1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
|
/* contrib/arm-neon/linux-auxv.c
*
* Copyright (c) 2014 Glenn Randers-Pehrson
* Written by Mans Rullgard, 2011.
* Last changed in libpng 1.6.10 [March 6, 2014]
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* SEE contrib/arm-neon/README before reporting bugs
*
* STATUS: COMPILED, TESTED
* BUG REPORTS: png-mng-implement@sourceforge.net
*
* png_have_neon implemented for Linux versions which allow access to
* /proc/self/auxv. This is probably faster, cleaner and safer than the code to
* read /proc/cpuinfo in contrib/arm-neon/linux, however it is yet another piece
* of potentially untested code and has more complex dependencies than the code
* to read cpuinfo.
*
* This generic __linux__ implementation requires reading /proc/self/auxv and
* looking at each element for one that records NEON capabilities.
*/
#include <unistd.h> /* for POSIX 1003.1 */
#include <errno.h> /* for EINTR */
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <elf.h>
#include <asm/hwcap.h>
/* A read call may be interrupted, in which case it returns -1 and sets errno to
* EINTR if nothing was done, otherwise (if something was done) a partial read
* may result.
*/
static size_t
safe_read(png_structp png_ptr, int fd, void *buffer_in, size_t nbytes)
{
size_t ntotal = 0;
char *buffer = png_voidcast(char*, buffer_in);
while (nbytes > 0)
{
unsigned int nread;
int iread;
/* Passing nread > INT_MAX to read is implementation defined in POSIX
* 1003.1, therefore despite the unsigned argument portable code must
* limit the value to INT_MAX!
*/
if (nbytes > INT_MAX)
nread = INT_MAX;
else
nread = (unsigned int)/*SAFE*/nbytes;
iread = read(fd, buffer, nread);
if (iread == -1)
{
/* This is the devil in the details, a read can terminate early with 0
* bytes read because of EINTR, yet it still returns -1 otherwise end
* of file cannot be distinguished.
*/
if (errno != EINTR)
{
png_warning(png_ptr, "/proc read failed");
return 0; /* I.e., a permanent failure */
}
}
else if (iread < 0)
{
/* Not a valid 'read' result: */
png_warning(png_ptr, "OS /proc read bug");
return 0;
}
else if (iread > 0)
{
/* Continue reading until a permanent failure, or EOF */
buffer += iread;
nbytes -= (unsigned int)/*SAFE*/iread;
ntotal += (unsigned int)/*SAFE*/iread;
}
else
return ntotal;
}
return ntotal; /* nbytes == 0 */
}
static int
png_have_neon(png_structp png_ptr)
{
int fd = open("/proc/self/auxv", O_RDONLY);
Elf32_auxv_t aux;
/* Failsafe: failure to open means no NEON */
if (fd == -1)
{
png_warning(png_ptr, "/proc/self/auxv open failed");
return 0;
}
while (safe_read(png_ptr, fd, &aux, sizeof aux) == sizeof aux)
{
if (aux.a_type == AT_HWCAP && (aux.a_un.a_val & HWCAP_NEON) != 0)
{
close(fd);
return 1;
}
}
close(fd);
return 0;
}
|
