[PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[Anshuman Khandual]

Late initialisation of EXECMEM inherently requires EXEMEM itself, and hence
this dependency should not be left with the subscribing platforms.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <kees@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This patch applies on v6.13-rc1

 arch/Kconfig       | 1 +
 arch/arm64/Kconfig | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 6682b2a53e34..17716f32dc44 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1058,6 +1058,7 @@ config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
 
 config ARCH_WANTS_EXECMEM_LATE
 	bool
+	depends on EXECMEM
 	help
 	  For architectures that do not allocate executable memory early on
 	  boot, but rather require its initialization late when there is
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b5479c8b454c..b146372bc365 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -113,7 +113,7 @@ config ARM64
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
 	select ARCH_WANT_LD_ORPHAN_WARN
-	select ARCH_WANTS_EXECMEM_LATE if EXECMEM
+	select ARCH_WANTS_EXECMEM_LATE
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
 	select ARCH_HAS_UBSAN
-- 
2.30.2

Re: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[kernel test robot]

Hi Anshuman,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/mm-execmem-Make-ARCH_WANTS_EXECMEM_LATE-depend-on-EXECMEM/20241209-111533
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20241209031251.515903-1-anshuman.khandual%40arm.com
patch subject: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM
config: arm64-kismet-CONFIG_ARCH_WANTS_EXECMEM_LATE-CONFIG_ARM64-0-0 (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/config)
reproduce: (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412092048.tTzJ5szH-lkp@intel.com/

kismet warnings: (new ones prefixed by >>)
>> kismet: WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE when selected by ARM64
   WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE
     Depends on [n]: EXECMEM [=n]
     Selected by [y]:
     - ARM64 [=y]

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[Anshuman Khandual]

On 12/9/24 18:06, kernel test robot wrote:
> Hi Anshuman,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on akpm-mm/mm-everything]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/mm-execmem-Make-ARCH_WANTS_EXECMEM_LATE-depend-on-EXECMEM/20241209-111533
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link:    https://lore.kernel.org/r/20241209031251.515903-1-anshuman.khandual%40arm.com
> patch subject: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM
> config: arm64-kismet-CONFIG_ARCH_WANTS_EXECMEM_LATE-CONFIG_ARM64-0-0 (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/config)
> reproduce: (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202412092048.tTzJ5szH-lkp@intel.com/
> 
> kismet warnings: (new ones prefixed by >>)
>>> kismet: WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE when selected by ARM64
>    WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE
>      Depends on [n]: EXECMEM [=n]
>      Selected by [y]:
>      - ARM64 [=y]

Although above mentioned config here has CONFIG_ARCH_WANTS_EXECMEM_LATE=y
and CONFIG_EXECMEM=n (actually absent), could that really happen though ?

Tried making CONFIG_EXECMEM=n (rather deselecting) but that did now allow
setting CONFIG_EXECMEM=n, it always remained set. Reverting this patch i.e
the current behaviour is also the same (CONFIG_EXECMEM always remains set).

select ARCH_WANTS_EXECMEM_LATE if EXECMEM

Above statement seems to be selecting EXECMEM as well but the intent seems
to be a dependency check instead! OR arch selection for a config brings in
all its dependencies as well.

If the selection is always, should this change be like the following ?

config ARCH_WANTS_EXECMEM_LATE
 	bool
	selects EXECMEM

Although a similar config ARCH_WANTS_EXECMEM_ROX is dependent on MMU and
!HIGHMEM at the generic memory level.

Re: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[Catalin Marinas]

On Mon, Dec 09, 2024 at 07:43:32PM +0530, Anshuman Khandual wrote:
> On 12/9/24 18:06, kernel test robot wrote:
> > kernel test robot noticed the following build warnings:
> > 
> > [auto build test WARNING on akpm-mm/mm-everything]
> > 
> > url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/mm-execmem-Make-ARCH_WANTS_EXECMEM_LATE-depend-on-EXECMEM/20241209-111533
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> > patch link:    https://lore.kernel.org/r/20241209031251.515903-1-anshuman.khandual%40arm.com
> > patch subject: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM
> > config: arm64-kismet-CONFIG_ARCH_WANTS_EXECMEM_LATE-CONFIG_ARM64-0-0 (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/config)
> > reproduce: (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202412092048.tTzJ5szH-lkp@intel.com/
> > 
> > kismet warnings: (new ones prefixed by >>)
> >>> kismet: WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE when selected by ARM64
> >    WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE
> >      Depends on [n]: EXECMEM [=n]
> >      Selected by [y]:
> >      - ARM64 [=y]
> 
> Although above mentioned config here has CONFIG_ARCH_WANTS_EXECMEM_LATE=y
> and CONFIG_EXECMEM=n (actually absent), could that really happen though ?
> 
> Tried making CONFIG_EXECMEM=n (rather deselecting) but that did now allow
> setting CONFIG_EXECMEM=n, it always remained set. Reverting this patch i.e
> the current behaviour is also the same (CONFIG_EXECMEM always remains set).
> 
> select ARCH_WANTS_EXECMEM_LATE if EXECMEM
> 
> Above statement seems to be selecting EXECMEM as well but the intent seems
> to be a dependency check instead! OR arch selection for a config brings in
> all its dependencies as well.
> 
> If the selection is always, should this change be like the following ?
> 
> config ARCH_WANTS_EXECMEM_LATE
>  	bool
> 	selects EXECMEM

