The call_test_function() contains some assembly that deliberately
causes the stack to be aligned to 32 bits rather than 128 bits on
x86-32. The intention is to catch bugs that surface when pixman is
called from code that only uses a 32 bit alignment.
However, recent versions of GCC apparently make the assumption (either
accidentally or deliberately) that that the incoming stack is aligned
to 128 bits, where older versions only seemed to make this assumption
when compiling with -msse2. This causes the vector code in the PRNG to
now segfault when called from call_test_function() on x86-32.
This patch fixes that by only making the stack unaligned on 32 bit
Windows, where it would definitely be incorrect for GCC to assume that
the incoming stack is aligned to 128 bits.
V2: Put "defined(...)" around __GNUC__
Reviewed-and-Tested-by: Matt Turner <mattst88@gmail.com>
Bugzilla: https://bugs.gentoo.org/show_bug.cgi?id=491110
(cherry picked from commit f473fd1e75)
GCC when compiling with -msse2 and -mssse3 will assume that the stack
is aligned to 16 bytes even on x86-32 and accordingly issue movdqa
instructions for stack allocated variables.
But despite what GCC thinks, the standard ABI on x86-32 only requires
a 4-byte aligned stack. This is true at least on Windows, but there
also was (and maybe still is) Linux code in the wild that assumed
this. When such code calls into pixman and hits something compiled
with -msse2, we get a segfault from the unaligned movdqas.
Pixman has worked around this issue in the past with the gcc attribute
"force_align_arg_pointer" but the problem has resurfaced now in
https://bugs.freedesktop.org/show_bug.cgi?id=68300
because pixman_composite_glyphs() is missing this attribute.
This patch makes fuzzer_test_main() call the test_function through a
trampoline, which, on x86-32, has a bit of assembly that deliberately
avoids aligning the stack to 16 bytes as GCC normally expects. The
result is that glyph-test now crashes.
V2: Mark caller-save registers as clobbered, rather than using
noinline on the trampoline.
Use a temporary variable s containing the absolute value of the stride
as the upper bound in the inner loops.
V2: Do this for the bpp == 16 case as well
Commit 4312f07736 claimed to have made
print_image() work with negative strides, but it didn't actually
work. When the stride was negative, the image buffer would be accessed
as if the stride were positive.
Fix the bug by not changing the stride variable and instead using a
temporary, s, that contains the absolute value of stride.
Pixman supports negative strides, but up until now they haven't been
tested outside of stress-test. This commit adds testing of negative
strides to blitters-test, scaling-test, affine-test, rotate-test, and
composite-traps-test.
The affine-test, blitters-test, and scaling-test all have the ability
to print out the bytes of the destination image. Share this code by
moving it to utils.c.
At the same time make the code work correctly with negative strides.
The check-formats programs reveals that the 8 bit pipeline cannot meet
the current 0.004 acceptable deviation specified in utils.c, so we
have to increase it. Some of the failing pixels were captured in
pixel-test, which with this commit now passes.
== a4r4g4b4 DISJOINT_XOR a8r8g8b8 ==
The DISJOINT_XOR operator applied to an a4r4g4b4 source pixel of
0xd0c0 and a destination pixel of 0x5300ea00 results in the exact
value:
fa = (1 - da) / sa = (1 - 0x53 / 255.0) / (0xd / 15.0) = 0.7782
fb = (1 - sa) / da = (1 - 0xd / 15.0) / (0x53 / 255.0) = 0.4096
r = fa * (0xc / 15.0) + fb * (0xea / 255.0) = 0.99853
But when computing in 8 bits, we get:
fa8 = ((255 - 0x53) * 255 + 0xdd / 2) / 0xdd = 0xc6
fb8 = ((255 - 0xdd) * 255 + 0x53 / 3) / 0x53 = 0x68
r8 = (fa8 * 0xcc + 127) / 255 + (fb8 * 0xea + 127) / 255 = 0xfd
and
0xfd / 255.0 = 0.9921568627450981
for a deviation of 0.00637118610187, which we then have to consider
acceptable given the current implementation.
By switching to computing the result with
r = (fa * s + fb * d + 127) / 255
rather than
r = (fa * s + 127) / 255 + (fb * d + 127) / 255
the deviation would be only 0.00244961747442, so at some point it may
be worth doing either this, or switching to floating point for
operators that involve divisions.
Note that the conversion from 4 bits to 8 bits does not cause any
error in this case because both rounding and bit replication produces
an exact result when the number of from-bits divide the number of
to-bits.
== a8r8g8b8 OVER r5g6b5 ==
When OVER compositing the a8r8g8b8 pixel 0x0f00c300 with the x14r6g6b6
pixel 0x03c0, the true floating point value of the resulting green
channel is:
0xc3 / 255.0 + (1.0 - 0x0f / 255.0) * (0x0f / 63.0) = 0.9887955
but when compositing 8 bit values, where the 6-bit green channel is
converted to 8 bit through bit replication, the 8-bit result is:
0xc3 + ((255 - 0x0f) * 0x3c + 127) / 255 = 251
which corresponds to a real value of 0.984314. The difference from the
true value is 0.004482 which is bigger than the acceptable deviation
of 0.004. So, if we were to compute all the CONJOINT/DISJOINT
operators in floating point, or otherwise make them more accurate, the
acceptable deviation could be set at 0.0045.
If we were doing the 6-bit conversion with rounding:
(x / 63.0 * 255.0 + 0.5)
instead of bit replication, the deviation in this particular case
would be only 0.0005, so we may want to consider this at some
point.
