From 592133af39074bbdc3d2d57105e3b9d4a0632d57 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Fri, 5 Aug 2022 17:27:01 -0300
Subject: [PATCH] ACPI tables support

Added parsing for the (X)RSDT and RSDP, as well as table searching.
---
 src/arch/x86_64/acpi.c              | 82 +++++++++++++++++++++++++++++
 src/arch/x86_64/include/arch/acpi.h | 44 ++++++++++++++++
 src/arch/x86_64/main.c              |  3 ++
 3 files changed, 129 insertions(+)
 create mode 100644 src/arch/x86_64/acpi.c
 create mode 100644 src/arch/x86_64/include/arch/acpi.h

diff --git a/src/arch/x86_64/acpi.c b/src/arch/x86_64/acpi.c
new file mode 100644
index 00000000..330b3f4c
--- /dev/null
+++ b/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);
+
+}
diff --git a/src/arch/x86_64/include/arch/acpi.h b/src/arch/x86_64/include/arch/acpi.h
new file mode 100644
index 00000000..0cd24ace
--- /dev/null
+++ b/src/arch/x86_64/include/arch/acpi.h
@@ -0,0 +1,44 @@
+#ifndef _ACPI_H_INCLUDE
+#define _ACPI_H_INCLUDE
+
+#include <stddef.h>
+#include <stdint.h>
+
+typedef struct {
+	char signature[8];
+	uint8_t checksum;
+	char oem[6];
+	uint8_t revision;
+	uint32_t rsdtaddr;
+	
+	uint32_t length;
+	uint64_t xsdtaddr;
+	uint8_t  xchecksum;
+} __attribute__((packed))rsdp_t;
+
+typedef struct {
+	char signature[4];
+	uint32_t length;
+	uint8_t  revision;
+	uint8_t  checksum;
+	char oem[6];
+	char oemtable[8];
+	uint32_t oemrevision;
+	uint32_t creator;
+	uint32_t creatorrevision;
+} __attribute__((packed)) sdt_t;
+
+typedef struct {
+	sdt_t header;
+	uint64_t pointers[];
+} __attribute__((packed)) xsdt_t;
+
+typedef struct {
+	sdt_t header;
+	uint32_t pointers[];
+} __attribute__((packed)) rsdt_t;
+
+void* acpi_gettable(char* sig, size_t n);
+void  acpi_init();
+
+#endif
diff --git a/src/arch/x86_64/main.c b/src/arch/x86_64/main.c
index a4bfb6b4..b357fcfc 100644
--- a/src/arch/x86_64/main.c
+++ b/src/arch/x86_64/main.c
@@ -8,6 +8,7 @@
 #include <kernel/alloc.h>
 #include <arch/panic.h>
 #include <kernel/vfs.h>
+#include <arch/acpi.h>
 
 static volatile struct limine_terminal_request liminettyr = {
     .id = LIMINE_TERMINAL_REQUEST,
@@ -56,6 +57,8 @@ void kmain(){
 		_panic("Failed to mount tmpfs", 0);
 	
 	initrd_parse();
+	
+	acpi_init();
 
 	_panic("End of kmain()", 0);