Re: [RFC 2/3] x86: Switch all C consumers of kernel_stack to this_cpu_sp0

[Denys Vlasenko]

On 02/27/2015 01:07 AM, Andy Lutomirski wrote:
> This will make modifying the semantics of kernel_stack easier.
> 
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/thread_info.h | 3 +--
>  arch/x86/kernel/traps.c            | 2 +-
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index e82e95abc92b..92549053d86d 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -163,8 +163,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack);
>  static inline struct thread_info *current_thread_info(void)
>  {
>  	struct thread_info *ti;
> -	ti = (void *)(this_cpu_read_stable(kernel_stack) +
> -		      KERNEL_STACK_OFFSET - THREAD_SIZE);
> +	ti = (void *)(this_cpu_sp0() - THREAD_SIZE);
>  	return ti;
>  }

This makes modpost unhappy, it says these modules need init_tss symbol
to be visible to them:

  Building modules, stage 2.
  MODPOST 2556 modules
ERROR: "init_tss" [sound/usb/usx2y/snd-usb-usx2y.ko] undefined!
ERROR: "init_tss" [sound/pci/hda/snd-hda-codec.ko] undefined!
ERROR: "init_tss" [sound/pci/emu10k1/snd-emu10k1.ko] undefined!
ERROR: "init_tss" [sound/core/snd-pcm.ko] undefined!
ERROR: "init_tss" [sound/core/snd-hwdep.ko] undefined!
ERROR: "init_tss" [sound/core/seq/snd-seq.ko] undefined!
ERROR: "init_tss" [sound/core/oss/snd-pcm-oss.ko] undefined!
ERROR: "init_tss" [net/sunrpc/sunrpc.ko] undefined!
ERROR: "init_tss" [net/sctp/sctp.ko] undefined!
ERROR: "init_tss" [net/rds/rds_tcp.ko] undefined!
ERROR: "init_tss" [net/core/pktgen.ko] undefined!
ERROR: "init_tss" [net/batman-adv/batman-adv.ko] undefined!
ERROR: "init_tss" [net/9p/9pnet.ko] undefined!
ERROR: "init_tss" [fs/reiserfs/reiserfs.ko] undefined!
ERROR: "init_tss" [fs/ocfs2/dlmfs/ocfs2_dlmfs.ko] undefined!
ERROR: "init_tss" [fs/ocfs2/cluster/ocfs2_nodemanager.ko] undefined!
ERROR: "init_tss" [fs/nfsd/nfsd.ko] undefined!
ERROR: "init_tss" [fs/fscache/fscache.ko] undefined!
ERROR: "init_tss" [fs/fat/fat.ko] undefined!
ERROR: "init_tss" [fs/ecryptfs/ecryptfs.ko] undefined!
ERROR: "init_tss" [fs/cachefiles/cachefiles.ko] undefined!
ERROR: "init_tss" [fs/btrfs/btrfs.ko] undefined!
ERROR: "init_tss" [fs/9p/9p.ko] undefined!
ERROR: "init_tss" [drivers/xen/xen-privcmd.ko] undefined!
ERROR: "init_tss" [drivers/vhost/vhost.ko] undefined!
ERROR: "init_tss" [drivers/tty/n_hdlc.ko] undefined!
ERROR: "init_tss" [drivers/target/target_core_file.ko] undefined!
ERROR: "init_tss" [drivers/scsi/pmcraid.ko] undefined!
ERROR: "init_tss" [drivers/scsi/lpfc/lpfc.ko] undefined!
ERROR: "init_tss" [drivers/parport/parport.ko] undefined!
ERROR: "init_tss" [drivers/net/ethernet/broadcom/tg3.ko] undefined!
ERROR: "init_tss" [drivers/net/bonding/bonding.ko] undefined!
ERROR: "init_tss" [drivers/mtd/mtd.ko] undefined!
ERROR: "init_tss" [drivers/misc/vmw_vmci/vmw_vmci.ko] undefined!
ERROR: "init_tss" [drivers/media/v4l2-core/videodev.ko] undefined!
ERROR: "init_tss" [drivers/media/usb/uvc/uvcvideo.ko] undefined!
ERROR: "init_tss" [drivers/media/pci/saa7134/saa7134.ko] undefined!
ERROR: "init_tss" [drivers/media/pci/ivtv/ivtvfb.ko] undefined!
ERROR: "init_tss" [drivers/media/i2c/vpx3220.ko] undefined!
ERROR: "init_tss" [drivers/md/bcache/bcache.ko] undefined!
ERROR: "init_tss" [drivers/isdn/i4l/isdn.ko] undefined!
ERROR: "init_tss" [drivers/input/misc/uinput.ko] undefined!
ERROR: "init_tss" [drivers/infiniband/hw/qib/ib_qib.ko] undefined!
ERROR: "init_tss" [drivers/infiniband/hw/ipath/ib_ipath.ko] undefined!
ERROR: "init_tss" [drivers/infiniband/core/ib_uverbs.ko] undefined!
ERROR: "init_tss" [drivers/hid/uhid.ko] undefined!
ERROR: "init_tss" [drivers/gpu/drm/radeon/radeon.ko] undefined!
ERROR: "init_tss" [drivers/gpu/drm/qxl/qxl.ko] undefined!
ERROR: "init_tss" [drivers/gpu/drm/i915/i915.ko] undefined!
ERROR: "init_tss" [drivers/gpu/drm/drm.ko] undefined!
ERROR: "init_tss" [drivers/firewire/firewire-core.ko] undefined!
ERROR: "init_tss" [drivers/char/tpm/tpm_tis.ko] undefined!
ERROR: "init_tss" [drivers/char/tpm/tpm.ko] undefined!
ERROR: "init_tss" [drivers/char/pcmcia/cm4000_cs.ko] undefined!
ERROR: "init_tss" [drivers/char/lp.ko] undefined!
ERROR: "init_tss" [drivers/char/ipmi/ipmi_devintf.ko] undefined!
ERROR: "init_tss" [drivers/block/drbd/drbd.ko] undefined!
ERROR: "init_tss" [drivers/acpi/acpi_pad.ko] undefined!
ERROR: "init_tss" [arch/x86/oprofile/oprofile.ko] undefined!
ERROR: "init_tss" [arch/x86/kvm/kvm.ko] undefined!
ERROR: "init_tss" [arch/x86/kvm/kvm-intel.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

I took one and investigated how it references init_tss.

drivers/hid/uhid.c:

static int uhid_event_from_user(const char __user *buffer, size_t len,
                                struct uhid_event *event)
{
        if (is_compat_task()) {   <=========== HERE
                u32 type;

                if (get_user(type, buffer))
                        return -EFAULT;

                if (type == UHID_CREATE) {


-- 
vda

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