Commit-ID: 6a0b41d1e23dd3318568461593ae5e36d966981e Gitweb: http://git.kernel.org/tip/6a0b41d1e23dd3318568461593ae5e36d966981e Author: Dmitry Safonov <dsafo...@virtuozzo.com> AuthorDate: Mon, 6 Mar 2017 17:17:17 +0300 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Mon, 13 Mar 2017 14:59:22 +0100
x86/mm: Introduce arch_rnd() to compute 32/64 mmap random base The compat (32bit) mmap() sycall issued by a 64-bit task results in a mapping above 4GB. That's outside the compat mode address space and prevents CRIU to restore 32bit processes from a 64bit application. As a first step to address this, split out the address base randomizing calculation from arch_mmap_rnd() into a helper function, which can be used independent of mmap_ia32() based decisions. [ tglx: Massaged changelog ] Suggested-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Dmitry Safonov <dsafo...@virtuozzo.com> Cc: 0x7f454...@gmail.com Cc: linux...@kvack.org Cc: Andy Lutomirski <l...@kernel.org> Cc: Cyrill Gorcunov <gorcu...@openvz.org> Cc: Borislav Petkov <b...@suse.de> Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com> Link: http://lkml.kernel.org/r/20170306141721.9188-2-dsafo...@virtuozzo.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- arch/x86/mm/mmap.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 7940166..f31ed70 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -55,6 +55,14 @@ static unsigned long stack_maxrandom_size(void) #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 +#else +# define mmap32_rnd_bits mmap_rnd_bits +# define mmap64_rnd_bits mmap_rnd_bits +#endif + static int mmap_is_legacy(void) { if (current->personality & ADDR_COMPAT_LAYOUT) @@ -66,20 +74,14 @@ static int mmap_is_legacy(void) return sysctl_legacy_va_layout; } -unsigned long arch_mmap_rnd(void) +static unsigned long arch_rnd(unsigned int rndbits) { - unsigned long rnd; - - if (mmap_is_ia32()) -#ifdef CONFIG_COMPAT - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); -#else - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); -#endif - else - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); + return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; +} - return rnd << PAGE_SHIFT; +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)
