1 files changed, 64 insertions, 0 deletions
diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
new file mode 100644
index 000000000..bba1abd05
--- /dev/null
+++ b/arch/x86/kernel/resource.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/ioport.h>
+#include <linux/printk.h>
+#include <asm/e820/api.h>
+#include <asm/pci_x86.h>
+
+static void resource_clip(struct resource *res, resource_size_t start,
+			  resource_size_t end)
+{
+	resource_size_t low = 0, high = 0;
+
+	if (res->end < start || res->start > end)
+		return;		/* no conflict */
+
+	if (res->start < start)
+		low = start - res->start;
+
+	if (res->end > end)
+		high = res->end - end;
+
+	/* Keep the area above or below the conflict, whichever is larger */
+	if (low > high)
+		res->end = start - 1;
+	else
+		res->start = end + 1;
+}
+
+static void remove_e820_regions(struct resource *avail)
+{
+	int i;
+	struct e820_entry *entry;
+	u64 e820_start, e820_end;
+	struct resource orig = *avail;
+
+	if (!pci_use_e820)
+		return;
+
+	for (i = 0; i < e820_table->nr_entries; i++) {
+		entry = &e820_table->entries[i];
+		e820_start = entry->addr;
+		e820_end = entry->addr + entry->size - 1;
+
+		resource_clip(avail, e820_start, e820_end);
+		if (orig.start != avail->start || orig.end != avail->end) {
+			pr_info("clipped %pR to %pR for e820 entry [mem %#010Lx-%#010Lx]\n",
+				 &orig, avail, e820_start, e820_end);
+			orig = *avail;
+		}
+	}
+}
+
+void arch_remove_reservations(struct resource *avail)
+{
+	/*
+	 * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
+	 * the low 1MB unconditionally, as this area is needed for some ISA
+	 * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
+	 */
+	if (avail->flags & IORESOURCE_MEM) {
+		resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
+
+		remove_e820_regions(avail);
+	}
+}