Linux's variant uses the syscall as intended. Redox's variant uses fpath to build a path to pass to mkdir from the file descriptor plus the file name, which isn't atomic due to the fpath lookup being subject to TOCTOU when paired with mkdir.
Init no longer changes the default scheme to initfs at any point in
time. And for sandboxing you would be switching scheme namespace, not
default scheme.
It should be possible to mix and match relibc version from before and
after this change without breaking exec, though I haven't tested it.
Calculating it earlier is a micro-optimization that doesn't seem like it
matters at all compared to all other costs of spawning a process. But at
the same time it makes things more fragile. And in fact bootstrap
actually passed the wrong value. It passed the
total_args_envs_auxvpointee_size that it computed rather than the
total_args_envs_size. While over-approximation doesn't cause UB, it
unnecessarily increases the amount of memory used after exec.
In addition pass &[&[u8]] rather than iterators for args and envs to
enable precomputing the total arg and env size. This also prevents you
from forgetting to pass a reversed iterator.
This commit fixes multiple issues with `fstatat` implementation for
Redox.
1. `flags` are now properly handled. The `flags` argument specifies AT_* flags
not O_* flags.
2. Open with O_PATH to avoid actually *opening* the file which may block
or cause permission issues.
3. Close the temporary file descriptor regardless of success of failure.
Signed-off-by: Anhad Singh <andypython@protonmail.com>
`posix_fallocate` ensures that a byte range in a file is allocated so
that subsequent writes don't fail. Unlike ftruncate, posix_fallocate
does not shrink files.
The Linux syscall fallocate is similar to posix_fallocate except with
far more control over how byte ranges are allocated (e.g. it supports
file holes and other features). This MR doesn't implement fallocate as
it requires syscall and redoxfs support.
Finally, I changed the flags for flock from usize to c_int. That matches
what we have in libc and also avoids some silly, needless type casting.
sourceturner