x86_64, vsyscall: Turn vsyscalls all the way off when vsyscall==none

I see no point in having an unusable read-only page sitting at
0xffffffffff600000 when vsyscall=none. Instead, skip mapping it and
remove it from /proc/PID/maps.

I kept the ratelimited warning when programs try to use a vsyscall
in this mode, since it may help admins avoid confusion.

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/0dddbadc1d4e3bfbaf887938ff42afc97a7cc1f2.1414618407.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 5 deletions

diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 419e83b58436..2d912629c96e 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -307,6 +307,8 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
         if (!mm || mm->context.ia32_compat)
                 return NULL;
 #endif
+        if (vsyscall_mode == NONE)
+                return NULL;
         return &gate_vma;
 }
 
@@ -327,7 +329,7 @@ int in_gate_area(struct mm_struct *mm, unsigned long addr)
  */
 int in_gate_area_no_mm(unsigned long addr)
 {
-        return (addr & PAGE_MASK) == VSYSCALL_ADDR;
+        return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR;
 }
 
 void __init map_vsyscall(void)
@@ -335,10 +337,12 @@ void __init map_vsyscall(void)
         extern char __vsyscall_page;
         unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
 
-        __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
-                     vsyscall_mode == NATIVE
-                     ? PAGE_KERNEL_VSYSCALL
-                     : PAGE_KERNEL_VVAR);
+        if (vsyscall_mode != NONE)
+                __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
+                             vsyscall_mode == NATIVE
+                             ? PAGE_KERNEL_VSYSCALL
+                             : PAGE_KERNEL_VVAR);
+
         BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
                      (unsigned long)VSYSCALL_ADDR);
 }