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Tue, 03 Feb 2026 18:28:21 -0800 (PST) Received: by ikb-h07-29-noble.in.iijlab.net (Postfix, from userid 1010) id DDC2C1200C35; Wed, 4 Feb 2026 11:28:19 +0900 (JST) From: Hajime Tazaki To: linux-um@lists.infradead.org Cc: thehajime@gmail.com, ricarkol@google.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org Subject: [PATCH v14 03/13] um: nommu: memory handling Date: Wed, 4 Feb 2026 11:28:01 +0900 Message-ID: <0e06cec4e7b715cd3c0a3fa8bec7e00c4e4c27ec.1770170302.git.thehajime@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: 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" This commit adds memory operations on UML under !MMU environment. Some part of the original UML code relying on CONFIG_MMU are excluded from compilation when !CONFIG_MMU. Additionally, generic functions such as uaccess, futex, memcpy/strnlen/strncpy can be used as user- and kernel-space share the address space in !CONFIG_MMU mode. Signed-off-by: Hajime Tazaki Signed-off-by: Ricardo Koller --- arch/um/Makefile | 4 ++++ arch/um/include/asm/futex.h | 4 ++++ arch/um/include/asm/mmu.h | 3 +++ arch/um/include/asm/mmu_context.h | 2 ++ arch/um/include/asm/uaccess.h | 7 ++++--- arch/um/kernel/mem.c | 3 ++- arch/um/os-Linux/mem.c | 4 ++++ arch/um/os-Linux/process.c | 4 ++-- 8 files changed, 25 insertions(+), 6 deletions(-) diff --git a/arch/um/Makefile b/arch/um/Makefile index 721b652ffb65..5e9bf2a8aa6d 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -46,6 +46,10 @@ ARCH_INCLUDE :=3D -I$(srctree)/$(SHARED_HEADERS) ARCH_INCLUDE +=3D -I$(srctree)/$(HOST_DIR)/um/shared KBUILD_CPPFLAGS +=3D -I$(srctree)/$(HOST_DIR)/um =20 +ifneq ($(CONFIG_MMU),y) +core-y +=3D $(ARCH_DIR)/nommu/ +endif + # -Dstrrchr=3Dkernel_strrchr (as well as the various in6addr symbols) prev= ents # anything from referencing # libc symbols with the same name, which can cause a linker error. diff --git a/arch/um/include/asm/futex.h b/arch/um/include/asm/futex.h index 780aa6bfc050..785fd6649aa2 100644 --- a/arch/um/include/asm/futex.h +++ b/arch/um/include/asm/futex.h @@ -7,8 +7,12 @@ #include =20 =20 +#ifdef CONFIG_MMU int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *= uaddr); int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval, u32 newval); +#else +#include +#endif =20 #endif diff --git a/arch/um/include/asm/mmu.h b/arch/um/include/asm/mmu.h index 82a919132aff..c0b9ce3215c4 100644 --- a/arch/um/include/asm/mmu.h +++ b/arch/um/include/asm/mmu.h @@ -22,10 +22,13 @@ typedef struct mm_context { unsigned long sync_tlb_range_from; unsigned long sync_tlb_range_to; =20 +#ifndef CONFIG_MMU + unsigned long end_brk; #ifdef CONFIG_BINFMT_ELF_FDPIC unsigned long exec_fdpic_loadmap; unsigned long interp_fdpic_loadmap; #endif +#endif /* !CONFIG_MMU */ } mm_context_t; =20 #define INIT_MM_CONTEXT(mm) \ diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_co= ntext.h index c727e56ba116..528b217da285 100644 --- a/arch/um/include/asm/mmu_context.h +++ b/arch/um/include/asm/mmu_context.h @@ -18,11 +18,13 @@ static inline void switch_mm(struct mm_struct *prev, st= ruct mm_struct *next, { } =20 +#ifdef CONFIG_MMU #define init_new_context init_new_context extern int init_new_context(struct task_struct *task, struct mm_struct *mm= ); =20 #define destroy_context destroy_context extern void destroy_context(struct mm_struct *mm); +#endif =20 #include =20 diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h index 0df9ea4abda8..031b357800b7 100644 --- a/arch/um/include/asm/uaccess.h +++ b/arch/um/include/asm/uaccess.h @@ -18,6 +18,7 @@ #define __addr_range_nowrap(addr, size) \ ((unsigned long) (addr) <=3D ((unsigned long) (addr) + (size))) =20 +#ifdef CONFIG_MMU extern unsigned long raw_copy_from_user(void *to, const void __user *from,= unsigned long n); extern unsigned long raw_copy_to_user(void __user *to, const void *from, u= nsigned long n); extern unsigned long __clear_user(void __user *mem, unsigned long len); @@ -29,9 +30,6 @@ static inline int __access_ok(const void __user *ptr, uns= igned long size); =20 #define INLINE_COPY_FROM_USER #define INLINE_COPY_TO_USER - -#include - static inline int __access_ok(const void __user *ptr, unsigned long size) { unsigned long addr =3D (unsigned long)ptr; @@ -63,5 +61,8 @@ do { \ barrier(); \ current->thread.segv_continue =3D NULL; \ } while (0) +#endif + +#include =20 #endif diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c index f3258680bfbe..e599b637c5fb 100644 --- a/arch/um/kernel/mem.c +++ b/arch/um/kernel/mem.c @@ -71,7 +71,8 @@ void __init arch_mm_preinit(void) * to be turned on. */ brk_end =3D PAGE_ALIGN((unsigned long) sbrk(0)); - map_memory(brk_end, __pa(brk_end), uml_reserved - brk_end, 1, 1, 0); + map_memory(brk_end, __pa(brk_end), uml_reserved - brk_end, 1, 1, + !IS_ENABLED(CONFIG_MMU)); memblock_free((void *)brk_end, uml_reserved - brk_end); uml_reserved =3D brk_end; min_low_pfn =3D PFN_UP(__pa(uml_reserved)); diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c index 72f302f4d197..4f5d9a94f8e2 100644 --- a/arch/um/os-Linux/mem.c +++ b/arch/um/os-Linux/mem.c @@ -213,6 +213,10 @@ int __init create_mem_file(unsigned long long len) { int err, fd; =20 + /* NOMMU kernel uses -1 as a fd for further use (e.g., mmap) */ + if (!IS_ENABLED(CONFIG_MMU)) + return -1; + fd =3D create_tmp_file(len); =20 err =3D os_set_exec_close(fd); diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c index 734d143417c8..b338a89ecf1e 100644 --- a/arch/um/os-Linux/process.c +++ b/arch/um/os-Linux/process.c @@ -100,8 +100,8 @@ int os_map_memory(void *virt, int fd, unsigned long lon= g off, unsigned long len, prot =3D (r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) | (x ? PROT_EXEC : 0); =20 - loc =3D mmap64((void *) virt, len, prot, MAP_SHARED | MAP_FIXED, - fd, off); + loc =3D mmap64((void *) virt, len, prot, MAP_SHARED | MAP_FIXED | + (!IS_ENABLED(CONFIG_MMU) ? MAP_ANONYMOUS : 0), fd, off); if (loc =3D=3D MAP_FAILED) return -errno; return 0; --=20 2.43.0