diff options
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 38 |
1 files changed, 28 insertions, 10 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 1504fd2b9bc4..7c49be90468b 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -360,6 +360,28 @@ void arch_setup_new_exec(void) } } +static void switch_to_update_io_bitmap(struct tss_struct *tss, + struct io_bitmap *iobm) +{ + /* + * Copy at least the byte range of the incoming tasks bitmap which + * covers the permitted I/O ports. + * + * If the previous task which used an I/O bitmap had more bits + * permitted, then the copy needs to cover those as well so they + * get turned off. + */ + memcpy(tss->io_bitmap.bitmap, iobm->bitmap, + max(tss->io_bitmap.prev_max, iobm->max)); + + /* + * Store the new max and the sequence number of this bitmap + * and a pointer to the bitmap itself. + */ + tss->io_bitmap.prev_max = iobm->max; + tss->io_bitmap.prev_sequence = iobm->sequence; +} + static inline void switch_to_bitmap(struct thread_struct *next, unsigned long tifp, unsigned long tifn) { @@ -369,18 +391,14 @@ static inline void switch_to_bitmap(struct thread_struct *next, struct io_bitmap *iobm = next->io_bitmap; /* - * Copy at least the size of the incoming tasks bitmap - * which covers the last permitted I/O port. - * - * If the previous task which used an io bitmap had more - * bits permitted, then the copy needs to cover those as - * well so they get turned off. + * Only copy bitmap data when the sequence number + * differs. The update time is accounted to the incoming + * task. */ - memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap, - max(tss->io_bitmap.prev_max, next->io_bitmap->max)); + if (tss->io_bitmap.prev_sequence != iobm->sequence) + switch_to_update_io_bitmap(tss, iobm); - /* Store the new max and set io_bitmap_base valid */ - tss->io_bitmap.prev_max = next->io_bitmap->max; + /* Enable the bitmap */ tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID; /* |