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

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

After the first call to ExitBootServices(), avoid calling any boot
services (except GetMemoryMap() and ExitBootServices()) by setting
setting efi_bs to NULL and halting in blexit(). Only GetMemoryMap() and
ExitBootServices() are explicitly allowed to be called after the first
call to ExitBootServices() and so are are called via
SystemTable->BootServices.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---

Change in V5: Clarify commit message.

 xen/arch/arm/efi/efi-boot.h |  5 +++++
 xen/arch/x86/efi/efi-boot.h |  7 +++++++
 xen/common/efi/boot.c       | 13 ++++++++++---
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index 3297f27..47efdfc 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -522,6 +522,11 @@ static void __init efi_arch_blexit(void)
         efi_bs->FreePool(memmap);
 }
 
+static void __init efi_arch_halt(void)
+{
+    stop_cpu();
+}
+
 static void __init efi_arch_load_addr_check(EFI_LOADED_IMAGE *loaded_image)
 {
     if ( (unsigned long)loaded_image->ImageBase & ((1 << 12) - 1) )
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index cd14c19..9f41793 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -614,6 +614,13 @@ static void __init efi_arch_blexit(void)
         efi_bs->FreePages(ucode.addr, PFN_UP(ucode.size));
 }
 
+static void __init efi_arch_halt(void)
+{
+    local_irq_disable();
+    for ( ; ; )
+        halt();
+}
+
 static void __init efi_arch_load_addr_check(EFI_LOADED_IMAGE *loaded_image)
 {
     xen_phys_start = (UINTN)loaded_image->ImageBase;
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 60c1b8d..4b816f2 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -216,6 +216,9 @@ static void __init noreturn blexit(const CHAR16 *str)
         PrintStr((CHAR16 *)str);
     PrintStr(newline);
 
+    if ( !efi_bs )
+        efi_arch_halt();
+
     if ( cfg.addr )
         efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
     if ( kernel.addr )
@@ -1063,8 +1066,10 @@ 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 +1078,9 @@ 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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