Re: [PATCH 04/11] include support for a simple pseudo number generator

Re: [PATCH 04/11] include support for a simple pseudo number generator

['Sascha Hauer']

On Thu, Jun 17, 2010 at 02:26:58PM +0100, Andy Pont wrote:
> Sascha Hauer wrote...
> 
> > +#define RAND_MAX 32767
> > +
> > +/* return a pseudo-random integer in the range [0, RAND_MAX] */
> > +unsigned int rand(void);
> 
> *Snip*
> 
> > +unsigned int rand(void)
> > +{
> > +	random_seed = random_seed * 1103515245 + 12345;
> > +	return (random_seed / 65536) % 32768;
> > +}
> 
> The return value on this function seems wrong as it will always return a
> value between 0 and 32767 irrespective of what RAND_MAX is set to which
> doesn't agree with the comment on the function prototype.

Well the way the rand function is implemented it is not suitable for
RAND_MAX > 32767. Ok, changed it for the attached patch.

I originally thought there would be discussion about the pros and cons
of random ethernet addresses, but about not this patch ;)

Sascha

commit dcd5248b7dceb918c5c5d9b045893421ddc6c112
Author: Sascha Hauer <s.hauer@pengutronix.de>
Date:   Fri Jun 11 14:10:36 2010 +0200

    include support for a simple pseudo number generator
    
    Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

diff --git a/include/net.h b/include/net.h
index 8db83d8..709e76c 100644
--- a/include/net.h
+++ b/include/net.h
@@ -16,6 +16,7 @@
 #include <linux/types.h>
 #include <param.h>
 #include <malloc.h>
+#include <stdlib.h>
 #include <asm/byteorder.h>	/* for nton* / ntoh* stuff */
 
 
diff --git a/include/stdlib.h b/include/stdlib.h
new file mode 100644
index 0000000..dc72013
--- /dev/null
+++ b/include/stdlib.h
@@ -0,0 +1,16 @@
+#ifndef __STDLIB_H
+#define __STDLIB_H
+
+#define RAND_MAX 32767
+
+/* return a pseudo-random integer in the range [0, RAND_MAX] */
+unsigned int rand(void);
+
+/* set the seed for rand () */
+void srand(unsigned int seed);
+
+/* fill a buffer with pseudo-random data */
+void get_random_bytes(char *buf, int len);
+
+
+#endif /* __STDLIB_H */
diff --git a/lib/Makefile b/lib/Makefile
index b072fb6..4a33aaa 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
 obj-y			+= glob.o
 obj-y			+= notifier.o
 obj-y			+= copy_file.o
+obj-y			+= random.o
 obj-y			+= lzo/
 obj-$(CONFIG_LZO_DECOMPRESS)		+= decompress_unlzo.o
 obj-$(CONFIG_PROCESS_ESCAPE_SEQUENCE)	+= process_escape_sequence.o
diff --git a/lib/random.c b/lib/random.c
new file mode 100644
index 0000000..352d6bf
--- /dev/null
+++ b/lib/random.c
@@ -0,0 +1,26 @@
+#include <common.h>
+#include <stdlib.h>
+
+static unsigned int random_seed;
+
+#if RAND_MAX > 32767
+#error this rand implementation is for RAND_MAX < 32678 only.
+#endif
+
+unsigned int rand(void)
+{
+	random_seed = random_seed * 1103515245 + 12345;
+	return (random_seed / 65536) % (RAND_MAX + 1);
+}
+
+void srand(unsigned int seed)
+{
+	random_seed = seed;
+}
+
+void get_random_bytes(char *buf, int len)
+{
+	while (len--)
+		*buf++ = rand() % 256;
+}
+
-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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More patches

[Sascha Hauer]

Hi all,

Here are some more patches, most notably the the possibility to merge
the default environment together from different directories. We can then
introduce a generic default environment which can be used from multiple
boards. Each board can make specific additions to this default environment.

Also, maybe this is controversal, the network stack now generates a random
MAC address if now valid address is found.

