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From 5a52ee4b5cd152fa4ccd1c1f938ce2eba652af52 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyfox@gentoo.org>
Date: Mon, 14 Dec 2015 23:59:17 +0000
Subject: [PATCH] Add %esp to list of clobbered registers
GCC assumes that it can combine stacks from
outer
grub_stage2()
and inner
trampoline doit()
functions (optimisation -fcombine-stack-adjustments).
But doit() function clobbers %esp in inline
assebly statement as:
asm volatile ("movl %%esp, %0\n\tmovl %1, %%esp\n"
: "=&r" (realstack) : "r" (simstack));
which tricks gcc into computing invalid local variable
offsets from current %esp value.
Fix by hinting gcc about %esp change in clobber list.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
grub/asmstub.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/grub/asmstub.c b/grub/asmstub.c
index 6354806..44b056f 100644
--- a/grub/asmstub.c
+++ b/grub/asmstub.c
@@ -174,7 +174,7 @@ grub_stage2 (void)
{
/* Make sure our stack lives in the simulated memory area. */
asm volatile ("movl %%esp, %0\n\tmovl %1, %%esp\n"
- : "=&r" (realstack) : "r" (simstack));
+ : "=&r" (realstack) : "r" (simstack) : "%esp");
/* Do a setjmp here for the stop command. */
if (! setjmp (env_for_exit))
@@ -191,7 +191,7 @@ grub_stage2 (void)
}
/* Replace our stack before we use any local variables. */
- asm volatile ("movl %0, %%esp\n" : : "r" (realstack));
+ asm volatile ("movl %0, %%esp\n" : : "r" (realstack) : "%esp");
}
assert (grub_scratch_mem == 0);
--
2.6.3
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