On Fri, Jun 23, 2023 at 6:06 PM Kyle Tso <kyletso@xxxxxxxxxx> wrote: > > On Fri, Jun 23, 2023 at 3:51 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, Jun 22, 2023 at 11:04:23PM +0800, Kyle Tso wrote: > > > The buffer address used in sysfs_emit should be aligned to PAGE_SIZE. > > > > Why? Are you getting warnings about this? > > > > thanks, > > > > greg k-h > > Yes, here is the warning. > > [ 223.243123] invalid sysfs_emit: buf:00000000eda2d647 > [ 223.243197] WARNING: CPU: 4 PID: 8860 at fs/sysfs/file.c:735 > sysfs_emit+0xb0/0xc0 > [ 223.244335] CPU: 4 PID: 8860 Comm: cat > [ 223.244363] pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) > [ 223.244378] pc : sysfs_emit+0xb0/0xc0 > [ 223.244394] lr : sysfs_emit+0xac/0xc0 > ... > [ 223.244560] Call trace: > [ 223.244568] sysfs_emit+0xb0/0xc0 > [ 223.244582] select_usb_power_delivery_show+0x134/0x18c > [ 223.244626] dev_attr_show+0x38/0x74 > [ 223.244654] sysfs_kf_seq_show+0xb4/0x130 > [ 223.244668] kernfs_seq_show+0x44/0x54 > [ 223.244683] seq_read_iter+0x158/0x4ec > [ 223.244727] kernfs_fop_read_iter+0x68/0x1b0 > [ 223.244739] vfs_read+0x1d8/0x2b0 > [ 223.244775] ksys_read+0x78/0xe8 > > The warning comes from > https://elixir.bootlin.com/linux/v6.3.9/source/fs/sysfs/file.c#L734 > > if (WARN(!buf || offset_in_page(buf), "invalid sysfs_emit: buf:%p\n", buf)) > return 0; > > Kyle BTW, to print the buf address, it should use %pK ... Kyle
