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brk: document randomize_va_space and CONFIG_COMPAT_BRK (was Re:

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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>
This commit is contained in:
Jiri Kosina 2008-02-09 23:24:08 +01:00 committed by Thomas Gleixner
parent 6697c05296
commit 1ec7fd50ba
1 changed files with 29 additions and 0 deletions
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29
Documentation/sysctl/kernel.txt
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@ -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