share/png/arm/arm_init.c

   1
   2 /* arm_init.c - NEON optimised filter functions
   3  *
   4  * Copyright (c) 2013 Glenn Randers-Pehrson
   5  * Written by Mans Rullgard, 2011.
   6  * Last changed in libpng 1.6.6 [September 16, 2013]
   7  *
   8  * This code is released under the libpng license.
   9  * For conditions of distribution and use, see the disclaimer
  10  * and license in png.h
  11  */
  12 /* Below, after checking __linux__, various non-C90 POSIX 1003.1 functions are
  13  * called.
  14  */
  15 #define _POSIX_SOURCE 1
  16
  17 #include "../pngpriv.h"
  18
  19 #ifdef PNG_READ_SUPPORTED
  20 #if PNG_ARM_NEON_OPT > 0
  21 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
  22 #include <signal.h> /* for sig_atomic_t */
  23
  24 #ifdef __ANDROID__
  25 /* Linux provides access to information about CPU capabilites via
  26  * /proc/self/auxv, however Android blocks this while still claiming to be
  27  * Linux.  The Andoid NDK, however, provides appropriate support.
  28  *
  29  * Documentation: http://www.kandroid.org/ndk/docs/CPU-ARM-NEON.html
  30  */
  31 #include <cpu-features.h>
  32
  33 static int
  34 png_have_neon(png_structp png_ptr)
  35 {
  36    /* This is a whole lot easier than the mess below, however it is probably
  37     * implemented as below, therefore it is better to cache the result (these
  38     * function calls may be slow!)
  39     */
  40    PNG_UNUSED(png_ptr)
  41    return android_getCpuFamily() == ANDROID_CPU_FAMILY_ARM &&
  42       (android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
  43 }
  44 #elif defined(__linux__)
  45 /* The generic __linux__ implementation requires reading /proc/self/auxv and
  46  * looking at each element for one that records NEON capabilities.
  47  */
  48 #include <unistd.h> /* for POSIX 1003.1 */
  49 #include <errno.h>  /* for EINTR */
  50
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53 #include <fcntl.h>
  54 #include <elf.h>
  55 #include <asm/hwcap.h>
  56
  57 /* A read call may be interrupted, in which case it returns -1 and sets errno to
  58  * EINTR if nothing was done, otherwise (if something was done) a partial read
  59  * may result.
  60  */
  61 static size_t
  62 safe_read(png_structp png_ptr, int fd, void *buffer_in, size_t nbytes)
  63 {
  64    size_t ntotal = 0;
  65    char *buffer = png_voidcast(char*, buffer_in);
  66
  67    while (nbytes > 0)
  68    {
  69       unsigned int nread;
  70       int iread;
  71
  72       /* Passing nread > INT_MAX to read is implementation defined in POSIX
  73        * 1003.1, therefore despite the unsigned argument portable code must
  74        * limit the value to INT_MAX!
  75        */
  76       if (nbytes > INT_MAX)
  77          nread = INT_MAX;
  78
  79       else
  80          nread = (unsigned int)/*SAFE*/nbytes;
  81
  82       iread = read(fd, buffer, nread);
  83
  84       if (iread == -1)
  85       {
  86          /* This is the devil in the details, a read can terminate early with 0
  87           * bytes read because of EINTR, yet it still returns -1 otherwise end
  88           * of file cannot be distinguished.
