xen/arm: add warning if memory modules overlap
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Message ID 1570650447-3225-1-git-send-email-brian.woods@xilinx.com
State Superseded
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Series
  • xen/arm: add warning if memory modules overlap
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Commit Message

Brian Woods Oct. 9, 2019, 7:47 p.m. UTC
It's possible for a misconfigured device tree to cause Xen to crash when
there are overlapping addresses in the memory modules.  Add a warning
when printing the addresses to let the user know there's a possible
issue when DEBUG is enabled.

Signed-off-by: Brian Woods <brian.woods@xilinx.com>
---
sample output:
...
(XEN) MODULE[0]: 0000000001400000 - 000000000153b8f1 Xen         
(XEN) MODULE[1]: 00000000076d2000 - 00000000076dc080 Device Tree 
(XEN) MODULE[2]: 00000000076df000 - 0000000007fff364 Ramdisk     
(XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel      
(XEN)  RESVD[0]: 00000000076d2000 - 00000000076dc000
(XEN)  RESVD[1]: 00000000076df000 - 0000000007fff364
(XEN) 
(XEN) WARNING: modules Xen          and Kernel       overlap
(XEN) 
(XEN) Command line: console=dtuart dtuart=serial0 dom0_mem=1G bootscrub=0 maxcpus=1 timer_slop=0
...

 xen/arch/arm/bootfdt.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

Comments

Julien Grall Oct. 10, 2019, 3:39 p.m. UTC | #1
Hi Brian,

Thank you for the patch.

On 10/9/19 8:47 PM, Brian Woods wrote:
> It's possible for a misconfigured device tree to cause Xen to crash when
> there are overlapping addresses in the memory modules.  Add a warning
> when printing the addresses to let the user know there's a possible
> issue when DEBUG is enabled.
> 
> Signed-off-by: Brian Woods <brian.woods@xilinx.com>
> ---
> sample output:
> ...
> (XEN) MODULE[0]: 0000000001400000 - 000000000153b8f1 Xen
> (XEN) MODULE[1]: 00000000076d2000 - 00000000076dc080 Device Tree
> (XEN) MODULE[2]: 00000000076df000 - 0000000007fff364 Ramdisk
> (XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel
> (XEN)  RESVD[0]: 00000000076d2000 - 00000000076dc000
> (XEN)  RESVD[1]: 00000000076df000 - 0000000007fff364
> (XEN)
> (XEN) WARNING: modules Xen          and Kernel       overlap
> (XEN)
> (XEN) Command line: console=dtuart dtuart=serial0 dom0_mem=1G bootscrub=0 maxcpus=1 timer_slop=0
> ...
> 
>   xen/arch/arm/bootfdt.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
> index 08fb59f..3cb0c43 100644
> --- a/xen/arch/arm/bootfdt.c
> +++ b/xen/arch/arm/bootfdt.c
> @@ -387,6 +387,23 @@ static void __init early_print_info(void)
>                  mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
>       }
>       printk("\n");
> +
> +#ifndef NDEBUG
> +    /*
> +     * Assuming all combinations are checked, only the starting address
> +     * has to be checked if it's in another memory module's range.
> +     */
> +    for ( i = 0 ; i < mods->nr_mods; i++ )
> +        for ( j = 0 ; j < mods->nr_mods; j++ )
> +            if ( (i != j) &&
> +                 (mods->module[i].start >= mods->module[j].start) &&
> +                 (mods->module[i].start <
> +                  mods->module[j].start + mods->module[j].size) )
> +                printk("WARNING: modules %-12s and %-12s overlap\n",
> +                       boot_module_kind_as_string(mods->module[i].kind),
> +                       boot_module_kind_as_string(mods->module[j].kind));

I am not entirely happy with the double for-loop here.

As we already go through all the modules in add_boot_module(). Could you 
look whether this check could be part of it?

This should also allow to have this check for non-debug build as well.

