On Thu, Feb 14, 2013 at 02:59:48PM +0100, Maxime Ripard wrote: > Hi Sascha, > > Le 14/02/2013 12:35, Sascha Hauer a écrit : > > On Thu, Feb 14, 2013 at 10:40:38AM +0100, Maxime Ripard wrote: > >> Hi Sascha, > >> > >> Le 13/02/2013 18:16, Sascha Hauer a écrit : > >>> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> > >>> --- > >>> common/memsize.c | 3 +++ > >>> 1 file changed, 3 insertions(+) > >>> > >>> diff --git a/common/memsize.c b/common/memsize.c > >>> index d149e41..ef6381b 100644 > >>> --- a/common/memsize.c > >>> +++ b/common/memsize.c > >>> @@ -33,6 +33,9 @@ > >>> * Check memory range for valid RAM. A simple memory test determines > >>> * the actually available RAM size between addresses `base' and > >>> * `base + maxsize'. > >>> + * > >>> + * This function modifies the RAM. Do not use it if you're running from > >>> + * the RAM you are going to detect! > >>> */ > >> > >> Actually, I don't see how it modifies the RAM, at least permanently. The > >> values it erase are backed up, and there's no concurrency at barebox > >> level, so we are sure that the value saved will still be the one that > >> would need to be backed up at the end of the function, right? > > > > Yes, it restores the values, but how do you make sure the function does > > not modify the instructions you are currently executing? You need bad > > luck to hit this, but sooner or later this will happen. > > Ah, yes, this would be nasty indeed. Is there a way to know the end > address of barebox into RAM ? or the address it has been loaded to and > the size of its binary, so that we can just check the part that doesn't > hold barebox? See include/asm-generic/sections.h. You have to avoid modifying everything between _text and __bss_stop. I haven't looked how exactly get_dram_size works. Normally this function would have to test every location at a power of 2, that would be: 1 2 4 ... 64MiB 128MiB It seems you have to make sure that your binary does not cross a power of 2 boundary, then you should be safe. 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 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
