On Mon, Sep 30, 2019 at 09:06:36AM -0700, Linus Torvalds wrote:
> Obviously, that can be a problem if you then need sshd in order to get
> into a headless box, so my patch fixes things for you too, but at
> least your box doesn't show the problem that Ahmed had, and the boot
> completing presumably means that you got more entropy from other disk
> IO being done by the rest of the boot.
Right, another observation I did was that when it would wait for
entropy, if I press random keys, it would get done faster because
apparently it would collect entropy from the key presses too.
> If you want to test my hacky "do /dev/urandom too", it was this one-liner:
>
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -2027,6 +2027,7 @@ urandom_read(struct file *file, char __user
> *buf, size_t nbytes, loff_t *ppos)
> static int maxwarn = 10;
> int ret;
>
> + if (!crng_ready()) try_to_generate_entropy();
> if (!crng_ready() && maxwarn > 0) {
> maxwarn--;
> if (__ratelimit(&urandom_warning))
>
> and that should get rid of the warnings.
So when I add this by hand and do git diff, it adds a second hunk:
---
diff --git a/drivers/char/random.c b/drivers/char/random.c
index c2f7de9dc543..93bad17bef98 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2027,6 +2027,7 @@ urandom_read(struct file *file, char __user *buf, size_t
nbytes, loff_t *ppos)
static int maxwarn = 10;
int ret;
+ if (!crng_ready()) try_to_generate_entropy();
if (!crng_ready() && maxwarn > 0) {
maxwarn--;
if (__ratelimit(&urandom_warning))
@@ -2520,4 +2521,4 @@ void add_bootloader_randomness(const void *buf, unsigned
int size)
else
add_device_randomness(buf, size);
}
-EXPORT_SYMBOL_GPL(add_bootloader_randomness);
\ No newline at end of file
+EXPORT_SYMBOL_GPL(add_bootloader_randomness);
---
and I kinda get what it is trying to tell me but this is new. And when I
do
$ xxd drivers/char/random.c
..
000125e0: 646f 6d6e 6573 7329 3b0a domness);.
there's a 0xa at the end so what's git really trying to tell me?
Anyway, that does get rid of the warns too.
> Doing something like the above to /dev/urandom is likely the right
> thing to do eventually, but I didn't want to mix up "we can perhaps
> improve the urandom situation too" with the basic "let's fix the boot
> problem". The urandom behavior change would be a separate thing.
So make it a separate patch and let's hammer on it during the next weeks
and see what happens?
> Also, talking about "future changes". Right now
> "try_to_generate_entropy()" is actually uninterruptible once it gets
> started. I think we should add a test for signal_pending() too, but it
Wouldn't that even increase its entropy, which would be a good thing?
> should generally complete really fairly quickly so I left it without
> one just to see if anybody even notices.
Right.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