Cheers,
Brian Woods Oct. 11, 2019, 4:43 p.m. UTC | #2
On Thu, Oct 10, 2019 at 04:39:07PM +0100, Julien Grall wrote:
> Hi Brian,
> 
> Thank you for the patch.
> 
> On 10/9/19 8:47 PM, Brian Woods wrote:
> >It's possible for a misconfigured device tree to cause Xen to crash when
> >there are overlapping addresses in the memory modules.  Add a warning
> >when printing the addresses to let the user know there's a possible
> >issue when DEBUG is enabled.
> >
> >Signed-off-by: Brian Woods <brian.woods@xilinx.com>
> >---
> >sample output:
> >...
> >(XEN) MODULE[0]: 0000000001400000 - 000000000153b8f1 Xen
> >(XEN) MODULE[1]: 00000000076d2000 - 00000000076dc080 Device Tree
> >(XEN) MODULE[2]: 00000000076df000 - 0000000007fff364 Ramdisk
> >(XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel
> >(XEN)  RESVD[0]: 00000000076d2000 - 00000000076dc000
> >(XEN)  RESVD[1]: 00000000076df000 - 0000000007fff364
> >(XEN)
> >(XEN) WARNING: modules Xen          and Kernel       overlap
> >(XEN)
> >(XEN) Command line: console=dtuart dtuart=serial0 dom0_mem=1G bootscrub=0 maxcpus=1 timer_slop=0
> >...
> >
> >  xen/arch/arm/bootfdt.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> >diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
> >index 08fb59f..3cb0c43 100644
> >--- a/xen/arch/arm/bootfdt.c
> >+++ b/xen/arch/arm/bootfdt.c
> >@@ -387,6 +387,23 @@ static void __init early_print_info(void)
> >                 mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
> >      }
> >      printk("\n");
> >+
> >+#ifndef NDEBUG
> >+    /*
> >+     * Assuming all combinations are checked, only the starting address
> >+     * has to be checked if it's in another memory module's range.
> >+     */
> >+    for ( i = 0 ; i < mods->nr_mods; i++ )
> >+        for ( j = 0 ; j < mods->nr_mods; j++ )
> >+            if ( (i != j) &&
> >+                 (mods->module[i].start >= mods->module[j].start) &&
> >+                 (mods->module[i].start <
> >+                  mods->module[j].start + mods->module[j].size) )
> >+                printk("WARNING: modules %-12s and %-12s overlap\n",
> >+                       boot_module_kind_as_string(mods->module[i].kind),
> >+                       boot_module_kind_as_string(mods->module[j].kind));
> 
> I am not entirely happy with the double for-loop here.
> 
> As we already go through all the modules in add_boot_module(). Could you
> look whether this check could be part of it?
> 
> This should also allow to have this check for non-debug build as well.
> 
> Cheers,
> 
> -- 
> Julien Grall

To make sure the module is going to get added, you'd need to do the
check after the for loop.  This means there's going to be multiple for
loops just spread over the course of adding the boot modules rather than
one place.

I had this before but decided against it but after changing it to both
starts rather than the stand and end (ends look much uglier), it looks
cleaner.

    for ( i = 0 ; i < mods->nr_mods-1; i++ )
        for ( j = i+1 ; j < mods->nr_mods; j++ )
            if ( ((mods->module[i].start >= mods->module[j].start) &&
                  (mods->module[i].start <=
                   mods->module[j].start + mods->module[j].size)) ||
                 ((mods->module[j].start >= mods->module[i].start) &&
                  (mods->module[j].start <=
                   mods->module[i].start + mods->module[i].size)) )
                printk("WARNING: modules %-12s and %-12s overlap\n",
                       boot_module_kind_as_string(mods->module[i].kind),
                       boot_module_kind_as_string(mods->module[j].kind));

That's also a possibility.

I just don't see a way around it, computationally.  You can split where
the loops are executed but in the end the same amount of checks/total
iterations have to be run.

I was talking to someone and he suggested you could just check Xen at
early boot and then check other modules later.
Julien Grall Oct. 11, 2019, 4:58 p.m. UTC | #3
Hi,

