[PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[nixiaoming]

mark_rodata_ro is only called by the function mark_readonly when
CONFIG_STRICT_KERNEL_RWX=y,
if CONFIG_STRICT_KERNEL_RWX is not set
a compile warning may be triggered: unused function

Signed-off-by: nixiaoming <nixiaoming@huawei.com>
---
 arch/arm64/mm/mmu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9..849f326 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -491,6 +491,7 @@ static void __init map_mem(pgd_t *pgdp)
 #endif
 }
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
 void mark_rodata_ro(void)
 {
 	unsigned long section_size;
@@ -505,6 +506,7 @@ void mark_rodata_ro(void)
 
 	debug_checkwx();
 }
+#endif
 
 static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
 				      pgprot_t prot, struct vm_struct *vma,
-- 
2.10.1

Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Will Deacon]

On Tue, May 29, 2018 at 09:36:15PM +0800, nixiaoming wrote:
> mark_rodata_ro is only called by the function mark_readonly when
> CONFIG_STRICT_KERNEL_RWX=y,
> if CONFIG_STRICT_KERNEL_RWX is not set
> a compile warning may be triggered: unused function

How are you achieving this configuration? In our Kconfig we select this
unconditionally.

Will

RE: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Nixiaoming]

Unable to set CONFIG_STRICT_KERNEL_RWX=n by make menuconfig ARCH=arm64

When reading the code, I feel it is more appropriate to add macro control here.


-----Original Message-----
From: Will Deacon [mailto:will.deacon@arm.com] 
Sent: Tuesday, May 29, 2018 11:45 PM
To: Nixiaoming <nixiaoming@huawei.com>
Cc: catalin.marinas@arm.com; ard.biesheuvel@linaro.org; marc.zyngier@arm.com; james.morse@arm.com; kristina.martsenko@arm.com; steve.capper@arm.com; tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; akpm@linux-foundation.org; vbabka@suse.cz; mhocko@suse.com; dave.hansen@linux.intel.com; dan.j.williams@intel.com; kirill.shutemov@linux.intel.com; zhang.jia@linux.alibaba.com; schwidefsky@de.ibm.com; heiko.carstens@de.ibm.com; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; x86@kernel.org; linux-s390@vger.kernel.org
Subject: Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

On Tue, May 29, 2018 at 09:36:15PM +0800, nixiaoming wrote:
> mark_rodata_ro is only called by the function mark_readonly when
> CONFIG_STRICT_KERNEL_RWX=y,
> if CONFIG_STRICT_KERNEL_RWX is not set
> a compile warning may be triggered: unused function

How are you achieving this configuration? In our Kconfig we select this
unconditionally.

Will

Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Mark Rutland]

On Wed, May 30, 2018 at 03:31:38AM +0000, Nixiaoming wrote:
> Unable to set CONFIG_STRICT_KERNEL_RWX=n by make menuconfig ARCH=arm64

Indeed. Making this mandatory was a deliberate decision, in part because this
allows simplification of code (e.g. removal of #ifdef guards).

> When reading the code, I feel it is more appropriate to add macro control
> here.

I must disagree. I do not think it makes sense to add an #ifdef for a
configuration option that is mandatory.

There are other places in the kernel that should behave differently if
CONFIG_STRICT_KERNEL_RWX were disabled, so this wouldn't be sufficient even if
we were to make CONFIG_STRICT_KERNEL_RWX optional. i.e. the #ifdef would give
the misleading impression that STRICT_KERNEL_RWX *could* be made optional, even
though this might not function correctly.

Having an #ifdef here makes the code more complicated and confusing, for the
benefit of a case which cannot occur.

Thanks,
Mark.

> -----Original Message-----
> From: Will Deacon [mailto:will.deacon@arm.com] 
> Sent: Tuesday, May 29, 2018 11:45 PM
> To: Nixiaoming <nixiaoming@huawei.com>
> Cc: catalin.marinas@arm.com; ard.biesheuvel@linaro.org; marc.zyngier@arm.com; james.morse@arm.com; kristina.martsenko@arm.com; steve.capper@arm.com; tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; akpm@linux-foundation.org; vbabka@suse.cz; mhocko@suse.com; dave.hansen@linux.intel.com; dan.j.williams@intel.com; kirill.shutemov@linux.intel.com; zhang.jia@linux.alibaba.com; schwidefsky@de.ibm.com; heiko.carstens@de.ibm.com; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; x86@kernel.org; linux-s390@vger.kernel.org
> Subject: Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro
> 
> On Tue, May 29, 2018 at 09:36:15PM +0800, nixiaoming wrote:
> > mark_rodata_ro is only called by the function mark_readonly when
> > CONFIG_STRICT_KERNEL_RWX=y,
> > if CONFIG_STRICT_KERNEL_RWX is not set
> > a compile warning may be triggered: unused function
> 
> How are you achieving this configuration? In our Kconfig we select this
> unconditionally.
> 
> Will

