linux-stable.git/arch/um/include/asm, branch linux-4.9.y

um: use fallback for random_get_entropy() instead of zero

2022-06-25T09:45:13+00:00

commit 9f13fb0cd11ed2327abff69f6501a2c124c88b5a upstream.

In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner 
Cc: Arnd Bergmann 
Cc: Richard Weinberger 
Cc: Anton Ivanov 
Acked-by: Johannes Berg 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

hugetlbfs: flush TLBs correctly after huge_pmd_unshare

2021-12-08T07:45:03+00:00

commit a4a118f2eead1d6c49e00765de89878288d4b890 upstream.

When __unmap_hugepage_range() calls to huge_pmd_unshare() succeed, a TLB
flush is missing.  This TLB flush must be performed before releasing the
i_mmap_rwsem, in order to prevent an unshared PMDs page from being
released and reused before the TLB flush took place.

Arguably, a comprehensive solution would use mmu_gather interface to
batch the TLB flushes and the PMDs page release, however it is not an
easy solution: (1) try_to_unmap_one() and try_to_migrate_one() also call
huge_pmd_unshare() and they cannot use the mmu_gather interface; and (2)
deferring the release of the page reference for the PMDs page until
after i_mmap_rwsem is dropeed can confuse huge_pmd_unshare() into
thinking PMDs are shared when they are not.

Fix __unmap_hugepage_range() by adding the missing TLB flush, and
forcing a flush when unshare is successful.

Fixes: 24669e58477e ("hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages)" # 3.6
Signed-off-by: Nadav Amit 
Reviewed-by: Mike Kravetz 
Cc: Aneesh Kumar K.V 
Cc: KAMEZAWA Hiroyuki 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

um: Silence lockdep complaint about mmap_sem

2019-08-04T07:33:39+00:00

[ Upstream commit 80bf6ceaf9310b3f61934c69b382d4912deee049 ]

When we get into activate_mm(), lockdep complains that we're doing
something strange:

    WARNING: possible circular locking dependency detected
    5.1.0-10252-gb00152307319-dirty #121 Not tainted
    ------------------------------------------------------
    inside.sh/366 is trying to acquire lock:
    (____ptrval____) (&(&p->alloc_lock)->rlock){+.+.}, at: flush_old_exec+0x703/0x8d7

    but task is already holding lock:
    (____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7

    which lock already depends on the new lock.

    the existing dependency chain (in reverse order) is:

    -> #1 (&mm->mmap_sem){++++}:
           [...]
           __lock_acquire+0x12ab/0x139f
           lock_acquire+0x155/0x18e
           down_write+0x3f/0x98
           flush_old_exec+0x748/0x8d7
           load_elf_binary+0x2ca/0xddb
           [...]

    -> #0 (&(&p->alloc_lock)->rlock){+.+.}:
           [...]
           __lock_acquire+0x12ab/0x139f
           lock_acquire+0x155/0x18e
           _raw_spin_lock+0x30/0x83
           flush_old_exec+0x703/0x8d7
           load_elf_binary+0x2ca/0xddb
           [...]

    other info that might help us debug this:

     Possible unsafe locking scenario:

           CPU0                    CPU1
           ----                    ----
      lock(&mm->mmap_sem);
                                   lock(&(&p->alloc_lock)->rlock);
                                   lock(&mm->mmap_sem);
      lock(&(&p->alloc_lock)->rlock);

     *** DEADLOCK ***

    2 locks held by inside.sh/366:
     #0: (____ptrval____) (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file+0x12d/0x869
     #1: (____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7

    stack backtrace:
    CPU: 0 PID: 366 Comm: inside.sh Not tainted 5.1.0-10252-gb00152307319-dirty #121
    Stack:
     [...]
    Call Trace:
     [<600420de>] show_stack+0x13b/0x155
     [<6048906b>] dump_stack+0x2a/0x2c
     [<6009ae64>] print_circular_bug+0x332/0x343
     [<6009c5c6>] check_prev_add+0x669/0xdad
     [<600a06b4>] __lock_acquire+0x12ab/0x139f
     [<6009f3d0>] lock_acquire+0x155/0x18e
     [<604a07e0>] _raw_spin_lock+0x30/0x83
     [<60151e6a>] flush_old_exec+0x703/0x8d7
     [<601a8eb8>] load_elf_binary+0x2ca/0xddb
     [...]

I think it's because in exec_mmap() we have

	down_read(&old_mm->mmap_sem);
...
        task_lock(tsk);
...
	activate_mm(active_mm, mm);
	(which does down_write(&mm->mmap_sem))

I'm not really sure why lockdep throws in the whole knowledge
about the task lock, but it seems that old_mm and mm shouldn't
ever be the same (and it doesn't deadlock) so tell lockdep that
they're different.

Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: Fix FP register size for XSTATE/XSAVE

2019-08-04T07:33:31+00:00

commit 6f602afda7275c24c20ba38b5b6cd4ed08561fff upstream.

Hard code max size. Taken from
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/common/x86-xstate.h

Signed-off-by: Thomas Meyer 
Signed-off-by: Richard Weinberger 
Signed-off-by: Alessio Balsini 
Signed-off-by: Greg Kroah-Hartman

um: Avoid marking pages with "changed protection"

2019-02-12T18:44:58+00:00

[ Upstream commit 8892d8545f2d0342b9c550defbfb165db237044b ]

Changing protection is a very high cost operation in UML
because in addition to an extra syscall it also interrupts
mmap merge sequences generated by the tlb.

While the condition is not particularly common it is worth
avoiding.

Signed-off-by: Anton Ivanov 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: Don't discard .text.exit section

2016-08-23T21:16:16+00:00

Commit e41f501d3912 ("vmlinux.lds: account for destructor sections")
added '.text.exit' to EXIT_TEXT which is discarded at link time by default.
This breaks compilation of UML:
     `.text.exit' referenced in section `.fini_array' of
     /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libc.a(sdlerror.o):
     defined in discarded section `.text.exit' of
     /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libc.a(sdlerror.o)

Apparently UML doesn't want to discard exit text, so let's place all EXIT_TEXT
sections in .exit.text.

Fixes: e41f501d3912 ("vmlinux.lds: account for destructor sections")
Reported-by: Stefan Traby 
Signed-off-by: Andrey Ryabinin 
Cc: 
Acked-by: Dmitry Vyukov 
Signed-off-by: Richard Weinberger

Merge branch 'for-linus-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

2016-08-04T23:37:59+00:00

Pull UML updates from Richard Weinberger:
 "Beside of various fixes this also contains patches to enable features
  such was Kcov, kmemleak and TRACE_IRQFLAGS_SUPPORT on UML"

* 'for-linus-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
  hostfs: Freeing an ERR_PTR in hostfs_fill_sb_common()
  um: Support kcov
  um: Enable TRACE_IRQFLAGS_SUPPORT
  um: Use asm-generic/irqflags.h
  um: Fix possible deadlock in sig_handler_common()
  um: Select HAVE_DEBUG_KMEMLEAK
  um: Setup physical memory in setup_arch()
  um: Eliminate null test after alloc_bootmem

um: Use asm-generic/irqflags.h

2016-08-03T22:18:04+00:00

Instead proving its own arch_local_irq_save() and arch_irqs_disabled()
version use the generic version from asm-generic/irqflags.h.

A nice side effect is that um gets a few additional arch_ functions
as well.

Signed-off-by: Daniel Wagner 
[rw: Massaged commit message]
Signed-off-by: Richard Weinberger

mm/mmu_gather: track page size with mmu gather and force flush if page size change

2016-07-26T23:19:19+00:00

This allows an arch which needs to do special handing with respect to
different page size when flushing tlb to implement the same in mmu
gather.

Link: http://lkml.kernel.org/r/1465049193-22197-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Cc: Benjamin Herrenschmidt 
Cc: Michael Ellerman 
Cc: Hugh Dickins 
Cc: "Kirill A. Shutemov" 
Cc: Andrea Arcangeli 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: David Rientjes 
Cc: Vlastimil Babka 
Cc: Minchan Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: change the interface for __tlb_remove_page()

2016-07-26T23:19:19+00:00

This updates the generic and arch specific implementation to return true
if we need to do a tlb flush.  That means if a __tlb_remove_page
indicate a flush is needed, the page we try to remove need to be tracked
and added again after the flush.  We need to track it because we have
already update the pte to none and we can't just loop back.

This change is done to enable us to do a tlb_flush when we try to flush
a range that consists of different page sizes.  For architectures like
ppc64, we can do a range based tlb flush and we need to track page size
for that.  When we try to remove a huge page, we will force a tlb flush
and starts a new mmu gather.

[aneesh.kumar@linux.vnet.ibm.com: mm-change-the-interface-for-__tlb_remove_page-v3]
  Link: http://lkml.kernel.org/r/1465049193-22197-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1464860389-29019-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Cc: Benjamin Herrenschmidt 
Cc: Michael Ellerman 
Cc: Hugh Dickins 
Cc: "Kirill A. Shutemov" 
Cc: Andrea Arcangeli 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: David Rientjes 
Cc: Vlastimil Babka 
Cc: Minchan Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds