Date: Sun, 19 Jul 2015 16:05:23 +0000 (UTC) From: Mark Murray <markm@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r285690 - head/sys/dev/random Message-ID: <201507191605.t6JG5NV0038485@repo.freebsd.org>
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Author: markm Date: Sun Jul 19 16:05:23 2015 New Revision: 285690 URL: https://svnweb.freebsd.org/changeset/base/285690 Log: Optimise the buffer-size calculation. It was possible to get one block too many. Approved by: so (/dev/random blanket) Modified: head/sys/dev/random/randomdev.c Modified: head/sys/dev/random/randomdev.c ============================================================================== --- head/sys/dev/random/randomdev.c Sun Jul 19 15:44:51 2015 (r285689) +++ head/sys/dev/random/randomdev.c Sun Jul 19 16:05:23 2015 (r285690) @@ -64,6 +64,9 @@ __FBSDID("$FreeBSD$"); #define RANDOM_UNIT 0 +/* Return the largest number >= x that is a multiple of m */ +#define CEIL_TO_MULTIPLE(x, m) ((((x) + (m) - 1)/(m))*(m)) + static d_read_t randomdev_read; static d_write_t randomdev_write; static d_poll_t randomdev_poll; @@ -191,15 +194,15 @@ read_random_uio(struct uio *uio, bool no * which is what the underlying generator is expecting. * See the random_buf size requirements in the Yarrow/Fortuna code. */ - read_len += RANDOM_BLOCKSIZE; - read_len -= read_len % RANDOM_BLOCKSIZE; + read_len = CEIL_TO_MULTIPLE(read_len, RANDOM_BLOCKSIZE); + /* Work in chunks page-sized or less */ read_len = MIN(read_len, PAGE_SIZE); random_alg_context.ra_read(random_buf, read_len); c = MIN(uio->uio_resid, read_len); error = uiomove(random_buf, c, uio); total_read += c; } - if (total_read != uio->uio_resid && (error == ERESTART || error == EINTR) ) + if (total_read != uio->uio_resid && (error == ERESTART || error == EINTR)) /* Return partial read, not error. */ error = 0; } @@ -217,7 +220,7 @@ read_random_uio(struct uio *uio, bool no u_int read_random(void *random_buf, u_int len) { - u_int read_len, total_read, c; + u_int read_len; uint8_t local_buf[len + RANDOM_BLOCKSIZE]; KASSERT(random_buf != NULL, ("No suitable random buffer in %s", __func__)); @@ -228,22 +231,16 @@ read_random(void *random_buf, u_int len) /* XXX: FIX!! Next line as an atomic operation? */ read_rate += (len + sizeof(uint32_t))/sizeof(uint32_t); #endif - read_len = len; - /* - * Belt-and-braces. - * Round up the read length to a crypto block size multiple, - * which is what the underlying generator is expecting. - */ - read_len += RANDOM_BLOCKSIZE; - read_len -= read_len % RANDOM_BLOCKSIZE; - total_read = 0; - while (read_len) { - c = MIN(read_len, PAGE_SIZE); - random_alg_context.ra_read(&local_buf[total_read], c); - read_len -= c; - total_read += c; + if (len > 0) { + /* + * Belt-and-braces. + * Round up the read length to a crypto block size multiple, + * which is what the underlying generator is expecting. + */ + read_len = CEIL_TO_MULTIPLE(len, RANDOM_BLOCKSIZE); + random_alg_context.ra_read(local_buf, read_len); + memcpy(random_buf, local_buf, len); } - memcpy(random_buf, local_buf, len); } else len = 0; return (len);
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