On 8/23/21 1:46 PM, Rob Herring wrote: > On Sun, Aug 22, 2021 at 11:01:15PM -0500, Frank Rowand wrote: >> Hi Marc, >> >> On 8/20/21 9:47 AM, Marc Zyngier wrote: >>> Trying to boot without SYSFS, but with OF_DYNAMIC quickly >>> results in a crash: >>> >>> [ 0.088460] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000070 >>> [...] >>> [ 0.103927] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc3 #4179 >>> [ 0.105810] Hardware name: linux,dummy-virt (DT) >>> [ 0.107147] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--) >>> [ 0.108876] pc : kernfs_find_and_get_ns+0x3c/0x7c >>> [ 0.110244] lr : kernfs_find_and_get_ns+0x3c/0x7c >>> [...] >>> [ 0.134087] Call trace: >>> [ 0.134800] kernfs_find_and_get_ns+0x3c/0x7c >>> [ 0.136054] safe_name+0x4c/0xd0 >>> [ 0.136994] __of_attach_node_sysfs+0xf8/0x124 >>> [ 0.138287] of_core_init+0x90/0xfc >>> [ 0.139296] driver_init+0x30/0x4c >>> [ 0.140283] kernel_init_freeable+0x160/0x1b8 >>> [ 0.141543] kernel_init+0x30/0x140 >>> [ 0.142561] ret_from_fork+0x10/0x18 >>> >>> While not having sysfs isn't a very common option these days, >>> it is still expected that such configuration would work. >>> >>> Paper over it by bailing out from __of_attach_node_sysfs() if >>> CONFIG_SYSFS isn't enabled. >> >> CONFIG_SYSFS should be automatically selected when CONFIG_OF_DYNAMIC >> is enabled, and it should not be possible to disable CONFIG_SYSFS >> in this case. > > That used to be true, but isn't now. OK. I agree with you, but when I investigated the original patch email I came to a different conclusion because of the way that I used make menuconfig to debug the situation. It is true when I start with a .config created from 'make qcom_defconfig', then select OF_UNITTEST, which is the only way I can see OF_DYNAMIC. It is the "if OF_UNITTEST" that means SYSFS can not be disabled. If I start with the .config that Marc supplied, then make menuconfig still does not show the OC_DYNAMIC option, but leaves it set since it was already set. In this case SYSFS remains disabled because OF_UNITTEST is also disabled. Using '/OF_DYNAMIC' from within make menuconfig, to get more info about OF_DYNAMIC tells me that the prompt for OF_DYNAMIC is visible if OF && OF_UNITTEST. This is due to the "if OF_UNITTEST" in line 58 of drivers/of/Kconfig in the OF_DYNAMIC specification. Thus I can't figure out how to use make menuconfig to set OF_DYNAMIC without setting OF_UNITTEST. I tried setting OF_UNITTEST, then setting OF_DYNAMIC, saving the changes, then another make menuconfig to disable OF_UNITTEST, which then has the side effect of unsetting OF_DYNAMIC. Would you accept a patch that removes the "if OF_UNITTEST" from the Kconfig entry for OF_DYNAMIC? -Frank > > Rob >
