On Fri, Jul 24, 2015 at 04:18:30PM +0800, kbuild test robot wrote:
> tree: git://git.cmpxchg.org/linux-mmotm.git master
> head: 61f5f835b6f06fbc233481b5d3c0afd71ecf54e8
> commit: b9e95c5dd1134d35b6c9aeaa3967ab5b3945ba73 [371/385] mm, mpx: add "vm_flags_t vm_flags" arg to do_mmap_pgoff()
> reproduce:
> # apt-get install sparse
> git checkout b9e95c5dd1134d35b6c9aeaa3967ab5b3945ba73
> make ARCH=x86_64 allmodconfig
> make C=1 CF=-D__CHECK_ENDIAN__
>
>
> sparse warnings: (new ones prefixed by >>)
>
> >> arch/x86/mm/mpx.c:71:54: sparse: implicit cast to nocast type
> arch/x86/mm/mpx.c:312:27: sparse: incompatible types in comparison expression (different address spaces)
> --
> >> include/linux/mm.h:1812:54: sparse: implicit cast to nocast type
> --
> mm/mmap.c:1343:47: sparse: implicit cast to nocast type
> mm/mmap.c:1345:45: sparse: implicit cast to nocast type
> mm/mmap.c:1354:45: sparse: implicit cast to nocast type
> mm/mmap.c:1375:47: sparse: implicit cast to nocast type
> mm/mmap.c:1395:37: sparse: implicit cast to nocast type
> mm/mmap.c:1399:37: sparse: implicit cast to nocast type
> mm/mmap.c:1443:33: sparse: implicit cast to nocast type
> mm/mmap.c:1578:29: sparse: implicit cast to nocast type
> mm/internal.h:253:43: sparse: implicit cast to nocast type
> mm/mmap.c:2650:37: sparse: implicit cast to nocast type
> mm/mmap.c:2690:34: sparse: implicit cast to nocast type
> mm/mmap.c:2693:34: sparse: implicit cast to nocast type
> >> include/linux/mm.h:1812:54: sparse: implicit cast to nocast type
> mm/internal.h:253:43: sparse: implicit cast to nocast type
sparse complains on each and every vm_flags_t initialization, even with
proper VM_* constants.
Do we really want to fix that?
To me it's too much pain and no gain. __nocast is not beneficial here.
And I'm not sure that vm_flags_t typedef was a good idea after all.
Originally, it was intended to become 64-bit one day, but four years later
it's still unsigned long. Plain unsigned long works fine for other bit
field.
What is special about vm_flags?
> vim +71 arch/x86/mm/mpx.c
>
> 55 * bounds tables (the bounds directory is user-allocated).
> 56 *
> 57 * Later on, we use the vma->vm_ops to uniquely identify these
> 58 * VMAs.
> 59 */
> 60 static unsigned long mpx_mmap(unsigned long len)
> 61 {
> 62 struct mm_struct *mm = current->mm;
> 63 unsigned long addr, populate;
> 64
> 65 /* Only bounds table can be allocated here */
> 66 if (len != mpx_bt_size_bytes(mm))
> 67 return -EINVAL;
> 68
> 69 down_write(&mm->mmap_sem);
> 70 addr = do_mmap(NULL, 0, len, PROT_READ | PROT_WRITE,
> > 71 MAP_ANONYMOUS | MAP_PRIVATE, VM_MPX, 0, &populate);
> 72 up_write(&mm->mmap_sem);
> 73 if (populate)
> 74 mm_populate(addr, populate);
> 75
> 76 return addr;
> 77 }
> 78
> 79 enum reg_type {
>
> ---
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>
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--
Kirill A. Shutemov
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