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Subject[PATCHv2 2/5] x86/mm: introduce mmap_{,legacy}_base
Date
In the following patch they will be used to compute:
- mmap_base in compat sys_mmap() in native 64-bit binary
and vice-versa
- mmap_base for native sys_mmap() in compat x32/ia32-bit binary.

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
arch/x86/include/asm/elf.h | 9 +++++++--
arch/x86/include/asm/processor.h | 2 +-
arch/x86/mm/hugetlbpage.c | 2 +-
arch/x86/mm/mmap.c | 31 +++++++++++++++++++------------
4 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index ee1a87782b2c..9655a8390da4 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 { \
@@ -320,7 +322,7 @@ if (test_thread_flag(TIF_X32)) \
else \
ARCH_DLINFO_IA32

-#define COMPAT_ELF_ET_DYN_BASE (TASK_UNMAPPED_BASE + 0x1000000)
+#define COMPAT_ELF_ET_DYN_BASE (TASK_UNMAPPED_BASE(TASK_SIZE) + 0x1000000)

#endif /* !CONFIG_X86_32 */

@@ -353,6 +355,9 @@ static inline int mmap_is_ia32(void)
extern unsigned long arch_compat_rnd(void);
#endif
extern unsigned long arch_native_rnd(void);
+extern unsigned long mmap_base(unsigned long rnd, unsigned long task_size);
+extern unsigned long mmap_legacy_base(unsigned long rnd,
+ unsigned long task_size);

/* Do not change the values. See get_align_mask() */
enum align_flags {
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index eaf100508c36..2bf5787fac37 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -844,7 +844,7 @@ 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 KSTK_EIP(task) (task_pt_regs(task)->ip)

diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index 2ae8584b44c7..62dfa3fa3ee0 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -113,7 +113,7 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
if (addr & ~PAGE_MASK) {
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
- info.low_limit = TASK_UNMAPPED_BASE;
+ info.low_limit = TASK_UNMAPPED_BASE(TASK_SIZE);
info.high_limit = TASK_SIZE;
addr = vm_unmapped_area(&info);
}
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 0b2007b08194..b64362270165 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 +90,21 @@ unsigned long arch_mmap_rnd(void)
return arch_native_rnd();
}

-static unsigned long mmap_base(unsigned long rnd)
+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);
+}
+
+unsigned long mmap_legacy_base(unsigned long rnd, unsigned long task_size)
+{
+ return TASK_UNMAPPED_BASE(task_size) + rnd;
}

/*
@@ -111,13 +118,13 @@ 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
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