xref: /openbmc/linux/arch/arm64/include/asm/mmu.h (revision e7f127b2)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright (C) 2012 ARM Ltd.
4  */
5 #ifndef __ASM_MMU_H
6 #define __ASM_MMU_H
7 
8 #include <asm/cputype.h>
9 
10 #define MMCF_AARCH32	0x1	/* mm context flag for AArch32 executables */
11 #define USER_ASID_BIT	48
12 #define USER_ASID_FLAG	(UL(1) << USER_ASID_BIT)
13 #define TTBR_ASID_MASK	(UL(0xffff) << 48)
14 
15 #ifndef __ASSEMBLY__
16 
17 #include <linux/refcount.h>
18 #include <asm/cpufeature.h>
19 
20 typedef struct {
21 	atomic64_t	id;
22 #ifdef CONFIG_COMPAT
23 	void		*sigpage;
24 #endif
25 	refcount_t	pinned;
26 	void		*vdso;
27 	unsigned long	flags;
28 } mm_context_t;
29 
30 /*
31  * We use atomic64_read() here because the ASID for an 'mm_struct' can
32  * be reallocated when scheduling one of its threads following a
33  * rollover event (see new_context() and flush_context()). In this case,
34  * a concurrent TLBI (e.g. via try_to_unmap_one() and ptep_clear_flush())
35  * may use a stale ASID. This is fine in principle as the new ASID is
36  * guaranteed to be clean in the TLB, but the TLBI routines have to take
37  * care to handle the following race:
38  *
39  *    CPU 0                    CPU 1                          CPU 2
40  *
41  *    // ptep_clear_flush(mm)
42  *    xchg_relaxed(pte, 0)
43  *    DSB ISHST
44  *    old = ASID(mm)
45  *         |                                                  <rollover>
46  *         |                   new = new_context(mm)
47  *         \-----------------> atomic_set(mm->context.id, new)
48  *                             cpu_switch_mm(mm)
49  *                             // Hardware walk of pte using new ASID
50  *    TLBI(old)
51  *
52  * In this scenario, the barrier on CPU 0 and the dependency on CPU 1
53  * ensure that the page-table walker on CPU 1 *must* see the invalid PTE
54  * written by CPU 0.
55  */
56 #define ASID(mm)	(atomic64_read(&(mm)->context.id) & 0xffff)
57 
58 static inline bool arm64_kernel_unmapped_at_el0(void)
59 {
60 	return cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);
61 }
62 
63 extern void arm64_memblock_init(void);
64 extern void paging_init(void);
65 extern void bootmem_init(void);
66 extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
67 extern void init_mem_pgprot(void);
68 extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
69 			       unsigned long virt, phys_addr_t size,
70 			       pgprot_t prot, bool page_mappings_only);
71 extern void *fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot);
72 extern void mark_linear_text_alias_ro(void);
73 extern bool kaslr_requires_kpti(void);
74 
75 #define INIT_MM_CONTEXT(name)	\
76 	.pgd = init_pg_dir,
77 
78 #endif	/* !__ASSEMBLY__ */
79 #endif
80