releases/5.0.1/x86-boot-compressed-64-do-not-read-legacy-rom-on-efi-system.patch

   1 From 6f913de3231e1d70a871135b38219da7810df218 Mon Sep 17 00:00:00 2001
   2 From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
   3 Date: Tue, 19 Feb 2019 10:52:24 +0300
   4 Subject: x86/boot/compressed/64: Do not read legacy ROM on EFI system
   5
   6 From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
   7
   8 commit 6f913de3231e1d70a871135b38219da7810df218 upstream.
   9
  10 EFI systems do not necessarily provide a legacy ROM. If the ROM is missing
  11 the memory is not mapped at all.
  12
  13 Trying to dereference values in the legacy ROM area leads to a crash on
  14 Macbook Pro.
  15
  16 Only look for values in the legacy ROM area for non-EFI system.
  17
  18 Fixes: 3548e131ec6a ("x86/boot/compressed/64: Find a place for 32-bit trampoline")
  19 Reported-by: Pitam Mitra <pitamm@gmail.com>
  20 Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
  21 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  22 Tested-by: Bockjoo Kim <bockjoo@phys.ufl.edu>
  23 Cc: bp@alien8.de
  24 Cc: hpa@zytor.com
  25 Cc: stable@vger.kernel.org
  26 Link: https://lkml.kernel.org/r/20190219075224.35058-1-kirill.shutemov@linux.intel.com
  27 Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202351
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29
  30 ---
  31  arch/x86/boot/compressed/pgtable_64.c |   19 ++++++++++++++++---
  32  1 file changed, 16 insertions(+), 3 deletions(-)
  33
  34 --- a/arch/x86/boot/compressed/pgtable_64.c
  35 +++ b/arch/x86/boot/compressed/pgtable_64.c
  36 @@ -1,5 +1,7 @@
  37 +#include <linux/efi.h>
  38  #include <asm/e820/types.h>
  39  #include <asm/processor.h>
  40 +#include <asm/efi.h>
  41  #include "pgtable.h"
  42  #include "../string.h"
  43
  44 @@ -37,9 +39,10 @@ int cmdline_find_option_bool(const char
  45
  46  static unsigned long find_trampoline_placement(void)
  47  {
  48 -       unsigned long bios_start, ebda_start;
  49 +       unsigned long bios_start = 0, ebda_start = 0;
  50         unsigned long trampoline_start;
  51         struct boot_e820_entry *entry;
  52 +       char *signature;
  53         int i;
  54
  55         /*
  56 @@ -47,8 +50,18 @@ static unsigned long find_trampoline_pla
  57          * This code is based on reserve_bios_regions().
  58          */
  59
  60 -       ebda_start = *(unsigned short *)0x40e << 4;
  61 -       bios_start = *(unsigned short *)0x413 << 10;
  62 +       /*
  63 +        * EFI systems may not provide legacy ROM. The memory may not be mapped
  64 +        * at all.
  65 +        *
  66 +        * Only look for values in the legacy ROM for non-EFI system.
  67 +        */
  68 +       signature = (char *)&boot_params->efi_info.efi_loader_signature;
  69 +       if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) &&
  70 +           strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) {
  71 +               ebda_start = *(unsigned short *)0x40e << 4;
  72 +               bios_start = *(unsigned short *)0x413 << 10;
  73 +       }
  74
  75         if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX)
  76                 bios_start = BIOS_START_MAX;