This function returns the name of the given format code, which is
useful for printing out debug information. The function is written as
a switch without a default value so that the compiler will warn if new
formats are added in the future. The fake formats used in the fast
path tables are also recognized.
The function is used in alpha_map.c, where it replaces an existing
format_name() function, and in blitters-test.c, affine-test.c, and
scaling-test.c.
This function returns the name of the given operator, which is useful
for printing out debug information. The function is done as a switch
without a default value so that the compiler will warn if new
operators are added in the future.
The function is used in affine-test.c, scaling-test.c, and
blitters-test.c.
Also dropped redundant volatile keyword because any object
can be accessed via char* pointer without breaking aliasing
rules. The compilers are able to optimize this function to either
constant 0 or 1.
These modifications fix lots of compiler warnings for systems where
sizeof(unsigned long) != sizeof(void *).
This is especially true for MinGW-w64 (64 bit Windows).
Signed-off-by: Stefan Weil <sw@weilnetz.de>
This test runs the new floating point combiners on random input with
divide-by-zero exceptions turned on.
With the floating point combiners the only thing we guarantee is that
divide-by-zero exceptions are not generated, so change
enable_fp_exceptions() to only enable those, and rename accordingly.
The sRGB conversion has to be done every time the limits are being
computed. Without this fix, pixel_checker_get_min/max() will produce
the wrong results when called from somewhere other than
pixel_checker_check().
Composite checks random combinations of operations that now also have
sRGB sources, masks and destinations, and stress-test validates the
read/write primitives.
When a destination image I has an alpha map A, the following rules apply:
- If I has an alpha channel itself, the content of that channel is
undefined
- If A has RGB channels, the content of those channels is
undefined.
Hence in order to compute the CRC32 for such an image, we have to mask
off the alpha channel of the image, and the RGB channels of the alpha
map.
V2: Shifting by 32 is undefined in C
This function converts from a8r8g8b8 to non-premultiplied RGBA (the
PNG or GdkPixbuf format that has the channels in this order: R, G, B,
A in memory regardless of the computer's endianness). The function's
new name is a8r8g8b8_to_rgba_np().
Add a new pixel_checker_t object to test/utils.[ch]. This object
should be initialized with a format and can then be used to check
whether a given "real" pixel in that format is close enough to a
"perfect" pixel given as a double precision ARGB struct.
The acceptable deviation is calcuated as follows. Each channel of the
perfect pixel has 0.004 subtracted from it and is then converted to
the format. The resulting value is the minimum value that will be
accepted. Similarly, to compute the maximum value, the channel has
0.004 added to it and is then converted to the given format. Checking
a pixel is then a matter of splitting it into channels and checking
that each is within the computed bounds.
The value of 0.004 was chosen because it is the minimum one that will
make the existing composite test pass (see next commit). A problem
with this value is that it causes 0xFE to be acceptable when the
correct value is 1.0, and 0x01 to be acceptable when the correct value
is 0. It would be better if, when the result is exactly 0 or exactly
1, an a8r8g8b8 pixel were required to produce exactly 0x00 or 0xff to
preserve full black and full white. A deviation value of 0.003 would
produce this, but currently this would cause tests with operators that
involve divisions to fail.
All the tests are linked to libutil, hence it makes sence to always
include utils.h and reuse what it provides (config.h inclusion, access
to private pixman APIs, ARRAY_LENGTH, ...).
When debugging it is often very useful to be able to save an image as
a png file. This commit adds a function "write_png()" that does that.
If libpng is not available, then the function becomes a noop.
This test generates random regions and checks whether random boxes and
points are contained within them. The results are combined and a CRC32
value is computed and compared to a known-correct one.
This patch makes so that composite and stress-test will start from a
random seed if the PIXMAN_RANDOMIZE_TESTS environment variable is
set. Running the test suite in this mode is useful to get more test
coverage.
Also, in stress-test.c make it so that setting the initial seed causes
threads to be turned off. This makes it much easier to see when
something fails.
This patch removes an unnecessary typecast of MAP_FAILED,
replaces an erroneous free() by the correct munmap() in the
error path for a failing mprotect(), and, finally, removes
redundant calls to mprotect() that aren't necessary, because
munmap() doesn't call for any specific memory protection.
Not all systems are regular Unices, so let's be careful with the
mmap()-related stuff, which might be unavailable. This patch makes
sure that mmap() and friends is used only when the <sys/mman.h>
header is found.
Impending benchmark code will need a function to get current time
in seconds, and this patch introduces such routine. We try to use
the POSIX gettimeofday() function when available, and fall back to
clock() when not.
The aligned_malloc() routine will be used in more than one test utility.
At least, a low-level blitter benchmark needs it. Therefore, let's make
this function a part of common test utilities code.
These variants of malloc() and free() try to surround the allocated
memory with protected pages so that out-of-bounds accessess will cause
a segmentation fault.
If mprotect() and getpagesize() are not available, these functions are
simply equivalent to malloc() and free().
This tests what happens if you attempt to make an image with an alpha
map that has the image as its alpha map. This results in an infinite
loop in _pixman_image_validate(), so the test sets up a SIGALRM to
exit if it runs for more than five seconds.
This patch adds extra guards around our use of
OpenMP pragmas and checks that the pragmas won't
cause link errors. This fixes the build on
Tru64 and Solaris with the native compilers and clang.
