Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 307 insertions, 0 deletions

diff --git a/Documentation/fb/api.rst b/Documentation/fb/api.rst
new file mode 100644
index 000000000..4f00e7196
--- /dev/null
+++ b/Documentation/fb/api.rst
@@ -0,0 +1,307 @@
+===========================
+The Frame Buffer Device API
+===========================
+
+Last revised: June 21, 2011
+
+
+0. Introduction
+---------------
+
+This document describes the frame buffer API used by applications to interact
+with frame buffer devices. In-kernel APIs between device drivers and the frame
+buffer core are not described.
+
+Due to a lack of documentation in the original frame buffer API, drivers
+behaviours differ in subtle (and not so subtle) ways. This document describes
+the recommended API implementation, but applications should be prepared to
+deal with different behaviours.
+
+
+1. Capabilities
+---------------
+
+Device and driver capabilities are reported in the fixed screen information
+capabilities field::
+
+  struct fb_fix_screeninfo {
+	...
+	__u16 capabilities;		/* see FB_CAP_*			*/
+	...
+  };
+
+Application should use those capabilities to find out what features they can
+expect from the device and driver.
+
+- FB_CAP_FOURCC
+
+The driver supports the four character code (FOURCC) based format setting API.
+When supported, formats are configured using a FOURCC instead of manually
+specifying color components layout.
+
+
+2. Types and visuals
+--------------------
+
+Pixels are stored in memory in hardware-dependent formats. Applications need
+to be aware of the pixel storage format in order to write image data to the
+frame buffer memory in the format expected by the hardware.
+
+Formats are described by frame buffer types and visuals. Some visuals require
+additional information, which are stored in the variable screen information
+bits_per_pixel, grayscale, red, green, blue and transp fields.
+
+Visuals describe how color information is encoded and assembled to create
+macropixels. Types describe how macropixels are stored in memory. The following
+types and visuals are supported.
+
+- FB_TYPE_PACKED_PIXELS
+
+Macropixels are stored contiguously in a single plane. If the number of bits
+per macropixel is not a multiple of 8, whether macropixels are padded to the
+next multiple of 8 bits or packed together into bytes depends on the visual.
+
+Padding at end of lines may be present and is then reported through the fixed
+screen information line_length field.
+
+- FB_TYPE_PLANES
+
+Macropixels are split across multiple planes. The number of planes is equal to
+the number of bits per macropixel, with plane i'th storing i'th bit from all
+macropixels.
+
+Planes are located contiguously in memory.
+
+- FB_TYPE_INTERLEAVED_PLANES
+
+Macropixels are split across multiple planes. The number of planes is equal to
+the number of bits per macropixel, with plane i'th storing i'th bit from all
+macropixels.
+
+Planes are interleaved in memory. The interleave factor, defined as the
+distance in bytes between the beginning of two consecutive interleaved blocks
+belonging to different planes, is stored in the fixed screen information
+type_aux field.
+
+- FB_TYPE_FOURCC
+
+Macropixels are stored in memory as described by the format FOURCC identifier
+stored in the variable screen information grayscale field.
+
+- FB_VISUAL_MONO01
+
+Pixels are black or white and stored on a number of bits (typically one)
+specified by the variable screen information bpp field.
+
+Black pixels are represented by all bits set to 1 and white pixels by all bits
+set to 0. When the number of bits per pixel is smaller than 8, several pixels
+are packed together in a byte.
+
+FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.
+
+- FB_VISUAL_MONO10
+
+Pixels are black or white and stored on a number of bits (typically one)
+specified by the variable screen information bpp field.
+
+Black pixels are represented by all bits set to 0 and white pixels by all bits
+set to 1. When the number of bits per pixel is smaller than 8, several pixels
+are packed together in a byte.
+
+FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only.
+
+- FB_VISUAL_TRUECOLOR
+
+Pixels are broken into red, green and blue components, and each component
+indexes a read-only lookup table for the corresponding value. Lookup tables
+are device-dependent, and provide linear or non-linear ramps.
+
+Each component is stored in a macropixel according to the variable screen
+information red, green, blue and transp fields.
