[Xen-devel] [PATCH v3 2/2] efi: Avoid calling boot services after ExitBootServices()

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

After the first call to ExitBootServices(), avoid calling any boot
services by setting setting efi_bs to NULL and entering an infinite loop
in blexit().

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 xen/common/efi/boot.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 60c1b8d..5c5c158 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -216,6 +216,12 @@ static void __init noreturn blexit(const CHAR16 *str)
         PrintStr((CHAR16 *)str);
     PrintStr(newline);
 
+    if ( !efi_bs )
+    {
+        for ( ; ; )
+            ;
+    }
+
     if ( cfg.addr )
         efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
     if ( kernel.addr )
@@ -1063,8 +1069,10 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
     for ( retry = 0; ; retry = 1 )
     {
         efi_memmap_size = map_alloc_size;
-        status = efi_bs->GetMemoryMap(&efi_memmap_size, efi_memmap, &map_key,
-                                      &efi_mdesc_size, &mdesc_ver);
+        status = SystemTable->BootServices->GetMemoryMap(&efi_memmap_size,
+                                                         efi_memmap, &map_key,
+                                                         &efi_mdesc_size,
+                                                         &mdesc_ver);
         if ( EFI_ERROR(status) )
             PrintErrMesg(L"Cannot obtain memory map", status);
 
@@ -1073,7 +1081,9 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
 
         efi_arch_pre_exit_boot();
 
-        status = efi_bs->ExitBootServices(ImageHandle, map_key);
+        status = SystemTable->BootServices->ExitBootServices(ImageHandle,
+                                                             map_key);
+        efi_bs = NULL;
         if ( status != EFI_INVALID_PARAMETER || retry )
             break;
     }
-- 
2.1.0


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