[PATCH] um: Add mark_rodata_ro support.

[PATCH] um: Add mark_rodata_ro support.

[Thomas Meyer]

This is actually a no-op as all read-only should be read-only in the ELF.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
---
 arch/um/Kconfig.common | 1 +
 arch/um/kernel/mem.c   | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
index 85f6dd2..061009b 100644
--- a/arch/um/Kconfig.common
+++ b/arch/um/Kconfig.common
@@ -2,6 +2,7 @@ config UML
 	bool
 	default y
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_STRICT_KERNEL_RWX
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_UID16
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index e7437ec..027ed03 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -168,7 +168,6 @@ void __init paging_init(void)
  * This can't do anything because nothing in the kernel image can be freed
  * since it's not in kernel physical memory.
  */
-
 void free_initmem(void)
 {
 }
@@ -238,3 +237,7 @@ void *uml_kmalloc(int size, int flags)
 {
 	return kmalloc(size, flags);
 }
+
+void mark_rodata_ro(void)
+{
+}

Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Richard Weinberger]

Thomas,

On Thu, May 18, 2017 at 12:11 AM, Thomas Meyer <thomas@m3y3r.de> wrote:
> This is actually a no-op as all read-only should be read-only in the ELF.

What problem does this patch fix? Or what is the purpose?

-- 
Thanks,
//richard

Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Thomas Meyer]

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> Am 21.05.2017 um 23:28 schrieb Richard Weinberger <richard.weinberger@gmail.com>:
> 
> Thomas,
> 
>> On Thu, May 18, 2017 at 12:11 AM, Thomas Meyer <thomas@m3y3r.de> wrote:
>> This is actually a no-op as all read-only should be read-only in the ELF.
> 
> What problem does this patch fix? Or what is the purpose?

Hi,

It's purely cosmetic; to get rid of the boot message: "This architecture does not have kernel memory protection." in init/main.c

Which isn't true for UML as all read only stuff should end up in a read only ELF section. Shouldn't it?

> 
> -- 
> Thanks,
> //richard
> 
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
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Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Richard Weinberger]

Thomas,

Am 22.05.2017 um 20:14 schrieb Thomas Meyer:
> It's purely cosmetic; to get rid of the boot message: "This architecture does not have kernel memory protection." in init/main.c
> 
> Which isn't true for UML as all read only stuff should end up in a read only ELF section. Shouldn't it?

Hmm, reading /proc/<pid of uml>/maps tells a different story on my host.
Did you check?

Thanks,
//richard

Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Thomas Meyer]

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> Am 22.05.2017 um 20:34 schrieb Richard Weinberger <richard@nod.at>:
> 
> Thomas,
> 
>> Am 22.05.2017 um 20:14 schrieb Thomas Meyer:
>> It's purely cosmetic; to get rid of the boot message: "This architecture does not have kernel memory protection." in init/main.c
>> 
>> Which isn't true for UML as all read only stuff should end up in a read only ELF section. Shouldn't it?
> 
> Hmm, reading /proc/<pid of uml>/maps tells a different story on my host.
> Did you check?

No... I may should have done so...

Okay, but it should be possible to mprotect those regions ?
> 
> Thanks,
> //richard

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Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Richard Weinberger]

Thomas,

Am 22.05.2017 um 21:18 schrieb Thomas Meyer:
> 
>> Am 22.05.2017 um 20:34 schrieb Richard Weinberger <richard@nod.at>:
>>
>> Thomas,
>>
>>> Am 22.05.2017 um 20:14 schrieb Thomas Meyer:
>>> It's purely cosmetic; to get rid of the boot message: "This architecture does not have kernel memory protection." in init/main.c
>>>
>>> Which isn't true for UML as all read only stuff should end up in a read only ELF section. Shouldn't it?
>>
>> Hmm, reading /proc/<pid of uml>/maps tells a different story on my host.
>> Did you check?
> 
> No... I may should have done so...
> 
> Okay, but it should be possible to mprotect those regions ?

Yes, it should.
Can you give it a try?

Thanks,
//richard

Re: [uml-devel] [PATCH] um: Add mark_rodata_ro support.

[Thomas Meyer]

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> Am 22.05.2017 um 21:37 schrieb Richard Weinberger <richard@nod.at>:
> 
> Thomas,
> 
>> Am 22.05.2017 um 21:18 schrieb Thomas Meyer:
>> 
>>> Am 22.05.2017 um 20:34 schrieb Richard Weinberger <richard@nod.at>:
>>> 
>>> Thomas,
>>> 
>>>> Am 22.05.2017 um 20:14 schrieb Thomas Meyer:
>>>> It's purely cosmetic; to get rid of the boot message: "This architecture does not have kernel memory protection." in init/main.c
>>>> 
>>>> Which isn't true for UML as all read only stuff should end up in a read only ELF section. Shouldn't it?
>>> 
>>> Hmm, reading /proc/<pid of uml>/maps tells a different story on my host.
>>> Did you check?
>> 
>> No... I may should have done so...
>> 
>> Okay, but it should be possible to mprotect those regions ?
> 
> Yes, it should.
> Can you give it a try?

Will do so!

> 
> Thanks,
> //richard
> 
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> User-mode-linux-devel mailing list
> User-mode-linux-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel

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