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authorIngo Molnar <mingo@elte.hu>2006-06-27 02:53:50 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-27 17:32:38 -0700
commite6e5494cb23d1933735ee47cc674ffe1c4afed6f (patch)
treec8945bb3ae5bec38693d801fb589d22d48d6f8eb /include/asm-i386/unwind.h
parentd5fb34261dcd32c9cb3b28121fdc46308db513a1 (diff)
downloadop-kernel-dev-e6e5494cb23d1933735ee47cc674ffe1c4afed6f.zip
op-kernel-dev-e6e5494cb23d1933735ee47cc674ffe1c4afed6f.tar.gz
[PATCH] vdso: randomize the i386 vDSO by moving it into a vma
Move the i386 VDSO down into a vma and thus randomize it. Besides the security implications, this feature also helps debuggers, which can COW a vma-backed VDSO just like a normal DSO and can thus do single-stepping and other debugging features. It's good for hypervisors (Xen, VMWare) too, which typically live in the same high-mapped address space as the VDSO, hence whenever the VDSO is used, they get lots of guest pagefaults and have to fix such guest accesses up - which slows things down instead of speeding things up (the primary purpose of the VDSO). There's a new CONFIG_COMPAT_VDSO (default=y) option, which provides support for older glibcs that still rely on a prelinked high-mapped VDSO. Newer distributions (using glibc 2.3.3 or later) can turn this option off. Turning it off is also recommended for security reasons: attackers cannot use the predictable high-mapped VDSO page as syscall trampoline anymore. There is a new vdso=[0|1] boot option as well, and a runtime /proc/sys/vm/vdso_enabled sysctl switch, that allows the VDSO to be turned on/off. (This version of the VDSO-randomization patch also has working ELF coredumping, the previous patch crashed in the coredumping code.) This code is a combined work of the exec-shield VDSO randomization code and Gerd Hoffmann's hypervisor-centric VDSO patch. Rusty Russell started this patch and i completed it. [akpm@osdl.org: cleanups] [akpm@osdl.org: compile fix] [akpm@osdl.org: compile fix 2] [akpm@osdl.org: compile fix 3] [akpm@osdl.org: revernt MAXMEM change] Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Cc: Gerd Hoffmann <kraxel@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Zachary Amsden <zach@vmware.com> Cc: Andi Kleen <ak@muc.de> Cc: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-i386/unwind.h')
-rw-r--r--include/asm-i386/unwind.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/include/asm-i386/unwind.h b/include/asm-i386/unwind.h
index d480f2e..69f0f1d 100644
--- a/include/asm-i386/unwind.h
+++ b/include/asm-i386/unwind.h
@@ -78,8 +78,8 @@ static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
return user_mode_vm(&info->regs);
#else
return info->regs.eip < PAGE_OFFSET
- || (info->regs.eip >= __fix_to_virt(FIX_VSYSCALL)
- && info->regs.eip < __fix_to_virt(FIX_VSYSCALL) + PAGE_SIZE)
+ || (info->regs.eip >= __fix_to_virt(FIX_VDSO)
+ && info->regs.eip < __fix_to_virt(FIX_VDSO) + PAGE_SIZE)
|| info->regs.esp < PAGE_OFFSET;
#endif
}
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