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    Subject[PATCH v2 5/8] x86/kaslr: Simplify __process_mem_region
    Date
    Get rid of unnecessary temporary variables and redundant tests in
    __process_mem_region.

    Fix one minor bug: in case of an overlap, the beginning of the region
    should be used even if it is exactly image_size, not just strictly
    larger.

    Change type of minimum/image_size arguments in process_mem_region to
    unsigned long. These actually can never be above 4G (even on x86_64),
    and they're unsigned long in every other function except this one.

    Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
    ---
    arch/x86/boot/compressed/kaslr.c | 50 ++++++++------------------------
    1 file changed, 12 insertions(+), 38 deletions(-)

    diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
    index 758d78433f94..d3d8f1f6d5d3 100644
    --- a/arch/x86/boot/compressed/kaslr.c
    +++ b/arch/x86/boot/compressed/kaslr.c
    @@ -622,42 +622,24 @@ static void __process_mem_region(struct mem_vector *entry,
    unsigned long image_size)
    {
    struct mem_vector region, overlap;
    - unsigned long start_orig, end;
    - struct mem_vector cur_entry;
    + unsigned long region_end;

    - /* Ignore entries entirely below our minimum. */
    - if (entry->start + entry->size < minimum)
    - return;
    -
    - /* Ignore entries above memory limit */
    - end = min(entry->size + entry->start, mem_limit);
    - if (entry->start >= end)
    - return;
    - cur_entry.start = entry->start;
    - cur_entry.size = end - entry->start;
    -
    - region.start = cur_entry.start;
    - region.size = cur_entry.size;
    + /* Clamp region to minimum and memory limit. */
    + region.start = clamp_val(entry->start, minimum, mem_limit);
    + region_end = clamp_val(entry->start + entry->size, minimum, mem_limit);

    /* Give up if slot area array is full. */
    while (slot_area_index < MAX_SLOT_AREA) {
    - start_orig = region.start;
    -
    - /* Potentially raise address to minimum location. */
    - if (region.start < minimum)
    - region.start = minimum;
    -
    /* Potentially raise address to meet alignment needs. */
    region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);

    /* Did we raise the address above the passed in memory entry? */
    - if (region.start > cur_entry.start + cur_entry.size)
    + if (region.start > region_end)
    return;

    - /* Reduce size by any delta from the original address. */
    - region.size -= region.start - start_orig;
    + region.size = region_end - region.start;

    - /* Return if region can't contain decompressed kernel */
    + /* Return if region can't contain decompressed kernel. */
    if (region.size < image_size)
    return;

    @@ -668,27 +650,19 @@ static void __process_mem_region(struct mem_vector *entry,
    }

    /* Store beginning of region if holds at least image_size. */
    - if (overlap.start > region.start + image_size) {
    - struct mem_vector beginning;
    -
    - beginning.start = region.start;
    - beginning.size = overlap.start - region.start;
    - process_gb_huge_pages(&beginning, image_size);
    + if (overlap.start >= region.start + image_size) {
    + region.size = overlap.start - region.start;
    + process_gb_huge_pages(&region, image_size);
    }

    - /* Return if overlap extends to or past end of region. */
    - if (overlap.start + overlap.size >= region.start + region.size)
    - return;
    -
    /* Clip off the overlapping region and start over. */
    - region.size -= overlap.start - region.start + overlap.size;
    region.start = overlap.start + overlap.size;
    }
    }

    static bool process_mem_region(struct mem_vector *region,
    - unsigned long long minimum,
    - unsigned long long image_size)
    + unsigned long minimum,
    + unsigned long image_size)
    {
    int i;
    /*
    --
    2.26.2
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