gnu-efi/apps/debughook.c

   1 #include <efi.h>
   2 #include <efilib.h>
   3
   4 EFI_STATUS
   5 GetVariableAttr(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner,
   6                   UINT32 *attributes)
   7 {
   8         EFI_STATUS efi_status;
   9
  10         *len = 0;
  11
  12         efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
  13                                        NULL, len, NULL);
  14         if (efi_status != EFI_BUFFER_TOO_SMALL)
  15                 return efi_status;
  16
  17         *data = AllocateZeroPool(*len);
  18         if (!*data)
  19                 return EFI_OUT_OF_RESOURCES;
  20
  21         efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
  22                                        attributes, len, *data);
  23
  24         if (efi_status != EFI_SUCCESS) {
  25                 FreePool(*data);
  26                 *data = NULL;
  27         }
  28         return efi_status;
  29 }
  30
  31 EFI_STATUS
  32 GetVariable(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner)
  33 {
  34         return GetVariableAttr(var, data, len, owner, NULL);
  35 }
  36
  37 EFI_GUID DUMMY_GUID =
  38 {0x55aad538, 0x8f82, 0x4e2a, {0xa4,0xf0,0xbe, 0x59, 0x13, 0xb6, 0x5f, 0x1e}};
  39
  40 #if defined(__clang__)
  41 # define _OPTNONE __attribute__((optnone))
  42 #else
  43 # define _OPTNONE __attribute__((__optimize__("0")))
  44 #endif
  45
  46 static _OPTNONE void
  47 DebugHook(void)
  48 {
  49         EFI_GUID guid = DUMMY_GUID;
  50         UINT8 *data = NULL;
  51         UINTN dataSize = 0;
  52         EFI_STATUS efi_status;
  53         register volatile unsigned long long x = 0;
  54         extern char _text, _data;
  55
  56         if (x)
  57                 return;
  58
  59         efi_status = GetVariable(L"DUMMY_DEBUG", &data, &dataSize, guid);
  60         if (EFI_ERROR(efi_status)) {
  61                 return;
  62         }
  63
  64         Print(L"add-symbol-file /usr/lib/debug/boot/efi/debughook.debug "
  65               L"0x%08x -s .data 0x%08x\n", &_text, &_data);
  66
  67         Print(L"Pausing for debugger attachment.\n");
  68         Print(L"To disable this, remove the EFI variable DUMMY_DEBUG-%g .\n",
  69               &guid);
  70         x = 1;
  71         while (x++) {
  72                 /* Make this so it can't /totally/ DoS us. */
  73 #if defined(__x86_64__) || defined(__i386__) || defined(__i686__)
  74                 if (x > 4294967294ULL)
  75                         break;
  76                 __asm__ __volatile__("pause");
  77 #elif defined(__aarch64__)
  78                 if (x > 1000)
  79                         break;
  80                 __asm__ __volatile__("wfi");
  81 #else
  82                 if (x > 12000)
  83                         break;
  84                 uefi_call_wrapper(BS->Stall, 1, 5000);
  85 #endif
  86         }
  87         x = 1;
  88 }
  89
  90
  91 EFI_STATUS
  92 efi_main (EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
  93 {
  94         InitializeLib(image, systab);
  95         DebugHook();
  96         return EFI_SUCCESS;
  97 }