PCI/ASPM: Handle PCI-to-PCIe bridges as roots of PCIe hierarchies

In a struct pcie_link_state, link->root points to the pcie_link_state of
the root of the PCIe hierarchy.  For the topmost link, this points to
itself (link->root = link).  For others, we copy the pointer from the
parent (link->root = link->parent->root).

Previously we recognized that Root Ports originated PCIe hierarchies, but
we treated PCI/PCI-X to PCIe Bridges as being in the middle of the
hierarchy, and when we tried to copy the pointer from link->parent->root,
there was no parent, and we dereferenced a NULL pointer:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
  IP: [<ffffffff9e424350>] pcie_aspm_init_link_state+0x170/0x820

Recognize that PCI/PCI-X to PCIe Bridges originate PCIe hierarchies just
like Root Ports do, so link->root for these devices should also point to
itself.

Fixes: 51ebfc92b72b ("PCI: Enumerate switches below PCI-to-PCIe bridges")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=193411
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1022181
Tested-by: lists@ssl-mail.com
Tested-by: Jayachandran C. <jnair@caviumnetworks.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.2+

path: root/ring_rx.h

/*
 * netsniff-ng - the packet sniffing beast
 * Copyright 2009, 2010 Daniel Borkmann.
 * Subject to the GPL, version 2.
 */

#ifndef RX_RING_H
#define RX_RING_H

#include "ring.h"
#include "built_in.h"

extern void destroy_rx_ring(int sock, struct ring *ring);
extern void create_rx_ring(int sock, struct ring *ring, int verbose);
extern void mmap_rx_ring(int sock, struct ring *ring);
extern void alloc_rx_ring_frames(struct ring *ring);
extern void bind_rx_ring(int sock, struct ring *ring, int ifindex);
extern void setup_rx_ring_layout(int sock, struct ring *ring,
				 unsigned int size, int jumbo_support);

static inline int user_may_pull_from_rx(struct tpacket2_hdr *hdr)
{
	return ((hdr->tp_status & TP_STATUS_USER) == TP_STATUS_USER);
}

static inline void kernel_may_pull_from_rx(struct tpacket2_hdr *hdr)
{
	hdr->tp_status = TP_STATUS_KERNEL;
}

#endif /* RX_RING_H */