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Commit 8f3e474f authored by Dmitry Safonov's avatar Dmitry Safonov Committed by Thomas Gleixner
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x86/mm: Add task_size parameter to mmap_base() 



To correctly handle 32-bit and 64-bit mmap() syscalls in 64bit applications
its required to have separate address bases to place a mapping.

The tasksize can be used as an indicator to select the proper parameters
for mmap_base().

This requires the following changes:

 - Add task_size argument to mmap_base() and make the calculation based on it.
 - Provide mmap_legacy_base() as a seperate function
 - Use the new functions in arch_pick_mmap_layout()

[ tglx: Massaged changelog ]

Signed-off-by: default avatarDmitry Safonov <dsafonov@virtuozzo.com>
Cc: 0x7f454c46@gmail.com
Cc: linux-mm@kvack.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20170306141721.9188-3-dsafonov@virtuozzo.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 6a0b41d1

arch/x86/include/asm/elf.h

+13 −11
Original line number Diff line number Diff line
@@ -293,8 +293,19 @@ do { \ 
	}								\

} while (0)



/*

 * True on X86_32 or when emulating IA32 on X86_64

 */

static inline int mmap_is_ia32(void)

{

	return IS_ENABLED(CONFIG_X86_32) ||

	       (IS_ENABLED(CONFIG_COMPAT) &&

		test_thread_flag(TIF_ADDR32));

}



#ifdef CONFIG_X86_32



#define __STACK_RND_MASK(is32bit) (0x7ff)

#define STACK_RND_MASK (0x7ff)



#define ARCH_DLINFO		ARCH_DLINFO_IA32
@@ -304,7 +315,8 @@ do { \ 
#else /* CONFIG_X86_32 */



/* 1GB for 64bit, 8MB for 32bit */

#define STACK_RND_MASK (test_thread_flag(TIF_ADDR32) ? 0x7ff : 0x3fffff)

#define __STACK_RND_MASK(is32bit) ((is32bit) ? 0x7ff : 0x3fffff)

#define STACK_RND_MASK __STACK_RND_MASK(mmap_is_ia32())



#define ARCH_DLINFO							\

do {									\
@@ -348,16 +360,6 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 
					      int uses_interp);

#define compat_arch_setup_additional_pages compat_arch_setup_additional_pages



/*

 * True on X86_32 or when emulating IA32 on X86_64

 */

static inline int mmap_is_ia32(void)

{

	return IS_ENABLED(CONFIG_X86_32) ||

	       (IS_ENABLED(CONFIG_COMPAT) &&

		test_thread_flag(TIF_ADDR32));

}



/* Do not change the values. See get_align_mask() */

enum align_flags {

	ALIGN_VA_32	= BIT(0),

arch/x86/include/asm/processor.h

+3 −1
Original line number Diff line number Diff line
@@ -797,6 +797,7 @@ static inline void spin_lock_prefetch(const void *x) 
/*

 * User space process size: 3GB (default).

 */

#define IA32_PAGE_OFFSET	PAGE_OFFSET

#define TASK_SIZE		PAGE_OFFSET

#define TASK_SIZE_MAX		TASK_SIZE

#define STACK_TOP		TASK_SIZE
@@ -873,7 +874,8 @@ extern void start_thread(struct pt_regs *regs, unsigned long new_ip, 
 * This decides where the kernel will search for a free chunk of vm

 * space during mmap's.

 */

#define TASK_UNMAPPED_BASE	(PAGE_ALIGN(TASK_SIZE / 3))

#define __TASK_UNMAPPED_BASE(task_size)	(PAGE_ALIGN(task_size / 3))

#define TASK_UNMAPPED_BASE		__TASK_UNMAPPED_BASE(TASK_SIZE)



#define KSTK_EIP(task)		(task_pt_regs(task)->ip)

arch/x86/mm/mmap.c

+32 −18
Original line number Diff line number Diff line
@@ -36,25 +36,23 @@ struct va_alignment __read_mostly va_align = { 
	.flags = -1,

};



static unsigned long stack_maxrandom_size(void)

static inline unsigned long tasksize_32bit(void)

{

	return IA32_PAGE_OFFSET;

}



static unsigned long stack_maxrandom_size(unsigned long task_size)

{

	unsigned long max = 0;

	if ((current->flags & PF_RANDOMIZE) &&

		!(current->personality & ADDR_NO_RANDOMIZE)) {

		max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;

		max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());

		max <<= PAGE_SHIFT;

	}



	return max;

}



/*

 * Top of mmap area (just below the process stack).

 *

 * Leave an at least ~128 MB hole with possible stack randomization.

 */

#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())

#define MAX_GAP (TASK_SIZE/6*5)



#ifdef CONFIG_COMPAT

# define mmap32_rnd_bits  mmap_rnd_compat_bits

# define mmap64_rnd_bits  mmap_rnd_bits
@@ -63,6 +61,8 @@ static unsigned long stack_maxrandom_size(void) 
# define mmap64_rnd_bits  mmap_rnd_bits

#endif



#define SIZE_128M    (128 * 1024 * 1024UL)



static int mmap_is_legacy(void)

{

	if (current->personality & ADDR_COMPAT_LAYOUT)
@@ -84,16 +84,30 @@ unsigned long arch_mmap_rnd(void) 
	return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);

}



static unsigned long mmap_base(unsigned long rnd)

static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)

{

	unsigned long gap = rlimit(RLIMIT_STACK);

	unsigned long gap_min, gap_max;



	if (gap < MIN_GAP)

		gap = MIN_GAP;

	else if (gap > MAX_GAP)

		gap = MAX_GAP;

	/*

	 * Top of mmap area (just below the process stack).

	 * Leave an at least ~128 MB hole with possible stack randomization.

	 */

	gap_min = SIZE_128M + stack_maxrandom_size(task_size);

	gap_max = (task_size / 6) * 5;



	return PAGE_ALIGN(TASK_SIZE - gap - rnd);

	if (gap < gap_min)

		gap = gap_min;

	else if (gap > gap_max)

		gap = gap_max;



	return PAGE_ALIGN(task_size - gap - rnd);

}



static unsigned long mmap_legacy_base(unsigned long rnd,

				      unsigned long task_size)

{

	return __TASK_UNMAPPED_BASE(task_size) + rnd;

}



/*
@@ -107,13 +121,13 @@ void arch_pick_mmap_layout(struct mm_struct *mm) 
	if (current->flags & PF_RANDOMIZE)

		random_factor = arch_mmap_rnd();



	mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor;

	mm->mmap_legacy_base = mmap_legacy_base(random_factor, TASK_SIZE);



	if (mmap_is_legacy()) {

		mm->mmap_base = mm->mmap_legacy_base;

		mm->get_unmapped_area = arch_get_unmapped_area;

	} else {

		mm->mmap_base = mmap_base(random_factor);

		mm->mmap_base = mmap_base(random_factor, TASK_SIZE);

		mm->get_unmapped_area = arch_get_unmapped_area_topdown;

	}

}