diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2019-11-11 23:03:28 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-11-16 11:24:05 +0100 |
| commit | c8137ace56383688af911fea5934c71ad158135e (patch) | |
| tree | 27f653f628e61a868ef0e4d9ece62185e1c24952 /arch/x86/kernel/cpu | |
| parent | be9afb4b529d9e3a68da1212e33be677bbfc8d2c (diff) | |
x86/iopl: Restrict iopl() permission scope
The access to the full I/O port range can be also provided by the TSS I/O
bitmap, but that would require to copy 8k of data on scheduling in the
task. As shown with the sched out optimization TSS.io_bitmap_base can be
used to switch the incoming task to a preallocated I/O bitmap which has all
bits zero, i.e. allows access to all I/O ports.
Implementing this allows to provide an iopl() emulation mode which restricts
the IOPL level 3 permissions to I/O port access but removes the STI/CLI
permission which is coming with the hardware IOPL mechansim.
Provide a config option to switch IOPL to emulation mode, make it the
default and while at it also provide an option to disable IOPL completely.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 79dd544bb974..7bf402be13bb 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1864,6 +1864,11 @@ void cpu_init(void) tss->io_bitmap.prev_max = 0; tss->io_bitmap.prev_sequence = 0; memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap)); + /* + * Invalidate the extra array entry past the end of the all + * permission bitmap as required by the hardware. + */ + tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL; set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss); load_TR_desc(); |