[PATCH 4.14 008/146] x86/pti: Add the pti= cmdline option and documentation

Greg Kroah-Hartman
2018-01-01T15:08:14Z

From: Borislav Petkov <bp@suse.de>

commit 41f4c20b57a4890ea7f56ff8717cc83fefb8d537 upstream.

Keep the "nopti" optional for traditional reasons.

[ tglx: Don't allow force on when running on XEN PV and made 'on'
printout conditional ]

Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Link: https://lkml.kernel.org/r/20171212133952.10177-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
Documentation/admin-guide/kernel-parameters.txt | 6 +++++
arch/x86/mm/pti.c | 26 +++++++++++++++++++++++-
2 files changed, 31 insertions(+), 1 deletion(-)

--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3255,6 +3255,12 @@
pt. [PARIDE]
See Documentation/blockdev/paride.txt.

+ pti= [X86_64]
+ Control user/kernel address space isolation:
+ on - enable
+ off - disable
+ auto - default setting
+
pty.legacy_count=
[KNL] Number of legacy pty's. Overwrites compiled-in
default number.
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -54,21 +54,45 @@ static void __init pti_print_if_insecure
pr_info("%s\n", reason);
}

+static void __init pti_print_if_secure(const char *reason)
+{
+ if (!boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+ pr_info("%s\n", reason);
+}
+
void __init pti_check_boottime_disable(void)
{
+ char arg[5];
+ int ret;
+
if (hypervisor_is_type(X86_HYPER_XEN_PV)) {
pti_print_if_insecure("disabled on XEN PV.");
return;
}

+ ret = cmdline_find_option(boot_command_line, "pti", arg, sizeof(arg));
+ if (ret > 0) {
+ if (ret == 3 && !strncmp(arg, "off", 3)) {
+ pti_print_if_insecure("disabled on command line.");
+ return;
+ }
+ if (ret == 2 && !strncmp(arg, "on", 2)) {
+ pti_print_if_secure("force enabled on command line.");
+ goto enable;
+ }
+ if (ret == 4 && !strncmp(arg, "auto", 4))
+ goto autosel;
+ }
+
if (cmdline_find_option_bool(boot_command_line, "nopti")) {
pti_print_if_insecure("disabled on command line.");
return;
}

+autosel:
if (!boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
return;
-
+enable:
setup_force_cpu_cap(X86_FEATURE_PTI);
}