Commit 61e9b367 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar

x86/mm/pti: Add mapping helper functions

Add the pagetable helper functions do manage the separate user space page
tables.

[ tglx: Split out from the big combo kaiser patch. Folded Andys
	simplification and made it out of line as Boris suggested ]
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 41f4c20b
......@@ -909,7 +909,11 @@ static inline int pgd_none(pgd_t pgd)
* pgd_offset() returns a (pgd_t *)
* pgd_index() is used get the offset into the pgd page's array of pgd_t's;
*/
#define pgd_offset(mm, address) ((mm)->pgd + pgd_index((address)))
#define pgd_offset_pgd(pgd, address) (pgd + pgd_index((address)))
/*
* a shortcut to get a pgd_t in a given mm
*/
#define pgd_offset(mm, address) pgd_offset_pgd((mm)->pgd, (address))
/*
* a shortcut which implies the use of the kernel's pgd, instead
* of a process's
......
......@@ -131,9 +131,97 @@ static inline pud_t native_pudp_get_and_clear(pud_t *xp)
#endif
}
#ifdef CONFIG_PAGE_TABLE_ISOLATION
/*
* All top-level PAGE_TABLE_ISOLATION page tables are order-1 pages
* (8k-aligned and 8k in size). The kernel one is at the beginning 4k and
* the user one is in the last 4k. To switch between them, you
* just need to flip the 12th bit in their addresses.
*/
#define PTI_PGTABLE_SWITCH_BIT PAGE_SHIFT
/*
* This generates better code than the inline assembly in
* __set_bit().
*/
static inline void *ptr_set_bit(void *ptr, int bit)
{
unsigned long __ptr = (unsigned long)ptr;
__ptr |= BIT(bit);
return (void *)__ptr;
}
static inline void *ptr_clear_bit(void *ptr, int bit)
{
unsigned long __ptr = (unsigned long)ptr;
__ptr &= ~BIT(bit);
return (void *)__ptr;
}
static inline pgd_t *kernel_to_user_pgdp(pgd_t *pgdp)
{
return ptr_set_bit(pgdp, PTI_PGTABLE_SWITCH_BIT);
}
static inline pgd_t *user_to_kernel_pgdp(pgd_t *pgdp)
{
return ptr_clear_bit(pgdp, PTI_PGTABLE_SWITCH_BIT);
}
static inline p4d_t *kernel_to_user_p4dp(p4d_t *p4dp)
{
return ptr_set_bit(p4dp, PTI_PGTABLE_SWITCH_BIT);
}
static inline p4d_t *user_to_kernel_p4dp(p4d_t *p4dp)
{
return ptr_clear_bit(p4dp, PTI_PGTABLE_SWITCH_BIT);
}
#endif /* CONFIG_PAGE_TABLE_ISOLATION */
/*
* Page table pages are page-aligned. The lower half of the top
* level is used for userspace and the top half for the kernel.
*
* Returns true for parts of the PGD that map userspace and
* false for the parts that map the kernel.
*/
static inline bool pgdp_maps_userspace(void *__ptr)
{
unsigned long ptr = (unsigned long)__ptr;
return (ptr & ~PAGE_MASK) < (PAGE_SIZE / 2);
}
#ifdef CONFIG_PAGE_TABLE_ISOLATION
pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd);
/*
* Take a PGD location (pgdp) and a pgd value that needs to be set there.
* Populates the user and returns the resulting PGD that must be set in
* the kernel copy of the page tables.
*/
static inline pgd_t pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
{
if (!static_cpu_has(X86_FEATURE_PTI))
return pgd;
return __pti_set_user_pgd(pgdp, pgd);
}
#else
static inline pgd_t pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
{
return pgd;
}
#endif
static inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
{
#if defined(CONFIG_PAGE_TABLE_ISOLATION) && !defined(CONFIG_X86_5LEVEL)
p4dp->pgd = pti_set_user_pgd(&p4dp->pgd, p4d.pgd);
#else
*p4dp = p4d;
#endif
}
static inline void native_p4d_clear(p4d_t *p4d)
......@@ -147,7 +235,11 @@ static inline void native_p4d_clear(p4d_t *p4d)
static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd)
{
#ifdef CONFIG_PAGE_TABLE_ISOLATION
*pgdp = pti_set_user_pgd(pgdp, pgd);
#else
*pgdp = pgd;
#endif
}
static inline void native_pgd_clear(pgd_t *pgd)
......
......@@ -96,6 +96,47 @@ void __init pti_check_boottime_disable(void)
setup_force_cpu_cap(X86_FEATURE_PTI);
}
pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
{
/*
* Changes to the high (kernel) portion of the kernelmode page
* tables are not automatically propagated to the usermode tables.
*
* Users should keep in mind that, unlike the kernelmode tables,
* there is no vmalloc_fault equivalent for the usermode tables.
* Top-level entries added to init_mm's usermode pgd after boot
* will not be automatically propagated to other mms.
*/
if (!pgdp_maps_userspace(pgdp))
return pgd;
/*
* The user page tables get the full PGD, accessible from
* userspace:
*/
kernel_to_user_pgdp(pgdp)->pgd = pgd.pgd;
/*
* If this is normal user memory, make it NX in the kernel
* pagetables so that, if we somehow screw up and return to
* usermode with the kernel CR3 loaded, we'll get a page fault
* instead of allowing user code to execute with the wrong CR3.
*
* As exceptions, we don't set NX if:
* - _PAGE_USER is not set. This could be an executable
* EFI runtime mapping or something similar, and the kernel
* may execute from it
* - we don't have NX support
* - we're clearing the PGD (i.e. the new pgd is not present).
*/
if ((pgd.pgd & (_PAGE_USER|_PAGE_PRESENT)) == (_PAGE_USER|_PAGE_PRESENT) &&
(__supported_pte_mask & _PAGE_NX))
pgd.pgd |= _PAGE_NX;
/* return the copy of the PGD we want the kernel to use: */
return pgd;
}
/*
* Initialize kernel page table isolation
*/
......
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