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Add code that allows to create READONLY shared memory.

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This commit is contained in:
Enrico Fraccaroli (Galfurian)
2023-08-22 09:24:01 -04:00
parent c37fbf6f40
commit 08d87ea439
1 changed files with 10 additions and 7 deletions
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mentos/src/ipc/shm.c
+10 -7
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@@ -73,7 +73,6 @@ static inline shm_info_t *__shm_info_alloc(key_t key, size_t size, int shmflg)
// Allocate the memory.
uint32_t order = find_nearest_order_greater(0, size);
shm_info->shm_location = _alloc_pages(GFP_KERNEL, order);
pr_crit("page: %p\n", shm_info->shm_location);
// Return the shared memory structure.
return shm_info;
}
@@ -223,6 +222,7 @@ void *sys_shmat(int shmid, const void *shmaddr, int shmflg)
shm_info_t *shm_info = NULL;
task_struct *task = NULL;
uint32_t vm_start, phy_start;
uint32_t flags = MM_RW | MM_PRESENT | MM_USER | MM_UPDADDR;
// The id is less than zero.
if (shmid < 0) {
@@ -238,11 +238,14 @@ void *sys_shmat(int shmid, const void *shmaddr, int shmflg)
}
// Check if the shared memory exists for the given key, but the calling
// process does not have permission to access the set.
if ((shmflg & SHM_RDONLY) && !ipc_valid_permissions(O_RDONLY, &shm_info->shmid.shm_perm)) {
pr_err("The shared memory exists for the given key, but the calling process does not have permission to access the set.\n");
return (void *)-EACCES;
}
if (!ipc_valid_permissions(O_RDWR, &shm_info->shmid.shm_perm)) {
if (shmflg & SHM_RDONLY) {
if (!ipc_valid_permissions(O_RDONLY, &shm_info->shmid.shm_perm)) {
pr_err("The shared memory exists for the given key, but the calling process does not have permission to access the set.\n");
return (void *)-EACCES;
}
// Remove the read-write flag.
flags = bitmask_clear(flags, MM_RW);
} else if (!ipc_valid_permissions(O_RDWR, &shm_info->shmid.shm_perm)) {
pr_err("The shared memory exists for the given key, but the calling process does not have permission to access the set.\n");
return (void *)-EACCES;
}
@@ -261,7 +264,7 @@ void *sys_shmat(int shmid, const void *shmaddr, int shmflg)
vm_start,
phy_start,
shm_info->shmid.shm_segsz,
MM_RW | MM_PRESENT | MM_USER | MM_UPDADDR);
flags);
return (void *)vm_start;
}