/*
 * Functions used by both the SCSI initiator code and the SCSI target code.
 */

#ifndef _SCSI_COMMON_H_
#define _SCSI_COMMON_H_

#include <linux/types.h>
#include <scsi/scsi_proto.h>

static inline unsigned
scsi_varlen_cdb_length(const void *hdr)
{
	return ((struct scsi_varlen_cdb_hdr *)hdr)->additional_cdb_length + 8;
}

extern const unsigned char scsi_command_size_tbl[8];
#define COMMAND_SIZE(opcode) scsi_command_size_tbl[((opcode) >> 5) & 7]

static inline unsigned
scsi_command_size(const unsigned char *cmnd)
{
	return (cmnd[0] == VARIABLE_LENGTH_CMD) ?
		scsi_varlen_cdb_length(cmnd) : COMMAND_SIZE(cmnd[0]);
}

/* Returns a human-readable name for the device */
extern const char *scsi_device_type(unsigned type);

extern void int_to_scsilun(u64, struct scsi_lun *);
extern u64 scsilun_to_int(struct scsi_lun *);

/*
 * This is a slightly modified SCSI sense "descriptor" format header.
 * The addition is to allow the 0x70 and 0x71 response codes. The idea
 * is to place the salient data from either "fixed" or "descriptor" sense
 * format into one structure to ease application processing.
 *
 * The original sense buffer should be kept around for those cases
 * in which more information is required (e.g. the LBA of a MEDIUM ERROR).
 */
struct scsi_sense_hdr {		/* See SPC-3 section 4.5 */
	u8 response_code;	/* permit: 0x0, 0x70, 0x71, 0x72, 0x73 */
	u8 sense_key;
	u8 asc;
	u8 ascq;
	u8 byte4;
	u8 byte5;
	u8 byte6;
	u8 additional_length;	/* always 0 for fixed sense format */
};

static inline bool scsi_sense_valid(const struct scsi_sense_hdr *sshdr)
{
	if (!sshdr)
		return false;

	return (sshdr->response_code & 0x70) == 0x70;
}

extern bool scsi_normalize_sense(const u8 *sense_buffer, int sb_len,
				 struct scsi_sense_hdr *sshdr);

extern void scsi_build_sense_buffer(int desc, u8 *buf, u8 key, u8 asc, u8 ascq);
int scsi_set_sense_information(u8 *buf, int buf_len, u64 info);
int scsi_set_sense_field_pointer(u8 *buf, int buf_len, u16 fp, u8 bp, bool cd);
extern const u8 * scsi_sense_desc_find(const u8 * sense_buffer, int sb_len,
				       int desc_type);

#endif /* _SCSI_COMMON_H_ */
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<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/trace?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/trace?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
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<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/trace?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/trace?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'include/trace')</div><table summary='diffstat' class='diffstat'>