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| author | Andy Lutomirski <luto@amacapital.net> | 2014-10-29 14:33:47 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2014-11-03 21:44:57 +0100 |
| commit | 1ad83c858c7d4ea210429142c99a1548e6715a35 (patch) | |
| tree | 9c40dd5e49b646ae68e252c9a3e8afbd01a6a588 /arch/x86/Kconfig | |
| parent | 95c46b56922409ed8838b3b420b11cfebb8c6c88 (diff) | |
| download | linux-1ad83c858c7d4ea210429142c99a1548e6715a35.tar.bz2 | |
x86_64,vsyscall: Make vsyscall emulation configurable
This adds CONFIG_X86_VSYSCALL_EMULATION, guarded by CONFIG_EXPERT.
Turning it off completely disables vsyscall emulation, saving ~3.5k
for vsyscall_64.c, 4k for vsyscall_emu_64.S (the fake vsyscall
page), some tiny amount of core mm code that supports a gate area,
and possibly 4k for a wasted pagetable. The latter is because the
vsyscall addresses are misaligned and fit poorly in the fixmap.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/406db88b8dd5f0cbbf38216d11be34bbb43c7eae.1414618407.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f2327e88e07c..cd10436d7d1c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -984,6 +984,24 @@ config X86_ESPFIX64 def_bool y depends on X86_16BIT && X86_64 +config X86_VSYSCALL_EMULATION + bool "Enable vsyscall emulation" if EXPERT + default y + depends on X86_64 + ---help--- + This enables emulation of the legacy vsyscall page. Disabling + it is roughly equivalent to booting with vsyscall=none, except + that it will also disable the helpful warning if a program + tries to use a vsyscall. With this option set to N, offending + programs will just segfault, citing addresses of the form + 0xffffffffff600?00. + + This option is required by many programs built before 2013, and + care should be used even with newer programs if set to N. + + Disabling this option saves about 7K of kernel size and + possibly 4K of additional runtime pagetable memory. + config TOSHIBA tristate "Toshiba Laptop support" depends on X86_32 |