Re: [PATCH, RFC] random: introduce getrandom(2) system call

SYNOPSIS
	#include <linux/random.h>

	int getrandom(void *buf, size_t buflen, unsigned int flags);

I certainly like the idea of getting entropy without having to worry
about fds.

	If the GRND_RANDOM flags bit is not set, then the /dev/raundom

(raundom typo)

RETURN VALUE
       On success, the number of bytes that was returned is returned.

The description talks about filling the buffer, maybe say 'the number of
bytes filled is returned'?  

+DECLARE_COMPLETION(urandom_initialized);

static?

+SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
+		unsigned int, flags)
+{
+	int r;
+

Michael Kerrisk wants you to return -EINVAL on unknown flags :)

http://lwn.net/Articles/588444/

+	if (count > 256)
+		return -EINVAL;

I'd vote for not having the limit.  It seems easy enough to iterate over
the buffer.  We'd need to clamp the count to ssize_t, though.

+	if (flags & GRND_RANDOM) {
+		return _random_read(!(flags & GRND_BLOCK), buf, count);
+	}

Do we want it to block by default and have the flag be _NONBLOCK?  Feels
more.. familiar.

+	if (flags & GRND_BLOCK) {
+		r = wait_for_completion_interruptible(&urandom_initialized);
+		if (r)
+			return r;

I can *never* remember the rules for -ERESTARTSYS.  The syscall callers
take care of this?

+	return urandom_read(NULL, buf, count, NULL);

I wonder if we want to refactor the entry points a bit more instead of
directly calling the device read functions.  get_random_bytes() and
urandom_read() both have their own uninitialied use warning message and
tracing.  Does the syscall want its own little extraction function as
well?

- z