[PATCH v3 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
From: Daniel Cashman <hidden>
Date: 2015-11-18 23:21:08
Also in:
linux-mm, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
From: dcashman <redacted> arm64: arch_mmap_rnd() uses STACK_RND_MASK to generate the random offset for the mmap base address. This value represents a compromise between increased ASLR effectiveness and avoiding address-space fragmentation. Replace it with a Kconfig option, which is sensibly bounded, so that platform developers may choose where to place this compromise. Keep default values as new minimums. Signed-off-by: Daniel Cashman <redacted> --- arch/arm64/Kconfig | 23 +++++++++++++++++++++++ arch/arm64/mm/mmap.c | 6 ++++-- 2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9ac16a4..be38e4c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig@@ -51,6 +51,8 @@ config ARM64 select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP select HAVE_ARCH_KGDB + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_BPF_JIT
@@ -104,6 +106,27 @@ config ARCH_PHYS_ADDR_T_64BIT config MMU def_bool y +config ARCH_MMAP_RND_BITS_MIN + default 15 if ARM64_64K_PAGES + default 19 + +config ARCH_MMAP_RND_BITS_MAX + default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39 + default 24 if ARCH_VA_BITS=39 + default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42 + default 27 if ARCH_VA_BITS=42 + default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48 + default 33 if ARCH_VA_BITS=48 + default 15 if ARM64_64K_PAGES + default 19 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 7 if ARM64_64K_PAGES + default 11 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config NO_IOPORT_MAP def_bool y if !PCI
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index ed17747..b84d5b1 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c@@ -51,8 +51,10 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; - rnd = (unsigned long)get_random_int() & STACK_RND_MASK; - + if (test_thread_flag(TIF_32BIT)) + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits); + else + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); return rnd << PAGE_SHIFT; }
--
2.6.0.rc2.230.g3dd15c0