+
+- FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR
+
+Pixel values are encoded as indices into a colormap that stores red, green and
+blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR
+and read-write for FB_VISUAL_PSEUDOCOLOR.
+
+Each pixel value is stored in the number of bits reported by the variable
+screen information bits_per_pixel field.
+
+- FB_VISUAL_DIRECTCOLOR
+
+Pixels are broken into red, green and blue components, and each component
+indexes a programmable lookup table for the corresponding value.
+
+Each component is stored in a macropixel according to the variable screen
+information red, green, blue and transp fields.
+
+- FB_VISUAL_FOURCC
+
+Pixels are encoded and  interpreted as described by the format FOURCC
+identifier stored in the variable screen information grayscale field.
+
+
+3. Screen information
+---------------------
+
+Screen information are queried by applications using the FBIOGET_FSCREENINFO
+and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a
+fb_fix_screeninfo and fb_var_screeninfo structure respectively.
+
+struct fb_fix_screeninfo stores device independent unchangeable information
+about the frame buffer device and the current format. Those information can't
+be directly modified by applications, but can be changed by the driver when an
+application modifies the format::
+
+  struct fb_fix_screeninfo {
+	char id[16];			/* identification string eg "TT Builtin" */
+	unsigned long smem_start;	/* Start of frame buffer mem */
+					/* (physical address) */
+	__u32 smem_len;			/* Length of frame buffer mem */
+	__u32 type;			/* see FB_TYPE_*		*/
+	__u32 type_aux;			/* Interleave for interleaved Planes */
+	__u32 visual;			/* see FB_VISUAL_*		*/
+	__u16 xpanstep;			/* zero if no hardware panning  */
+	__u16 ypanstep;			/* zero if no hardware panning  */
+	__u16 ywrapstep;		/* zero if no hardware ywrap    */
+	__u32 line_length;		/* length of a line in bytes    */
+	unsigned long mmio_start;	/* Start of Memory Mapped I/O   */
+					/* (physical address) */
+	__u32 mmio_len;			/* Length of Memory Mapped I/O  */
+	__u32 accel;			/* Indicate to driver which	*/
+					/*  specific chip/card we have	*/
+	__u16 capabilities;		/* see FB_CAP_*			*/
+	__u16 reserved[2];		/* Reserved for future compatibility */
+  };
+
+struct fb_var_screeninfo stores device independent changeable information
+about a frame buffer device, its current format and video mode, as well as
+other miscellaneous parameters::
+
+  struct fb_var_screeninfo {
+	__u32 xres;			/* visible resolution		*/
+	__u32 yres;
+	__u32 xres_virtual;		/* virtual resolution		*/
+	__u32 yres_virtual;
+	__u32 xoffset;			/* offset from virtual to visible */
+	__u32 yoffset;			/* resolution			*/
+
+	__u32 bits_per_pixel;		/* guess what			*/
+	__u32 grayscale;		/* 0 = color, 1 = grayscale,	*/
+					/* >1 = FOURCC			*/
+	struct fb_bitfield red;		/* bitfield in fb mem if true color, */
+	struct fb_bitfield green;	/* else only length is significant */
+	struct fb_bitfield blue;
+	struct fb_bitfield transp;	/* transparency			*/
+
+	__u32 nonstd;			/* != 0 Non standard pixel format */
+
+	__u32 activate;			/* see FB_ACTIVATE_*		*/
+
+	__u32 height;			/* height of picture in mm    */
+	__u32 width;			/* width of picture in mm     */
+
+	__u32 accel_flags;		/* (OBSOLETE) see fb_info.flags */
+
+	/* Timing: All values in pixclocks, except pixclock (of course) */
+	__u32 pixclock;			/* pixel clock in ps (pico seconds) */
+	__u32 left_margin;		/* time from sync to picture	*/
+	__u32 right_margin;		/* time from picture to sync	*/
+	__u32 upper_margin;		/* time from sync to picture	*/
+	__u32 lower_margin;
+	__u32 hsync_len;		/* length of horizontal sync	*/
+	__u32 vsync_len;		/* length of vertical sync	*/
+	__u32 sync;			/* see FB_SYNC_*		*/
+	__u32 vmode;			/* see FB_VMODE_*		*/
+	__u32 rotate;			/* angle we rotate counter clockwise */
+	__u32 colorspace;		/* colorspace for FOURCC-based modes */
+	__u32 reserved[4];		/* Reserved for future compatibility */
+  };
+
+To modify variable information, applications call the FBIOPUT_VSCREENINFO
+ioctl with a pointer to a fb_var_screeninfo structure. If the call is
+successful, the driver will update the fixed screen information accordingly.
