linux-kernel - [PATCH 1/2] mm: Change mmap_rnd_bits_max to __ro_after

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Date:   Fri, 29 Sep 2023 21:11:57 +0000
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 1/2] mm: Change mmap_rnd_bits_max to __ro_after_init

Allow mmap_rnd_bits_max to be updated on architectures that
determine virtual address space size at runtime instead of relying
on Kconfig options by changing it from const to __ro_after_init.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 include/linux/mm.h | 2 +-
 mm/mmap.c          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf5d0b1b16f4..72a98b2afaf9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -86,7 +86,7 @@ extern int sysctl_legacy_va_layout;
 
 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
 extern const int mmap_rnd_bits_min;
-extern const int mmap_rnd_bits_max;
+extern int mmap_rnd_bits_max __ro_after_init;
 extern int mmap_rnd_bits __read_mostly;
 #endif
 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
diff --git a/mm/mmap.c b/mm/mmap.c
index b56a7f0c9f85..ed1b178b223a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -64,7 +64,7 @@
 
 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
-const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
+int mmap_rnd_bits_max __ro_after_init = CONFIG_ARCH_MMAP_RND_BITS_MAX;
 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
 #endif
 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
-- 
2.42.0.582.g8ccd20d70d-goog