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Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 page table isolation updates from Thomas Gleixner:
 "This is the final set of enabling page table isolation on x86:

   - Infrastructure patches for handling the extra page tables.

   - Patches which map the various bits and pieces which are required to
     get in and out of user space into the user space visible page
     tables.

   - The required changes to have CR3 switching in the entry/exit code.

   - Optimizations for the CR3 switching along with documentation how
     the ASID/PCID mechanism works.

   - Updates to dump pagetables to cover the user space page tables for
     W+X scans and extra debugfs files to analyze both the kernel and
     the user space visible page tables

  The whole functionality is compile time controlled via a config switch
  and can be turned on/off on the command line as well"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  x86/ldt: Make the LDT mapping RO
  x86/mm/dump_pagetables: Allow dumping current pagetables
  x86/mm/dump_pagetables: Check user space page table for WX pages
  x86/mm/dump_pagetables: Add page table directory to the debugfs VFS hierarchy
  x86/mm/pti: Add Kconfig
  x86/dumpstack: Indicate in Oops whether PTI is configured and enabled
  x86/mm: Clarify the whole ASID/kernel PCID/user PCID naming
  x86/mm: Use INVPCID for __native_flush_tlb_single()
  x86/mm: Optimize RESTORE_CR3
  x86/mm: Use/Fix PCID to optimize user/kernel switches
  x86/mm: Abstract switching CR3
  x86/mm: Allow flushing for future ASID switches
  x86/pti: Map the vsyscall page if needed
  x86/pti: Put the LDT in its own PGD if PTI is on
  x86/mm/64: Make a full PGD-entry size hole in the memory map
  x86/events/intel/ds: Map debug buffers in cpu_entry_area
  x86/cpu_entry_area: Add debugstore entries to cpu_entry_area
  x86/mm/pti: Map ESPFIX into user space
  x86/mm/pti: Share entry text PMD
  x86/entry: Align entry text section to PMD boundary
  ...
This commit is contained in:
Linus Torvalds
2017-12-29 17:02:49 -08:00
父節點 61233580f1 9f5cb6b32d
當前提交 5aa90a8458
共有 45 個文件被更改，包括 1636 次插入 和 202 次删除
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202
arch/x86/include/asm/tlbflush.h
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@@ -10,38 +10,90 @@
#include <asm/special_insns.h>
#include <asm/smp.h>
#include <asm/invpcid.h>
#include <asm/pti.h>
#include <asm/processor-flags.h>
static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
{
/*
* Bump the generation count. This also serves as a full barrier
* that synchronizes with switch_mm(): callers are required to order
* their read of mm_cpumask after their writes to the paging
* structures.
*/
return atomic64_inc_return(&mm->context.tlb_gen);
}
/*
* The x86 feature is called PCID (Process Context IDentifier). It is similar
* to what is traditionally called ASID on the RISC processors.
*
* We don't use the traditional ASID implementation, where each process/mm gets
* its own ASID and flush/restart when we run out of ASID space.
*
* Instead we have a small per-cpu array of ASIDs and cache the last few mm's
* that came by on this CPU, allowing cheaper switch_mm between processes on
* this CPU.
*
* We end up with different spaces for different things. To avoid confusion we
* use different names for each of them:
*
* ASID - [0, TLB_NR_DYN_ASIDS-1]
* the canonical identifier for an mm
*
* kPCID - [1, TLB_NR_DYN_ASIDS]
* the value we write into the PCID part of CR3; corresponds to the
* ASID+1, because PCID 0 is special.
*
* uPCID - [2048 + 1, 2048 + TLB_NR_DYN_ASIDS]
* for KPTI each mm has two address spaces and thus needs two
* PCID values, but we can still do with a single ASID denomination
* for each mm. Corresponds to kPCID + 2048.
*
*/
/* There are 12 bits of space for ASIDS in CR3 */
#define CR3_HW_ASID_BITS 12
/*
* When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
* user/kernel switches
*/
#define PTI_CONSUMED_ASID_BITS 0
#ifdef CONFIG_PAGE_TABLE_ISOLATION
# define PTI_CONSUMED_PCID_BITS 1
#else
# define PTI_CONSUMED_PCID_BITS 0
#endif
#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - PTI_CONSUMED_ASID_BITS)
/*
* ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid. -1 below to account
* for them being zero-based. Another -1 is because ASID 0 is reserved for
* for them being zero-based. Another -1 is because PCID 0 is reserved for
* use by non-PCID-aware users.
*/
#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_ASID_BITS) - 2)
#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
/*
* 6 because 6 should be plenty and struct tlb_state will fit in two cache
* lines.
*/
#define TLB_NR_DYN_ASIDS 6
/*
* Given @asid, compute kPCID
*/
static inline u16 kern_pcid(u16 asid)
{
VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
#ifdef CONFIG_PAGE_TABLE_ISOLATION
/*
* Make sure that the dynamic ASID space does not confict with the
* bit we are using to switch between user and kernel ASIDs.
*/
BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_SWITCH_BIT));
/*
* The ASID being passed in here should have respected the
* MAX_ASID_AVAILABLE and thus never have the switch bit set.
*/
VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_SWITCH_BIT));
#endif
/*
* The dynamically-assigned ASIDs that get passed in are small
* (<TLB_NR_DYN_ASIDS). They never have the high switch bit set,
