Commit 67f3977f authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Linus Torvalds
Browse files

arm64, mm: move generic mmap layout functions to mm 

arm64 handles top-down mmap layout in a way that can be easily reused by
other architectures, so make it available in mm.  It then introduces a new
config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT that can be set by other
architectures to benefit from those functions.  Note that this new config
depends on MMU being enabled, if selected without MMU support, a warning
will be thrown.

Link: http://lkml.kernel.org/r/20190730055113.23635-5-alex@ghiti.fr


Signed-off-by: default avatarAlexandre Ghiti <alex@ghiti.fr>
Suggested-by: default avatarChristoph Hellwig <hch@infradead.org>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: James Hogan <jhogan@kernel.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e8d54b62

arch/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -706,6 +706,16 @@ config HAVE_ARCH_COMPAT_MMAP_BASES 
	  and vice-versa 32-bit applications to call 64-bit mmap().

	  Required for applications doing different bitness syscalls.



# This allows to use a set of generic functions to determine mmap base

# address by giving priority to top-down scheme only if the process

# is not in legacy mode (compat task, unlimited stack size or

# sysctl_legacy_va_layout).

# Architecture that selects this option can provide its own version of:

# - STACK_RND_MASK

config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

	bool

	depends on MMU



config HAVE_COPY_THREAD_TLS

	bool

	help

arch/arm64/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ config ARM64 
	select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG

	select ARCH_SUPPORTS_NUMA_BALANCING

	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT

	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

	select ARCH_WANT_FRAME_POINTERS

	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)

	select ARCH_HAS_UBSAN_SANITIZE_ALL

arch/arm64/include/asm/processor.h

+0 −2
Original line number Diff line number Diff line
@@ -280,8 +280,6 @@ static inline void spin_lock_prefetch(const void *ptr) 
		     "nop") : : "p" (ptr));

}



#define HAVE_ARCH_PICK_MMAP_LAYOUT



extern unsigned long __ro_after_init signal_minsigstksz; /* sigframe size */

extern void __init minsigstksz_setup(void);

arch/arm64/mm/mmap.c

+0 −76
Original line number Diff line number Diff line
@@ -20,82 +20,6 @@ 


#include <asm/cputype.h>



/*

 * Leave enough space between the mmap area and the stack to honour ulimit in

 * the face of randomisation.

 */

#define MIN_GAP (SZ_128M)

#define MAX_GAP	(STACK_TOP/6*5)



static int mmap_is_legacy(struct rlimit *rlim_stack)

{

	if (current->personality & ADDR_COMPAT_LAYOUT)

		return 1;



	if (rlim_stack->rlim_cur == RLIM_INFINITY)

		return 1;



	return sysctl_legacy_va_layout;

}



unsigned long arch_mmap_rnd(void)

{

	unsigned long rnd;



#ifdef CONFIG_COMPAT

	if (is_compat_task())

		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);

	else

#endif

		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);

	return rnd << PAGE_SHIFT;

}



static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)

{

	unsigned long gap = rlim_stack->rlim_cur;

	unsigned long pad = stack_guard_gap;



	/* Account for stack randomization if necessary */

	if (current->flags & PF_RANDOMIZE)

		pad += (STACK_RND_MASK << PAGE_SHIFT);



	/* Values close to RLIM_INFINITY can overflow. */

	if (gap + pad > gap)

		gap += pad;



	if (gap < MIN_GAP)

		gap = MIN_GAP;

	else if (gap > MAX_GAP)

		gap = MAX_GAP;



	return PAGE_ALIGN(STACK_TOP - gap - rnd);

}



/*

 * This function, called very early during the creation of a new process VM

 * image, sets up which VM layout function to use:

 */

void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)

{

	unsigned long random_factor = 0UL;



	if (current->flags & PF_RANDOMIZE)

		random_factor = arch_mmap_rnd();



	/*

	 * Fall back to the standard layout if the personality bit is set, or

	 * if the expected stack growth is unlimited:

	 */

	if (mmap_is_legacy(rlim_stack)) {

		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;

		mm->get_unmapped_area = arch_get_unmapped_area;

	} else {

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

		mm->get_unmapped_area = arch_get_unmapped_area_topdown;

	}

}



/*

 * You really shouldn't be using read() or write() on /dev/mem.  This might go

 * away in the future.

kernel/sysctl.c

+4 −2
Original line number Diff line number Diff line
@@ -264,7 +264,8 @@ extern struct ctl_table epoll_table[]; 
extern struct ctl_table firmware_config_table[];

#endif



#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT

#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \

    defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)

int sysctl_legacy_va_layout;

#endif
@@ -1573,7 +1574,8 @@ static struct ctl_table vm_table[] = { 
		.proc_handler	= proc_dointvec,

		.extra1		= SYSCTL_ZERO,

	},

#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT

#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \

    defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)

	{

		.procname	= "legacy_va_layout",

		.data		= &sysctl_legacy_va_layout,

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