1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_MMU_CONTEXT_H
3 #define _ASM_X86_MMU_CONTEXT_H
6 #include <linux/atomic.h>
7 #include <linux/mm_types.h>
8 #include <linux/pkeys.h>
10 #include <trace/events/tlb.h>
12 #include <asm/pgalloc.h>
13 #include <asm/tlbflush.h>
14 #include <asm/paravirt.h>
17 extern atomic64_t last_mm_ctx_id
;
19 #ifndef CONFIG_PARAVIRT
20 static inline void paravirt_activate_mm(struct mm_struct
*prev
,
21 struct mm_struct
*next
)
24 #endif /* !CONFIG_PARAVIRT */
26 #ifdef CONFIG_PERF_EVENTS
27 extern struct static_key rdpmc_always_available
;
29 static inline void load_mm_cr4(struct mm_struct
*mm
)
31 if (static_key_false(&rdpmc_always_available
) ||
32 atomic_read(&mm
->context
.perf_rdpmc_allowed
))
33 cr4_set_bits(X86_CR4_PCE
);
35 cr4_clear_bits(X86_CR4_PCE
);
38 static inline void load_mm_cr4(struct mm_struct
*mm
) {}
41 #ifdef CONFIG_MODIFY_LDT_SYSCALL
43 * ldt_structs can be allocated, used, and freed, but they are never
44 * modified while live.
48 * Xen requires page-aligned LDTs with special permissions. This is
49 * needed to prevent us from installing evil descriptors such as
50 * call gates. On native, we could merge the ldt_struct and LDT
51 * allocations, but it's not worth trying to optimize.
53 struct desc_struct
*entries
;
54 unsigned int nr_entries
;
58 * Used for LDT copy/destruction.
60 int init_new_context_ldt(struct task_struct
*tsk
, struct mm_struct
*mm
);
61 void destroy_context_ldt(struct mm_struct
*mm
);
62 #else /* CONFIG_MODIFY_LDT_SYSCALL */
63 static inline int init_new_context_ldt(struct task_struct
*tsk
,
68 static inline void destroy_context_ldt(struct mm_struct
*mm
) {}
71 static inline void load_mm_ldt(struct mm_struct
*mm
)
73 #ifdef CONFIG_MODIFY_LDT_SYSCALL
74 struct ldt_struct
*ldt
;
76 /* READ_ONCE synchronizes with smp_store_release */
77 ldt
= READ_ONCE(mm
->context
.ldt
);
80 * Any change to mm->context.ldt is followed by an IPI to all
81 * CPUs with the mm active. The LDT will not be freed until
82 * after the IPI is handled by all such CPUs. This means that,
83 * if the ldt_struct changes before we return, the values we see
84 * will be safe, and the new values will be loaded before we run
87 * NB: don't try to convert this to use RCU without extreme care.
88 * We would still need IRQs off, because we don't want to change
89 * the local LDT after an IPI loaded a newer value than the one
94 set_ldt(ldt
->entries
, ldt
->nr_entries
);
102 static inline void switch_ldt(struct mm_struct
*prev
, struct mm_struct
*next
)
104 #ifdef CONFIG_MODIFY_LDT_SYSCALL
106 * Load the LDT if either the old or new mm had an LDT.
108 * An mm will never go from having an LDT to not having an LDT. Two
109 * mms never share an LDT, so we don't gain anything by checking to
110 * see whether the LDT changed. There's also no guarantee that
111 * prev->context.ldt actually matches LDTR, but, if LDTR is non-NULL,
112 * then prev->context.ldt will also be non-NULL.
114 * If we really cared, we could optimize the case where prev == next
115 * and we're exiting lazy mode. Most of the time, if this happens,
116 * we don't actually need to reload LDTR, but modify_ldt() is mostly
117 * used by legacy code and emulators where we don't need this level of
120 * This uses | instead of || because it generates better code.
