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    Subject[PATCH v3 02/10] resource: add walk_system_ram_res_rev()
    Date
    This function, being a variant of walk_system_ram_res() introduced in
    commit 8c86e70acead ("resource: provide new functions to walk through
    resources"), walks through a list of all the resources of System RAM
    in reversed order, i.e., from higher to lower.

    It will be used in kexec_file implementation on arm64.

    Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    Cc: Vivek Goyal <vgoyal@redhat.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    ---
    include/linux/ioport.h | 3 +++
    kernel/resource.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 62 insertions(+)

    diff --git a/include/linux/ioport.h b/include/linux/ioport.h
    index 6230064d7f95..9a212266299f 100644
    --- a/include/linux/ioport.h
    +++ b/include/linux/ioport.h
    @@ -271,6 +271,9 @@ extern int
    walk_system_ram_res(u64 start, u64 end, void *arg,
    int (*func)(u64, u64, void *));
    extern int
    +walk_system_ram_res_rev(u64 start, u64 end, void *arg,
    + int (*func)(u64, u64, void *));
    +extern int
    walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
    void *arg, int (*func)(u64, u64, void *));

    diff --git a/kernel/resource.c b/kernel/resource.c
    index 9b5f04404152..572f2f91ce9c 100644
    --- a/kernel/resource.c
    +++ b/kernel/resource.c
    @@ -23,6 +23,8 @@
    #include <linux/pfn.h>
    #include <linux/mm.h>
    #include <linux/resource_ext.h>
    +#include <linux/string.h>
    +#include <linux/vmalloc.h>
    #include <asm/io.h>


    @@ -469,6 +471,63 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
    return ret;
    }

    +int walk_system_ram_res_rev(u64 start, u64 end, void *arg,
    + int (*func)(u64, u64, void *))
    +{
    + struct resource res, *rams;
    + u64 orig_end;
    + int count, i;
    + int ret = -1;
    +
    + count = 16; /* initial */
    +
    + /* create a list */
    + rams = vmalloc(sizeof(struct resource) * count);
    + if (!rams)
    + return ret;
    +
    + res.start = start;
    + res.end = end;
    + res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
    + orig_end = res.end;
    + i = 0;
    + while ((res.start < res.end) &&
    + (!find_next_iomem_res(&res, IORES_DESC_NONE, true))) {
    + if (i >= count) {
    + /* re-alloc */
    + struct resource *rams_new;
    + int count_new;
    +
    + count_new = count + 16;
    + rams_new = vmalloc(sizeof(struct resource) * count_new);
    + if (!rams_new)
    + goto out;
    +
    + memcpy(rams_new, rams, count);
    + vfree(rams);
    + rams = rams_new;
    + count = count_new;
    + }
    +
    + rams[i].start = res.start;
    + rams[i++].end = res.end;
    +
    + res.start = res.end + 1;
    + res.end = orig_end;
    + }
    +
    + /* go reverse */
    + for (i--; i >= 0; i--) {
    + ret = (*func)(rams[i].start, rams[i].end, arg);
    + if (ret)
    + break;
    + }
    +
    +out:
    + vfree(rams);
    + return ret;
    +}
    +
    #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)

    /*
    --
    2.14.1
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