diff --git a/sys/yellowstone/CMakeLists.txt b/sys/yellowstone/CMakeLists.txt
index 9e0b3ae..83a3d24 100644
--- a/sys/yellowstone/CMakeLists.txt
+++ b/sys/yellowstone/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_executable(yellowstone
+  hw/gpt.cpp
   hw/pcie.cpp
   yellowstone.cpp
   )
diff --git a/sys/yellowstone/hw/gpt.cpp b/sys/yellowstone/hw/gpt.cpp
new file mode 100644
index 0000000..6664183
--- /dev/null
+++ b/sys/yellowstone/hw/gpt.cpp
@@ -0,0 +1,109 @@
+#include "hw/gpt.h"
+
+#include <mammoth/debug.h>
+#include <zcall.h>
+#include <zglobal.h>
+
+struct MbrPartition {
+  uint8_t boot_indicator;
+  uint8_t starting_chs[3];
+  uint8_t os_type;
+  uint8_t ending_chs[3];
+  uint32_t starting_lba;
+  uint32_t ending_lba;
+} __attribute__((packed));
+
+z_err_t CheckMbrIsGpt(uint64_t mem_cap) {
+  uint64_t vaddr;
+  RET_ERR(ZAddressSpaceMap(gSelfVmasCap, 0, mem_cap, &vaddr));
+  uint16_t* mbr_sig = reinterpret_cast<uint16_t*>(vaddr + 0x1FE);
+  if (*mbr_sig != 0xAA55) {
+    return Z_ERR_INVALID;
+  }
+
+  MbrPartition* first_partition =
+      reinterpret_cast<MbrPartition*>(vaddr + 0x1BE);
+  if (first_partition->boot_indicator != 0) {
+    dbgln("Boot indicator set: %u", first_partition->boot_indicator);
+    return Z_ERR_INVALID;
+  }
+  if (first_partition->os_type != 0xEE) {
+    dbgln("Incorrect OS type: %x", first_partition->os_type);
+  }
+  dbgln("LBAs: (%x, %x)", first_partition->starting_lba,
+        first_partition->ending_lba);
+  return Z_OK;
+}
+
+const uint64_t kGptPartitionSignature = 0x54524150'20494645;
+struct ParititionHeader {
+  uint64_t signature;
+  uint32_t revision;
+  uint32_t header_size;
+  uint32_t crc_32;
+  uint32_t reserved;
+  uint64_t lba_self;
+  uint64_t lba_mirror;
+  uint64_t lba_min;
+  uint64_t lba_max;
+  uint64_t guid_low;
+  uint64_t guid_high;
+  uint64_t lba_partition_entries;
+  uint32_t num_partitions;
+  uint32_t parition_entry_size;
+  uint32_t partition_entry_crc32;
+} __attribute__((packed));
+
+z_err_t ReadPartitionHeader(uint64_t mem_cap) {
+  uint64_t vaddr;
+  RET_ERR(ZAddressSpaceMap(gSelfVmasCap, 0, mem_cap, &vaddr));
+  ParititionHeader* header = reinterpret_cast<ParititionHeader*>(vaddr);
+
+  dbgln("signature %lx", header->signature);
+
+  dbgln("lba_partition_entries %lx", header->lba_partition_entries);
+  dbgln("num_partitions: %x", header->num_partitions);
+  dbgln("partition_entry_size: %x", header->parition_entry_size);
+  dbgln("Num blocks: %x",
+        (header->num_partitions * header->parition_entry_size) / 512);
+
+  dbgln("LBA: (%x, %x)", header->lba_min, header->lba_max);
+
+  return Z_OK;
+}
+
+struct PartitionEntry {
+  uint64_t type_guid_low;
+  uint64_t type_guid_high;
+  uint64_t part_guid_low;
+  uint64_t part_guid_high;
+  uint64_t lba_start;
+  uint64_t lba_end;
+  uint64_t attributes;
+  char partition_name[72];
+} __attribute__((packed));
+
+z_err_t ReadPartitionEntries(uint64_t mem_cap) {
+  uint64_t vaddr;
+  RET_ERR(ZAddressSpaceMap(gSelfVmasCap, 0, mem_cap, &vaddr));
+  ParititionHeader* header = reinterpret_cast<ParititionHeader*>(vaddr);
+
+  // FIXME: Dont hard code these.
+  uint64_t num_parts = 0x28;
+  uint64_t entry_size = 0x80;
+
+  dbgln("Entries");
+  for (uint64_t i = 0; i < num_parts; i++) {
+    PartitionEntry* entry =
+        reinterpret_cast<PartitionEntry*>(vaddr + (i * entry_size));
+    if (entry->type_guid_low != 0 || entry->type_guid_high != 0) {
+      dbgln("Entry %u", i);
+      dbgln("T Guid: %lx-%lx", entry->type_guid_high, entry->type_guid_low);
+      dbgln("P Guid: %lx-%lx", entry->part_guid_high, entry->part_guid_low);
+      dbgln("LBA: %lx, %lx", entry->lba_start, entry->lba_end);
+      dbgln("Attrs: %lx", entry->attributes);
+    }
+  }
+
+  return Z_OK;
+}
diff --git a/sys/yellowstone/hw/gpt.h b/sys/yellowstone/hw/gpt.h
new file mode 100644
index 0000000..ac2cc31
--- /dev/null
+++ b/sys/yellowstone/hw/gpt.h
@@ -0,0 +1,10 @@
+#pragma once
+
+#include <stdint.h>
+#include <ztypes.h>
+
+z_err_t CheckMbrIsGpt(uint64_t mem_cap);
+
+z_err_t ReadPartitionHeader(uint64_t mem_cap);
+
+z_err_t ReadPartitionEntries(uint64_t mem_cap);
diff --git a/sys/yellowstone/yellowstone.cpp b/sys/yellowstone/yellowstone.cpp
index 954321e..e1d8d85 100644
--- a/sys/yellowstone/yellowstone.cpp
+++ b/sys/yellowstone/yellowstone.cpp
@@ -5,12 +5,15 @@
 #include <mammoth/process.h>
 #include <zcall.h>
 