  89           */
  90          if (errno != EINTR)
  91          {
  92             png_warning(png_ptr, "/proc read failed");
  93             return 0; /* I.e., a permanent failure */
  94          }
  95       }
  96
  97       else if (iread < 0)
  98       {
  99          /* Not a valid 'read' result: */
 100          png_warning(png_ptr, "OS /proc read bug");
 101          return 0;
 102       }
 103
 104       else if (iread > 0)
 105       {
 106          /* Continue reading until a permanent failure, or EOF */
 107          buffer += iread;
 108          nbytes -= (unsigned int)/*SAFE*/iread;
 109          ntotal += (unsigned int)/*SAFE*/iread;
 110       }
 111
 112       else
 113          return ntotal;
 114    }
 115
 116    return ntotal; /* nbytes == 0 */
 117 }
 118
 119 static int
 120 png_have_neon(png_structp png_ptr)
 121 {
 122    int fd = open("/proc/self/auxv", O_RDONLY);
 123    Elf32_auxv_t aux;
 124
 125    /* Failsafe: failure to open means no NEON */
 126    if (fd == -1)
 127    {
 128       png_warning(png_ptr, "/proc/self/auxv open failed");
 129       return 0;
 130    }
 131
 132    while (safe_read(png_ptr, fd, &aux, sizeof aux) == sizeof aux)
 133    {
 134       if (aux.a_type == AT_HWCAP && (aux.a_un.a_val & HWCAP_NEON) != 0)
 135       {
 136          close(fd);
 137          return 1;
 138       }
 139    }
 140
 141    close(fd);
 142    return 0;
 143 }
 144 #else
 145    /* We don't know how to do a run-time check on this system */
 146 #  error "no support for run-time ARM NEON checks"
 147 #endif /* OS checks */
 148 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
 149
 150 #ifndef PNG_ALIGNED_MEMORY_SUPPORTED
 151 #  error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
 152 #endif
 153
 154 void
 155 png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
 156 {
 157    /* The switch statement is compiled in for ARM_NEON_API, the call to
 158     * png_have_neon is compiled in for ARM_NEON_CHECK.  If both are defined
 159     * the check is only performed if the API has not set the NEON option on
 160     * or off explicitly.  In this case the check controls what happens.
 161     *
 162     * If the CHECK is not compiled in and the option is UNSET the behavior prior
 163     * to 1.6.7 was to use the NEON code - this was a bug caused by having the
 164     * wrong order of the 'ON' and 'default' cases.  UNSET now defaults to OFF,
 165     * as documented in png.h
 166     */
 167 #ifdef PNG_ARM_NEON_API_SUPPORTED
 168    switch ((pp->options >> PNG_ARM_NEON) & 3)
 169    {
 170       case PNG_OPTION_UNSET:
 171          /* Allow the run-time check to execute if it has been enabled -
 172           * thus both API and CHECK can be turned on.  If it isn't supported
 173           * this case will fall through to the 'default' below, which just
 174           * returns.
 175           */
 176 #endif /* PNG_ARM_NEON_API_SUPPORTED */
 177 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
 178          {
 179             static volatile sig_atomic_t no_neon = -1; /* not checked */
 180
 181             if (no_neon < 0)
 182                no_neon = !png_have_neon(pp);
 183
 184             if (no_neon)
 185                return;
 186          }
 187 #ifdef PNG_ARM_NEON_API_SUPPORTED
 188          break;
 189 #endif
 190 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
 191
 192 #ifdef PNG_ARM_NEON_API_SUPPORTED
 193       default: /* OFF or INVALID */
 194          return;
 195
 196       case PNG_OPTION_ON:
 197          /* Option turned on */
 198          break;
 199    }
 200 #endif
 201
 202    /* IMPORTANT: any new external functions used here must be declared using
 203     * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
 204     * 'prefix' option to configure works:
 205     *
 206     *    ./configure --with-libpng-prefix=foobar_
 207     *
 208     * Verify you have got this right by running the above command, doing a build
 209     * and examining pngprefix.h; it must contain a #define for every external
 210     * function you add.  (Notice that this happens automatically for the
 211     * initialization function.)
 212     */
 213    pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
 214
 215    if (bpp == 3)
 216    {
 217       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
 218       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
 219       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
 220          png_read_filter_row_paeth3_neon;
 221    }
 222
 223    else if (bpp == 4)
 224    {
 225       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
 226       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
 227       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
 228           png_read_filter_row_paeth4_neon;
 229    }
 230 }
 231 #endif /* PNG_ARM_NEON_OPT > 0 */
 232 #endif /* PNG_READ_SUPPORTED */