On 11/6/24 23:49, Noah Goldstein wrote:
On Wed, Nov 6, 2024 at 3:30 PM Noah Goldstein <goldstein....@gmail.com> wrote:
On Wed, Nov 6, 2024 at 3:10 PM Richard Henderson
<richard.hender...@linaro.org> wrote:
On 11/6/24 18:13, Noah Goldstein wrote:
Question about impl regarding handling of `-execfd` with/without a program name.
1) `-execfd` + program name ie: `qemu -execfd <some_fd> ls -a`.
2) `-execfd` without program name i.e: `qemu -execfd <some_fd> -a`.
Do you want to allow both of these? If you want to allow (1), what should
we use for `argv[0]`/`exec_path`. The program pass ("ls") or
`readlink(<some_fd>)`?
The canonical response is, examine the kernel source.
We're not implementing this in a vacuum, you're replicating execveat(2).
I suspect the answer is (1), to be compared with
syscall(__NR_execveat, some_fd, "", &["ls", "-a"], env, AT_EMPTY_PATH);
Err, I think the reference for '-execfd' is `fexecve`:
https://man7.org/linux/man-pages/man3/fexecve.3.html
Which doesn't take a path. So I guess we just interpret the "ls" as
argv[0] but not
as "exec_path".
One more point, what should the behavior be if we have
AT_EXECFD from binfmt-misc?
You mean precedence of AT_EXECFD vs the command-line option?
Arbitrary, since it would be a usage error to have both. You'd have to do something silly
with the binfmt-misc rule for that to happen.
Perhaps
static int execfd = -1;
// option processing
// main
if (execfd < 0) {
errno = 0;
execfd = qemu_getauxval(AT_EXECFD);
if (errno != 0) {
execfd = open(...);
}
}
just because that's a simple change to what's currently present.
r~
