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| author |   Andy Lutomirski <luto@amacapital.net> | 2014-09-23 10:50:54 -0700 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2014-10-28 11:22:11 +0100 |
| commit | 9c0080ef93bce34db130db6dc3bd946348e6a203 (patch) | |
| tree | de4e8e425a37cdc576a83547595febc935410cb9 /arch/x86/vdso | |
| parent | x86/vdso: Change the PER_CPU segment to use struct desc_struct (diff) | |
| download | linux-dev-9c0080ef93bce34db130db6dc3bd946348e6a203.tar.xz linux-dev-9c0080ef93bce34db130db6dc3bd946348e6a203.zip | |
x86/vdso: Make the PER_CPU segment start out accessed
The first userspace attempt to read or write the PER_CPU segment
will write the accessed bit to the GDT. This is visible to
userspace using the LAR instruction, and it also pointlessly
dirties a cache line.
Set the segment's accessed bit at boot to prevent userspace
access to segments from having side effects.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/ac63814ca4c637a08ec2fd0360d67ca67560a9ee.1411494540.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/vdso')
| -rw-r--r-- | arch/x86/vdso/vma.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c index 261b1349acc9..0c7997467be0 100644 --- a/arch/x86/vdso/vma.c +++ b/arch/x86/vdso/vma.c @@ -264,7 +264,7 @@ static void vsyscall_set_cpu(int cpu) d = (struct desc_struct) { .limit0 = cpu | ((node & 0xf) << 12), .limit = node >> 4, - .type = 4, /* RO data, expand down */ + .type = 5, /* RO data, expand down, accessed */ .dpl = 3, /* Visible to user code */ .s = 1, /* Not a system segment */ .p = 1, /* Present */ |