linux-kernel - [PATCH v9 1/4] mm: Allow arch specific arch_randomize_brk() with CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP

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Message-Id: <72c1c5f1a3f28137eb9e379f927fc9908699c249.1649401201.git.christophe.leroy@csgroup.eu>
Date:   Fri,  8 Apr 2022 09:24:59 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, Alexandre Ghiti <alex@...ti.fr>
Subject: [PATCH v9 1/4] mm: Allow arch specific arch_randomize_brk() with CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

Commit e7142bf5d231 ("arm64, mm: make randomization selected by
generic topdown mmap layout") introduced a default version of
arch_randomize_brk() provided when
CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT is selected.

powerpc could select CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
but needs to provide its own arch_randomize_brk().

In order to allow that, define generic version of arch_randomize_brk()
as a __weak symbol.

Cc: Alexandre Ghiti <alex@...ti.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 mm/util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/util.c b/mm/util.c
index 54e5e761a9a9..0787fe4af4ac 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -344,7 +344,7 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 }
 
 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
-unsigned long arch_randomize_brk(struct mm_struct *mm)
+unsigned long __weak arch_randomize_brk(struct mm_struct *mm)
 {
 	/* Is the current task 32bit ? */
 	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
-- 
2.35.1