This implements the required asm functions for sparc64_sysv_elf and was tested on an OpenBSD/sparc64 system.
Jump_fcontext uses an extra C call frame to store the frame-pointer and return address. Because of this the code is simply a save (to new reg window), then forcing a window flush and finally switch stack and restore from there.
Since jump_fcontext() uses a register window and stack frame, make_fcontext() reserves two call frames on the stack (one for jump_fcontext() and the other for the callback function).
OpenBSD/sparc64 uses stackghost which prevents userland from overriding the return-address on the stack because of this make_fcontext() uses an extra trampoline to implement the _exit(0) call if the callback returns.
All tests pass with this on OpenBSD/sparc64 (also the tests for fiber, coroutine and coroutine2).
olk
commented
8 months ago
This implements the required asm functions for sparc64_sysv_elf and was tested on an OpenBSD/sparc64 system.
Jump_fcontext uses an extra C call frame to store the frame-pointer and return address. Because of this the code is simply a save (to new reg window), then forcing a window flush and finally switch stack and restore from there.
Since jump_fcontext() uses a register window and stack frame, make_fcontext() reserves two call frames on the stack (one for jump_fcontext() and the other for the callback function).
OpenBSD/sparc64 uses stackghost which prevents userland from overriding the return-address on the stack because of this make_fcontext() uses an extra trampoline to implement the _exit(0) call if the callback returns.
All tests pass with this on OpenBSD/sparc64 (also the tests for fiber, coroutine and coroutine2).