Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

2022-02-06 Thread Michael Ellerman
Christophe Leroy  writes:
> Le 03/02/2022 à 06:39, Michael Ellerman a écrit :
>> Luis Chamberlain  writes:
>>> On Thu, Jan 27, 2022 at 11:28:12AM +, Christophe Leroy wrote:
 book3s/32 and 8xx have a separate area for allocating modules,
 defined by MODULES_VADDR / MODULES_END.

 On book3s/32, it is not possible to protect against execution
 on a page basis. A full 256M segment is either Exec or NoExec.
 The module area is in an Exec segment while vmalloc area is
 in a NoExec segment.

 In order to protect module data against execution, select
 ARCH_WANTS_MODULES_DATA_IN_VMALLOC.

 For the 8xx (and possibly other 32 bits platform in the future),
 there is no such constraint on Exec/NoExec protection, however
 there is a critical distance between kernel functions and callers
 that needs to remain below 32Mbytes in order to avoid costly
 trampolines. By allocating data outside of module area, we
 increase the chance for module text to remain within acceptable
 distance from kernel core text.

 So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.

 Signed-off-by: Christophe Leroy 
 Cc: Michael Ellerman 
 Cc: Benjamin Herrenschmidt 
 Cc: Paul Mackerras 
>>>
>>> Cc list first and then the SOB.
>> 
>> Just delete the Cc: list, it's meaningless.
>> 
>
> Was an easy way to copy you automatically with 'git send-email', but 
> getting it through linuxppc-dev list is enough I guess ?

It's useful for making the tooling Cc the right people, it's fine to use
them for that.

But there's no value in committing them to the git history, I actively
strip them when applying. The fact that someone is Cc'ed on a patch
tells you nothing, given the volume of mail maintainers receive.

The link tag back to the original submission gives you the Cc list
anyway.

cheers


Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

2022-02-02 Thread Christophe Leroy


Le 03/02/2022 à 06:39, Michael Ellerman a écrit :
> Luis Chamberlain  writes:
>> On Thu, Jan 27, 2022 at 11:28:12AM +, Christophe Leroy wrote:
>>> book3s/32 and 8xx have a separate area for allocating modules,
>>> defined by MODULES_VADDR / MODULES_END.
>>>
>>> On book3s/32, it is not possible to protect against execution
>>> on a page basis. A full 256M segment is either Exec or NoExec.
>>> The module area is in an Exec segment while vmalloc area is
>>> in a NoExec segment.
>>>
>>> In order to protect module data against execution, select
>>> ARCH_WANTS_MODULES_DATA_IN_VMALLOC.
>>>
>>> For the 8xx (and possibly other 32 bits platform in the future),
>>> there is no such constraint on Exec/NoExec protection, however
>>> there is a critical distance between kernel functions and callers
>>> that needs to remain below 32Mbytes in order to avoid costly
>>> trampolines. By allocating data outside of module area, we
>>> increase the chance for module text to remain within acceptable
>>> distance from kernel core text.
>>>
>>> So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.
>>>
>>> Signed-off-by: Christophe Leroy 
>>> Cc: Michael Ellerman 
>>> Cc: Benjamin Herrenschmidt 
>>> Cc: Paul Mackerras 
>>
>> Cc list first and then the SOB.
> 
> Just delete the Cc: list, it's meaningless.
> 

Was an easy way to copy you automatically with 'git send-email', but 
getting it through linuxppc-dev list is enough I guess ?

Christophe

Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

2022-02-02 Thread Michael Ellerman
Luis Chamberlain  writes:
> On Thu, Jan 27, 2022 at 11:28:12AM +, Christophe Leroy wrote:
>> book3s/32 and 8xx have a separate area for allocating modules,
>> defined by MODULES_VADDR / MODULES_END.
>> 
>> On book3s/32, it is not possible to protect against execution
>> on a page basis. A full 256M segment is either Exec or NoExec.
>> The module area is in an Exec segment while vmalloc area is
>> in a NoExec segment.
>> 
>> In order to protect module data against execution, select
>> ARCH_WANTS_MODULES_DATA_IN_VMALLOC.
>> 
>> For the 8xx (and possibly other 32 bits platform in the future),
>> there is no such constraint on Exec/NoExec protection, however
>> there is a critical distance between kernel functions and callers
>> that needs to remain below 32Mbytes in order to avoid costly
>> trampolines. By allocating data outside of module area, we
>> increase the chance for module text to remain within acceptable
>> distance from kernel core text.
>> 
>> So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.
>> 
>> Signed-off-by: Christophe Leroy 
>> Cc: Michael Ellerman 
>> Cc: Benjamin Herrenschmidt 
>> Cc: Paul Mackerras 
>
> Cc list first and then the SOB.

Just delete the Cc: list, it's meaningless.

cheers


Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

2022-02-02 Thread Luis Chamberlain
On Thu, Jan 27, 2022 at 11:28:12AM +, Christophe Leroy wrote:
> book3s/32 and 8xx have a separate area for allocating modules,
> defined by MODULES_VADDR / MODULES_END.
> 
> On book3s/32, it is not possible to protect against execution
> on a page basis. A full 256M segment is either Exec or NoExec.
> The module area is in an Exec segment while vmalloc area is
> in a NoExec segment.
> 
> In order to protect module data against execution, select
> ARCH_WANTS_MODULES_DATA_IN_VMALLOC.
> 
> For the 8xx (and possibly other 32 bits platform in the future),
> there is no such constraint on Exec/NoExec protection, however
> there is a critical distance between kernel functions and callers
> that needs to remain below 32Mbytes in order to avoid costly
> trampolines. By allocating data outside of module area, we
> increase the chance for module text to remain within acceptable
> distance from kernel core text.
> 
> So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.
> 
> Signed-off-by: Christophe Leroy 
> Cc: Michael Ellerman 
> Cc: Benjamin Herrenschmidt 
> Cc: Paul Mackerras 

Cc list first and then the SOB.

  Luis


[PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

2022-01-27 Thread Christophe Leroy
book3s/32 and 8xx have a separate area for allocating modules,
defined by MODULES_VADDR / MODULES_END.

On book3s/32, it is not possible to protect against execution
on a page basis. A full 256M segment is either Exec or NoExec.
The module area is in an Exec segment while vmalloc area is
in a NoExec segment.

In order to protect module data against execution, select
ARCH_WANTS_MODULES_DATA_IN_VMALLOC.

For the 8xx (and possibly other 32 bits platform in the future),
there is no such constraint on Exec/NoExec protection, however
there is a critical distance between kernel functions and callers
that needs to remain below 32Mbytes in order to avoid costly
trampolines. By allocating data outside of module area, we
increase the chance for module text to remain within acceptable
distance from kernel core text.

So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.

Signed-off-by: Christophe Leroy 
Cc: Michael Ellerman 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
---
 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b779603978e1..242eed8cedf8 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -152,6 +152,7 @@ config PPC
select ARCH_WANT_IPC_PARSE_VERSION
select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
select ARCH_WANT_LD_ORPHAN_WARN
+   select ARCH_WANTS_MODULES_DATA_IN_VMALLOC   if PPC_BOOK3S_32 || 
PPC_8xx
select ARCH_WEAK_RELEASE_ACQUIRE
select BINFMT_ELF
select BUILDTIME_TABLE_SORT
-- 
2.33.1