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x86/ldt: Split out sanity check in map_ldt_struct()

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This splits out the mapping sanity check and the actual mapping of the LDT
to user-space from the map_ldt_struct() function in a way so that it is
re-usable for PAE paging.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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: 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: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-36-git-send-email-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2018-07-18 11:41:12 +02:00 committed by Thomas Gleixner
parent 8195d869d1
commit 9bae3197e1
1 changed files with 58 additions and 24 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

82
arch/x86/kernel/ldt.c
View file

@ -100,6 +100,49 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
return new_ldt;
}
#ifdef CONFIG_PAGE_TABLE_ISOLATION
static void do_sanity_check(struct mm_struct *mm,
bool had_kernel_mapping,
bool had_user_mapping)
{
if (mm->context.ldt) {
/*
* We already had an LDT. The top-level entry should already
* have been allocated and synchronized with the usermode
* tables.
*/
WARN_ON(!had_kernel_mapping);
if (static_cpu_has(X86_FEATURE_PTI))
WARN_ON(!had_user_mapping);
} else {
/*
* This is the first time we're mapping an LDT for this process.
* Sync the pgd to the usermode tables.
*/
WARN_ON(had_kernel_mapping);
if (static_cpu_has(X86_FEATURE_PTI))
WARN_ON(had_user_mapping);
}
}
static void map_ldt_struct_to_user(struct mm_struct *mm)
{
pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR);
if (static_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt)
set_pgd(kernel_to_user_pgdp(pgd), *pgd);
}
static void sanity_check_ldt_mapping(struct mm_struct *mm)
{
pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR);
bool had_kernel = (pgd->pgd != 0);
bool had_user = (kernel_to_user_pgdp(pgd)->pgd != 0);
do_sanity_check(mm, had_kernel, had_user);
}
/*
* If PTI is enabled, this maps the LDT into the kernelmode and
* usermode tables for the given mm.
@ -115,9 +158,8 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
static int
map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
{
#ifdef CONFIG_PAGE_TABLE_ISOLATION
bool is_vmalloc, had_top_level_entry;
unsigned long va;
bool is_vmalloc;
spinlock_t *ptl;
pgd_t *pgd;
int i;
@ -131,13 +173,15 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
*/
WARN_ON(ldt->slot != -1);
/* Check if the current mappings are sane */
sanity_check_ldt_mapping(mm);
/*
* Did we already have the top level entry allocated? We can't
* use pgd_none() for this because it doens't do anything on
* 4-level page table kernels.
*/
pgd = pgd_offset(mm, LDT_BASE_ADDR);
had_top_level_entry = (pgd->pgd != 0);
is_vmalloc = is_vmalloc_addr(ldt->entries);
@ -172,35 +216,25 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
pte_unmap_unlock(ptep, ptl);
}
if (mm->context.ldt) {
/*
* We already had an LDT. The top-level entry should already
* have been allocated and synchronized with the usermode
* tables.
*/
WARN_ON(!had_top_level_entry);
if (static_cpu_has(X86_FEATURE_PTI))
WARN_ON(!kernel_to_user_pgdp(pgd)->pgd);
} else {
/*
* This is the first time we're mapping an LDT for this process.
* Sync the pgd to the usermode tables.
*/
WARN_ON(had_top_level_entry);
if (static_cpu_has(X86_FEATURE_PTI)) {
WARN_ON(kernel_to_user_pgdp(pgd)->pgd);
set_pgd(kernel_to_user_pgdp(pgd), *pgd);
}
}
/* Propagate LDT mapping to the user page-table */
map_ldt_struct_to_user(mm);
va = (unsigned long)ldt_slot_va(slot);
flush_tlb_mm_range(mm, va, va + LDT_SLOT_STRIDE, 0);
ldt->slot = slot;
#endif
return 0;
}
#else /* !CONFIG_PAGE_TABLE_ISOLATION */
static int
map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
{
return 0;
}
#endif /* CONFIG_PAGE_TABLE_ISOLATION */
static void free_ldt_pgtables(struct mm_struct *mm)
{
#ifdef CONFIG_PAGE_TABLE_ISOLATION