122 if (unlikely((unsigned long)prev
->context
.ldt
|
123 (unsigned long)next
->context
.ldt
))
127 DEBUG_LOCKS_WARN_ON(preemptible());
130 void enter_lazy_tlb(struct mm_struct
*mm
, struct task_struct
*tsk
);
132 static inline int init_new_context(struct task_struct
*tsk
,
133 struct mm_struct
*mm
)
135 mm
->context
.ctx_id
= atomic64_inc_return(&last_mm_ctx_id
);
136 atomic64_set(&mm
->context
.tlb_gen
, 0);
138 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
139 if (cpu_feature_enabled(X86_FEATURE_OSPKE
)) {
140 /* pkey 0 is the default and always allocated */
141 mm
->context
.pkey_allocation_map
= 0x1;
142 /* -1 means unallocated or invalid */
143 mm
->context
.execute_only_pkey
= -1;
146 return init_new_context_ldt(tsk
, mm
);
148 static inline void destroy_context(struct mm_struct
*mm
)
150 destroy_context_ldt(mm
);
153 extern void switch_mm(struct mm_struct
*prev
, struct mm_struct
*next
,
154 struct task_struct
*tsk
);
156 extern void switch_mm_irqs_off(struct mm_struct
*prev
, struct mm_struct
*next
,
157 struct task_struct
*tsk
);
158 #define switch_mm_irqs_off switch_mm_irqs_off
160 #define activate_mm(prev, next) \
162 paravirt_activate_mm((prev), (next)); \
163 switch_mm((prev), (next), NULL); \
167 #define deactivate_mm(tsk, mm) \
172 #define deactivate_mm(tsk, mm) \
175 loadsegment(fs, 0); \
179 static inline void arch_dup_mmap(struct mm_struct
*oldmm
,
180 struct mm_struct
*mm
)
182 paravirt_arch_dup_mmap(oldmm
, mm
);
185 static inline void arch_exit_mmap(struct mm_struct
*mm
)
187 paravirt_arch_exit_mmap(mm
);
191 static inline bool is_64bit_mm(struct mm_struct
*mm
)
193 return !IS_ENABLED(CONFIG_IA32_EMULATION
) ||
194 !(mm
->context
.ia32_compat
== TIF_IA32
);
197 static inline bool is_64bit_mm(struct mm_struct
*mm
)
203 static inline void arch_bprm_mm_init(struct mm_struct
*mm
,
204 struct vm_area_struct
*vma
)
209 static inline void arch_unmap(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
210 unsigned long start
, unsigned long end
)
213 * mpx_notify_unmap() goes and reads a rarely-hot
214 * cacheline in the mm_struct. That can be expensive
215 * enough to be seen in profiles.
217 * The mpx_notify_unmap() call and its contents have been
218 * observed to affect munmap() performance on hardware
219 * where MPX is not present.
221 * The unlikely() optimizes for the fast case: no MPX
222 * in the CPU, or no MPX use in the process. Even if
223 * we get this wrong (in the unlikely event that MPX
224 * is widely enabled on some system) the overhead of
225 * MPX itself (reading bounds tables) is expected to
226 * overwhelm the overhead of getting this unlikely()
227 * consistently wrong.
229 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX
)))
230 mpx_notify_unmap(mm
, vma
, start
, end
);
233 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
234 static inline int vma_pkey(struct vm_area_struct
*vma
)
236 unsigned long vma_pkey_mask
= VM_PKEY_BIT0
| VM_PKEY_BIT1
|
237 VM_PKEY_BIT2
| VM_PKEY_BIT3
;
239 return (vma
->vm_flags
& vma_pkey_mask
) >> VM_PKEY_SHIFT
;
242 static inline int vma_pkey(struct vm_area_struct
*vma
)
249 * We only want to enforce protection keys on the current process
250 * because we effectively have no access to PKRU for other
251 * processes or any way to tell *which * PKRU in a threaded
252 * process we could use.
254 * So do not enforce things if the VMA is not from the current
255 * mm, or if we are in a kernel thread.
257 static inline bool vma_is_foreign(struct vm_area_struct
*vma
)
262 * Should PKRU be enforced on the access to this VMA? If
263 * the VMA is from another process, then PKRU has no
264 * relevance and should not be enforced.
266 if (current
->mm
!= vma
->vm_mm
)
272 static inline bool arch_vma_access_permitted(struct vm_area_struct
*vma
,
273 bool write
, bool execute
, bool foreign
)
275 /* pkeys never affect instruction fetches */
278 /* allow access if the VMA is not one from this process */
279 if (foreign
|| vma_is_foreign(vma
))
281 return __pkru_allows_pkey(vma_pkey(vma
), write
);
285 * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID
286 * bits. This serves two purposes. It prevents a nasty situation in
287 * which PCID-unaware code saves CR3, loads some other value (with PCID
288 * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if
289 * the saved ASID was nonzero. It also means that any bugs involving
290 * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger
294 static inline unsigned long build_cr3(struct mm_struct
*mm
, u16 asid
)
296 if (static_cpu_has(X86_FEATURE_PCID
)) {
297 VM_WARN_ON_ONCE(asid
> 4094);
298 return __sme_pa(mm
->pgd
) | (asid
+ 1);
300 VM_WARN_ON_ONCE(asid
!= 0);
301 return __sme_pa(mm
->pgd
);
305 static inline unsigned long build_cr3_noflush(struct mm_struct
*mm
, u16 asid
)
307 VM_WARN_ON_ONCE(asid
> 4094);
308 return __sme_pa(mm
->pgd
) | (asid
+ 1) | CR3_NOFLUSH
;
312 * This can be used from process context to figure out what the value of
313 * CR3 is without needing to do a (slow) __read_cr3().
315 * It's intended to be used for code like KVM that sneakily changes CR3
316 * and needs to restore it. It needs to be used very carefully.
318 static inline unsigned long __get_current_cr3_fast(void)
320 unsigned long cr3
= build_cr3(this_cpu_read(cpu_tlbstate
.loaded_mm
),
321 this_cpu_read(cpu_tlbstate
.loaded_mm_asid
));
323 /* For now, be very restrictive about when this can be called. */
324 VM_WARN_ON(in_nmi() || preemptible());
326 VM_BUG_ON(cr3
!= __read_cr3());
330 #endif /* _ASM_X86_MMU_CONTEXT_H */