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authormirabilos <tg@mirbsd.org>2015-07-25 18:51:26 +0200
committerWaldemar Brodkorb <wbx@uclibc-ng.org>2015-08-02 10:44:27 +0200
commitf5fa14e19c3dcd5f9648a8caaba63bc430f536da (patch)
tree9540a8a5819ae4ee80ff33c383ae0ba76d472e82
parentcdfebe7629971fc671a10c9b419f33f9ff928cbd (diff)
fix inline asm changing the stack pointer leading to segfaults problem
-rw-r--r--libc/sysdeps/linux/i386/brk.c20
1 files changed, 12 insertions, 8 deletions
diff --git a/libc/sysdeps/linux/i386/brk.c b/libc/sysdeps/linux/i386/brk.c
index c2c93271e..a513886e3 100644
--- a/libc/sysdeps/linux/i386/brk.c
+++ b/libc/sysdeps/linux/i386/brk.c
@@ -1,6 +1,7 @@
/* brk system call for Linux/i386.
Copyright (C) 1995, 1996, 2000 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
+ Copyright (c) 2015 mirabilos <tg@mirbsd.org>
+ This file is part of uclibc-ng, derived from the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
@@ -27,15 +28,18 @@ int brk(void *addr)
{
void *newbrk;
- /* %ebx is used in PIC code, need to save/restore it manually.
- * gcc won't do it for us if we will request it in constraints
+ /*
+ * EBC is used in PIC code, we need to save/restore it manually.
+ * Unfortunately, GCC won't do that for us even if we use con-
+ * straints, and we cannot push it either as ESP clobbers are
+ * silently ignored, but EDX is preserved, so it's scratch space.
*/
- __asm__("pushl %%ebx\n"
- "movl %2, %%ebx\n"
- "int $0x80\n"
- "popl %%ebx\n"
+ __asm__("xchgl %%edx,%%ebx"
+ "\n int $0x80"
+ "\n xchgl %%edx,%%ebx"
: "=a" (newbrk)
- : "0" (__NR_brk), "g" (addr)
+ : "0" (__NR_brk), "d" (addr)
+ : "cc"
);
__curbrk = newbrk;