ACPI tables support

Added parsing for the (X)RSDT and RSDP, as well as table searching.

src/arch/x86_64/acpi.c

@@ -0,0 +1,82 @@
+#include <arch/acpi.h>
+#include <limine.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <arch/panic.h>
+#include <string.h>
+#include <kernel/pmm.h>
+
+static bool  usersdt = false;
+static sdt_t* sdt;
+static size_t sdtentrycount;
+
+
+static volatile struct limine_rsdp_request rsdpreq = {
+	.id = LIMINE_RSDP_REQUEST,
+	.revision = 0
+};
+
+static bool checksumok(sdt_t* table){
+	uint8_t sum;
+	uint8_t* ptr = (uint8_t*)table;
+	
+	for(size_t i = 0; i < table->length; ++i)
+		sum += *ptr++;
+
+	return sum == 0;
+}
+
+void* acpi_gettable(char* sig, size_t n){
+	size_t ptrsize = usersdt ? 4 : 8;
+	
+	void* ptr = (char*)sdt + sizeof(sdt_t);
+	
+
+	for(size_t i = 0; i < sdtentrycount; ++i){
+		
+		sdt_t* table = usersdt ? (*(uint32_t*)ptr & 0xFFFFFFFF) : *(uint64_t*)ptr;
+		
+		table = (uint8_t*)table + (size_t)limine_hhdm_offset;
+
+		if(!strncmp(sig, table->signature, 4)){
+			if(n-- == 0)
+				return (uint8_t*)table + (size_t) limine_hhdm_offset;
+				
+		}
+		
+		ptr += ptrsize;
+
+	}
+
+	return NULL;
+	
+}
+
+void acpi_init(){
+	if(!rsdpreq.response){
+		// TODO search for ourselves
+		_panic("No reponse for the RSDP request", 0);
+	}
+
+	rsdp_t* rsdp = rsdpreq.response->address;
+
+	printf("RSDP at: %p\n", rsdp);
+	
+	sdt = rsdp->xsdtaddr;
+
+	if(rsdp->revision == 0){
+		printf("WARNING: XSDT does not exist in revision 0, falling back to RSDT!\n");
+		sdt = rsdp->rsdtaddr;
+		usersdt = true;
+	}
+	
+	sdt = (uint8_t*)sdt + (size_t)limine_hhdm_offset;
+
+	sdtentrycount = (sdt->length - sizeof(sdt_t)) / (usersdt ? 4 : 8);
+
+	printf("Root System Description Table address: %p with %lu tables\n", sdt, sdtentrycount);
+
+	if(!checksumok(sdt))
+		_panic("Invalid RSDT checksum!", 0);
+
+}