LXR linux/arch/x86/kernel/resource.c

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/ioport.h>
   3#include <asm/e820/api.h>
   4
   5static void resource_clip(struct resource *res, resource_size_t start,
   6                          resource_size_t end)
   7{
   8        resource_size_t low = 0, high = 0;
   9
  10        if (res->end < start || res->start > end)
  11                return;         /* no conflict */
  12
  13        if (res->start < start)
  14                low = start - res->start;
  15
  16        if (res->end > end)
  17                high = res->end - end;
  18
  19        /* Keep the area above or below the conflict, whichever is larger */
  20        if (low > high)
  21                res->end = start - 1;
  22        else
  23                res->start = end + 1;
  24}
  25
  26static void remove_e820_regions(struct resource *avail)
  27{
  28        int i;
  29        struct e820_entry *entry;
  30
  31        for (i = 0; i < e820_table->nr_entries; i++) {
  32                entry = &e820_table->entries[i];
  33
  34                resource_clip(avail, entry->addr,
  35                              entry->addr + entry->size - 1);
  36        }
  37}
  38
  39void arch_remove_reservations(struct resource *avail)
  40{
  41        /*
  42         * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
  43         * the low 1MB unconditionally, as this area is needed for some ISA
  44         * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
  45         */
  46        if (avail->flags & IORESOURCE_MEM) {
  47                resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
  48
  49                remove_e820_regions(avail);
  50        }
  51}
  52