[Xen-devel] [PATCH v2 7/8] xen/x86/efi: Verify dom0 kernel with SHIM_LOCK protocol in efi_multiboot2()

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
---
v2 - suggestions/fixes:
   - add const to *dom0_kernel efi_multiboot2() argument,
     (suggested by Jan Beulich),
   - improve comments
     (suggested by Konrad Rzeszutek Wilk).
---
 xen/arch/x86/boot/head.S    |   23 +++++++++++++++++++++--
 xen/arch/x86/efi/efi-boot.h |   10 +++++++++-
 xen/arch/x86/efi/stub.c     |    6 +++++-
 3 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 582dc51..48f1b00 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -395,9 +395,13 @@ __efi64_mb2_start:
         jmp     x86_32_switch
 
 .Lefi_multiboot2_proto:
-        /* Zero EFI SystemTable and EFI ImageHandle addresses. */
+        /*
+         * Zero EFI SystemTable, EFI ImageHandle and
+         * dom0 kernel module struct addresses.
+         */
         xor     %esi,%esi
         xor     %edi,%edi
+        xor     %r14d,%r14d
 
         /* Skip Multiboot2 information fixed part. */
         lea     (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx
@@ -435,6 +439,18 @@ __efi64_mb2_start:
         cmove   MB2_efi64_ih(%rcx),%rdi
         je      .Lefi_mb2_next_tag
 
+        /*
+         * Get dom0 kernel module struct address from Multiboot2
+         * information and ignore the rest of modules.
+         */
+        cmpl    $MULTIBOOT2_TAG_TYPE_MODULE,MB2_tag_type(%rcx)
+        jne     .Lefi_mb2_end
+
+        test    %r14d,%r14d
+        cmovz   %ecx,%r14d
+        jmp     .Lefi_mb2_next_tag
+
+.Lefi_mb2_end:
         /* Is it the end of Multiboot2 information? */
         cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
         je      .Lrun_bs
@@ -496,9 +512,12 @@ __efi64_mb2_start:
         /* Keep the stack aligned. Do not pop a single item off it. */
         mov     (%rsp),%rdi
 
+        mov     %r14d,%edx
+
         /*
          * efi_multiboot2() is called according to System V AMD64 ABI:
-         *   - IN:  %rdi - EFI ImageHandle, %rsi - EFI SystemTable.
+         *   - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
+         *         %rdx - if passed, dom0 kernel module struct address.
          */
         call    efi_multiboot2
 
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 5f0e821..f8aaa37 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -3,6 +3,8 @@
  * is intended to be included by common/efi/boot.c _only_, and
  * therefore can define arch specific global variables.
  */
+#include <xen/types.h>
+#include <xen/multiboot2.h>
 #include <xen/vga.h>
 #include <asm/e820.h>
 #include <asm/edd.h>
@@ -694,7 +696,9 @@ efi_mb_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
     efi_start(ImageHandle, SystemTable);
 }
 
-void __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
+void __init efi_multiboot2(EFI_HANDLE ImageHandle,
+                           EFI_SYSTEM_TABLE *SystemTable,
+                           const multiboot2_tag_module_t *dom0_kernel)
 {
     EFI_GRAPHICS_OUTPUT_PROTOCOL *gop;
     UINTN cols, gop_mode = ~0, rows;
@@ -710,6 +714,10 @@ void __init efi_multiboot2(EFI_HANDLE ImageHandle, 
EFI_SYSTEM_TABLE *SystemTable
                            &cols, &rows) == EFI_SUCCESS )
         efi_arch_console_init(cols, rows);
 
+    if ( dom0_kernel && dom0_kernel->mod_end > dom0_kernel->mod_start )
+        efi_shim_lock((VOID *)(unsigned long)dom0_kernel->mod_start,
+                      dom0_kernel->mod_end - dom0_kernel->mod_start);
+
     gop = efi_get_gop();
 
     if ( gop )
diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
index 2142932..5918536 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.c
@@ -1,7 +1,9 @@
+#include <xen/types.h>
 #include <xen/efi.h>
 #include <xen/errno.h>
 #include <xen/init.h>
 #include <xen/lib.h>
+#include <xen/multiboot2.h>
 #include <asm/page.h>
 #include <asm/efibind.h>
 #include <efi/efidef.h>
@@ -24,11 +26,13 @@ asm (
     "efi_mb_start:                     \n"
     "    mov    %rcx,%rdi              \n"
     "    mov    %rdx,%rsi              \n"
+    "    xor    %rdx,%rdx              \n"
     "    call   efi_multiboot2         \n"
     );
 
 void __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
-                                    EFI_SYSTEM_TABLE *SystemTable)
+                                    EFI_SYSTEM_TABLE *SystemTable,
+                                    const multiboot2_tag_module_t *dom0_kernel)
 {
     static const CHAR16 __initconst err[] =
         L"Xen does not have EFI code build in!\r\nSystem halted!\r\n";
-- 
1.7.10.4


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