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um: nommu: memory handling

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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>
[drop unnecessary bits]
Link: https://patch.msgid.link/20260723113633.1206c739d6c0.I88b7ddf5613d072b934ce5fd9ef133ea5a4aa2b6@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Hajime Tazaki 2026-07-23 11:35:44 +02:00 committed by Johannes Berg
parent 130031906f
commit cf2dd04179
5 changed files with 15 additions and 3 deletions
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4
arch/um/include/asm/futex.h
View File

@ -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

3
arch/um/include/asm/mmu.h
View File

@ -22,10 +22,13 @@ 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;
#define INIT_MM_CONTEXT(mm) \

2
arch/um/include/asm/mmu_context.h
View File

@ -18,11 +18,13 @@ 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>

6
arch/um/include/asm/uaccess.h
View File

@ -18,6 +18,7 @@
#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);
@ -29,8 +30,6 @@ static inline int __access_ok(const void __user *ptr, unsigned long size);
#define INLINE_COPY_USER
#include <asm-generic/uaccess.h>
static inline int __access_ok(const void __user *ptr, unsigned long size)
{
unsigned long addr = (unsigned long)ptr;
@ -62,5 +61,8 @@ do { \
barrier(); \
current->thread.segv_continue = NULL; \
} while (0)
#endif
#include <asm-generic/uaccess.h>
#endif

3
arch/um/kernel/mem.c
View File

@ -64,7 +64,8 @@ void __init arch_mm_preinit(void)
* to be turned on.
*/
brk_end = 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 = brk_end;
min_low_pfn = PFN_UP(__pa(uml_reserved));