+#include "hw/gpt.h"
 #include "hw/pcie.h"
 
 uint64_t main(uint64_t port_cap) {
   dbgln("Yellowstone Initializing.");
   check(ParseInitPort(port_cap));
 
+  DumpPciEDevices();
+
   uint64_t vaddr;
   check(ZAddressSpaceMap(gSelfVmasCap, 0, gBootDenaliVmmoCap, &vaddr));
 
@@ -22,21 +25,29 @@ uint64_t main(uint64_t port_cap) {
       .lba = 0,
       .size = 1,
   };
-  check(ZChannelSend(local.cap(), sizeof(DenaliRead),
-                     reinterpret_cast<uint8_t*>(&read), 0, nullptr));
-
+  check(local.WriteStruct(&read));
   DenaliReadResponse resp;
-  uint64_t mem_cap, bytes, caps;
+  uint64_t mem_cap;
+  check(local.ReadStructAndCap(&resp, &mem_cap));
+  check(CheckMbrIsGpt(mem_cap));
 
-  check(ZChannelRecv(local.cap(), sizeof(resp),
-                     reinterpret_cast<uint8_t*>(&resp), 1, &mem_cap, &bytes,
-                     &caps));
+  DenaliRead read_lba1{
+      .device_id = 0,
+      .lba = 1,
+      .size = 1,
+  };
+  check(local.WriteStruct(&read_lba1));
+  check(local.ReadStructAndCap(&resp, &mem_cap));
+  check(ReadPartitionHeader(mem_cap));
 
-  check(ZAddressSpaceMap(gSelfVmasCap, 0, mem_cap, &vaddr));
-  uint32_t* mbr = reinterpret_cast<uint32_t*>(vaddr + 0x1FE);
-  dbgln("MBR: %x", *mbr);
-
-  DumpPciEDevices();
+  DenaliRead read_parts{
+      .device_id = 0,
+      .lba = 2,
+      .size = 10,  // FIXME: Dont hardcode this.
+  };
+  check(local.WriteStruct(&read_parts));
+  check(local.ReadStructAndCap(&resp, &mem_cap));
+  check(ReadPartitionEntries(mem_cap));
 
   dbgln("Yellowstone Finished Successfully.");
   return 0;