arch/x86/kernel/resource.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/ioport.h>
   3 #include <asm/e820/api.h>
   4
   5 static 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
  26 static 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
  39 void 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 }