Sascha

The following changes since commit 52f760cd61e3f6ca6deb8e5c47eef168b598a674:

  dhcp: do not call net_unregister if net_udp_new failed (2010-06-14 09:39:29 +0200)

are available in the git repository at:
  git://git.pengutronix.de/git/barebox.git pu

Sascha Hauer (11):
      pcm037: Add MMU support
      bootu: Allow passing in devices as parameter
      Allow to merge default environment from more than one directory
      include support for a simple pseudo number generator
      net: implement random_ether_addr
      net: use a random mac address if the current device does not have one
      add a generic default environment
      pcm038: use generic default env
      pcm043: use generic default env
      pcm037: use generic default env
      pca100: use generic default env

 Makefile                                           |   15 ---
 arch/arm/configs/pca100_defconfig                  |    2 +-
 arch/arm/configs/pcm037_defconfig                  |    2 +-
 arch/arm/configs/pcm038_defconfig                  |    2 +-
 arch/arm/configs/pcm043_defconfig                  |    2 +-
 arch/arm/lib/armlinux.c                            |   10 ++-
 arch/arm/mach-imx/Kconfig                          |    2 +
 board/pcm037/env/bin/boot                          |   47 ---------
 board/pcm037/env/bin/init                          |   37 -------
 board/pcm037/env/bin/update_root                   |   16 ---
 board/pcm037/env/config                            |   62 ++++++++---
 board/pcm037/pcm037.c                              |   31 ++++++
 board/pcm038/env/bin/_update                       |   36 -------
 board/pcm038/env/bin/boot                          |   47 ---------
 board/pcm038/env/bin/hush_hack                     |    1 -
 board/pcm038/env/bin/init                          |   37 -------
 board/pcm038/env/bin/update_kernel                 |   15 ---
 board/pcm038/env/bin/update_root                   |   16 ---
 board/pcm038/env/config                            |   62 ++++++++---
 board/pcm043/env/bin/_update                       |   36 -------
 board/pcm043/env/bin/boot                          |   47 ---------
 board/pcm043/env/bin/hush_hack                     |    1 -
 board/pcm043/env/bin/update_kernel                 |   15 ---
 board/pcm043/env/config                            |   65 +++++++++---
 board/phycard-i.MX27/env/bin/_update               |   36 -------
 board/phycard-i.MX27/env/bin/boot                  |   40 -------
 board/phycard-i.MX27/env/bin/hush_hack             |    1 -
 board/phycard-i.MX27/env/bin/init                  |   37 -------
 board/phycard-i.MX27/env/bin/update_kernel         |   15 ---
 board/phycard-i.MX27/env/bin/update_root           |   16 ---
 board/phycard-i.MX27/env/config                    |   57 ++++++++---
 common/Kconfig                                     |    4 +-
 common/Makefile                                    |    6 +-
 {board/pcm037/env => defaultenv}/bin/_update       |    5 +-
 defaultenv/bin/boot                                |  110 ++++++++++++++++++++
 {board/pcm037/env => defaultenv}/bin/hush_hack     |    0
 {board/pcm043/env => defaultenv}/bin/init          |   11 +--
 {board/pcm037/env => defaultenv}/bin/update_kernel |    2 +-
 .../update_root => defaultenv/bin/update_rootfs    |    4 +-
 include/net.h                                      |   17 +++
 include/random.h                                   |    7 ++
 lib/Makefile                                       |    1 +
 lib/random.c                                       |   22 ++++
 net/net.c                                          |   11 ++-
 scripts/genenv                                     |   17 +++
 45 files changed, 424 insertions(+), 601 deletions(-)
 delete mode 100644 board/pcm037/env/bin/boot
 delete mode 100644 board/pcm037/env/bin/init
 delete mode 100644 board/pcm037/env/bin/update_root
 delete mode 100644 board/pcm038/env/bin/_update
 delete mode 100644 board/pcm038/env/bin/boot
 delete mode 100644 board/pcm038/env/bin/hush_hack
 delete mode 100644 board/pcm038/env/bin/init
 delete mode 100644 board/pcm038/env/bin/update_kernel
 delete mode 100644 board/pcm038/env/bin/update_root
 delete mode 100644 board/pcm043/env/bin/_update
 delete mode 100644 board/pcm043/env/bin/boot
 delete mode 100644 board/pcm043/env/bin/hush_hack
 delete mode 100644 board/pcm043/env/bin/update_kernel
 delete mode 100644 board/phycard-i.MX27/env/bin/_update
 delete mode 100644 board/phycard-i.MX27/env/bin/boot
 delete mode 100644 board/phycard-i.MX27/env/bin/hush_hack
 delete mode 100644 board/phycard-i.MX27/env/bin/init
 delete mode 100644 board/phycard-i.MX27/env/bin/update_kernel
 delete mode 100644 board/phycard-i.MX27/env/bin/update_root
 rename {board/pcm037/env => defaultenv}/bin/_update (86%)
 create mode 100644 defaultenv/bin/boot
 rename {board/pcm037/env => defaultenv}/bin/hush_hack (100%)
 rename {board/pcm043/env => defaultenv}/bin/init (59%)
 rename {board/pcm037/env => defaultenv}/bin/update_kernel (91%)
 rename board/pcm043/env/bin/update_root => defaultenv/bin/update_rootfs (91%)
 create mode 100644 include/random.h
 create mode 100644 lib/random.c
 create mode 100755 scripts/genenv

