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[2003:dc:6f1d:f00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b01902d0e99sm541005766b.12.2025.09.01.02.19.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Sep 2025 02:19:38 -0700 (PDT) From: Max Kellermann To: akpm@linux-foundation.org, david@redhat.com, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, vishal.moola@gmail.com, linux@armlinux.org.uk, James.Bottomley@HansenPartnership.com, deller@gmx.de, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, weixugc@google.com, baolin.wang@linux.alibaba.com, rientjes@google.com, shakeel.butt@linux.dev, max.kellermann@ionos.com, thuth@redhat.com, broonie@kernel.org, osalvador@suse.de, jfalempe@redhat.com, mpe@ellerman.id.au, nysal@linux.ibm.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v4 08/12] mm/util, s390, sparc, x86: add const to arch_pick_mmap_layout() parameter Date: Mon, 1 Sep 2025 11:19:11 +0200 Message-ID: <20250901091916.3002082-9-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250901091916.3002082-1-max.kellermann@ionos.com> References: <20250901091916.3002082-1-max.kellermann@ionos.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The memory management (mm) subsystem is a fundamental low-level component of the Linux kernel. Establishing const-correctness at this foundational level enables higher-level subsystems, such as filesystems and drivers, to also adopt const-correctness in their interfaces. This patch lays the groundwork for broader const-correctness throughout the kernel by starting with the core mm subsystem. This patch adds const qualifiers to mm_struct and rlimit pointer parameters in arch_pick_mmap_layout() across multiple architectures, improving type safety and enabling compiler optimizations. Functions improved: - arch_pick_mmap_layout() (s390, sparc, x86, and generic mm/util.c) - mmap_base() (x86) Signed-off-by: Max Kellermann --- arch/s390/mm/mmap.c | 5 +++-- arch/sparc/kernel/sys_sparc_64.c | 3 ++- arch/x86/mm/mmap.c | 7 ++++--- include/linux/sched/mm.h | 4 ++-- mm/util.c | 9 ++++++--- 5 files changed, 17 insertions(+), 11 deletions(-) diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c index c0f619fb9ab3..a47c7133d82a 100644 --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -47,7 +47,7 @@ static unsigned long mmap_base_legacy(unsigned long rnd) } =20 static inline unsigned long mmap_base(unsigned long rnd, - struct rlimit *rlim_stack) + const struct rlimit *const rlim_stack) { unsigned long gap =3D rlim_stack->rlim_cur; unsigned long pad =3D stack_maxrandom_size() + stack_guard_gap; @@ -169,7 +169,8 @@ unsigned long arch_get_unmapped_area_topdown(struct fil= e *filp, unsigned long ad * This function, called very early during the creation of a new * process VM image, sets up which VM layout function to use: */ -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) +void arch_pick_mmap_layout(struct mm_struct *const mm, + const struct rlimit *const rlim_stack) { unsigned long random_factor =3D 0UL; =20 diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc= _64.c index 785e9909340f..1c243bb461b2 100644 --- a/arch/sparc/kernel/sys_sparc_64.c +++ b/arch/sparc/kernel/sys_sparc_64.c @@ -294,7 +294,8 @@ static unsigned long mmap_rnd(void) return rnd << PAGE_SHIFT; } =20 -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) +void arch_pick_mmap_layout(struct mm_struct *const mm, + const struct rlimit *const rlim_stack) { unsigned long random_factor =3D mmap_rnd(); unsigned long gap; diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 708f85dc9380..13bde4ba2f24 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -80,7 +80,7 @@ unsigned long arch_mmap_rnd(void) } =20 static unsigned long mmap_base(unsigned long rnd, unsigned long task_size, - struct rlimit *rlim_stack) + const struct rlimit *const rlim_stack) { unsigned long gap =3D rlim_stack->rlim_cur; unsigned long pad =3D stack_maxrandom_size(task_size) + stack_guard_gap; @@ -110,7 +110,7 @@ static unsigned long mmap_legacy_base(unsigned long rnd, */ static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy= _base, unsigned long random_factor, unsigned long task_size, - struct rlimit *rlim_stack) + const struct rlimit *const rlim_stack) { *legacy_base =3D mmap_legacy_base(random_factor, task_size); if (mmap_is_legacy()) @@ -119,7 +119,8 @@ static void arch_pick_mmap_base(unsigned long *base, un= signed long *legacy_base, *base =3D mmap_base(random_factor, task_size, rlim_stack); } =20 -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) +void arch_pick_mmap_layout(struct mm_struct *const mm, + const struct rlimit *const rlim_stack) { if (mmap_is_legacy()) mm_flags_clear(MMF_TOPDOWN, mm); diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 2201da0afecc..0232d983b715 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -178,7 +178,7 @@ static inline void mm_update_next_owner(struct mm_struc= t *mm) #endif =20 extern void arch_pick_mmap_layout(struct mm_struct *mm, - struct rlimit *rlim_stack); + const struct rlimit *rlim_stack); =20 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, @@ -211,7 +211,7 @@ generic_get_unmapped_area_topdown(struct file *filp, un= signed long addr, unsigned long flags, vm_flags_t vm_flags); #else static inline void arch_pick_mmap_layout(struct mm_struct *mm, - struct rlimit *rlim_stack) {} + const struct rlimit *rlim_stack) {} #endif =20 static inline bool in_vfork(struct task_struct *tsk) diff --git a/mm/util.c b/mm/util.c index f5a35efba7bf..24f08217cd95 100644 --- a/mm/util.c +++ b/mm/util.c @@ -431,7 +431,8 @@ static int mmap_is_legacy(const struct rlimit *const rl= im_stack) #define MIN_GAP (SZ_128M) #define MAX_GAP (STACK_TOP / 6 * 5) =20 -static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stac= k) +static unsigned long mmap_base(const unsigned long rnd, + const struct rlimit *const rlim_stack) { #ifdef CONFIG_STACK_GROWSUP /* @@ -462,7 +463,8 @@ static unsigned long mmap_base(unsigned long rnd, struc= t rlimit *rlim_stack) #endif } =20 -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) +void arch_pick_mmap_layout(struct mm_struct *const mm, + const struct rlimit *const rlim_stack) { unsigned long random_factor =3D 0UL; =20 @@ -478,7 +480,8 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct= rlimit *rlim_stack) } } #elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) +void arch_pick_mmap_layout(struct mm_struct *const mm, + const struct rlimit *const rlim_stack) { mm->mmap_base =3D TASK_UNMAPPED_BASE; mm_flags_clear(MMF_TOPDOWN, mm); --=20 2.47.2