On 10/11/19 5:43 PM, Brian Woods wrote:
> On Thu, Oct 10, 2019 at 04:39:07PM +0100, Julien Grall wrote:
>> Hi Brian,
>>
>> Thank you for the patch.
>>
>> On 10/9/19 8:47 PM, Brian Woods wrote:
>>> It's possible for a misconfigured device tree to cause Xen to crash when
>>> there are overlapping addresses in the memory modules.  Add a warning
>>> when printing the addresses to let the user know there's a possible
>>> issue when DEBUG is enabled.
>>>
>>> Signed-off-by: Brian Woods <brian.woods@xilinx.com>
>>> ---
>>> sample output:
>>> ...
>>> (XEN) MODULE[0]: 0000000001400000 - 000000000153b8f1 Xen
>>> (XEN) MODULE[1]: 00000000076d2000 - 00000000076dc080 Device Tree
>>> (XEN) MODULE[2]: 00000000076df000 - 0000000007fff364 Ramdisk
>>> (XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel
>>> (XEN)  RESVD[0]: 00000000076d2000 - 00000000076dc000
>>> (XEN)  RESVD[1]: 00000000076df000 - 0000000007fff364
>>> (XEN)
>>> (XEN) WARNING: modules Xen          and Kernel       overlap
>>> (XEN)
>>> (XEN) Command line: console=dtuart dtuart=serial0 dom0_mem=1G bootscrub=0 maxcpus=1 timer_slop=0
>>> ...
>>>
>>>   xen/arch/arm/bootfdt.c | 17 +++++++++++++++++
>>>   1 file changed, 17 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
>>> index 08fb59f..3cb0c43 100644
>>> --- a/xen/arch/arm/bootfdt.c
>>> +++ b/xen/arch/arm/bootfdt.c
>>> @@ -387,6 +387,23 @@ static void __init early_print_info(void)
>>>                  mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
>>>       }
>>>       printk("\n");
>>> +
>>> +#ifndef NDEBUG
>>> +    /*
>>> +     * Assuming all combinations are checked, only the starting address
>>> +     * has to be checked if it's in another memory module's range.
>>> +     */
>>> +    for ( i = 0 ; i < mods->nr_mods; i++ )
>>> +        for ( j = 0 ; j < mods->nr_mods; j++ )
>>> +            if ( (i != j) &&
>>> +                 (mods->module[i].start >= mods->module[j].start) &&
>>> +                 (mods->module[i].start <
>>> +                  mods->module[j].start + mods->module[j].size) )
>>> +                printk("WARNING: modules %-12s and %-12s overlap\n",
>>> +                       boot_module_kind_as_string(mods->module[i].kind),
>>> +                       boot_module_kind_as_string(mods->module[j].kind));
>>
>> I am not entirely happy with the double for-loop here.
>>
>> As we already go through all the modules in add_boot_module(). Could you
>> look whether this check could be part of it?
>>
>> This should also allow to have this check for non-debug build as well.
>>
>> Cheers,
>>
>> -- 
>> Julien Grall

Please at least remove the signature in the e-mail you reply to. The 
best would be to trim the e-mail and answer right below the specific 
paragraph.

> 
> To make sure the module is going to get added, you'd need to do the
> check after the for loop.  This means there's going to be multiple for
> loops just spread over the course of adding the boot modules rather than
> one place.

I don't think you need to do the check after the loop. The only way to 
go out of the loop in add_boot_module() is when i reached mods->nr_mods.

> 
> I had this before but decided against it but after changing it to both
> starts rather than the stand and end (ends look much uglier), it looks
> cleaner.
> 
>      for ( i = 0 ; i < mods->nr_mods-1; i++ )
>          for ( j = i+1 ; j < mods->nr_mods; j++ )
>              if ( ((mods->module[i].start >= mods->module[j].start) &&
>                    (mods->module[i].start <=
>                     mods->module[j].start + mods->module[j].size)) ||
>                   ((mods->module[j].start >= mods->module[i].start) &&
>                    (mods->module[j].start <=
>                     mods->module[i].start + mods->module[i].size)) )
>                  printk("WARNING: modules %-12s and %-12s overlap\n",
>                         boot_module_kind_as_string(mods->module[i].kind),
>                         boot_module_kind_as_string(mods->module[j].kind));
> 
> That's also a possibility.
> 
> I just don't see a way around it, computationally.  You can split where
> the loops are executed but in the end the same amount of checks/total
> iterations have to be run.
> 
> I was talking to someone and he suggested you could just check Xen at
> early boot and then check other modules later.

What's wrong with:

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 705a917abf..ecd09ec698 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -254,6 +254,10 @@ struct bootmodule __init 
*add_boot_module(bootmodule_kind kind,
                  mod->domU = false;
              return mod;
          }
+
+        if ((mod->start >= start) &&
+            (mod->start < (start + size)))
+            printk("WARNING: modules...\n");
      }

      mod = &mods->module[mods->nr_mods++];

Cheers,
Brian Woods Oct. 11, 2019, 6:06 p.m. UTC | #4
On Fri, Oct 11, 2019 at 05:58:35PM +0100, Julien Grall wrote:
> Hi,
> 
> Please at least remove the signature in the e-mail you reply to. The best
> would be to trim the e-mail and answer right below the specific paragraph.
> 
> >
> >To make sure the module is going to get added, you'd need to do the
> >check after the for loop.  This means there's going to be multiple for
> >loops just spread over the course of adding the boot modules rather than
> >one place.
> 
> I don't think you need to do the check after the loop. The only way to go
> out of the loop in add_boot_module() is when i reached mods->nr_mods.