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[PATCH 04/11] include support for a simple pseudo number generator

[Sascha Hauer]

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 include/random.h |    7 +++++++
 lib/Makefile     |    1 +
 lib/random.c     |   22 ++++++++++++++++++++++
 3 files changed, 30 insertions(+), 0 deletions(-)
 create mode 100644 include/random.h
 create mode 100644 lib/random.c

diff --git a/include/random.h b/include/random.h
new file mode 100644
index 0000000..29911d8
--- /dev/null
+++ b/include/random.h
@@ -0,0 +1,7 @@
+#ifndef __RANDOM_H
+#define __RANDOM_H
+
+void get_random_bytes(char *buf, int len);
+void srand(unsigned int);
+
+#endif /* __RANDOM_H */
diff --git a/lib/Makefile b/lib/Makefile
index b072fb6..4a33aaa 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
 obj-y			+= glob.o
 obj-y			+= notifier.o
 obj-y			+= copy_file.o
+obj-y			+= random.o
 obj-y			+= lzo/
 obj-$(CONFIG_LZO_DECOMPRESS)		+= decompress_unlzo.o
 obj-$(CONFIG_PROCESS_ESCAPE_SEQUENCE)	+= process_escape_sequence.o
diff --git a/lib/random.c b/lib/random.c
new file mode 100644
index 0000000..25315e7
--- /dev/null
+++ b/lib/random.c
@@ -0,0 +1,22 @@
+#include <common.h>
+#include <random.h>
+
+static int random_seed;
+
+static unsigned char rand(void)
+{
+	random_seed = random_seed * 1103515245 + 12345;
+	return (unsigned char)(random_seed / 65536) % 256;
+}
+
+void srand(unsigned int seed)
+{
+	random_seed = seed;
+}
+
+void get_random_bytes(char *buf, int len)
+{
+	while (len--)
+		*buf++ = rand();
+}
+
-- 
1.7.1


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Re: [PATCH 04/11] include support for a simple pseudo number generator

[Peter Korsgaard]

>>>>> "Sascha" == Sascha Hauer <s.hauer@pengutronix.de> writes:

 Sascha> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
 Sascha> ---
 Sascha>  include/random.h |    7 +++++++
 Sascha>  lib/Makefile     |    1 +
 Sascha>  lib/random.c     |   22 ++++++++++++++++++++++
 Sascha>  3 files changed, 30 insertions(+), 0 deletions(-)
 Sascha>  create mode 100644 include/random.h
 Sascha>  create mode 100644 lib/random.c

 Sascha> diff --git a/lib/random.c b/lib/random.c
 Sascha> new file mode 100644
 Sascha> index 0000000..25315e7
 Sascha> --- /dev/null
 Sascha> +++ b/lib/random.c
 Sascha> @@ -0,0 +1,22 @@
 Sascha> +#include <common.h>
 Sascha> +#include <random.h>
 Sascha> +
 Sascha> +static int random_seed;
 Sascha> +
 Sascha> +static unsigned char rand(void)
 Sascha> +{
 Sascha> +	random_seed = random_seed * 1103515245 + 12345;
 Sascha> +	return (unsigned char)(random_seed / 65536) % 256;
 Sascha> +}

Any reason to not make this public and return int instead similar to
rand(3)?

We could presumably simply do:

#define RAND_MAX 255

And to be completely correct, these prototypes should be in stdlib.h
instead.

-- 
Bye, Peter Korsgaard

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Re: [PATCH 04/11] include support for a simple pseudo number generator

[Sascha Hauer]

Hi Peter,

On Tue, Jun 15, 2010 at 11:39:39AM +0200, Peter Korsgaard wrote:
> >>>>> "Sascha" == Sascha Hauer <s.hauer@pengutronix.de> writes:
> 
>  Sascha> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>  Sascha> ---
>  Sascha>  include/random.h |    7 +++++++
>  Sascha>  lib/Makefile     |    1 +
>  Sascha>  lib/random.c     |   22 ++++++++++++++++++++++
>  Sascha>  3 files changed, 30 insertions(+), 0 deletions(-)
>  Sascha>  create mode 100644 include/random.h
>  Sascha>  create mode 100644 lib/random.c
> 
>  Sascha> diff --git a/lib/random.c b/lib/random.c
>  Sascha> new file mode 100644
>  Sascha> index 0000000..25315e7
>  Sascha> --- /dev/null
>  Sascha> +++ b/lib/random.c
>  Sascha> @@ -0,0 +1,22 @@
>  Sascha> +#include <common.h>
>  Sascha> +#include <random.h>
>  Sascha> +
>  Sascha> +static int random_seed;
>  Sascha> +
>  Sascha> +static unsigned char rand(void)
>  Sascha> +{
>  Sascha> +	random_seed = random_seed * 1103515245 + 12345;
>  Sascha> +	return (unsigned char)(random_seed / 65536) % 256;
>  Sascha> +}
> 
> Any reason to not make this public and return int instead similar to
> rand(3)?

