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: Alexandre Ghiti <alex@ghiti.fr>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index 0fcf8ec1e09883a2fbab69f02f02068dd913afc3..dfce421b8e8ac04fc86735f32c45e5eb35b8dd82 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -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

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 37c610963eeeda6f6560a0d5f7c61e869ed99881..2d4b7044063c0fda118e4148f81a20da3a24829e 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -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

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index c67848c55009d9744ff68deea54eb58844d1c7f1..5623685c7d138556dd5268db6363ee8faeb99cd4 100644 (file)
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -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);
 

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index e4acaead67dea497768a529d9a25646b3b465743..3028bacbc4e9c40135b1f84a28a67500218c3078 100644 (file)
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -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.

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 078950d9605ba2f6c109c5837f52b1a6cc07d186..00fcea236ebacffa71236af5ddfcaf2df8d0855d 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -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,

diff --git a/mm/util.c b/mm/util.c
index bf8af5e07c4a24e26ecc0fae785fe24255b8a494..7922726f0a8fa7f7ef18fed3912ee48d413352ea 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -17,7 +17,12 @@
 #include <linux/vmalloc.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/elf.h>
+#include <linux/elf-randomize.h>
+#include <linux/personality.h>
 #include <linux/random.h>
+#include <linux/processor.h>
+#include <linux/sizes.h>
+#include <linux/compat.h>
 
 #include <linux/uaccess.h>
 
@@ -315,7 +320,78 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 #endif
 }
 
-#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
+#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+unsigned long arch_mmap_rnd(void)
+{
+       unsigned long rnd;
+
+#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
+       if (is_compat_task())
+               rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
+       else
+#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
+               rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+
+       return rnd << PAGE_SHIFT;
+}
+#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */
+
+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;
+}
+
+/*
+ * 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 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);
+}
+
+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();
+
+       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;
+       }
+}
+#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 {
        mm->mmap_base = TASK_UNMAPPED_BASE;