mm: expose arch_mmap_rnd when available

When an architecture fully supports randomizing the ELF load location,
a per-arch mmap_rnd() function is used to find a randomized mmap base.
In preparation for randomizing the location of ET_DYN binaries
separately from mmap, this renames and exports these functions as
arch_mmap_rnd(). Additionally introduces CONFIG_ARCH_HAS_ELF_RANDOMIZE
for describing this feature on architectures that support it
(which is a superset of ARCH_BINFMT_ELF_RANDOMIZE_PIE, since s390
already supports a separated ET_DYN ASLR from mmap ASLR without the
ARCH_BINFMT_ELF_RANDOMIZE_PIE logic).

Signed-off-by: Kees Cook <[email protected]>
Cc: Hector Marco-Gisbert <[email protected]>
Cc: Russell King <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "David A. Long" <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Arun Chandran <[email protected]>
Cc: Yann Droneaud <[email protected]>
Cc: Min-Hua Chen <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Alex Smith <[email protected]>
Cc: Markos Chandras <[email protected]>
Cc: Vineeth Vijayan <[email protected]>
Cc: Jeff Bailey <[email protected]>
Cc: Michael Holzheu <[email protected]>
Cc: Ben Hutchings <[email protected]>
Cc: Behan Webster <[email protected]>
Cc: Ismael Ripoll <[email protected]>
Cc: Jan-Simon Mller <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index ba776c01b552..ed177475dd8c 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -47,7 +47,7 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
 {
 	unsigned long rnd;
 
@@ -77,7 +77,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 	unsigned long random_factor = 0UL;
 
 	if (current->flags & PF_RANDOMIZE)
-		random_factor = mmap_rnd();
+		random_factor = arch_mmap_rnd();
 
 	/*
 	 * Fall back to the standard layout if the personality bit is set, or