The reason was that I did not need rand but get_random_bytes and I
wasn't aware that rand() is that close to the corresponding libc
function.

> 
> We could presumably simply do:
> 
> #define RAND_MAX 255
> 
> And to be completely correct, these prototypes should be in stdlib.h
> instead.

Ok, will do.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH 04/11] include support for a simple pseudo number generator

[Sascha Hauer]

Here is an updated version. I have put get_random_bytes() into
stdlib.h aswell, though of course this is no stdlib function.

Sascha

[PATCH 04/24] include support for a simple pseudo number generator

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 include/net.h    |    1 +
 include/stdlib.h |   16 ++++++++++++++++
 lib/Makefile     |    1 +
 lib/random.c     |   22 ++++++++++++++++++++++
 4 files changed, 40 insertions(+), 0 deletions(-)
 create mode 100644 include/stdlib.h
 create mode 100644 lib/random.c

diff --git a/include/net.h b/include/net.h
index 8db83d8..709e76c 100644
--- a/include/net.h
+++ b/include/net.h
@@ -16,6 +16,7 @@
 #include <linux/types.h>
 #include <param.h>
 #include <malloc.h>
+#include <stdlib.h>
 #include <asm/byteorder.h>	/* for nton* / ntoh* stuff */
 
 
diff --git a/include/stdlib.h b/include/stdlib.h
new file mode 100644
index 0000000..dc72013
--- /dev/null
+++ b/include/stdlib.h
@@ -0,0 +1,16 @@
+#ifndef __STDLIB_H
+#define __STDLIB_H
+
+#define RAND_MAX 32767
+
+/* return a pseudo-random integer in the range [0, RAND_MAX] */
+unsigned int rand(void);
+
+/* set the seed for rand () */
+void srand(unsigned int seed);
+
+/* fill a buffer with pseudo-random data */
+void get_random_bytes(char *buf, int len);
+
+
+#endif /* __STDLIB_H */
diff --git a/lib/Makefile b/lib/Makefile
index b072fb6..4a33aaa 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
 obj-y			+= glob.o
 obj-y			+= notifier.o
 obj-y			+= copy_file.o
+obj-y			+= random.o
 obj-y			+= lzo/
 obj-$(CONFIG_LZO_DECOMPRESS)		+= decompress_unlzo.o
 obj-$(CONFIG_PROCESS_ESCAPE_SEQUENCE)	+= process_escape_sequence.o
diff --git a/lib/random.c b/lib/random.c
new file mode 100644
index 0000000..48c923f
--- /dev/null
+++ b/lib/random.c
@@ -0,0 +1,22 @@
+#include <common.h>
+#include <stdlib.h>
+
+static unsigned int random_seed;
+
+unsigned int rand(void)
+{
+	random_seed = random_seed * 1103515245 + 12345;
+	return (random_seed / 65536) % 32768;
+}
+
+void srand(unsigned int seed)
+{
+	random_seed = seed;
+}
+
+void get_random_bytes(char *buf, int len)
+{
+	while (len--)
+		*buf++ = rand() % 256;
+}
+
-- 
1.7.1


-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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RE: [PATCH 04/11] include support for a simple pseudo number generator

[Andy Pont]

Sascha Hauer wrote...

> +#define RAND_MAX 32767
> +
> +/* return a pseudo-random integer in the range [0, RAND_MAX] */
> +unsigned int rand(void);

*Snip*

> +unsigned int rand(void)
> +{
> +	random_seed = random_seed * 1103515245 + 12345;
> +	return (random_seed / 65536) % 32768;
> +}

The return value on this function seems wrong as it will always return a
value between 0 and 32767 irrespective of what RAND_MAX is set to which
doesn't agree with the comment on the function prototype.

Although it may just be me being dim as my hayfever is driving me mad today
:-)

A.



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Re: [PATCH 04/11] include support for a simple pseudo number generator

[Peter Korsgaard]

>>>>> "Sascha" == Sascha Hauer <s.hauer@pengutronix.de> writes:

 Sascha> Here is an updated version. I have put get_random_bytes() into
 Sascha> stdlib.h aswell, though of course this is no stdlib function.

 Sascha> Sascha

Looks good to me, thanks

Acked-by: Peter Korsgaard <jacmet@sunsite.dk>

-- 
Bye, Peter Korsgaard

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