This is wrong. What ARCH_WANTS_EXECMEM_LATE means is that, _if_ EXECMEM
is enabled, the arch code require its late initialisation. Currently for
arm64 EXECMEM is selected by KPROBES, BPF_JIT and MODULES. So if you
don't have any of these on, you don't need EXECMEM either, no point in
selecting it above just because arm64 wants a specific behaviour (late
initialisation) for EXECMEM.

If you do want a patch for this, I think for arm64 we simply need to
select ARCH_WANTS_EXECMEM_LATE unconditionally. Not much use in having
any dependencies really, it just adds to the clutter. And don't change
the core Kconfig either.

-- 
Catalin

Re: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM

[Anshuman Khandual]

On 12/9/24 22:39, Catalin Marinas wrote:
> On Mon, Dec 09, 2024 at 07:43:32PM +0530, Anshuman Khandual wrote:
>> On 12/9/24 18:06, kernel test robot wrote:
>>> kernel test robot noticed the following build warnings:
>>>
>>> [auto build test WARNING on akpm-mm/mm-everything]
>>>
>>> url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/mm-execmem-Make-ARCH_WANTS_EXECMEM_LATE-depend-on-EXECMEM/20241209-111533
>>> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
>>> patch link:    https://lore.kernel.org/r/20241209031251.515903-1-anshuman.khandual%40arm.com
>>> patch subject: [PATCH] mm/execmem: Make ARCH_WANTS_EXECMEM_LATE depend on EXECMEM
>>> config: arm64-kismet-CONFIG_ARCH_WANTS_EXECMEM_LATE-CONFIG_ARM64-0-0 (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/config)
>>> reproduce: (https://download.01.org/0day-ci/archive/20241209/202412092048.tTzJ5szH-lkp@intel.com/reproduce)
>>>
>>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>>> the same patch/commit), kindly add following tags
>>> | Reported-by: kernel test robot <lkp@intel.com>
>>> | Closes: https://lore.kernel.org/oe-kbuild-all/202412092048.tTzJ5szH-lkp@intel.com/
>>>
>>> kismet warnings: (new ones prefixed by >>)
>>>>> kismet: WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE when selected by ARM64
>>>    WARNING: unmet direct dependencies detected for ARCH_WANTS_EXECMEM_LATE
>>>      Depends on [n]: EXECMEM [=n]
>>>      Selected by [y]:
>>>      - ARM64 [=y]
>>
>> Although above mentioned config here has CONFIG_ARCH_WANTS_EXECMEM_LATE=y
>> and CONFIG_EXECMEM=n (actually absent), could that really happen though ?
>>
>> Tried making CONFIG_EXECMEM=n (rather deselecting) but that did now allow
>> setting CONFIG_EXECMEM=n, it always remained set. Reverting this patch i.e
>> the current behaviour is also the same (CONFIG_EXECMEM always remains set).
>>
>> select ARCH_WANTS_EXECMEM_LATE if EXECMEM
>>
>> Above statement seems to be selecting EXECMEM as well but the intent seems
>> to be a dependency check instead! OR arch selection for a config brings in
>> all its dependencies as well.
>>
>> If the selection is always, should this change be like the following ?
>>
>> config ARCH_WANTS_EXECMEM_LATE
>>  	bool
>> 	selects EXECMEM
> 
> This is wrong. What ARCH_WANTS_EXECMEM_LATE means is that, _if_ EXECMEM
> is enabled, the arch code require its late initialisation. Currently for

Which implies that even if ARCH_WANTS_EXECMEM_LATE is only applicable when
EXECMEM is enabled, there is no real dependence on the later for platforms
that need a certain init behaviour.

> arm64 EXECMEM is selected by KPROBES, BPF_JIT and MODULES. So if you

EXECMEM gets enabled from the above, not via ARCH_WANTS_EXECMEM_LATE as I
had anticipated earlier.

> don't have any of these on, you don't need EXECMEM either, no point in
> selecting it above just because arm64 wants a specific behaviour (late
> initialisation) for EXECMEM.

Right, specific behaviour preference for a function on a platform should
not necessarily pull in that function itself.

> 
> If you do want a patch for this, I think for arm64 we simply need to
> select ARCH_WANTS_EXECMEM_LATE unconditionally. Not much use in having
> any dependencies really, it just adds to the clutter. And don't change
> the core Kconfig either.

Sure, will do.