See below.

> >
> >I had this before but decided against it but after changing it to both
> >starts rather than the stand and end (ends look much uglier), it looks
> >cleaner.
> >
> >     for ( i = 0 ; i < mods->nr_mods-1; i++ )
> >         for ( j = i+1 ; j < mods->nr_mods; j++ )
> >             if ( ((mods->module[i].start >= mods->module[j].start) &&
> >                   (mods->module[i].start <=
> >                    mods->module[j].start + mods->module[j].size)) ||
> >                  ((mods->module[j].start >= mods->module[i].start) &&
> >                   (mods->module[j].start <=
> >                    mods->module[i].start + mods->module[i].size)) )
> >                 printk("WARNING: modules %-12s and %-12s overlap\n",
> >                        boot_module_kind_as_string(mods->module[i].kind),
> >                        boot_module_kind_as_string(mods->module[j].kind));
> >
> >That's also a possibility.
> >
> >I just don't see a way around it, computationally.  You can split where
> >the loops are executed but in the end the same amount of checks/total
> >iterations have to be run.
> >
> >I was talking to someone and he suggested you could just check Xen at
> >early boot and then check other modules later.
> 
> What's wrong with:
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 705a917abf..ecd09ec698 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -254,6 +254,10 @@ struct bootmodule __init
> *add_boot_module(bootmodule_kind kind,
>                  mod->domU = false;
>              return mod;
>          }
> +
> +        if ((mod->start >= start) &&
> +            (mod->start < (start + size)))
> +            printk("WARNING: modules...\n");
>      }
> 
>      mod = &mods->module[mods->nr_mods++];
> 
> Cheers,
> 
> -- 
> Julien Grall

For that, you'd need to either check the start and end of the added
module or the start of both.  So something like:

if ( ((mod->start >= start) && (mod->start < (start + size))) ||
     ((start >= mod->start) && (start < (mod->start + mod->size))) )
    printk("WARNING: ...");

If you don't you run the risk of having a module overlap but not at the
start of the added module (unless there's a guaranteed order).  You're
still running all of the checks from what I can tell, just not in nested
for loop so. Plus I'm not sure how many times add_boot_module gets run
and the "mod->kind == kind .." if statement gets run and is true.
If the above is true, wouldn't that cause extra checks for the for loop
iterations before it was true?

Brian
Julien Grall Oct. 11, 2019, 6:17 p.m. UTC | #5
Hi,

On 10/11/19 7:06 PM, Brian Woods wrote:
> On Fri, Oct 11, 2019 at 05:58:35PM +0100, Julien Grall wrote:
> For that, you'd need to either check the start and end of the added
> module or the start of both.  So something like:
> 
> if ( ((mod->start >= start) && (mod->start < (start + size))) ||
>       ((start >= mod->start) && (start < (mod->start + mod->size))) )
>      printk("WARNING: ...");
> 
> If you don't you run the risk of having a module overlap but not at the
> start of the added module (unless there's a guaranteed order).  You're
> still running all of the checks from what I can tell, just not in nested
> for loop so. Plus I'm not sure how many times add_boot_module gets run
> and the "mod->kind == kind .." if statement gets run and is true.
> If the above is true, wouldn't that cause extra checks for the for loop
> iterations before it was true?

For non-dom0less case, we are talking about 4 modules max (Xen, Kernel, 
Initramfs, flask policy). Modules cannot be the shared here.

For dom0less, you are unlikely to have that many domains started from 
Xen. So the number of modules will still be limited (even more if you 
share it).

This code is also only called at boot where there are bigger time 
consuming part (such as domheap initialization). So I would be surprised 
if you see any improvement (other than a couple of cycles) in boot time 
here.

Therefore, I would favor a readable solution over a micro-optimized 
solution here.

