2018-05-29 14:01:30

by Xiaoming Ni

Subject: [PATCH 2/3] x86:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

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 <[email protected]>
---
arch/x86/mm/init_32.c | 2 ++
arch/x86/mm/init_64.c | 2 ++
2 files changed, 4 insertions(+)

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index c893c6a..121c567 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -920,6 +920,7 @@ static void mark_nxdata_nx(void)
set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
}

+#ifdef CONFIG_STRICT_KERNEL_RWX
void mark_rodata_ro(void)
{
unsigned long start = PFN_ALIGN(_text);
@@ -957,3 +958,4 @@ void mark_rodata_ro(void)
if (__supported_pte_mask & _PAGE_NX)
debug_checkwx();
}
+#endif /*end of CONFIG_STRICT_KERNEL_RWX*/
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0a40060..1b7a1a7 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1245,6 +1245,7 @@ void set_kernel_text_ro(void)
set_memory_ro(start, (end - start) >> PAGE_SHIFT);
}

+#ifdef CONFIG_STRICT_KERNEL_RWX
void mark_rodata_ro(void)
{
unsigned long start = PFN_ALIGN(_text);
@@ -1298,6 +1299,7 @@ void mark_rodata_ro(void)
*/
pti_clone_kernel_text();
}
+#endif

int kern_addr_valid(unsigned long addr)
{
--
2.10.1

2018-05-30 06:00:16

by Ingo Molnar

Subject: Re: [PATCH 2/3] x86:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

* nixiaoming <[email protected]> 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
>
> Signed-off-by: nixiaoming <[email protected]>
> ---
> arch/x86/mm/init_32.c | 2 ++
> arch/x86/mm/init_64.c | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index c893c6a..121c567 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -920,6 +920,7 @@ static void mark_nxdata_nx(void)
> set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
> }
>
> +#ifdef CONFIG_STRICT_KERNEL_RWX
> void mark_rodata_ro(void)
> {
> unsigned long start = PFN_ALIGN(_text);
> @@ -957,3 +958,4 @@ void mark_rodata_ro(void)
> if (__supported_pte_mask & _PAGE_NX)
> debug_checkwx();
> }
> +#endif /*end of CONFIG_STRICT_KERNEL_RWX*/
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 0a40060..1b7a1a7 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1245,6 +1245,7 @@ void set_kernel_text_ro(void)
> set_memory_ro(start, (end - start) >> PAGE_SHIFT);
> }
>
> +#ifdef CONFIG_STRICT_KERNEL_RWX
> void mark_rodata_ro(void)
> {
> unsigned long start = PFN_ALIGN(_text);
> @@ -1298,6 +1299,7 @@ void mark_rodata_ro(void)
> */
> pti_clone_kernel_text();
> }
> +#endif

NAK, this is very ugly and the changelog doesn't appear to be true: the build
warning does not trigger in the default build, correct?

Thanks,

Ingo

2018-05-30 06:08:21

by Ard Biesheuvel

Subject: Re: [PATCH 2/3] x86:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

On 30 May 2018 at 07:58, Ingo Molnar <[email protected]> wrote:
>
> * nixiaoming <[email protected]> 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
>>
>> Signed-off-by: nixiaoming <[email protected]>
>> ---
>> arch/x86/mm/init_32.c | 2 ++
>> arch/x86/mm/init_64.c | 2 ++
>> 2 files changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
>> index c893c6a..121c567 100644
>> --- a/arch/x86/mm/init_32.c
>> +++ b/arch/x86/mm/init_32.c
>> @@ -920,6 +920,7 @@ static void mark_nxdata_nx(void)
>> set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
>> }
>>
>> +#ifdef CONFIG_STRICT_KERNEL_RWX
>> void mark_rodata_ro(void)
>> {
>> unsigned long start = PFN_ALIGN(_text);
>> @@ -957,3 +958,4 @@ void mark_rodata_ro(void)
>> if (__supported_pte_mask & _PAGE_NX)
>> debug_checkwx();
>> }
>> +#endif /*end of CONFIG_STRICT_KERNEL_RWX*/
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index 0a40060..1b7a1a7 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -1245,6 +1245,7 @@ void set_kernel_text_ro(void)
>> set_memory_ro(start, (end - start) >> PAGE_SHIFT);
>> }
>>
>> +#ifdef CONFIG_STRICT_KERNEL_RWX
>> void mark_rodata_ro(void)
>> {
>> unsigned long start = PFN_ALIGN(_text);
>> @@ -1298,6 +1299,7 @@ void mark_rodata_ro(void)
>> */
>> pti_clone_kernel_text();
>> }
>> +#endif
>
> NAK, this is very ugly and the changelog doesn't appear to be true: the build
> warning does not trigger in the default build, correct?
>

I don't see how the build warning could trigger at all, given that
mark_rodata_ro() has external linkage.

2018-05-30 06:52:24

by Xiaoming Ni

Subject: RE: [PATCH 2/3] x86:add missing CONFIG_STRICT_KERNEL_RWX for mark_rodata_ro

On 30 May 2018 at 2:07PM Ard Biesheuvel [mailto:[email protected]] wrote:

>On 30 May 2018 at 07:58, Ingo Molnar <[email protected]> wrote:
>>
>> * nixiaoming <[email protected]> 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
>....
>>
>> NAK, this is very ugly and the changelog doesn't appear to be true: the build
>> warning does not trigger in the default build, correct?
>>
>
>I don't see how the build warning could trigger at all, given that
>mark_rodata_ro() has external linkage.
>

Unable to set CONFIG_STRICT_KERNEL_RWX=n by make menuconfig ARCH=x86_64
the build warning does not trigger in the default build,
but it should be more appropriate to add CONFIG control to the code.