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c1a2f7f0c0
The mm_struct always contains a cpumask bitmap, regardless of CONFIG_CPUMASK_OFFSTACK. That means the first step can be to simplify things, and simply have one bitmask at the end of the mm_struct for the mm_cpumask. This does necessitate moving everything else in mm_struct into an anonymous sub-structure, which can be randomized when struct randomization is enabled. The second step is to determine the correct size for the mm_struct slab object from the size of the mm_struct (excluding the CPU bitmap) and the size the cpumask. For init_mm we can simply allocate the maximum size this kernel is compiled for, since we only have one init_mm in the system, anyway. Pointer magic by Mike Galbraith, to evade -Wstringop-overflow getting confused by the dynamically sized array. Tested-by: Song Liu <songliubraving@fb.com> Signed-off-by: Rik van Riel <riel@surriel.com> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Rik van Riel <riel@surriel.com> Acked-by: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Cc: luto@kernel.org Link: http://lkml.kernel.org/r/20180716190337.26133-2-riel@surriel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
40 lines
1.2 KiB
C
40 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm_types.h>
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#include <linux/rbtree.h>
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#include <linux/rwsem.h>
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#include <linux/spinlock.h>
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#include <linux/list.h>
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#include <linux/cpumask.h>
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#include <linux/atomic.h>
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#include <linux/user_namespace.h>
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#include <asm/pgtable.h>
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#include <asm/mmu.h>
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#ifndef INIT_MM_CONTEXT
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#define INIT_MM_CONTEXT(name)
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#endif
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/*
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* For dynamically allocated mm_structs, there is a dynamically sized cpumask
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* at the end of the structure, the size of which depends on the maximum CPU
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* number the system can see. That way we allocate only as much memory for
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* mm_cpumask() as needed for the hundreds, or thousands of processes that
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* a system typically runs.
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*
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* Since there is only one init_mm in the entire system, keep it simple
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* and size this cpu_bitmask to NR_CPUS.
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*/
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struct mm_struct init_mm = {
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.mm_rb = RB_ROOT,
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.pgd = swapper_pg_dir,
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.mm_users = ATOMIC_INIT(2),
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.mm_count = ATOMIC_INIT(1),
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.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
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.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
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.arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
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.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
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.user_ns = &init_user_ns,
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.cpu_bitmap = { [BITS_TO_LONGS(NR_CPUS)] = 0},
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INIT_MM_CONTEXT(init_mm)
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};
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