From: Dave Hansen <[email protected]> The VSYSCALL page is mapped by kernel page tables at a kernel address. It is troublesome to support with KAISER in place, so disable the native case.
Also add some help text about how KAISER might affect the emulation case as well. Signed-off-by: Dave Hansen <[email protected]> Cc: Moritz Lipp <[email protected]> Cc: Daniel Gruss <[email protected]> Cc: Michael Schwarz <[email protected]> Cc: Richard Fellner <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Kees Cook <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: [email protected] --- b/arch/x86/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) diff -puN arch/x86/Kconfig~kaiser-no-vsyscall arch/x86/Kconfig --- a/arch/x86/Kconfig~kaiser-no-vsyscall 2017-11-08 10:45:39.157681370 -0800 +++ b/arch/x86/Kconfig 2017-11-08 10:45:39.162681370 -0800 @@ -2231,6 +2231,9 @@ choice config LEGACY_VSYSCALL_NATIVE bool "Native" + # The VSYSCALL page comes from the kernel page tables + # and is not available when KAISER is enabled. + depends on ! KAISER help Actual executable code is located in the fixed vsyscall address mapping, implementing time() efficiently. Since @@ -2248,6 +2251,11 @@ choice exploits. This configuration is recommended when userspace still uses the vsyscall area. + When KAISER is enabled, the vsyscall area will become + unreadable. This emulation option still works, but KAISER + will make it harder to do things like trace code using the + emulation. + config LEGACY_VSYSCALL_NONE bool "None" help _
