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Kernel+LibC: Make get_dir_entries syscall retriable

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The get_dir_entries syscall failed if the serialized form of all the
directory entries together was too large to fit in its temporary buffer.

Now the kernel uses a fixed size buffer, that is flushed to an output
buffer when it is full. If this flushing operation fails because there
is not enough space available, the syscall will return -EINVAL. That
error code is then used in userspace as a signal to allocate a larger
buffer and retry the syscall.
This commit is contained in:
Mart G 2021-05-11 18:35:36 +02:00 • committed by Andreas Kling
parent c7b60164ed
commit b00cdf8ed8
3 changed files with 65 additions and 21 deletions
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31
Userland/Libraries/LibC/dirent.cpp
View file

@ -98,15 +98,30 @@ static int allocate_dirp_buffer(DIR* dirp)
}
size_t size_to_allocate = max(st.st_size, static_cast<off_t>(4096));
dirp->buffer = (char*)malloc(size_to_allocate);
ssize_t nread = syscall(SC_get_dir_entries, dirp->fd, dirp->buffer, size_to_allocate);
if (nread < 0) {
// uh-oh, the syscall returned an error
free(dirp->buffer);
dirp->buffer = nullptr;
return -nread;
if (!dirp->buffer)
return ENOMEM;
for (;;) {
ssize_t nread = syscall(SC_get_dir_entries, dirp->fd, dirp->buffer, size_to_allocate);
if (nread < 0) {
if (nread == -EINVAL) {
size_to_allocate *= 2;
char* new_buffer = (char*)realloc(dirp->buffer, size_to_allocate);
if (new_buffer) {
dirp->buffer = new_buffer;
continue;
} else {
nread = -ENOMEM;
}
}
// uh-oh, the syscall returned an error
free(dirp->buffer);
dirp->buffer = nullptr;
return -nread;
}
dirp->buffer_size = nread;
dirp->nextptr = dirp->buffer;
break;
}
dirp->buffer_size = nread;
dirp->nextptr = dirp->buffer;
return 0;
}