* so do not bother to clear it.
*
* If PCID is on, ASID-aware code paths put the ASID+1 into the
* PCID bits. This serves two purposes. It prevents a nasty
* situation in which PCID-unaware code saves CR3, loads some other
@@ -53,6 +105,18 @@ static inline u16 kern_pcid(u16 asid)
return asid + 1;
}
/*
* Given @asid, compute uPCID
*/
static inline u16 user_pcid(u16 asid)
{
u16 ret = kern_pcid(asid);
#ifdef CONFIG_PAGE_TABLE_ISOLATION
ret |= 1 << X86_CR3_PTI_SWITCH_BIT;
#endif
return ret;
}
struct pgd_t;
static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
{
@@ -95,12 +159,6 @@ static inline bool tlb_defer_switch_to_init_mm(void)
return !static_cpu_has(X86_FEATURE_PCID);
}
/*
* 6 because 6 should be plenty and struct tlb_state will fit in
* two cache lines.
*/
#define TLB_NR_DYN_ASIDS 6
struct tlb_context {
u64 ctx_id;
u64 tlb_gen;
@@ -134,6 +192,24 @@ struct tlb_state {
*/
bool is_lazy;
/*
* If set we changed the page tables in such a way that we
* needed an invalidation of all contexts (aka. PCIDs / ASIDs).
* This tells us to go invalidate all the non-loaded ctxs[]
* on the next context switch.
*
* The current ctx was kept up-to-date as it ran and does not
* need to be invalidated.
*/
bool invalidate_other;
/*
* Mask that contains TLB_NR_DYN_ASIDS+1 bits to indicate
* the corresponding user PCID needs a flush next time we
* switch to it; see SWITCH_TO_USER_CR3.
*/
unsigned short user_pcid_flush_mask;
/*
* Access to this CR4 shadow and to H/W CR4 is protected by
* disabling interrupts when modifying either one.
@@ -214,6 +290,14 @@ static inline unsigned long cr4_read_shadow(void)
return this_cpu_read(cpu_tlbstate.cr4);
}
/*
* Mark all other ASIDs as invalid, preserves the current.
*/
static inline void invalidate_other_asid(void)
{
this_cpu_write(cpu_tlbstate.invalidate_other, true);
}
/*
* Save some of cr4 feature set we're using (e.g. Pentium 4MB
* enable and PPro Global page enable), so that any CPU's that boot
@@ -233,15 +317,42 @@ static inline void cr4_set_bits_and_update_boot(unsigned long mask)
extern void initialize_tlbstate_and_flush(void);
/*
* Given an ASID, flush the corresponding user ASID. We can delay this
* until the next time we switch to it.
*
* See SWITCH_TO_USER_CR3.
*/
static inline void invalidate_user_asid(u16 asid)
{
/* There is no user ASID if address space separation is off */
if (!IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION))
return;
/*
* We only have a single ASID if PCID is off and the CR3
* write will have flushed it.
*/
if (!cpu_feature_enabled(X86_FEATURE_PCID))
return;
if (!static_cpu_has(X86_FEATURE_PTI))
return;
__set_bit(kern_pcid(asid),
(unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
}
/*
* flush the entire current user mapping
*/
static inline void __native_flush_tlb(void)
{
invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
/*
* If current->mm == NULL then we borrow a mm which may change during a
* task switch and therefore we must not be preempted while we write CR3
* back:
* If current->mm == NULL then we borrow a mm which may change
* during a task switch and therefore we must not be preempted
* while we write CR3 back:
*/
preempt_disable();
native_write_cr3(__native_read_cr3());
@@ -259,6 +370,8 @@ static inline void __native_flush_tlb_global(void)
/*
* Using INVPCID is considerably faster than a pair of writes
* to CR4 sandwiched inside an IRQ flag save/restore.
*
* Note, this works with CR4.PCIDE=0 or 1.
*/
invpcid_flush_all();
return;
@@ -285,7 +398,21 @@ static inline void __native_flush_tlb_global(void)
*/
static inline void __native_flush_tlb_single(unsigned long addr)
{
u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
if (!static_cpu_has(X86_FEATURE_PTI))
return;
/*
* Some platforms #GP if we call invpcid(type=1/2) before CR4.PCIDE=1.
* Just use invalidate_user_asid() in case we are called early.
*/
if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE))
invalidate_user_asid(loaded_mm_asid);
else
invpcid_flush_one(user_pcid(loaded_mm_asid), addr);
}
/*
@@ -301,14 +428,6 @@ static inline void __flush_tlb_all(void)
*/
__flush_tlb();
}
/*
* Note: if we somehow had PCID but not PGE, then this wouldn't work --
* we'd end up flushing kernel translations for the current ASID but
* we might fail to flush kernel translations for other cached ASIDs.
*
* To avoid this issue, we force PCID off if PGE is off.
*/
}
/*
@@ -318,6 +437,16 @@ static inline void __flush_tlb_one(unsigned long addr)
{
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
__flush_tlb_single(addr);
if (!static_cpu_has(X86_FEATURE_PTI))
return;
/*
* __flush_tlb_single() will have cleared the TLB entry for this ASID,
* but since kernel space is replicated across all, we must also
* invalidate all others.
*/
invalidate_other_asid();
}
#define TLB_FLUSH_ALL -1UL
@@ -378,6 +507,17 @@ static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
void native_flush_tlb_others(const struct cpumask *cpumask,
const struct flush_tlb_info *info);
static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
{
/*
* Bump the generation count. This also serves as a full barrier
* that synchronizes with switch_mm(): callers are required to order
* their read of mm_cpumask after their writes to the paging
* structures.
*/
return atomic64_inc_return(&mm->context.tlb_gen);
}
static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
struct mm_struct *mm)
{