OpenMP fails on A64FX (AArch64 SVE)

[AssadHashmi]

Raised by user, see https://groups.google.com/g/dynamorio-users/c/S9dHoHjYHns

Describe the bug
Any OpenMP program with more than one thread fails on an A64FX SVE machine.

To Reproduce

$ OMP_NUM_THREADS=2 $DYNAMORIO_DIR/bin64/drrun -debug -- ./bin/is.A.x
<Starting application NPB3.4-OMP/bin/is.A.x (4028)>
<Initial options = -no_dynamic_options -code_api -stack_size 64K -signal_stack_size 64K -max_elide_jmp 0 -max_elide_call 0 -vmm_block_size 64K -initial_heap_unit_size 64K -initial_heap_nonpers_size 64K -initial_global_heap_unit_size 512K -max_heap_unit_size 4M -heap_commit_increment 64K -cache_commit_increment 64K -cache_bb_unit_init 64K -cache_bb_unit_max 64K -cache_bb_unit_quadruple 64K -cache_trace_unit_init 64K -cache_trace_unit_max 64K -cache_trace_unit_quadruple 64K -cache_shared_bb_unit_init 512K -cache_shared_bb_unit_max 512K -cache_shared_bb_unit_quadruple 512K -cache_shared_trace_unit_init 512K -cache_shared_trace_unit_max 512K -cache_shared_trace_unit_quadruple 512K -cache_bb_unit_upgrade 64K -cache_trace_unit_upgrade 64K -cache_shared_bb_unit_upgrade 512K -cache_shared_trace_unit_upgrade 512K -early_inject -emulate_brk -no_inline_ignored_syscalls -no_per_thread_guard_pages -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct >

 NAS Parallel Benchmarks (NPB3.4-OMP) - IS Benchmark

 Size:  8388608  (class A)
 Iterations:  10
 Number of available threads:  2

<Application NPB3.4.2/NPB3.4-OMP/bin/is.A.x (4028). Cannot correctly handle received signal 11 in thread 4029: default action in native thread.>

The crash seems to happen at thread creation when entering an OpenMP parallel region or pthread_create().
Stack trace:

(gdb) bt
#0  0x00004000004574c8 in get_clone_record (xsp=70368753806112) at /home/runner/work/dynamorio/dynamorio/core/unix/signal.c:944
#1  0x000040000043aed8 in new_thread_setup (mc=0x40000092eb20) at /home/runner/work/dynamorio/dynamorio/core/arch/x86_code.c:284
#2  0x0000400200696638 in ?? ()
#3  0x0000ffffffffceb0 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)

The user has mentioned this workaround, reducing the size of dstack_base allocated in core/unix/signal.c. By changing:

#ifdef AARCH64
    dstack_base = (byte *)ALIGN_FORWARD(xsp, PAGE_SIZE) + PAGE_SIZE;
#else
    dstack_base = (byte *)ALIGN_FORWARD(xsp, PAGE_SIZE);
#endif

To:

    dstack_base = (byte *)ALIGN_FORWARD(xsp, PAGE_SIZE);

Additional context
This error was probably introduced by the initial work on SVE support, see #5835

It should be fixed when #6317 is implemented.

[AssadHashmi]

Related to #5365.