+
+Instead of filling the complete fb_var_screeninfo structure manually,
+applications should call the FBIOGET_VSCREENINFO ioctl and modify only the
+fields they care about.
+
+
+4. Format configuration
+-----------------------
+
+Frame buffer devices offer two ways to configure the frame buffer format: the
+legacy API and the FOURCC-based API.
+
+
+The legacy API has been the only frame buffer format configuration API for a
+long time and is thus widely used by application. It is the recommended API
+for applications when using RGB and grayscale formats, as well as legacy
+non-standard formats.
+
+To select a format, applications set the fb_var_screeninfo bits_per_pixel field
+to the desired frame buffer depth. Values up to 8 will usually map to
+monochrome, grayscale or pseudocolor visuals, although this is not required.
+
+- For grayscale formats, applications set the grayscale field to one. The red,
+  blue, green and transp fields must be set to 0 by applications and ignored by
+  drivers. Drivers must fill the red, blue and green offsets to 0 and lengths
+  to the bits_per_pixel value.
+
+- For pseudocolor formats, applications set the grayscale field to zero. The
+  red, blue, green and transp fields must be set to 0 by applications and
+  ignored by drivers. Drivers must fill the red, blue and green offsets to 0
+  and lengths to the bits_per_pixel value.
+
+- For truecolor and directcolor formats, applications set the grayscale field
+  to zero, and the red, blue, green and transp fields to describe the layout of
+  color components in memory::
+
+    struct fb_bitfield {
+	__u32 offset;			/* beginning of bitfield	*/
+	__u32 length;			/* length of bitfield		*/
+	__u32 msb_right;		/* != 0 : Most significant bit is */
+					/* right */
+    };
+
+  Pixel values are bits_per_pixel wide and are split in non-overlapping red,
+  green, blue and alpha (transparency) components. Location and size of each
+  component in the pixel value are described by the fb_bitfield offset and
+  length fields. Offset are computed from the right.
+
+  Pixels are always stored in an integer number of bytes. If the number of
+  bits per pixel is not a multiple of 8, pixel values are padded to the next
+  multiple of 8 bits.
+
+Upon successful format configuration, drivers update the fb_fix_screeninfo
+type, visual and line_length fields depending on the selected format.
+
+
+The FOURCC-based API replaces format descriptions by four character codes
+(FOURCC). FOURCCs are abstract identifiers that uniquely define a format
+without explicitly describing it. This is the only API that supports YUV
+formats. Drivers are also encouraged to implement the FOURCC-based API for RGB
+and grayscale formats.
+
+Drivers that support the FOURCC-based API report this capability by setting
+the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field.
+
+FOURCC definitions are located in the linux/videodev2.h header. However, and
+despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2
+and don't require usage of the V4L2 subsystem. FOURCC documentation is
+available in Documentation/userspace-api/media/v4l/pixfmt.rst.
+
+To select a format, applications set the grayscale field to the desired FOURCC.
+For YUV formats, they should also select the appropriate colorspace by setting
+the colorspace field to one of the colorspaces listed in linux/videodev2.h and
+documented in Documentation/userspace-api/media/v4l/colorspaces.rst.
+
+The red, green, blue and transp fields are not used with the FOURCC-based API.
+For forward compatibility reasons applications must zero those fields, and
+drivers must ignore them. Values other than 0 may get a meaning in future
+extensions.
+
+Upon successful format configuration, drivers update the fb_fix_screeninfo
+type, visual and line_length fields depending on the selected format. The type
+and visual fields are set to FB_TYPE_FOURCC and FB_VISUAL_FOURCC respectively.