[PATCH kexec-tools 12/32] kexec: add helper to exlude a region from a set of memory ranges

[Pratyush Anand]

On Thu, May 26, 2016 at 2:26 PM, Russell King - ARM Linux
<linux at armlinux.org.uk> wrote:
> On Wed, May 25, 2016 at 01:30:44PM +0530, Pratyush Anand wrote:
>> On Tue, May 3, 2016 at 3:52 PM, Russell King <rmk at arm.linux.org.uk> wrote:
>> > +int mem_regions_exclude(struct memory_ranges *ranges,
>> > +                       const struct memory_range *range)
>> > +{
>> > +       int i;
>> > +
>> > +       for (i = 0; i < ranges->size; i++) {
>> > +               struct memory_range *r = ranges->ranges + i;
>> > +
>> > +               /*
>> > +                * We assume that crash area is fully contained in
>> > +                * some larger memory area.
>> > +                */
>> > +               if (r->start <= range->start && r->end >= range->end) {
>> > +                       if (r->start == range->start) {
>> > +                               /* Shrink the start of this memory range */
>> > +                               r->start = range->end + 1;
>> > +                       } else if (r->end == range->end) {
>> > +                               /* Shrink the end of this memory range */
>> > +                               r->end = range->start - 1;
>>
>> What if r->start == range->start) && (r->end == range->end)?
>
> I suppose that could happen, so what about this patch on top (untested).

I think, it should be fine, except.....

> This isn't something I'd be able to test on real hardware, it needs a
> separate test-suite to be written to do modular testing...
>
>  kexec/mem_regions.c | 94 +++++++++++++++++++++++++++++++----------------------
>  1 file changed, 55 insertions(+), 39 deletions(-)
>
> diff --git a/kexec/mem_regions.c b/kexec/mem_regions.c
> index c6ba942..4e7061b 100644
> --- a/kexec/mem_regions.c
> +++ b/kexec/mem_regions.c
> @@ -29,6 +29,50 @@ void mem_regions_sort(struct memory_ranges *ranges)
>  }
>
>  /**
> + * mem_regions_add() - add a memory region to a set of ranges
> + * @ranges: ranges to add the memory region to
> + * @max: maximum number of entries in memory region
> + * @base: base address of memory region
> + * @length: length of memory region in bytes
> + * @type: type of memory region
> + *
> + * Add the memory region to the set of ranges, and return %0 if successful,
> + * or %-1 if we ran out of space.
> + */
> +int mem_regions_add(struct memory_ranges *ranges, unsigned long long base,
> +                    unsigned long long length, int type)
> +{
> +       struct memory_range *range;
> +
> +       if (ranges->size >= ranges->max_size)
> +               return -1;
> +
> +       range = ranges->ranges + ranges->size++;
> +       range->start = base;
> +       range->end = base + length - 1;
> +       range->type = type;
> +
> +       return 0;
> +}
> +
> +static void mem_regions_remove(struct memory_ranges *ranges, int index)
> +{
> +       int tail_entries;
> +
> +       /* we are assured to have at least one entry */
> +       ranges->size -= 1;
> +
> +       /* if we have following entries, shuffle them down one place */
> +       tail_entries = ranges->size - index;
> +       if (tail_entries)
> +               memmove(ranges->ranges + index, ranges->ranges + index + 1,
> +                       tail_entries * sizeof(*ranges->ranges));
> +
> +       /* zero the new tail entry */
> +       memset(ranges->ranges + ranges->size, 0, sizeof(*ranges->ranges));
> +}
> +
> +/**
>   * mem_regions_exclude() - excludes a memory region from a set of memory ranges
>   * @ranges: memory ranges to exclude the region from
>   * @range: memory range to exclude
> @@ -40,7 +84,7 @@ void mem_regions_sort(struct memory_ranges *ranges)
>  int mem_regions_exclude(struct memory_ranges *ranges,
>                         const struct memory_range *range)
>  {
> -       int i;
> +       int i, ret;
>
>         for (i = 0; i < ranges->size; i++) {
>                 struct memory_range *r = ranges->ranges + i;
> @@ -51,25 +95,25 @@ int mem_regions_exclude(struct memory_ranges *ranges,
>                  */
>                 if (r->start <= range->start && r->end >= range->end) {
>                         if (r->start == range->start) {
> -                               /* Shrink the start of this memory range */
> -                               r->start = range->end + 1;
> +                               if (r->end == range->end)
> +                                       /* Remove this entry */
> +                                       mem_regions_remove(ranges, i);
> +                               else
> +                                       /* Shrink the start of this memory range */
> +                                       r->start = range->end + 1;
>                         } else if (r->end == range->end) {
>                                 /* Shrink the end of this memory range */
>                                 r->end = range->start - 1;
>                         } else {
> -                               struct memory_range *new;
> -
>                                 /*
>                                  * Split this area into 2 smaller ones and
>                                  * remove excluded range from between. First
>                                  * create new entry for the remaining area.
>                                  */
> -                               if (ranges->size >= ranges->max_size)
> -                                       return -1;
> -
> -                               new = ranges->ranges + ranges->size++;
> -                               new->start = range->end + 1;
> -                               new->end = r->end;
> +                               ret = mem_regions_add(ranges, range->end + 1,
> +                                                     r->end, 0);

3rd argument should be (r->end - range->end)

> +                               if (ret < 0)
> +                                       return ret;
>
>                                 /*
>                                  * Update this area to end before excluded
> @@ -82,31 +126,3 @@ int mem_regions_exclude(struct memory_ranges *ranges,
>         }
>         return 0;
>  }
> -
> -/**
> - * mem_regions_add() - add a memory region to a set of ranges
> - * @ranges: ranges to add the memory region to
> - * @max: maximum number of entries in memory region
> - * @base: base address of memory region
> - * @length: length of memory region in bytes
> - * @type: type of memory region
> - *
> - * Add the memory region to the set of ranges, and return %0 if successful,
> - * or %-1 if we ran out of space.
> - */
> -int mem_regions_add(struct memory_ranges *ranges, unsigned long long base,
> -                    unsigned long long length, int type)
> -{
> -       struct memory_range *range;
> -
> -       if (ranges->size >= ranges->max_size)
> -               return -1;
> -
> -       range = ranges->ranges + ranges->size++;
> -       range->start = base;
> -       range->end = base + length - 1;
> -       range->type = type;
> -
> -       return 0;
> -}
> -
>
>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.

~Pratyush