RE: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Nixiaoming]

Because CONFIG_STRICT_KERNEL_RWX=n cannot be set by make menuconfig on arm64/x86/s390 architecture 
So, these three patches should not be necessary
Sorry to disturb everyone
Thank you for your guidance

Thanks

-----Original Message-----
From: Mark Rutland [mailto:mark.rutland@arm.com] 
Sent: Wednesday, May 30, 2018 4:08 PM
To: Nixiaoming <nixiaoming@huawei.com>
Cc: Will Deacon <will.deacon@arm.com>; catalin.marinas@arm.com; ard.biesheuvel@linaro.org; marc.zyngier@arm.com; james.morse@arm.com; kristina.martsenko@arm.com; steve.capper@arm.com; tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; akpm@linux-foundation.org; vbabka@suse.cz; mhocko@suse.com; dave.hansen@linux.intel.com; dan.j.williams@intel.com; kirill.shutemov@linux.intel.com; zhang.jia@linux.alibaba.com; schwidefsky@de.ibm.com; heiko.carstens@de.ibm.com; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; x86@kernel.org; linux-s390@vger.kernel.org
Subject: Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

On Wed, May 30, 2018 at 03:31:38AM +0000, Nixiaoming wrote:
> Unable to set CONFIG_STRICT_KERNEL_RWX=n by make menuconfig ARCH=arm64

Indeed. Making this mandatory was a deliberate decision, in part because this
allows simplification of code (e.g. removal of #ifdef guards).

> When reading the code, I feel it is more appropriate to add macro control
> here.

I must disagree. I do not think it makes sense to add an #ifdef for a
configuration option that is mandatory.

There are other places in the kernel that should behave differently if
CONFIG_STRICT_KERNEL_RWX were disabled, so this wouldn't be sufficient even if
we were to make CONFIG_STRICT_KERNEL_RWX optional. i.e. the #ifdef would give
the misleading impression that STRICT_KERNEL_RWX *could* be made optional, even
though this might not function correctly.

Having an #ifdef here makes the code more complicated and confusing, for the
benefit of a case which cannot occur.

Thanks,
Mark.

> -----Original Message-----
> From: Will Deacon [mailto:will.deacon@arm.com] 
> Sent: Tuesday, May 29, 2018 11:45 PM
> To: Nixiaoming <nixiaoming@huawei.com>
> Cc: catalin.marinas@arm.com; ard.biesheuvel@linaro.org; marc.zyngier@arm.com; james.morse@arm.com; kristina.martsenko@arm.com; steve.capper@arm.com; tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; akpm@linux-foundation.org; vbabka@suse.cz; mhocko@suse.com; dave.hansen@linux.intel.com; dan.j.williams@intel.com; kirill.shutemov@linux.intel.com; zhang.jia@linux.alibaba.com; schwidefsky@de.ibm.com; heiko.carstens@de.ibm.com; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; x86@kernel.org; linux-s390@vger.kernel.org
> Subject: Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro
> 
> On Tue, May 29, 2018 at 09:36:15PM +0800, nixiaoming wrote:
> > mark_rodata_ro is only called by the function mark_readonly when
> > CONFIG_STRICT_KERNEL_RWX=y,
> > if CONFIG_STRICT_KERNEL_RWX is not set
> > a compile warning may be triggered: unused function
> 
> How are you achieving this configuration? In our Kconfig we select this
> unconditionally.
> 
> Will

Re: [PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[Will Deacon]

On Mon, May 28, 2018 at 11:33:53AM +0800, nixiaoming wrote:
> Signed-off-by: nixiaoming <nixiaoming@huawei.com>

Please can you write a commit message explaining what this fixes and also
give me a pointer to patches 2 and 3 from this series?

Will

> ---
>  arch/arm64/mm/mmu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 2dbb2c9..849f326 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -491,6 +491,7 @@ static void __init map_mem(pgd_t *pgdp)
>  #endif
>  }
>  
> +#ifdef CONFIG_STRICT_KERNEL_RWX
>  void mark_rodata_ro(void)
>  {
>  	unsigned long section_size;
> @@ -505,6 +506,7 @@ void mark_rodata_ro(void)
>  
>  	debug_checkwx();
>  }
> +#endif
>  
>  static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
>  				      pgprot_t prot, struct vm_struct *vma,
> -- 
> 2.10.1
> 

[PATCH 1/3] arm64:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

[nixiaoming]

Signed-off-by: nixiaoming <nixiaoming@huawei.com>
---
 arch/arm64/mm/mmu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9..849f326 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -491,6 +491,7 @@ static void __init map_mem(pgd_t *pgdp)
 #endif
 }
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
 void mark_rodata_ro(void)
 {
 	unsigned long section_size;
@@ -505,6 +506,7 @@ void mark_rodata_ro(void)
 
 	debug_checkwx();
 }
+#endif
 
 static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
 				      pgprot_t prot, struct vm_struct *vma,
-- 
2.10.1