<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [llvmpipe] SEGV in sse2_has_daz on ancient Pentium4-M" href="https://bugs.freedesktop.org/show_bug.cgi?id=87658#c17">Comment # 17</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [llvmpipe] SEGV in sse2_has_daz on ancient Pentium4-M" href="https://bugs.freedesktop.org/show_bug.cgi?id=87658">bug 87658</a> from <a class="email" href="mailto:ubizjak@gmail.com" title="ubizjak@gmail.com">ubizjak@gmail.com</a> <pre>(In reply to Patrick Baggett from <a href="show_bug.cgi?id=87658#c16">comment #16</a>) > That is strange...I would have expected an "illegal instruction" (SIGILL) if > the CPU simply did not support this, but this is SIGSEGV. Is the 'fxsave' > struct really aligned properly? It looks like should be...but it is still > giving SIGSEGV. Can you print the 'fxsave' address when it crashes? As said above, with 32bit gcc, you need to decorate the function with 'force_align_arg_pointer' On the Intel x86, the 'force_align_arg_pointer' attribute may be applied to individual function definitions, generating an alternate prologue and epilogue that realigns the run-time stack if necessary. This supports mixing legacy codes that run with a 4-byte aligned stack with modern codes that keep a 16-byte stack for SSE compatibility. "New" x86_32 ABI mandates 16-byte stack alignment, and the above attribute forces realignment of the incoming stack pointer. Maybe there is a hand-crafted assembly code in the MESA source, libc or somewhere else (that conforms to "old" x86_32 ABI with 4-byte stack alignment) that misaligns the SP. Alternatively, you can use posix_memalign, aligned_alloc or similar function to allocate aligned memory.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>