x86/efi: Fixup GOT in all boot code paths

Maarten reported that his Macbook pro 8.2 stopped booting after commit
f23cf8bd5c1f49 ("efi/x86: efistub: Move shared dependencies to
<asm/efi.h>"), the main feature of which is changing the visibility of
symbol 'efi_early' from local to global.

By making 'efi_early' global we end up requiring an entry in the Global
Offset Table. Unfortunately, while we do include code to fixup GOT
entries in the early boot code, it's only called after we've executed
the EFI boot stub.

What this amounts to is that references to 'efi_early' in the EFI boot
stub don't point to the correct place.

Since we've got multiple boot entry points we need to be prepared to
fixup the GOT in multiple places, while ensuring that we never do it
more than once, otherwise the GOT entries will still point to the wrong
place.

Reported-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Tested-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index cbed1407a5cdb7ead8fa0cae90d2e7902133aaa7..d6b8aa4c986c038fa12d3f76242ea7d738f2b329 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -30,6 +30,33 @@
 #include <asm/boot.h>
 #include <asm/asm-offsets.h>
 
+/*
+ * Adjust our own GOT
+ *
+ * The relocation base must be in %ebx
+ *
+ * It is safe to call this macro more than once, because in some of the
+ * code paths multiple invocations are inevitable, e.g. via the efi*
+ * entry points.
+ *
+ * Relocation is only performed the first time.
+ */
+.macro FIXUP_GOT
+       cmpb    $1, got_fixed(%ebx)
+       je      2f
+
+       leal    _got(%ebx), %edx
+       leal    _egot(%ebx), %ecx
+1:
+       cmpl    %ecx, %edx
+       jae     2f
+       addl    %ebx, (%edx)
+       addl    $4, %edx
+       jmp     1b
+2:
+       movb    $1, got_fixed(%ebx)
+.endm
+
        __HEAD
 ENTRY(startup_32)
 #ifdef CONFIG_EFI_STUB
@@ -56,6 +83,9 @@ ENTRY(efi_pe_entry)
        add     %esi, 88(%eax)
        pushl   %eax
 
+       movl    %esi, %ebx
+       FIXUP_GOT
+
        call    make_boot_params
        cmpl    $0, %eax
        je      fail
@@ -81,6 +111,10 @@ ENTRY(efi32_stub_entry)
        leal    efi32_config(%esi), %eax
        add     %esi, 88(%eax)
        pushl   %eax
+
+       movl    %esi, %ebx
+       FIXUP_GOT
+
 2:
        call    efi_main
        cmpl    $0, %eax
@@ -190,19 +224,7 @@ relocated:
        shrl    $2, %ecx
        rep     stosl
 
-/*
- * Adjust our own GOT
- */
-       leal    _got(%ebx), %edx
-       leal    _egot(%ebx), %ecx
-1:
-       cmpl    %ecx, %edx
-       jae     2f
-       addl    %ebx, (%edx)
-       addl    $4, %edx
-       jmp     1b
-2:
-
+       FIXUP_GOT
 /*
  * Do the decompression, and jump to the new kernel..
  */
@@ -225,8 +247,12 @@ relocated:
        xorl    %ebx, %ebx
        jmp     *%eax
 
-#ifdef CONFIG_EFI_STUB
        .data
+/* Have we relocated the GOT? */
+got_fixed:
+       .byte 0
+
+#ifdef CONFIG_EFI_STUB
 efi32_config:
        .fill 11,8,0
        .long efi_call_phys

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 2884e0c3e8a5880411ce63955b01c103e6eabd00..50f69c7eaaf4bc98b14ad68f76cd2d262982a19a 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -32,6 +32,33 @@
 #include <asm/processor-flags.h>
 #include <asm/asm-offsets.h>
 
+/*
+ * Adjust our own GOT
+ *
+ * The relocation base must be in %rbx
+ *
+ * It is safe to call this macro more than once, because in some of the
+ * code paths multiple invocations are inevitable, e.g. via the efi*
+ * entry points.
+ *
+ * Relocation is only performed the first time.
+ */
+.macro FIXUP_GOT
+       cmpb    $1, got_fixed(%rip)
+       je      2f
+
+       leaq    _got(%rip), %rdx
+       leaq    _egot(%rip), %rcx
+1:
+       cmpq    %rcx, %rdx
+       jae     2f
+       addq    %rbx, (%rdx)
+       addq    $8, %rdx
+       jmp     1b
+2:
+       movb    $1, got_fixed(%rip)
+.endm
+
        __HEAD
        .code32
 ENTRY(startup_32)
@@ -252,10 +279,13 @@ ENTRY(efi_pe_entry)
        subq    $1b, %rbp
 
        /*
-        * Relocate efi_config->call().
+        * Relocate efi_config->call() and the GOT entries.
         */
        addq    %rbp, efi64_config+88(%rip)
 
+       movq    %rbp, %rbx
+       FIXUP_GOT
+
        movq    %rax, %rdi
        call    make_boot_params
        cmpq    $0,%rax
@@ -271,10 +301,13 @@ handover_entry:
        subq    $1b, %rbp
 
        /*
-        * Relocate efi_config->call().
+        * Relocate efi_config->call() and the GOT entries.
         */
        movq    efi_config(%rip), %rax
        addq    %rbp, 88(%rax)
+
+       movq    %rbp, %rbx
+       FIXUP_GOT
 2:
        movq    efi_config(%rip), %rdi
        call    efi_main
@@ -385,19 +418,8 @@ relocated:
        shrq    $3, %rcx
        rep     stosq
 
-/*
- * Adjust our own GOT
- */
-       leaq    _got(%rip), %rdx
-       leaq    _egot(%rip), %rcx
-1:
-       cmpq    %rcx, %rdx
-       jae     2f
-       addq    %rbx, (%rdx)
-       addq    $8, %rdx
-       jmp     1b
-2:
-       
+       FIXUP_GOT
+
 /*
  * Do the decompression, and jump to the new kernel..
  */
@@ -437,6 +459,10 @@ gdt:
        .quad   0x0000000000000000      /* TS continued */
 gdt_end:
 
+/* Have we relocated the GOT? */
+got_fixed:
+       .byte   0
+
 #ifdef CONFIG_EFI_STUB
 efi_config:
        .quad   0