In the following patch they will be used to compute:
- mmap{,_legacy}_base for 64-bit mmap()
- mmap_compat{,_legacy}_base for 32-bit mmap()This patch makes it possible to calculate mmap bases for any specified task_size, which is needed to correctly choose the base address for mmap in 32-bit syscalls and 64-bit syscalls. Signed-off-by: Dmitry Safonov <[email protected]> --- arch/x86/include/asm/elf.h | 4 +++- arch/x86/include/asm/processor.h | 3 ++- arch/x86/mm/mmap.c | 32 ++++++++++++++++++++------------ 3 files changed, 25 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index e7f155c3045e..120b4f3d8a6a 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -286,6 +286,7 @@ do { \ #ifdef CONFIG_X86_32 +#define STACK_RND_MASK_MODE(native) (0x7ff) #define STACK_RND_MASK (0x7ff) #define ARCH_DLINFO ARCH_DLINFO_IA32 @@ -295,7 +296,8 @@ 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_MODE(native) ((native) ? 0x3fffff : 0x7ff) +#define STACK_RND_MASK STACK_RND_MASK_MODE(!test_thread_flag(TIF_ADDR32)) #define ARCH_DLINFO \ do { \ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 1be64da0384e..52086e65b422 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -862,7 +862,8 @@ 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) diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 42063e787717..98be520fd270 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -35,12 +35,14 @@ struct va_alignment __read_mostly va_align = { .flags = -1, }; -static unsigned long stack_maxrandom_size(void) +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); + max &= STACK_RND_MASK_MODE(task_size == TASK_SIZE_MAX); + max <<= PAGE_SHIFT; } return max; @@ -51,8 +53,8 @@ static unsigned long stack_maxrandom_size(void) * * 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) +#define MIN_GAP(task_size) (128*1024*1024UL + stack_maxrandom_size(task_size)) +#define MAX_GAP(task_size) (task_size/6*5) static int mmap_is_legacy(void) { @@ -88,16 +90,22 @@ unsigned long arch_mmap_rnd(void) return arch_native_rnd(); } -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); - if (gap < MIN_GAP) - gap = MIN_GAP; - else if (gap > MAX_GAP) - gap = MAX_GAP; + if (gap < MIN_GAP(task_size)) + gap = MIN_GAP(task_size); + else if (gap > MAX_GAP(task_size)) + gap = MAX_GAP(task_size); - return PAGE_ALIGN(TASK_SIZE - gap - rnd); + 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; } /* @@ -111,13 +119,13 @@ 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; } } -- 2.11.0
