Re: [Xen-devel] [PATCH v2] xen/arm: add warning if memory modules overlap

[Julien Grall <julien.grall.oss@gmail.com>]

Hi,

On Thu, 17 Oct 2019 at 21:08, Brian Woods <brian.woods@xilinx.com> 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.
>
> Signed-off-by: Brian Woods <brian.woods@xilinx.com>
> ---
> v1 -> v2
>         - removed nested loop and placed check in add_boot_module()
>
> Sample output:
> ...
> (XEN) MODULE[0]: 0000000001400000 - 0000000001542121 Xen
> (XEN) MODULE[1]: 0000000003846000 - 0000000003850080 Device Tree
> (XEN) MODULE[2]: 0000000003853000 - 0000000007fff676 Ramdisk
> (XEN) MODULE[3]: 0000000000080000 - 0000000003180000 Kernel
> (XEN)  RESVD[0]: 0000000003846000 - 0000000003850000
> (XEN)  RESVD[1]: 0000000003853000 - 0000000007fff676
> (XEN)
> (XEN) WARNING: overlap detected in the memory module addresses
> (XEN)
> (XEN) Command line: console=dtuart dtuart=serial0 dom0_mem=1G bootscrub=0 maxcpus=1 timer_slop=0
> ...
>
>  xen/arch/arm/bootfdt.c      | 4 ++++
>  xen/arch/arm/setup.c        | 6 ++++++
>  xen/include/asm-arm/setup.h | 1 +
>  3 files changed, 11 insertions(+)
>
> diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
> index 08fb59f..f8b34d4 100644
> --- a/xen/arch/arm/bootfdt.c
> +++ b/xen/arch/arm/bootfdt.c
> @@ -387,6 +387,10 @@ static void __init early_print_info(void)
>                 mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
>      }
>      printk("\n");
> +
> +    if ( mem_module_overlap )
> +        printk("WARNING: overlap detected in the memory module addresses.\n");

As a user such message would likely put me off. You tell me there are
an overlap, but you don't provide more information even if you likely
have the information in place. However...

> +
>      for ( i = 0 ; i < cmds->nr_mods; i++ )
>          printk("CMDLINE[%"PRIpaddr"]:%s %s\n", cmds->cmdline[i].start,
>                 cmds->cmdline[i].dt_name,
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 705a917..315a131 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -69,6 +69,8 @@ integer_param("xenheap_megabytes", opt_xenheap_megabytes);
>
>  domid_t __read_mostly max_init_domid;
>
> +bool __initdata mem_module_overlap;
> +
>  static __used void init_done(void)
>  {
>      /* Must be done past setting system_state. */
> @@ -254,6 +256,10 @@ struct bootmodule __init *add_boot_module(bootmodule_kind kind,
>                  mod->domU = false;
>              return mod;
>          }
> +
> +        if ( ((mod->start >= start) && (mod->start < start + size)) ||
> +             ((start >= mod->start) && (start < mod->start + mod->size)) )
> +            mem_module_overlap = true;

... What's wrong with just dumping the information here directly?

Cheers,

-- 
Julien Grall

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