[PATCH v6] Avoid crash calling PrintErrMesg from efi_multiboot2

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

Although code is compiled with -fpic option data is not position
independent. This causes data pointer to become invalid if
code is not relocated properly which is what happens for
efi_multiboot2 which is called by multiboot entry code.

Code tested adding
   PrintErrMesg(L"Test message", EFI_BUFFER_TOO_SMALL);
in efi_multiboot2 before calling efi_arch_edd (this function
can potentially call PrintErrMesg).

Before the patch (XenServer installation on Qemu, xen replaced
with vanilla xen.gz):
  Booting `XenServer (Serial)'Booting `XenServer (Serial)'
  Test message: !!!! X64 Exception Type - 0E(#PF - Page-Fault)  CPU Apic ID - 
00000000 !!!!
  ExceptionData - 0000000000000000  I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
  RIP  - 000000007EE21E9A, CS  - 0000000000000038, RFLAGS - 0000000000210246
  RAX  - 000000007FF0C1B5, RCX - 0000000000000050, RDX - 0000000000000010
  RBX  - 0000000000000000, RSP - 000000007FF0C180, RBP - 000000007FF0C210
  RSI  - FFFF82D040467CE8, RDI - 0000000000000000
  R8   - 000000007FF0C1C8, R9  - 000000007FF0C1C0, R10 - 0000000000000000
  R11  - 0000000000001020, R12 - FFFF82D040467CE8, R13 - 000000007FF0C1B8
  R14  - 000000007EA33328, R15 - 000000007EA332D8
  DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030
  GS   - 0000000000000030, SS  - 0000000000000030
  CR0  - 0000000080010033, CR2 - FFFF82D040467CE8, CR3 - 000000007FC01000
  CR4  - 0000000000000668, CR8 - 0000000000000000
  DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
  DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
  GDTR - 000000007F9DB000 0000000000000047, LDTR - 0000000000000000
  IDTR - 000000007F48E018 0000000000000FFF,   TR - 0000000000000000
  FXSAVE_STATE - 000000007FF0BDE0
  !!!! Find image based on IP(0x7EE21E9A) (No PDB)  
(ImageBase=000000007EE20000, EntryPoint=000000007EE23935) !!!!

After the patch:
  Booting `XenServer (Serial)'Booting `XenServer (Serial)'
  Test message: Buffer too small
  BdsDxe: loading Boot0000 "UiApp" from 
Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)
  BdsDxe: starting Boot0000 "UiApp" from 
Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)

This partially rollback commit 00d5d5ce23e6.

Fixes: 9180f5365524 ("x86: add multiboot2 protocol support for EFI platforms")
Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
---
Changes since v1:
- added "Fixes:" tag;
- fixed cast style change.

Changes since v2:
- wrap long line.

Changes since v3:
- fixed "Fixes:" tag.

Changes since v4:
- use switch instead of tables.

Changes since v5:
- added -fno-jump-tables option.
---
 xen/common/efi/boot.c        | 58 ++++++++++++++++++++++++------------
 xen/common/efi/efi-common.mk |  1 +
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index efbec00af9..143b5681ba 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -287,33 +287,53 @@ static bool __init match_guid(const EFI_GUID *guid1, 
const EFI_GUID *guid2)
 /* generic routine for printing error messages */
 static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode)
 {
-    static const CHAR16* const ErrCodeToStr[] __initconstrel = {
-        [~EFI_ERROR_MASK & EFI_NOT_FOUND]           = L"Not found",
-        [~EFI_ERROR_MASK & EFI_NO_MEDIA]            = L"The device has no 
media",
-        [~EFI_ERROR_MASK & EFI_MEDIA_CHANGED]       = L"Media changed",
-        [~EFI_ERROR_MASK & EFI_DEVICE_ERROR]        = L"Device error",
-        [~EFI_ERROR_MASK & EFI_VOLUME_CORRUPTED]    = L"Volume corrupted",
-        [~EFI_ERROR_MASK & EFI_ACCESS_DENIED]       = L"Access denied",
-        [~EFI_ERROR_MASK & EFI_OUT_OF_RESOURCES]    = L"Out of resources",
-        [~EFI_ERROR_MASK & EFI_VOLUME_FULL]         = L"Volume is full",
-        [~EFI_ERROR_MASK & EFI_SECURITY_VIOLATION]  = L"Security violation",
-        [~EFI_ERROR_MASK & EFI_CRC_ERROR]           = L"CRC error",
-        [~EFI_ERROR_MASK & EFI_COMPROMISED_DATA]    = L"Compromised data",
-        [~EFI_ERROR_MASK & EFI_BUFFER_TOO_SMALL]    = L"Buffer too small",
-    };
-    EFI_STATUS ErrIdx = ErrCode & ~EFI_ERROR_MASK;
-
     StdOut = StdErr;
     PrintErr(mesg);
     PrintErr(L": ");
 
-    if( (ErrIdx < ARRAY_SIZE(ErrCodeToStr)) && ErrCodeToStr[ErrIdx] )
-        mesg = ErrCodeToStr[ErrIdx];
-    else
+    switch (ErrCode)
     {
+    case EFI_NOT_FOUND:
+        mesg = L"Not found";
+        break;
+    case EFI_NO_MEDIA:
+        mesg = L"The device has no media";
+        break;
+    case EFI_MEDIA_CHANGED:
+        mesg = L"Media changed";
+        break;
+    case EFI_DEVICE_ERROR:
+        mesg = L"Device error";
+        break;
+    case EFI_VOLUME_CORRUPTED:
+        mesg = L"Volume corrupted";
+        break;
+    case EFI_ACCESS_DENIED:
+        mesg = L"Access denied";
+        break;
+    case EFI_OUT_OF_RESOURCES:
+        mesg = L"Out of resources";
+        break;
+    case EFI_VOLUME_FULL:
+        mesg = L"Volume is full";
+        break;
+    case EFI_SECURITY_VIOLATION:
+        mesg = L"Security violation";
+        break;
+    case EFI_CRC_ERROR:
+        mesg = L"CRC error";
+        break;
+    case EFI_COMPROMISED_DATA:
+        mesg = L"Compromised data";
+        break;
+    case EFI_BUFFER_TOO_SMALL:
+        mesg = L"Buffer too small";
+        break;
+    default:
         PrintErr(L"ErrCode: ");
         DisplayUint(ErrCode, 0);
         mesg = NULL;
+        break;
     }
     blexit(mesg);
 }
diff --git a/xen/common/efi/efi-common.mk b/xen/common/efi/efi-common.mk
index 23cafcf20c..06b1c19674 100644
--- a/xen/common/efi/efi-common.mk
+++ b/xen/common/efi/efi-common.mk
@@ -2,6 +2,7 @@ EFIOBJ-y := boot.init.o pe.init.o ebmalloc.o runtime.o
 EFIOBJ-$(CONFIG_COMPAT) += compat.o
 
 CFLAGS-y += -fshort-wchar
+CFLAGS-y += -fno-jump-tables
 CFLAGS-y += -iquote $(srctree)/common/efi
 CFLAGS-y += -iquote $(srcdir)
 
-- 
2.34.1