Søren Sandmann <[email protected]> writes: > The trampoline is marked noinline to work around what appears to be a > bug in GCC/OpenMP (and possibly later), where the test_function > pointer is not correctly passed to the assembly if the function is > inlined.
Turns out this was just because I had forgotten to mark the caller-save registers as clobbered. Søren From 764b97dd6016fa9f0286a64d7440a7de42b4818d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?S=C3=B8ren=20Sandmann=20Pedersen?= <[email protected]> Date: Wed, 2 Oct 2013 14:38:16 -0400 Subject: [PATCH 2/3] utils.c: On x86-32 unalign the stack before calling test_function 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. --- test/utils.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/test/utils.c b/test/utils.c index 0cd982e..281f6b4 100644 --- a/test/utils.c +++ b/test/utils.c @@ -641,6 +641,32 @@ draw_checkerboard (pixman_image_t *image, } } +static uint32_t +call_test_function (uint32_t (*test_function)(int testnum, int verbose), + int testnum, + int verbose) +{ + uint32_t retval; + +#if defined (__GNUC__) && (defined (__i386) || defined (__i386__)) + __asm__ ( + /* Deliberately avoid aligning the stack to 16 bytes */ + "pushl %1\n\t" + "pushl %2\n\t" + "call *%3\n\t" + "addl $8, %%esp\n\t" + : "=a" (retval) + : "r" (verbose), + "r" (testnum), + "r" (test_function) + : "edx", "ecx"); /* caller save registers */ +#else + retval = test_function (testnum, verbose); +#endif + + return retval; +} + /* * A function, which can be used as a core part of the test programs, * intended to detect various problems with the help of fuzzing input @@ -710,7 +736,9 @@ fuzzer_test_main (const char *test_name, else if (argc >= 2) { n2 = atoi (argv[1]); - checksum = test_function (n2, 1); + + checksum = call_test_function (test_function, n2, 1); + printf ("%d: checksum=%08X\n", n2, checksum); return 0; } @@ -726,7 +754,7 @@ fuzzer_test_main (const char *test_name, #endif for (i = n1; i <= n2; i++) { - uint32_t crc = test_function (i, 0); + uint32_t crc = call_test_function (test_function, i, 0); if (verbose) printf ("%d: %08X\n", i, crc); checksum += crc; -- 1.7.11.7 _______________________________________________ Pixman mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/pixman
