x86/EFI: make trampoline allocation more flexible

Certain UEFI implementations reserve all memory below 1Mb at boot time,
making it impossible to properly allocate the chunk necessary for the
trampoline. Fall back to simply grabbing a chunk from EfiBootServices*
regions immediately prior to calling ExitBootServices().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

diff --git a/xen/arch/x86/efi/boot.c b/xen/arch/x86/efi/boot.c
index 66a6fdba21bbf918b280258084f449244a15867d..68c9abe3ca9de16d543c9eae1864edb0195a4c48 100644 (file)
--- a/xen/arch/x86/efi/boot.c
+++ b/xen/arch/x86/efi/boot.c
@@ -746,6 +746,22 @@ static void __init relocate_image(unsigned long delta)
 extern const s32 __trampoline_rel_start[], __trampoline_rel_stop[];
 extern const s32 __trampoline_seg_start[], __trampoline_seg_stop[];
 
+static void __init relocate_trampoline(unsigned long phys)
+{
+    const s32 *trampoline_ptr;
+
+    trampoline_phys = phys;
+    /* Apply relocations to trampoline. */
+    for ( trampoline_ptr = __trampoline_rel_start;
+          trampoline_ptr < __trampoline_rel_stop;
+          ++trampoline_ptr )
+        *(u32 *)(*trampoline_ptr + (long)trampoline_ptr) += phys;
+    for ( trampoline_ptr = __trampoline_seg_start;
+          trampoline_ptr < __trampoline_seg_stop;
+          ++trampoline_ptr )
+        *(u16 *)(*trampoline_ptr + (long)trampoline_ptr) = phys >> 4;
+}
+
 void EFIAPI __init __attribute__((__noreturn__))
 efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
 {
@@ -765,7 +781,6 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *mode_info;
     EFI_FILE_HANDLE dir_handle;
     union string section = { NULL }, name;
-    const s32 *trampoline_ptr;
     struct e820entry *e;
     u64 efer;
     bool_t base_video = 0;
@@ -1268,23 +1283,13 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     cfg.size = trampoline_end - trampoline_start;
     status = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
                                    PFN_UP(cfg.size), &cfg.addr);
-    if ( EFI_ERROR(status) )
+    if ( status == EFI_SUCCESS )
+        relocate_trampoline(cfg.addr);
+    else
     {
         cfg.addr = 0;
-        blexit(L"No memory for trampoline\r\n");
+        PrintStr(L"Trampoline space cannot be allocated; will try fallback.\r\n");
     }
-    trampoline_phys = cfg.addr;
-    /* Apply relocations to trampoline. */
-    for ( trampoline_ptr = __trampoline_rel_start;
-          trampoline_ptr < __trampoline_rel_stop;
-          ++trampoline_ptr )
-        *(u32 *)(*trampoline_ptr + (long)trampoline_ptr) +=
-            trampoline_phys;
-    for ( trampoline_ptr = __trampoline_seg_start;
-          trampoline_ptr < __trampoline_seg_stop;
-          ++trampoline_ptr )
-        *(u16 *)(*trampoline_ptr + (long)trampoline_ptr) =
-            trampoline_phys >> 4;
 
     /* Initialise L2 identity-map and boot-map page table entries (16MB). */
     for ( i = 0; i < 8; ++i )
@@ -1400,10 +1405,14 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
             type = E820_RESERVED;
             break;
         case EfiConventionalMemory:
-        case EfiLoaderCode:
-        case EfiLoaderData:
         case EfiBootServicesCode:
         case EfiBootServicesData:
+            if ( !trampoline_phys && desc->PhysicalStart + len <= 0x100000 &&
+                 len >= cfg.size && desc->PhysicalStart + len > cfg.addr )
+                cfg.addr = (desc->PhysicalStart + len - cfg.size) & PAGE_MASK;
+            /* fall through */
+        case EfiLoaderCode:
+        case EfiLoaderData:
             if ( desc->Attribute & EFI_MEMORY_WB )
                 type = E820_RAM;
             else
@@ -1431,6 +1440,12 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
             ++e820nr;
         }
     }
+    if ( !trampoline_phys )
+    {
+        if ( !cfg.addr )
+            blexit(L"No memory for trampoline");
+        relocate_trampoline(cfg.addr);
+    }
 
     status = efi_bs->ExitBootServices(ImageHandle, map_key);
     if ( EFI_ERROR(status) )