x86_64: add a basic ACPI driver

arch/x86_64/acpi/rsdp.c

@@ -0,0 +1,102 @@
+#include <arch/acpi.h>
+#include <socks/vm.h>
+#include <socks/printk.h>
+#include <stddef.h>
+
+static struct acpi_rsdp rsdp;
+
+static struct acpi_rsdp_10 *search_for_rsdp(void)
+{
+	uint64_t *start = vm_phys_to_virt(0x80000);
+	uint64_t *end = vm_phys_to_virt(0xFFFFF);
+	
+	for (uint64_t *i = start; i < end; i++) {
+		if (*i == ACPI_SIG_RSDP) {
+			return (struct acpi_rsdp_10 *)i;
+		}
+	}
+
+	return NULL;
+}
+
+static int init_rsdt(void)
+{
+	struct acpi_rsdp_10 *x = search_for_rsdp();
+
+	if (!x) {
+		printk("acpi: not available");
+		return -1;
+	}
+
+	uint8_t *b = (uint8_t *)x;
+	size_t chksum = 0;
+	for (unsigned int i = 0; i < sizeof *x; i++) {
+		chksum += b[i];
+	}
+		
+	if (chksum & 0xFF) {
+		printk("acpi: not available");
+		return -1;
+	}
+
+	if (x->r_revision == 2) {
+		chksum = 0;
+		
+		for (unsigned int i = sizeof *x; i < sizeof(struct acpi_rsdp_20); i++) {
+			chksum += b[i];
+		}
+
+		if (chksum & 0xFF) {
+		    printk("acpi: not available");
+		    return -1;
+		}
+	}
+		
+	memcpy(&rsdp.rsdp_20, x, sizeof rsdp.rsdp_20);
+	return 0;
+}
+
+static struct acpi_sdt *find_via_rsdt(uint32_t sig)
+{
+	struct acpi_rsdt *rsdt = vm_phys_to_virt(rsdp.rsdp_10.r_rsdt_ptr);
+	unsigned long nr_tables = (rsdt->r_header.s_length - sizeof(struct acpi_sdt)) / sizeof(uint32_t);
+
+	for (unsigned long i = 0; i < nr_tables; i++) {
+		struct acpi_sdt *table = vm_phys_to_virt(rsdt->r_tables[i]);
+		if (*(uint32_t *)table == sig) {
+			return table;
+		}
+	}
+
+	return NULL;
+}
+
+static struct acpi_sdt *find_via_xsdt(uint32_t sig)
+{
+	struct acpi_xsdt *xsdt = vm_phys_to_virt(rsdp.rsdp_20.r_xsdt_ptr);
+	unsigned long nr_tables = (xsdt->x_header.s_length - sizeof(struct acpi_sdt)) / sizeof(uint64_t);
+
+	for (unsigned long i = 0; i < nr_tables; i++) {
+		struct acpi_sdt *table = vm_phys_to_virt(xsdt->x_tables[i]);
+		if (*(uint32_t *)table == sig) {
+			return table;
+		}
+	}
+
+	return NULL;
+}
+
+struct acpi_sdt *acpi_find_sdt(uint32_t sig)
+{
+	if (!rsdp.rsdp_10.r_sig[0]) {
+		if (init_rsdt() != 0) {
+			return NULL;
+		}
+	}
+
+	if (rsdp.rsdp_10.r_revision == 0) {
+		return find_via_rsdt(sig);
+	} else {
+		return find_via_xsdt(sig);
+	}
+}