| Message ID | 1274599824-17530-1-git-send-email-vapier@gentoo.org |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, 2010-05-23 at 03:30 -0400, Mike Frysinger wrote: > From: Bernd Schmidt <bernds_cb1@t-online.de> > > Currently, romfs XIP doesn't work in flash memory (the kernel crashes > with a null pointer dereference). The problem is that the mtd physmap > driver isn't setting up a get_unmapped_area pointer for the mtd > partitions it creates. > > Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> > Signed-off-by: Mike Frysinger <vapier@gentoo.org> Pushed both to my l2-mtd-2.6.git / dunno.
On Sat, 2010-06-12 at 17:26 +0300, Artem Bityutskiy wrote: > On Sun, 2010-05-23 at 03:30 -0400, Mike Frysinger wrote: > > From: Bernd Schmidt <bernds_cb1@t-online.de> > > > > Currently, romfs XIP doesn't work in flash memory (the kernel crashes > > with a null pointer dereference). The problem is that the mtd physmap > > driver isn't setting up a get_unmapped_area pointer for the mtd > > partitions it creates. > > > > Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> > > Signed-off-by: Mike Frysinger <vapier@gentoo.org> > > Pushed both to my l2-mtd-2.6.git / dunno. I'm confused by the second patch -- isn't this done in add_mtd_device() already, according to the device type? You're setting mtd_bdi_ro_mappable indiscriminately for all types of devices. For flash devices, that can be an issue -- if you schedule a userspace process while the kernel is writing to the flash, for example. If you want to allow XIP of writable flash devices, there's more to it than this.
On Wed, Aug 4, 2010 at 05:33, David Woodhouse wrote: > On Sat, 2010-06-12 at 17:26 +0300, Artem Bityutskiy wrote: >> On Sun, 2010-05-23 at 03:30 -0400, Mike Frysinger wrote: >> > Currently, romfs XIP doesn't work in flash memory (the kernel crashes >> > with a null pointer dereference). The problem is that the mtd physmap >> > driver isn't setting up a get_unmapped_area pointer for the mtd >> > partitions it creates. >> >> Pushed both to my l2-mtd-2.6.git / dunno. > > I'm confused by the second patch -- isn't this done in add_mtd_device() > already, according to the device type? > > You're setting mtd_bdi_ro_mappable indiscriminately for all types of > devices. For flash devices, that can be an issue -- if you schedule a > userspace process while the kernel is writing to the flash, for example. > > If you want to allow XIP of writable flash devices, there's more to it > than this. can you can safely do XIP on writable flash devices ? with nommu, you certainly cant. plus, it is only possible with certain filesystems right ? like ROMFS ? and that's already r/o ... if we delve a bit, what you're referring to is only possible i think if this change is merged (we posted this back in Jan w/no feedback): mtd-physmap: add support users can assign the probe type in board files otherwise, there's no way of declaring a physmap of a parallel nor flash and having it end up with read-only capabilities ... -mike
On Sat, 2010-08-07 at 19:26 -0400, Mike Frysinger wrote: > can you can safely do XIP on writable flash devices ? with nommu, you > certainly cant. plus, it is only possible with certain filesystems > right ? like ROMFS ? and that's already r/o ... As long as you don't allow any process to run that has part of the flash chip mapped, you ought to be able to do it. You might not want to use XIP for *everything* in that case -- but you could imagine a situation where your critical processes are in RAM but optional extra apps are XIP. It's hard to implement though, because you'd have to keep track of which processes need to be blocked and have some way to ensure it happens. > if we delve a bit, what you're referring to is only possible i think > if this change is merged (we posted this back in Jan w/no feedback): > mtd-physmap: add support users can assign the probe type in board files > > otherwise, there's no way of declaring a physmap of a parallel nor > flash and having it end up with read-only capabilities ... Hm, yeah -- that one looks sane enough. I can merge that, although part 1 of that 2-part series I still object to because I don't *want* different architectures to use different config symbols for the same thing. Driver code shouldn't have to cope with that.
On Sun, Aug 8, 2010 at 07:33, David Woodhouse wrote: > On Sat, 2010-08-07 at 19:26 -0400, Mike Frysinger wrote: >> if we delve a bit, what you're referring to is only possible i think >> if this change is merged (we posted this back in Jan w/no feedback): >> mtd-physmap: add support users can assign the probe type in board files >> >> otherwise, there's no way of declaring a physmap of a parallel nor >> flash and having it end up with read-only capabilities ... > > Hm, yeah -- that one looks sane enough. I can merge that, although part > 1 of that 2-part series I still object to because I don't *want* > different architectures to use different config symbols for the same > thing. Driver code shouldn't have to cope with that. the two arent really dependent on each other. i'll probably just change the Blackfin code to also enable the XIP_KERNEL symbol and forget about the whole damned mess. -mike
On Sat, 2010-06-12 at 17:26 +0300, Artem Bityutskiy wrote: > On Sun, 2010-05-23 at 03:30 -0400, Mike Frysinger wrote: > > From: Bernd Schmidt <bernds_cb1@t-online.de> > > > > Currently, romfs XIP doesn't work in flash memory (the kernel crashes > > with a null pointer dereference). The problem is that the mtd physmap > > driver isn't setting up a get_unmapped_area pointer for the mtd > > partitions it creates. > > > > Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> > > Signed-off-by: Mike Frysinger <vapier@gentoo.org> > > Pushed both to my l2-mtd-2.6.git / dunno. dwmw2 did not take these 2 patches, so I'm dropping them from my l2 tree as well. Artem.
diff --git a/drivers/mtd/maps/physmap.c b/drivers/mtd/maps/physmap.c index 09d89ff..370da18 100644 --- a/drivers/mtd/maps/physmap.c +++ b/drivers/mtd/maps/physmap.c @@ -72,6 +72,20 @@ static int physmap_flash_remove(struct platform_device *dev) return 0; } +/* + * Allow NOMMU mmap() to directly map the device (if not NULL) + * - return the address to which the offset maps + * - return -ENOSYS to indicate refusal to do the mapping + */ +static unsigned long physmap_unmapped_area(struct mtd_info *mtd, + unsigned long len, + unsigned long offset, + unsigned long flags) +{ + struct map_info *map = mtd->priv; + return (unsigned long) map->virt + offset; +} + static const char *rom_probe_types[] = { "cfi_probe", "jedec_probe", @@ -149,6 +163,8 @@ static int physmap_flash_probe(struct platform_device *dev) } else { devices_found++; } + if (info->mtd[i]->get_unmapped_area == NULL) + info->mtd[i]->get_unmapped_area = physmap_unmapped_area; info->mtd[i]->owner = THIS_MODULE; info->mtd[i]->dev.parent = &dev->dev; }