linux-kernel - [RFC patch 4/6] arm64: Use simpler API for random address requests

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Date:	Tue, 26 Jul 2016 03:01:58 +0000
From:	Jason Cooper <jason@...edaemon.net>
To:	william.c.roberts@...el.com, linux-mm@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Cc:	Jason Cooper <jason@...edaemon.net>, linux@....linux.org.uk,
	akpm@...ux-foundation.org, keescook@...omium.org, tytso@....edu,
	arnd@...db.de, gregkh@...uxfoundation.org, catalin.marinas@....com,
	will.deacon@....com, ralf@...ux-mips.org, benh@...nel.crashing.org,
	paulus@...ba.org, mpe@...erman.id.au, davem@...emloft.net,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, viro@...iv.linux.org.uk, nnk@...gle.com,
	jeffv@...gle.com, alyzyn@...roid.com, dcashman@...roid.com
Subject: [RFC patch 4/6] arm64: Use simpler API for random address requests

Currently, all callers to randomize_range() set the length to 0 and
calculate end by adding a constant to the start address.  We can
simplify the API to remove a bunch of needless checks and variables.

Use the new randomize_addr(start, range) call to set the requested
address.

Signed-off-by: Jason Cooper <jason@...edaemon.net>
---
 arch/arm64/kernel/process.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6cd2612236dc..11bf454baf86 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -374,12 +374,8 @@ unsigned long arch_align_stack(unsigned long sp)
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
-	unsigned long range_end = mm->brk;
-
 	if (is_compat_task())
-		range_end += 0x02000000;
+		return randomize_addr(mm->brk, 0x02000000);
 	else
-		range_end += 0x40000000;
-
-	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+		return randomize_addr(mm->brk, 0x40000000);
 }
-- 
2.9.2