| From foo@baz Wed Jan 3 20:37:21 CET 2018 |
| From: Hugh Dickins <hughd@google.com> |
| Date: Wed, 13 Sep 2017 14:03:10 -0700 |
| Subject: kaiser: KAISER depends on SMP |
| |
| From: Hugh Dickins <hughd@google.com> |
| |
| |
| It is absurd that KAISER should depend on SMP, but apparently nobody |
| has tried a UP build before: which breaks on implicit declaration of |
| function 'per_cpu_offset' in arch/x86/mm/kaiser.c. |
| |
| Now, you would expect that to be trivially fixed up; but looking at |
| the System.map when that block is #ifdef'ed out of kaiser_init(), |
| I see that in a UP build __per_cpu_user_mapped_end is precisely at |
| __per_cpu_user_mapped_start, and the items carefully gathered into |
| that section for user-mapping on SMP, dispersed elsewhere on UP. |
| |
| So, some other kind of section assignment will be needed on UP, |
| but implementing that is not a priority: just make KAISER depend |
| on SMP for now. |
| |
| Also inserted a blank line before the option, tidied up the |
| brief Kconfig help message, and added an "If unsure, Y". |
| |
| Signed-off-by: Hugh Dickins <hughd@google.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| security/Kconfig | 10 ++++++---- |
| 1 file changed, 6 insertions(+), 4 deletions(-) |
| |
| --- a/security/Kconfig |
| +++ b/security/Kconfig |
| @@ -30,14 +30,16 @@ config SECURITY |
| model will be used. |
| |
| If you are unsure how to answer this question, answer N. |
| + |
| config KAISER |
| bool "Remove the kernel mapping in user mode" |
| default y |
| - depends on X86_64 |
| - depends on !PARAVIRT |
| + depends on X86_64 && SMP && !PARAVIRT |
| help |
| - This enforces a strict kernel and user space isolation in order to close |
| - hardware side channels on kernel address information. |
| + This enforces a strict kernel and user space isolation, in order |
| + to close hardware side channels on kernel address information. |
| + |
| + If you are unsure how to answer this question, answer Y. |
| |
| config KAISER_REAL_SWITCH |
| bool "KAISER: actually switch page tables" |