Cheers,
Brian Woods Oct. 11, 2019, 7:07 p.m. UTC | #6
On Fri, Oct 11, 2019 at 07:17:29PM +0100, Julien Grall wrote:
> Hi,
> 
> On 10/11/19 7:06 PM, Brian Woods wrote:
> >On Fri, Oct 11, 2019 at 05:58:35PM +0100, Julien Grall wrote:
> >For that, you'd need to either check the start and end of the added
> >module or the start of both.  So something like:
> >
> >if ( ((mod->start >= start) && (mod->start < (start + size))) ||
> >      ((start >= mod->start) && (start < (mod->start + mod->size))) )
> >     printk("WARNING: ...");
> >
> >If you don't you run the risk of having a module overlap but not at the
> >start of the added module (unless there's a guaranteed order).  You're
> >still running all of the checks from what I can tell, just not in nested
> >for loop so. Plus I'm not sure how many times add_boot_module gets run
> >and the "mod->kind == kind .." if statement gets run and is true.
> >If the above is true, wouldn't that cause extra checks for the for loop
> >iterations before it was true?
> 
> For non-dom0less case, we are talking about 4 modules max (Xen, Kernel,
> Initramfs, flask policy). Modules cannot be the shared here.
> 
> For dom0less, you are unlikely to have that many domains started from Xen.
> So the number of modules will still be limited (even more if you share it).

Not arguing that.  With the second loop (checking two start addresses)
it's only n(n-1)/2 iterations. Even if you had 12 memory modules, it's
only 66 iterations.  In the large scheme of things, that isn't THAT
many.

> This code is also only called at boot where there are bigger time consuming
> part (such as domheap initialization). So I would be surprised if you see
> any improvement (other than a couple of cycles) in boot time here.
> 
> Therefore, I would favor a readable solution over a micro-optimized solution
> here.

Which is why I wanted to put it where it was in the patch.  Where the
user would see the warning after the information about the memory
modules were printed (and fair early).

Either way, take your pick of location and if it's only debug or not and
I can write it up and test it.

Brian
Julien Grall Oct. 17, 2019, 9:20 a.m. UTC | #7
Hi,

Sorry for the late answer.

On 11/10/2019 20:07, Brian Woods wrote:
> On Fri, Oct 11, 2019 at 07:17:29PM +0100, Julien Grall wrote:
>> This code is also only called at boot where there are bigger time consuming
>> part (such as domheap initialization). So I would be surprised if you see
>> any improvement (other than a couple of cycles) in boot time here.
>>
>> Therefore, I would favor a readable solution over a micro-optimized solution
>> here.
> 
> Which is why I wanted to put it where it was in the patch.  Where the
> user would see the warning after the information about the memory
> modules were printed (and fair early).

I had a think about it, dumping the modules informations before is useful if you 
know that you have one module max per kind. So you avoid to print the modules 
address/size in the warning.

However, it is possible to have multiple kernel module (as long as they don't 
have the same start address), you could end up with the following message:

"WARNING: modules Kernel and Kernel overlap"

To make the message more meaningful, we would need to print the modules 
address/size. Therefore, I don't view that it is important to check overlapping 
in early_print_info(). In this case I would favor any code that don't add a 
double for loop.

While thinking about this case, it made me realize that we only check the start 
address to consider a match. This means if the size is different, then it will 
be ignored. I think we ought to throw at least warning for this case as well.

Would you mind to have a look?

> 
> Either way, take your pick of location and if it's only debug or not and
> I can write it up and test it.

I would still prefer in add_boot_module(). See why above.

Cheers,
Brian Woods Oct. 17, 2019, 7:48 p.m. UTC | #8
On Thu, Oct 17, 2019 at 10:20:11AM +0100, Julien Grall wrote:
> Hi,
> 
> Sorry for the late answer.
> 
> On 11/10/2019 20:07, Brian Woods wrote:
> >Which is why I wanted to put it where it was in the patch.  Where the
> >user would see the warning after the information about the memory
> >modules were printed (and fair early).
> 
> I had a think about it, dumping the modules informations before is useful if
> you know that you have one module max per kind. So you avoid to print the
> modules address/size in the warning.
> 
> However, it is possible to have multiple kernel module (as long as they
> don't have the same start address), you could end up with the following
> message:
> 
> "WARNING: modules Kernel and Kernel overlap"
> 
> To make the message more meaningful, we would need to print the modules
> address/size. Therefore, I don't view that it is important to check
> overlapping in early_print_info(). In this case I would favor any code that
> don't add a double for loop.

Well, adding that information would be easy enough and cheap.  It would
make it multiline prinktk though:
WARNING: memory modules over lap:
	start_addr-end_addr: modulename
	start_addr-end_addr: modulename

If we're not doing that though, would it make sense to have a initdata
bool that checks it in add_boot_module() and then prints a simple
warning that there's a memory module overlap in early_print_info()?
That way there's no nested for loop and it gets printed where all the
addresses get printed (so you can actually figure out where the overlap
is).

