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Commit 9bae3197 authored by Joerg Roedel's avatar Joerg Roedel Committed by Thomas Gleixner
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x86/ldt: Split out sanity check in map_ldt_struct() 



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: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarPavel 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
parent 8195d869

arch/x86/kernel/ldt.c

+58 −24
Original line number Diff line number Diff line
@@ -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