diff options
| -rw-r--r-- | arch/x86/include/asm/io_bitmap.h | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/ioport.c | 48 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 39 |
3 files changed, 50 insertions, 42 deletions
diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h index 784a88edb25d..b664baadf736 100644 --- a/arch/x86/include/asm/io_bitmap.h +++ b/arch/x86/include/asm/io_bitmap.h @@ -2,15 +2,20 @@ #ifndef _ASM_X86_IOBITMAP_H #define _ASM_X86_IOBITMAP_H +#include <linux/refcount.h> #include <asm/processor.h> struct io_bitmap { u64 sequence; + refcount_t refcnt; /* The maximum number of bytes to copy so all zero bits are covered */ unsigned int max; unsigned long bitmap[IO_BITMAP_LONGS]; }; +struct task_struct; + +void io_bitmap_share(struct task_struct *tsk); void io_bitmap_exit(void); void tss_update_io_bitmap(void); diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index f9fc69aeb033..f82ca1c62e3e 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -16,6 +16,17 @@ static atomic64_t io_bitmap_sequence; +void io_bitmap_share(struct task_struct *tsk) + { + /* + * Take a refcount on current's bitmap. It can be used by + * both tasks as long as none of them changes the bitmap. + */ + refcount_inc(¤t->thread.io_bitmap->refcnt); + tsk->thread.io_bitmap = current->thread.io_bitmap; + set_tsk_thread_flag(tsk, TIF_IO_BITMAP); +} + void io_bitmap_exit(void) { struct io_bitmap *iobm = current->thread.io_bitmap; @@ -25,7 +36,8 @@ void io_bitmap_exit(void) preempt_disable(); tss_update_io_bitmap(); preempt_enable(); - kfree(iobm); + if (iobm && refcount_dec_and_test(&iobm->refcnt)) + kfree(iobm); } /* @@ -58,9 +70,32 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) return -ENOMEM; memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap)); + refcount_set(&iobm->refcnt, 1); + } + + /* + * If the bitmap is not shared, then nothing can take a refcount as + * current can obviously not fork at the same time. If it's shared + * duplicate it and drop the refcount on the original one. + */ + if (refcount_read(&iobm->refcnt) > 1) { + iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL); + if (!iobm) + return -ENOMEM; + refcount_set(&iobm->refcnt, 1); + io_bitmap_exit(); } /* + * Store the bitmap pointer (might be the same if the task already + * head one). Must be done here so freeing the bitmap when all + * permissions are dropped has the pointer set up. + */ + t->io_bitmap = iobm; + /* Mark it active for context switching and exit to user mode */ + set_thread_flag(TIF_IO_BITMAP); + + /* * Update the tasks bitmap. The update of the TSS bitmap happens on * exit to user mode. So this needs no protection. */ @@ -86,16 +121,11 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on) iobm->max = (max_long + 1) * sizeof(unsigned long); - /* Update the sequence number to force an update in switch_to() */ - iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence); - /* - * Store the bitmap pointer (might be the same if the task already - * head one). Set the TIF flag, just in case this is the first - * invocation. + * Update the sequence number to force a TSS update on return to + * user mode. */ - t->io_bitmap = iobm; - set_thread_flag(TIF_IO_BITMAP); + iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence); return 0; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7ba4d54aec17..0b19c137c442 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -122,37 +122,13 @@ static int set_new_tls(struct task_struct *p, unsigned long tls) return do_set_thread_area_64(p, ARCH_SET_FS, tls); } -static inline int copy_io_bitmap(struct task_struct *tsk) -{ - struct io_bitmap *iobm = current->thread.io_bitmap; - - if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP))) - return 0; - - tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL); - - if (!tsk->thread.io_bitmap) - return -ENOMEM; - - set_tsk_thread_flag(tsk, TIF_IO_BITMAP); - return 0; -} - -static inline void free_io_bitmap(struct task_struct *tsk) -{ - if (tsk->thread.io_bitmap) { - kfree(tsk->thread.io_bitmap); - tsk->thread.io_bitmap = NULL; - } -} - int copy_thread_tls(unsigned long clone_flags, unsigned long sp, unsigned long arg, struct task_struct *p, unsigned long tls) { struct inactive_task_frame *frame; struct fork_frame *fork_frame; struct pt_regs *childregs; - int ret; + int ret = 0; childregs = task_pt_regs(p); fork_frame = container_of(childregs, struct fork_frame, regs); @@ -199,16 +175,13 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, task_user_gs(p) = get_user_gs(current_pt_regs()); #endif - ret = copy_io_bitmap(p); - if (ret) - return ret; - /* Set a new TLS for the child thread? */ - if (clone_flags & CLONE_SETTLS) { + if (clone_flags & CLONE_SETTLS) ret = set_new_tls(p, tls); - if (ret) - free_io_bitmap(p); - } + + if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) + io_bitmap_share(p); + return ret; } |