> While thinking about this case, it made me realize that we only check the
> start address to consider a match. This means if the size is different, then
> it will be ignored. I think we ought to throw at least warning for this case
> as well.
> 
> Would you mind to have a look?

When you say starting address, do you mean like in the orginal patch?
If so, there's no functional change in checking the starts of n on m and
m on n then checking the start and end of n on m.

> >
> >Either way, take your pick of location and if it's only debug or not and
> >I can write it up and test it.
> 
> I would still prefer in add_boot_module(). See why above.

I wrote I suggested above and tested it so that'll be sent out soon.

Brian
Julien Grall Oct. 17, 2019, 8:23 p.m. UTC | #9
Hi,

On 17/10/2019 20:48, Brian Woods wrote:
> On Thu, Oct 17, 2019 at 10:20:11AM +0100, Julien Grall wrote:
>> Hi,
>>
>> Sorry for the late answer.
>>
>> On 11/10/2019 20:07, Brian Woods wrote:
>>> Which is why I wanted to put it where it was in the patch.  Where the
>>> user would see the warning after the information about the memory
>>> modules were printed (and fair early).
>>
>> I had a think about it, dumping the modules informations before is useful if
>> you know that you have one module max per kind. So you avoid to print the
>> modules address/size in the warning.
>>
>> However, it is possible to have multiple kernel module (as long as they
>> don't have the same start address), you could end up with the following
>> message:
>>
>> "WARNING: modules Kernel and Kernel overlap"
>>
>> To make the message more meaningful, we would need to print the modules
>> address/size. Therefore, I don't view that it is important to check
>> overlapping in early_print_info(). In this case I would favor any code that
>> don't add a double for loop.
> 
> Well, adding that information would be easy enough and cheap.  It would
> make it multiline prinktk though:
> WARNING: memory modules over lap:
> 	start_addr-end_addr: modulename
> 	start_addr-end_addr: modulename

Why do you need a multiline? A single 80-charaters should really be 
sufficient.

> 
> If we're not doing that though, would it make sense to have a initdata
> bool that checks it in add_boot_module() and then prints a simple
> warning that there's a memory module overlap in early_print_info()?
> That way there's no nested for loop and it gets printed where all the
> addresses get printed (so you can actually figure out where the overlap
> is).
Please no. There are no need to add a bool just for the sake of getting 
all the print together.

The more that if you print all the information as I suggested above, you 
don't need to have it printed by early_print_info().

To be honest, I really don't think this is Xen job to check that you 
specify your modules correctly. There are other way to screw up your 
device-tree anyway (like overlap in memory banks or reserved region...).

The modules overlap can really only happen if you try to have your DT 
pre-generated and don't bother to use the bootloader (U-boot/Grub) 
script to generate your DT/modules.

> 
>> While thinking about this case, it made me realize that we only check the
>> start address to consider a match. This means if the size is different, then
>> it will be ignored. I think we ought to throw at least warning for this case
>> as well.
>>
>> Would you mind to have a look?
> 
> When you say starting address, do you mean like in the orginal patch?
> If so, there's no functional change in checking the starts of n on m and
> m on n then checking the start and end of n on m.

No. I meant that you could have a device-tree describing two modules 
starting at the same address, but with a different size.

See the check in add_boot_module() to see if a module already exist of 
the same kind.

Cheers,

Patch
diff mbox series

diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 08fb59f..3cb0c43 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -387,6 +387,23 @@  static void __init early_print_info(void)
                mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
     }
     printk("\n");
+
+#ifndef NDEBUG
+    /*
+     * Assuming all combinations are checked, only the starting address
+     * has to be checked if it's in another memory module's range.
+     */
+    for ( i = 0 ; i < mods->nr_mods; i++ )
+        for ( j = 0 ; j < mods->nr_mods; j++ )
+            if ( (i != j) &&
+                 (mods->module[i].start >= mods->module[j].start) &&
+                 (mods->module[i].start <
+                  mods->module[j].start + mods->module[j].size) )
+                printk("WARNING: modules %-12s and %-12s overlap\n",
+                       boot_module_kind_as_string(mods->module[i].kind),
+                       boot_module_kind_as_string(mods->module[j].kind));
+#endif
+
     for ( i = 0 ; i < cmds->nr_mods; i++ )
         printk("CMDLINE[%"PRIpaddr"]:%s %s\n", cmds->cmdline[i].start,
                cmds->cmdline[i].dt_name,