[Devel,07/11] ms/x86/mm: Add task_size parameter to mmap_base()

Submitted by Dmitry Safonov on May 18, 2017, 6:39 p.m.

Details

Message ID 20170518183950.4372-8-dsafonov@virtuozzo.com
State New
Series "x86: C/R for ia32 tasks"
Headers show

Commit Message

Dmitry Safonov May 18, 2017, 6:39 p.m.
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: Dmitry 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: Thomas Gleixner <tglx@linutronix.de>

[ms commit 8f3e474f3cea]
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
 arch/x86/include/asm/elf.h       | 29 ++++++++++-----------
 arch/x86/include/asm/processor.h |  4 ++-
 arch/x86/mm/mmap.c               | 56 +++++++++++++++++++++-------------------
 3 files changed, 45 insertions(+), 44 deletions(-)

Patch hide | download patch | download mbox

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index e114fff00087..e7057133088d 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -277,8 +277,19 @@  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 VDSO_HIGH_BASE		(__fix_to_virt(FIX_VDSO))
@@ -292,7 +303,8 @@  do {									\
 #define VDSO_HIGH_BASE		0xffffe000U /* CONFIG_COMPAT_VDSO address */
 
 /* 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 {									\
@@ -343,21 +355,6 @@  extern int do_map_compat_vdso(unsigned long addr);
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define arch_randomize_brk arch_randomize_brk
 
-/*
- * True on X86_32 or when emulating IA32 on X86_64
- */
-static inline int mmap_is_ia32(void)
-{
-#ifdef CONFIG_X86_32
-	return 1;
-#endif
-#ifdef CONFIG_IA32_EMULATION
-	if (test_thread_flag(TIF_ADDR32))
-		return 1;
-#endif
-	return 0;
-}
-
 /* Do not change the values. See get_align_mask() */
 enum align_flags {
 	ALIGN_VA_32	= BIT(0),
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0c4e3faf8ac3..47a1ac9e1c10 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -841,6 +841,7 @@  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
@@ -949,7 +950,8 @@  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 83a986ef7651..d0c222d64bb1 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -35,25 +35,23 @@  struct __read_mostly va_alignment 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  8
 # define mmap64_rnd_bits  28
@@ -62,6 +60,8 @@  static unsigned long stack_maxrandom_size(void)
 # define mmap64_rnd_bits  28
 #endif
 
+#define SIZE_128M    (128 * 1024 * 1024UL)
+
 static int mmap_is_legacy(void)
 {
 	if (current->personality & ADDR_COMPAT_LAYOUT)
@@ -84,28 +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;
+
+	/*
+	 * 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;
 
-	if (gap < MIN_GAP)
-		gap = MIN_GAP;
-	else if (gap > MAX_GAP)
-		gap = MAX_GAP;
+	if (gap < gap_min)
+		gap = gap_min;
+	else if (gap > gap_max)
+		gap = gap_max;
 
-	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+	return PAGE_ALIGN(task_size - gap - rnd);
 }
 
-/*
- * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
- * does, but not when emulating X86_32
- */
-static unsigned long mmap_legacy_base(unsigned long rnd)
+static unsigned long mmap_legacy_base(unsigned long rnd,
+				      unsigned long task_size)
 {
-	if (mmap_is_ia32())
-		return TASK_UNMAPPED_BASE;
-	else
-		return TASK_UNMAPPED_BASE + rnd;
+	return __TASK_UNMAPPED_BASE(task_size) + rnd;
 }
 
 /*
@@ -119,14 +121,14 @@  void arch_pick_mmap_layout(struct mm_struct *mm)
 	if (current->flags & PF_RANDOMIZE)
 		random_factor = arch_mmap_rnd();
 
-	mm->mmap_legacy_base = mmap_legacy_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;
 		mm->unmap_area = arch_unmap_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;
 		mm->unmap_area = arch_unmap_area_topdown;
 	}