diff options
Diffstat (limited to 'kernel/futex.c')
-rw-r--r-- | kernel/futex.c | 39 |
1 files changed, 34 insertions, 5 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index c20f06f38ef3..46cb3a301bc1 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -179,7 +179,15 @@ int __read_mostly futex_cmpxchg_enabled; * Futex flags used to encode options to functions and preserve them across * restarts. */ -#define FLAGS_SHARED 0x01 +#ifdef CONFIG_MMU +# define FLAGS_SHARED 0x01 +#else +/* + * NOMMU does not have per process address space. Let the compiler optimize + * code away. + */ +# define FLAGS_SHARED 0x00 +#endif #define FLAGS_CLOCKRT 0x02 #define FLAGS_HAS_TIMEOUT 0x04 @@ -405,6 +413,16 @@ static void get_futex_key_refs(union futex_key *key) if (!key->both.ptr) return; + /* + * On MMU less systems futexes are always "private" as there is no per + * process address space. We need the smp wmb nevertheless - yes, + * arch/blackfin has MMU less SMP ... + */ + if (!IS_ENABLED(CONFIG_MMU)) { + smp_mb(); /* explicit smp_mb(); (B) */ + return; + } + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: ihold(key->shared.inode); /* implies smp_mb(); (B) */ @@ -436,6 +454,9 @@ static void drop_futex_key_refs(union futex_key *key) return; } + if (!IS_ENABLED(CONFIG_MMU)) + return; + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: iput(key->shared.inode); @@ -469,7 +490,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; - struct page *page; + struct page *page, *tail; struct address_space *mapping; int err, ro = 0; @@ -530,7 +551,15 @@ again: * considered here and page lock forces unnecessarily serialization * From this point on, mapping will be re-verified if necessary and * page lock will be acquired only if it is unavoidable - */ + * + * Mapping checks require the head page for any compound page so the + * head page and mapping is looked up now. For anonymous pages, it + * does not matter if the page splits in the future as the key is + * based on the address. For filesystem-backed pages, the tail is + * required as the index of the page determines the key. For + * base pages, there is no tail page and tail == page. + */ + tail = page; page = compound_head(page); mapping = READ_ONCE(page->mapping); @@ -654,7 +683,7 @@ again: key->both.offset |= FUT_OFF_INODE; /* inode-based key */ key->shared.inode = inode; - key->shared.pgoff = basepage_index(page); + key->shared.pgoff = basepage_index(tail); rcu_read_unlock(); } @@ -729,7 +758,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from) int ret; pagefault_disable(); - ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); + ret = __get_user(*dest, from); pagefault_enable(); return ret ? -EFAULT : 0; |