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authorJiri Kosina <jkosina@suse.cz>2008-02-10 01:24:08 +0300
committerThomas Gleixner <tglx@linutronix.de>2008-02-10 01:24:08 +0300
commit1ec7fd50ba4f845d1cf6b67acabd774577ef13b6 (patch)
tree267a1c61fa9a324c90ac8b59203e9bc1087f7dc7
parent6697c05296fab4d113c7144459b72b6172b485a5 (diff)
downloadlinux-1ec7fd50ba4f845d1cf6b67acabd774577ef13b6.tar.xz
brk: document randomize_va_space and CONFIG_COMPAT_BRK (was Re:
Document randomize_va_space and CONFIG_COMPAT_BRK. Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--Documentation/sysctl/kernel.txt29
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 8984a5396271..dc8801d4e944 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -41,6 +41,7 @@ show up in /proc/sys/kernel:
- pid_max
- powersave-nap [ PPC only ]
- printk
+- randomize_va_space
- real-root-dev ==> Documentation/initrd.txt
- reboot-cmd [ SPARC only ]
- rtsig-max
@@ -280,6 +281,34 @@ send before ratelimiting kicks in.
==============================================================
+randomize-va-space:
+
+This option can be used to select the type of process address
+space randomization that is used in the system, for architectures
+that support this feature.
+
+0 - Turn the process address space randomization off by default.
+
+1 - Make the addresses of mmap base, stack and VDSO page randomized.
+ This, among other things, implies that shared libraries will be
+ loaded to random addresses. Also for PIE-linked binaries, the location
+ of code start is randomized.
+
+ With heap randomization, the situation is a little bit more
+ complicated.
+ There a few legacy applications out there (such as some ancient
+ versions of libc.so.5 from 1996) that assume that brk area starts
+ just after the end of the code+bss. These applications break when
+ start of the brk area is randomized. There are however no known
+ non-legacy applications that would be broken this way, so for most
+ systems it is safe to choose full randomization. However there is
+ a CONFIG_COMPAT_BRK option for systems with ancient and/or broken
+ binaries, that makes heap non-randomized, but keeps all other
+ parts of process address space randomized if randomize_va_space
+ sysctl is turned on.
+
+==============================================================
+
reboot-cmd: (Sparc only)
??? This seems to be a way to give an argument to the Sparc