mmu' can probably be moved after the end of 'transfer_to_handler_cont' (as also removing what looks to be an unused label '1' for the branch to trace_hardirqs_off), but that's a minor thing. From the blacklisting point, this is not an issue. - Naveen
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
Le 31/03/2020 à 08:17, Naveen N. Rao a écrit : > 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? Yes it can. And that's the reason why I didn't blacklist it. However the 4: and 7: which are after reenable_mmu are called from earlier, at a time we are still in real mode. So I need to do something about that I guess. Christophe
Christophe Leroy wrote: > > > Le 31/03/2020 à 08:17, Naveen N. Rao a écrit : >> 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? > > Yes it can. And that's the reason why I didn't blacklist it. However the > 4: and 7: which are after reenable_mmu are called from earlier, at a > time we are still in real mode. So I need to do something about that I > guess. Ah yes, good catch. Makes sense to move 'reenable_mmu' after all. Thanks, Naveen
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) #ifndef CONFIG_VMAP_STACK /*
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(+)