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[libpng16] Moved OS dependent code from arm/arm_init.c, to allow the included
implementation of the ARM NEON discovery function to be set at build-time and provide sample implementations from the current code in the contrib/arm-neon subdirectory. The __linux__ code has also been changed to compile and link on Android by using /proc/cpuinfo, and the old linux code is in contrib/arm-neon/linux-auxv.c. The new code avoids POSIX and Linux dependencies apart from opening /proc/cpuinfo and is C90 compliant.
This commit is contained in:
John Bowler
committed by
Glenn Randers-Pehrson
Glenn Randers-Pehrson
parent
38ef9c9779
commit
dba54b8888
143
arm/arm_init.c
143
arm/arm_init.c
@@ -19,132 +19,33 @@
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#ifdef PNG_READ_SUPPORTED
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#if PNG_ARM_NEON_OPT > 0
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#ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
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#include <signal.h> /* for sig_atomic_t */
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#ifdef __ANDROID__
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/* Linux provides access to information about CPU capabilites via
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* /proc/self/auxv, however Android blocks this while still claiming to be
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* Linux. The Andoid NDK, however, provides appropriate support.
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/* WARNING: it is strongly recommended that you do not build libpng with
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* run-time checks for CPU features if at all possible. In the case of the ARM
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* NEON instructions there is no processor-specific way of detecting the
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* presense of the required support, therefore run-time detectioon is extremely
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* OS specific.
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*
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* Documentation: http://www.kandroid.org/ndk/docs/CPU-ARM-NEON.html
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* You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
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* a fragment of C source code which defines the png_have_neon function. There
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* are a number of implementations in contrib/arm-neon, but the only one that
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* has partial support is contrib/arm-neon/linux.c - a generic Linux
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* implementation which reads /proc/cpufino.
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*/
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#include <cpu-features.h>
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#ifndef PNG_ARM_NEON_FILE
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# ifdef __linux__
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# define PNG_ARM_NEON_FILE "contrib/arm-neon/linux.c"
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# endif
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#endif
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static int
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png_have_neon(png_structp png_ptr)
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{
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/* This is a whole lot easier than the mess below, however it is probably
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* implemented as below, therefore it is better to cache the result (these
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* function calls may be slow!)
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*/
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PNG_UNUSED(png_ptr)
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return android_getCpuFamily() == ANDROID_CPU_FAMILY_ARM &&
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(android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
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}
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#elif defined(__linux__)
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/* The generic __linux__ implementation requires reading /proc/self/auxv and
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* looking at each element for one that records NEON capabilities.
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*/
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#include <unistd.h> /* for POSIX 1003.1 */
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#include <errno.h> /* for EINTR */
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#ifdef PNG_ARM_NEON_FILE
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <elf.h>
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#include <asm/hwcap.h>
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#include <signal.h> /* for sig_atomic_t */
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static int png_have_neon(png_structp png_ptr);
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#include PNG_ARM_NEON_FILE
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/* A read call may be interrupted, in which case it returns -1 and sets errno to
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* EINTR if nothing was done, otherwise (if something was done) a partial read
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* may result.
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*/
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static size_t
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safe_read(png_structp png_ptr, int fd, void *buffer_in, size_t nbytes)
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{
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size_t ntotal = 0;
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char *buffer = png_voidcast(char*, buffer_in);
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while (nbytes > 0)
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{
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unsigned int nread;
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int iread;
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/* Passing nread > INT_MAX to read is implementation defined in POSIX
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* 1003.1, therefore despite the unsigned argument portable code must
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* limit the value to INT_MAX!
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*/
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if (nbytes > INT_MAX)
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nread = INT_MAX;
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else
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nread = (unsigned int)/*SAFE*/nbytes;
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iread = read(fd, buffer, nread);
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if (iread == -1)
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{
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/* This is the devil in the details, a read can terminate early with 0
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* bytes read because of EINTR, yet it still returns -1 otherwise end
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* of file cannot be distinguished.
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*/
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if (errno != EINTR)
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{
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png_warning(png_ptr, "/proc read failed");
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return 0; /* I.e., a permanent failure */
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}
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}
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else if (iread < 0)
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{
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/* Not a valid 'read' result: */
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png_warning(png_ptr, "OS /proc read bug");
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return 0;
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}
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else if (iread > 0)
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{
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/* Continue reading until a permanent failure, or EOF */
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buffer += iread;
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nbytes -= (unsigned int)/*SAFE*/iread;
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ntotal += (unsigned int)/*SAFE*/iread;
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}
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else
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return ntotal;
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}
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return ntotal; /* nbytes == 0 */
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}
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static int
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png_have_neon(png_structp png_ptr)
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{
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int fd = open("/proc/self/auxv", O_RDONLY);
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Elf32_auxv_t aux;
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/* Failsafe: failure to open means no NEON */
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if (fd == -1)
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{
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png_warning(png_ptr, "/proc/self/auxv open failed");
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return 0;
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}
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while (safe_read(png_ptr, fd, &aux, sizeof aux) == sizeof aux)
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{
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if (aux.a_type == AT_HWCAP && (aux.a_un.a_val & HWCAP_NEON) != 0)
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{
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close(fd);
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return 1;
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}
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}
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close(fd);
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return 0;
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}
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#else
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/* We don't know how to do a run-time check on this system */
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# error "no support for run-time ARM NEON checks"
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#endif /* OS checks */
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#else /* PNG_ARM_NEON_FILE */
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# error "PNG_ARM_NEON_FILE undefined: no support for run-time ARM NEON checks"
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#endif /* PNG_ARM_NEON_FILE */
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#endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
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#ifndef PNG_ALIGNED_MEMORY_SUPPORTED
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