Support UEFI booting from alternate load addresses

include/uefi.hh

@@ -7,6 +7,13 @@ struct efi_guid {
   u16 data2;
   u16 data3;
   u8  data4[8];
+
+  bool operator==(const efi_guid &b) const {
+    for (int i = 0; i < 8; i++)
+      if (data4[i] != b.data4[i])
+        return false;
+    return data1 == b.data1 && data2 == b.data2 && data3 == b.data3;
+  }
 };
 enum efi_locate_search_type { AllHandles, ByRegisterNotify, ByProtocol};
 
@@ -108,6 +115,11 @@ struct efi_runtime_services {
   void* reset_system;
 };
 
+struct efi_configuration_table {
+  efi_guid guid;
+  void* table;
+};
+
 struct efi_system_table {
   struct {
     u64 signature;
@@ -127,7 +139,7 @@ struct efi_system_table {
   efi_runtime_services* runtime_services;
   efi_boot_services* boot_services;
   u64 num_table_entries;
-  void* configuration_table;
+  efi_configuration_table* configuration_table;
 };
 
 struct efi_memory_descriptor {

kernel/boot.S

@@ -217,7 +217,10 @@ relocate64:
 efi_main:
     movl %eax, %edi
     movl %ebx, %esi
-    movq $PADDR(stack+STACK), %rsp
+
+    call 1f
+1:  pop %rsp
+    addq $(PADDR(stack+STACK)-PADDR(1b)), %rsp
     call efi_cmain
 
 .code32

kernel/uefi.cc

@@ -6,19 +6,35 @@
 #include "cmdline.hh"
 #include "amd64.h"
 
+efi_guid efi_acpi20_table_guid = {0x8868e871,0xe4f1,0x11d3, {0xbc,0x22,0x00,0x80,0xc7,0x3c,0x88,0x81}};
+efi_guid efi_acpi10_table_guid = {0xeb9d2d30,0x2d88,0x11d3, {0x9a,0x16,0x00,0x90,0x27,0x3f,0xc1,0x4d}};
+
 void multiboot2_early(u64 mbaddr, multiboot_saved* mb);
 
-extern u64 kpml4[];
+extern u64 physical_address_offset;
 
-extern "C" u64 efi_cmain (u64 mbmagic, u64 mbaddr, void* boot_system_table, void* boot_image_table)
+extern "C" u64 efi_cmain (u64 mbmagic, u64 mbaddr)
 {
+  u64 offset;
+  __asm volatile("call 1f; 1: pop %0; sub $(1b-%a1), %0" : "=r" (offset) : "i"(KCODE));
+  physical_address_offset = offset;
+
   multiboot_saved* mb = (multiboot_saved*)v2p(&multiboot);
   multiboot2_early(mbaddr, mb);
   efi_system_table* system_table = (efi_system_table*)mb->efi_system_table;
 
   auto get_memory_map = system_table->boot_services->get_memory_map;
   auto exit_boot_services = system_table->boot_services->exit_boot_services;
 
+  for (int i = 0; i < system_table->num_table_entries; i++) {
+    if (system_table->configuration_table[i].guid == efi_acpi10_table_guid) {
+      memcpy(mb->acpi_rsdpv1, system_table->configuration_table[i].table, 20);
+      mb->flags |= MULTIBOOT2_FLAG_ACPI_RSDP_V1;
+    } else if (system_table->configuration_table[i].guid == efi_acpi20_table_guid) {
+      memcpy(mb->acpi_rsdpv2, system_table->configuration_table[i].table, 36);
+      mb->flags |= MULTIBOOT2_FLAG_ACPI_RSDP_V2;
+    }
+  }
 
   u64 key;
   auto mem_descs = (efi_memory_descriptor*)&mb->efi_mmap[0];
@@ -51,10 +67,63 @@ extern "C" u64 efi_cmain (u64 mbmagic, u64 mbaddr, void* boot_system_table, void
   dtr.base = (u64)bootgdt;
   lgdt((void*)&dtr.limit);
 
-  // TODO: use trampoline_pml4
-  __asm volatile("movabs $(kpml4-%a1), %%rax; mov %%rax, %%cr3; add %0, %%rsp; movabs $1f, %%rax; jmp *%%rax; 1:"
-                 :: "r"(KBASE), "i"(KCODE) : "rax", "memory");
-  cmain(mbmagic, mbaddr);
+  __asm volatile(
+    "call 1f; 1: pop %%rax; sub $(1b-%a0), %%rax;"
+
+    "movq $(physical_address_offset-%a0), %%rbx;"
+    "addq %%rax, %%rbx;"
+    "movq %%rax, (%%rbx);"
+
+    "movl %%eax, %%ebx;"
+    "addl $(kpml4-%a0), %%ebx;"
+    "addl %%eax, 0xff0(%%ebx);"
+    "addl %%eax, 0xff8(%%ebx);"
+
+    "movl %%eax, %%ebx;"
+    "addl $(trampoline_pml4-%a0), %%ebx;"
+    "addl %%eax, (%%ebx);"
+    "addl %%eax, 0xff0(%%ebx);"
+    "addl %%eax, 0xff8(%%ebx);"
+
+    "movl %%eax, %%ebx;"
+    "addl $(pdpt0-%a0), %%ebx;"
+    "addl %%eax, (%%ebx);"
+
+    "movl %%eax, %%ebx;"
+    "addl $(pdptbase-%a0), %%ebx;"
+    "addl %%eax, 0x00(%%ebx);"
+    "addl %%eax, 0x08(%%ebx);"
+    "addl %%eax, 0x10(%%ebx);"
+    "addl %%eax, 0x18(%%ebx);"
+
+    "movl %%eax, %%ebx;"
+    "addl $(pdptcode-%a0), %%ebx;"
+    "addl %%eax, 0xff8(%%ebx);"
+
+    "movl 0xff8(%%ebx), %%ebx;"
+    "and $0xfffff000, %%ebx;"
+    "mov $0x1000, %%ecx;"
+    "1: sub $8, %%ecx;"
+    "addl %%eax, (%%ebx,%%ecx);"
+    "cmp $0, %%ecx;"
+    "jnz 1b;" :: "i"(KCODE) : "rax", "rbx", "rcx");
+
+  __asm volatile(
+    "call 1f; 1: pop %%rbx; sub $(1b-%a1), %%rbx;"
+    "movabs $(trampoline_pml4-%a1), %%rax;"
+    "addq %%rbx, %%rax;"
+    "mov %%rax, %%cr3;"
+
+    "add %0, %%rsp;"
+    "movabs $1f, %%rax;"
+    "jmp *%%rax; 1:"
+
+    "movabs $(kpml4-%a1), %%rax;"
+    "addq %%rbx, %%rax;"
+    "mov %%rax, %%cr3;"
+    "call cmain;"
+      :: "r"(KBASE), "i"(KCODE), "rdi"(mbmagic), "rsi"(mbaddr) : "rax", "rbx", "memory");
+
   panic("cmain should not return?");
 
   return 1;