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authorRoland McGrath <roland@gnu.org>2004-08-15 23:33:02 +0000
committerRoland McGrath <roland@gnu.org>2004-08-15 23:33:02 +0000
commita489c5298d5350e2b443af444e3303d01667e6a3 (patch)
tree8bd003a06dffca3decf417f0092a0758ce3e9850 /sysdeps/unix/sysv
parent2d26a7173c076ff8f40c9bbdbff80166ff0c781d (diff)
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[BZ #227]
2004-08-15 Roland McGrath <roland@redhat.com> [BZ #227] * sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_BRK_PAGE_ROUNDED): New macro. * sysdeps/unix/sysv/linux/dl-sysdep.c (frob_brk) [! __ASSUME_BRK_PAGE_ROUNDED]: Adjust the break up if it falls within the partial page after the dynamic linker's own data segment.
Diffstat (limited to 'sysdeps/unix/sysv')
-rw-r--r--sysdeps/unix/sysv/linux/dl-sysdep.c25
-rw-r--r--sysdeps/unix/sysv/linux/kernel-features.h6
2 files changed, 30 insertions, 1 deletions
diff --git a/sysdeps/unix/sysv/linux/dl-sysdep.c b/sysdeps/unix/sysv/linux/dl-sysdep.c
index b58f4c13e2..79f95df0a2 100644
--- a/sysdeps/unix/sysv/linux/dl-sysdep.c
+++ b/sysdeps/unix/sysv/linux/dl-sysdep.c
@@ -1,5 +1,5 @@
/* Dynamic linker system dependencies for Linux.
- Copyright (C) 1995, 1997, 2001 Free Software Foundation, Inc.
+ Copyright (C) 1995, 1997, 2001, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -21,6 +21,8 @@
the generic dynamic linker system interface code. */
#include <unistd.h>
+#include <ldsodefs.h>
+#include "kernel-features.h"
#define DL_SYSDEP_INIT frob_brk ()
@@ -28,6 +30,27 @@ static inline void
frob_brk (void)
{
__brk (0); /* Initialize the break. */
+
+#if ! __ASSUME_BRK_PAGE_ROUNDED
+ /* If the dynamic linker was executed as a program, then the break may
+ start immediately after our data segment. However, dl-minimal.c has
+ already stolen the remainder of the page for internal allocations.
+ If we don't adjust the break location recorded by the kernel, the
+ normal program startup will inquire, find the value at our &_end,
+ and start allocating its own data there, clobbering dynamic linker
+ data structures allocated there during startup.
+
+ Later Linux kernels have changed this behavior so that the initial
+ break value is rounded up to the page boundary before we start. */
+
+ extern void *__curbrk attribute_hidden;
+ extern void _end attribute_hidden;
+ void *const endpage = (void *) 0 + (((__curbrk - (void *) 0)
+ + GLRO(dl_pagesize) - 1)
+ & -GLRO(dl_pagesize));
+ if (__builtin_expect (__curbrk >= &_end && __curbrk < endpage, 0))
+ __brk (endpage);
+#endif
}
#include <sysdeps/generic/dl-sysdep.c>
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index ee089d550b..6f19fc6360 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -400,3 +400,9 @@
#if __LINUX_KERNEL_VERSION >= 132612
# define __ASSUME_GETDENTS32_D_TYPE 1
#endif
+
+/* Starting with version 2.5.3, the initial location returned by `brk'
+ after exec is always rounded up to the next page. */
+#if __LINUX_KERNEL_VERSION >= 132355
+# define __ASSUME_BRK_PAGE_ROUNDED 1
+#endif