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Fixed bug #855 Ludwig Nussel 2009-10-18 06:31:52 PDT an mprotect call was added to fix bug 528. However that results in a buffer that allows writing and code execution. Ie the no-execute security features of modern operating systems are defeated this way. Two mprotect calls are needed. One to make the buffer executable but not writeable when done and another one to make the buffer writeable again if the content needs to be changed.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 18 Oct 2009 17:31:37 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>SDL_Surface</TITLE
><META
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>SDL Library Documentation</TH
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><HR
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><H1
><A
NAME="SDLSURFACE"
></A
>SDL_Surface</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN3263"
></A
><H2
>Name</H2
>SDL_Surface&nbsp;--&nbsp;Graphical Surface Structure</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3266"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct SDL_Surface {
        Uint32 flags;                           /* Read-only */
        SDL_PixelFormat *format;                /* Read-only */
        int w, h;                               /* Read-only */
        Uint16 pitch;                           /* Read-only */
        void *pixels;                           /* Read-write */

        /* clipping information */
        SDL_Rect clip_rect;                     /* Read-only */

        /* Reference count -- used when freeing surface */
        int refcount;                           /* Read-mostly */

	/* This structure also contains private fields not shown here */
} SDL_Surface;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3269"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN3271"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>flags</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface flags</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Pixel <A
HREF="sdlpixelformat.html"
>format</A
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>w, h</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Width and height of the surface</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pitch</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Length of a surface scanline in bytes</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Pointer to the actual pixel data</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>clip_rect</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>surface clip <A
HREF="sdlrect.html"
>rectangle</A
></TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3300"
></A
><H2
>Description</H2
><P
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
>'s represent areas of "graphical"
memory, memory that can be drawn to. The video framebuffer is returned
as a <SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
> by
<A
HREF="sdlsetvideomode.html"
><TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
></A
>
and <A
HREF="sdlgetvideosurface.html"
><TT
CLASS="FUNCTION"
>SDL_GetVideoSurface</TT
></A
>.
Most of the fields should be pretty obvious.
<TT
CLASS="STRUCTFIELD"
><I
>w</I
></TT
> and <TT
CLASS="STRUCTFIELD"
><I
>h</I
></TT
> are the
width and height of the surface in pixels.
<TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
> is a pointer to the actual pixel data,
the surface should be <A
HREF="sdllocksurface.html"
>locked</A
>
before accessing this field. The <TT
CLASS="STRUCTFIELD"
><I
>clip_rect</I
></TT
> field
is the clipping rectangle as set by
<A
HREF="sdlsetcliprect.html"
><TT
CLASS="FUNCTION"
>SDL_SetClipRect</TT
></A
>.</P
><P
>The following are supported in the
<TT
CLASS="STRUCTFIELD"
><I
>flags</I
></TT
> field.</P
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN3318"
></A
><P
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface is stored in system memory</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface is stored in video memory</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_ASYNCBLIT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface uses asynchronous blits if possible</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_ANYFORMAT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Allows any pixel-format (Display surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWPALETTE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface has exclusive palette</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_DOUBLEBUF</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface is double buffered (Display surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_FULLSCREEN</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface is full screen (Display Surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_OPENGL</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface has an OpenGL context (Display Surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_OPENGLBLIT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface supports OpenGL blitting (Display Surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_RESIZABLE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface is resizable (Display Surface)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWACCEL</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface blit uses hardware acceleration</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface use colorkey blitting</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_RLEACCEL</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Colorkey blitting is accelerated with RLE</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SRCALPHA</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface blit uses alpha blending</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_PREALLOC</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Surface uses preallocated memory</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3381"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
></P
></DIV
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