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
png_have_neon(png_structp png_ptr)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
safe_read(png_structp png_ptr,int fd,void * buffer_in,size_t nbytes)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
png_have_neon(png_structp png_ptr)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
png_init_filter_functions_neon(png_structp pp,unsigned int bpp)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 */
233