[PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
From: jonathanh@nvidia.com (Jon Hunter)
Date: 2015-12-07 10:26:26
Also in:
linux-mm, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
On 01/12/15 20:10, Daniel Cashman wrote:
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 | 31 +++++++++++++++++++++++++++++++ arch/arm64/mm/mmap.c | 8 ++++++-- 2 files changed, 37 insertions(+), 2 deletions(-)
[snip]
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index ed17747..af461b9 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c@@ -51,8 +51,12 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; - rnd = (unsigned long)get_random_int() & STACK_RND_MASK; - +ifdef CONFIG_COMPAT + if (test_thread_flag(TIF_32BIT)) + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits); + else +#endif + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); return rnd << PAGE_SHIFT; }
The above is causing a build failure on -next today.
commit 42a6c8953112a9856dd09148c3d6a2cc106b6003
Author: Jon Hunter [off-list ref]
Date: Mon Dec 7 10:15:47 2015 +0000
ARM64: mm: Fix build failure caused by invalid ifdef statement
Commit 2e4614190421 ("arm64-mm-support-arch_mmap_rnd_bits-v4") caused the
following build failure due to a missing "#". Fix this.
arch/arm64/mm/mmap.c: In function ?arch_mmap_rnd?:
arch/arm64/mm/mmap.c:54:1: error: ?ifdef? undeclared (first use in this function)
ifdef CONFIG_COMPAT
^
Signed-off-by: Jon Hunter [off-list ref]
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index af461b935137..e59a75a308bc 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c@@ -51,7 +51,7 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; -ifdef CONFIG_COMPAT +#ifdef CONFIG_COMPAT if (test_thread_flag(TIF_32BIT)) rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits); else
Cheers Jon