git.squeep.com Git - portage-squeep/blob - sys-boot/grub/files/grub-0.97-Add-esp-to-list-of-clobbered-registers.patch

   1 From 5a52ee4b5cd152fa4ccd1c1f938ce2eba652af52 Mon Sep 17 00:00:00 2001
   2 From: Sergei Trofimovich <slyfox@gentoo.org>
   3 Date: Mon, 14 Dec 2015 23:59:17 +0000
   4 Subject: [PATCH] Add %esp to list of clobbered registers
   5
   6 GCC assumes that it can combine stacks from
   7 outer
   8     grub_stage2()
   9 and inner
  10     trampoline doit()
  11 functions (optimisation -fcombine-stack-adjustments).
  12
  13 But doit() function clobbers %esp in inline
  14 assebly statement as:
  15
  16   asm volatile ("movl %%esp, %0\n\tmovl %1, %%esp\n"
  17                : "=&r" (realstack) : "r" (simstack));
  18
  19 which tricks gcc into computing invalid local variable
  20 offsets from current %esp value.
  21
  22 Fix by hinting gcc about %esp change in clobber list.
  23
  24 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
  25 ---
  26  grub/asmstub.c | 4 ++--
  27  1 file changed, 2 insertions(+), 2 deletions(-)
  28
  29 diff --git a/grub/asmstub.c b/grub/asmstub.c
  30 index 6354806..44b056f 100644
  31 --- a/grub/asmstub.c
  32 +++ b/grub/asmstub.c
  33 @@ -174,7 +174,7 @@ grub_stage2 (void)
  34      {
  35        /* Make sure our stack lives in the simulated memory area. */
  36        asm volatile ("movl %%esp, %0\n\tmovl %1, %%esp\n"
  37 -                   : "=&r" (realstack) : "r" (simstack));
  38 +                   : "=&r" (realstack) : "r" (simstack) : "%esp");
  39
  40        /* Do a setjmp here for the stop command.  */
  41        if (! setjmp (env_for_exit))
  42 @@ -191,7 +191,7 @@ grub_stage2 (void)
  43         }
  44
  45        /* Replace our stack before we use any local variables. */
  46 -      asm volatile ("movl %0, %%esp\n" : : "r" (realstack));
  47 +      asm volatile ("movl %0, %%esp\n" : : "r" (realstack) : "%esp");
  48      }
  49
  50    assert (grub_scratch_mem == 0);
  51 --
  52 2.6.3
  53