[libpng16] Use approved/supported Android method to check for NEON, use
Linux/POSIX 1003.1 API to check /proc/self/auxv avoiding buffer allocation
and other library calls (ported from libpng15).
diff --git a/ANNOUNCE b/ANNOUNCE
index a4346cf..83068a7 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -40,6 +40,9 @@
scripts/pnglibconf.dfa formatting improvements back ported from libpng17.
Fixed a race condition in the creation of the build 'scripts' directory
while building with a parallel make.
+ Use approved/supported Android method to check for NEON, use Linux/POSIX
+ 1003.1 API to check /proc/self/auxv avoiding buffer allocation and other
+ library calls (ported from libpng15).
Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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diff --git a/CHANGES b/CHANGES
index 7ddf310..94d56f1 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4396,6 +4396,9 @@
scripts/pnglibconf.dfa formatting improvements back ported from libpng17.
Fixed a race condition in the creation of the build 'scripts' directory
while building with a parallel make.
+ Use approved/supported Android method to check for NEON, use Linux/POSIX
+ 1003.1 API to check /proc/self/auxv avoiding buffer allocation and other
+ library calls (ported from libpng15).
Send comments/corrections/commendations to png-mng-implement at lists.sf.net
(subscription required; visit
diff --git a/arm/arm_init.c b/arm/arm_init.c
index 8925f35..3a3e86e 100644
--- a/arm/arm_init.c
+++ b/arm/arm_init.c
@@ -1,7 +1,7 @@
/* arm_init.c - NEON optimised filter functions
*
- * Copyright (c) 2012 Glenn Randers-Pehrson
+ * Copyright (c) 2013 Glenn Randers-Pehrson
* Written by Mans Rullgard, 2011.
* Last changed in libpng 1.5.14 [(PENDING RELEASE)]
*
@@ -9,45 +9,154 @@
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
+/* Below, after checking __linux__, various non-C90 POSIX 1003.1 functions are
+ * called.
+ */
+#define _POSIX_SOURCE 1
+
#include "../pngpriv.h"
-/* __arm__ is defined by GCC, MSVC defines _M_ARM to the ARM version number */
+/* __arm__ is defined by GCC, MSVC defines _M_ARM to the ARM version number,
+ * Andoid intends to define __ANDROID__, however there are bugs in their
+ * toolchain; use -D__ANDROID__ to work round this.
+ */
#if defined __linux__ && defined __arm__
-#include <stdio.h>
+#define CHECK_NEON
+#include <signal.h> /* for sig_atomic_t */
+
+#ifdef __ANDROID__
+/* Linux provides access to information about CPU capabilites via
+ * /proc/self/auxv, however Android blocks this while still claiming to be
+ * Linux. The Andoid NDK, however, provides appropriate support.
+ *
+ * Documentation: http://www.kandroid.org/ndk/docs/CPU-ARM-NEON.html
+ */
+#include <cpu-features.h>
+
+static int
+png_have_neon(png_structp png_ptr)
+{
+ /* This is a whole lot easier than the mess below, however it is probably
+ * implemented as below, therefore it is better to cache the result (these
+ * function calls may be slow!)
+ */
+ return andoid_getCpuFamily() == ANDROID_CPU_FAMILY_ARM &&
+ (android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
+}
+#else
+/* The 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>
-static int png_have_hwcap(unsigned cap)
+/* A read call may be interupted, 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)
{
- FILE *f = fopen("/proc/self/auxv", "r");
- Elf32_auxv_t aux;
- int have_cap = 0;
+ size_t ntotal = 0;
+ char *buffer = png_voidcast(char*, buffer_in);
- if (!f)
- return 0;
-
- while (fread(&aux, sizeof(aux), 1, f) > 0)
+ while (nbytes > 0)
{
- if (aux.a_type == AT_HWCAP &&
- aux.a_un.a_val & cap)
+ 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)
{
- have_cap = 1;
- break;
+ /* 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;
}
}
- fclose(f);
-
- return have_cap;
+ close(fd);
+ return 0;
}
+#endif /* !__ANDROID__ */
#endif /* __linux__ && __arm__ */
void
png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
{
#ifdef __arm__
-#ifdef __linux__
- if (!png_have_hwcap(HWCAP_NEON))
+#ifdef CHECK_NEON
+ static volatile sig_atomic_t no_neon = -1; /* not checked */
+
+ if (no_neon < 0)
+ no_neon = !png_have_neon(pp);
+
+ if (no_neon)
return;
#endif
