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Added mmap support for MAP_SHARED + MAP_ANONYMOUS

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mmap() with MAP_ANON | MAP_SHARED is used for creating shared
memory mappings that can be shared among a process and its descendants
(think fork())

Currently shmget/at creates shared virtual files on the fly and calls
do_mmap to create anonymous shared mappings. Now sys_mmap uses this
interface to create virtual files on the fly and call do_mmap on those
files.

In the future a common shared virtual file creation method should be
added and commonly used by both interfaces.
This commit is contained in:
Bahadir Balban
2009-05-31 15:55:16 +03:00
parent d0652fcb21
commit 2bd26ce684
2 changed files with 24 additions and 0 deletions
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2
tasks/mm0/src/fault.c
View File

@@ -697,6 +697,8 @@ int __do_page_fault(struct fault_data *fault)
*/ */
} else if ((vma_flags & VMA_SHARED)) { } else if ((vma_flags & VMA_SHARED)) {
file_offset = fault_to_file_offset(fault); file_offset = fault_to_file_offset(fault);
/* Don't traverse, just take the first object */
BUG_ON(!(vmo_link = vma_next_link(&vma->vm_obj_list, BUG_ON(!(vmo_link = vma_next_link(&vma->vm_obj_list,
&vma->vm_obj_list))); &vma->vm_obj_list)));

22
tasks/mm0/src/mmap.c
View File

@@ -17,6 +17,7 @@
#include <shm.h> #include <shm.h>
#include <syscalls.h> #include <syscalls.h>
#include <user.h> #include <user.h>
#include <shm.h>
struct vm_area *vma_new(unsigned long pfn_start, unsigned long npages, struct vm_area *vma_new(unsigned long pfn_start, unsigned long npages,
unsigned int flags, unsigned long file_offset) unsigned int flags, unsigned long file_offset)
@@ -370,6 +371,27 @@ void *__sys_mmap(struct tcb *task, void *start, size_t length, int prot,
if (prot & PROT_EXEC) if (prot & PROT_EXEC)
vmflags |= VM_EXEC; vmflags |= VM_EXEC;
/*
* Currently MAP_SHARED && MAP_ANONYMOUS mappings use the
* shm interface to create virtual shared memory files and
* do_mmap is internally called through this interface.
*
* FIXME: A common method of creating virtual shm files
* should be used by both sys_mmap and sys_shmget. With the
* current method, a task that guesses the shmid of an
* anonymous shared mmap can attach to it via shmat.
*/
if ((flags & MAP_ANONYMOUS) &&
(flags & MAP_SHARED)) {
/* Create a new shared memory virtual file */
l4id_t shmid = sys_shmget(IPC_PRIVATE,
page_align_up(length),
0);
/* Find and mmap the file via do_shmat() */
return sys_shmat(task, shmid, 0, 0);
}
return do_mmap(file, file_offset, task, (unsigned long)start, return do_mmap(file, file_offset, task, (unsigned long)start,
vmflags, __pfn(page_align_up(length))); vmflags, __pfn(page_align_up(length)));
} }