diff mbox series

[v8,03/12] um: nommu: memory handling

Message ID 2598e5207a53e4ec1f2077b5c5a9f03fc3782506.1745980082.git.thehajime@gmail.com
State New
Headers show
Series nommu UML | expand

Commit Message

Hajime Tazaki April 30, 2025, 4:27 a.m. UTC 
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 <thehajime@gmail.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 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 mbox series

Patch

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 1d36a613aad8..fcf4bb915a31 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -46,6 +46,10 @@  ARCH_INCLUDE	:= -I$(srctree)/$(SHARED_HEADERS)
 ARCH_INCLUDE	+= -I$(srctree)/$(HOST_DIR)/um/shared
 KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/um
 
+ifneq ($(CONFIG_MMU),y)
+core-y += $(ARCH_DIR)/nommu/
+endif
+
 # -Dvmap=kernel_vmap prevents anything from referencing the libpcap.o symbol so
 # named - it's a common symbol in libpcap, so we get a binary which crashes.
 #
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 <asm/errno.h>
 
 
+#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 <asm-generic/futex.h>
+#endif
 
 #endif
diff --git a/arch/um/include/asm/mmu.h b/arch/um/include/asm/mmu.h
index 01422b761aa0..d4087f9499e2 100644
--- a/arch/um/include/asm/mmu.h
+++ b/arch/um/include/asm/mmu.h
@@ -15,10 +15,13 @@  typedef struct mm_context {
 	unsigned long sync_tlb_range_from;
 	unsigned long sync_tlb_range_to;
 
+#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;
 
 #endif
diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_context.h
index 23dcc914d44e..033a70166066 100644
--- a/arch/um/include/asm/mmu_context.h
+++ b/arch/um/include/asm/mmu_context.h
@@ -36,11 +36,13 @@  static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	}
 }
 
+#ifdef CONFIG_MMU
 #define init_new_context init_new_context
 extern int init_new_context(struct task_struct *task, struct mm_struct *mm);
 
 #define destroy_context destroy_context
 extern void destroy_context(struct mm_struct *mm);
+#endif
 
 #include <asm-generic/mmu_context.h>
 
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h
index 3a08f9029a3f..eb9b7d577062 100644
--- a/arch/um/include/asm/uaccess.h
+++ b/arch/um/include/asm/uaccess.h
@@ -23,6 +23,7 @@ 
 #define __addr_range_nowrap(addr, size) \
 	((unsigned long) (addr) <= ((unsigned long) (addr) + (size)))
 
+#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, unsigned long n);
 extern unsigned long __clear_user(void __user *mem, unsigned long len);
@@ -34,9 +35,6 @@  static inline int __access_ok(const void __user *ptr, unsigned long size);
 
 #define INLINE_COPY_FROM_USER
 #define INLINE_COPY_TO_USER
-
-#include <asm-generic/uaccess.h>
-
 static inline int __access_ok(const void __user *ptr, unsigned long size)
 {
 	unsigned long addr = (unsigned long)ptr;
@@ -68,5 +66,8 @@  do {									\
 	put_unaligned(*((type *)src), (type *)(dst));			\
 	current->thread.segv_continue = NULL;				\
 } while (0)
+#endif
+
+#include <asm-generic/uaccess.h>
 
 #endif
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index cbe8b9d03d8c..1e18384381e2 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -64,7 +64,8 @@  void __init mem_init(void)
 	 * to be turned on.
 	 */
 	brk_end = (unsigned long) UML_ROUND_UP(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 = brk_end;
 	min_low_pfn = 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;
 
+	/* NOMMU kernel uses -1 as a fd for further use (e.g., mmap) */
+	if (!IS_ENABLED(CONFIG_MMU))
+		return -1;
+
 	fd = create_tmp_file(len);
 
 	err = os_set_exec_close(fd);
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 2331e32c4898..8a615875d1a1 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -70,8 +70,8 @@  int os_map_memory(void *virt, int fd, unsigned long long off, unsigned long len,
 	prot = (r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) |
 		(x ? PROT_EXEC : 0);
 
-	loc = mmap64((void *) virt, len, prot, MAP_SHARED | MAP_FIXED,
-		     fd, off);
+	loc = mmap64((void *) virt, len, prot, MAP_SHARED | MAP_FIXED |
+		     (!IS_ENABLED(CONFIG_MMU) ? MAP_ANONYMOUS : 0), fd, off);
 	if (loc == MAP_FAILED)
 		return -errno;
 	return 0;