kernel/x86: disable trap and direction flag on signal handler entry

https://github.com/freebsd/freebsd-src/commit/846ac2266b625d13ce6d1fc9370c3c3cc2a960bb
https://github.com/freebsd/freebsd-src/commit/22eca0bf45fa506e27a58007cfc70f08ce4f3538
Change-Id: I19620d15372572ce4498d9145fd6b0df50f91bb9
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4043
Reviewed-by: X512 <[email protected]>
Reviewed-by: Adrien Destugues <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/system/kernel/arch/x86/32/thread.cpp

@@ -360,6 +360,7 @@ arch_setup_signal_frame(Thread* thread, struct sigaction* action,
 	frame->ip = x86_get_user_signal_handler_wrapper(
 		(action->sa_flags & SA_BEOS_COMPATIBLE_HANDLER) != 0,
 		thread->team->commpage_address);
+	frame->flags &= ~(X86_EFLAGS_TRAP | X86_EFLAGS_DIRECTION);
 
 	return B_OK;
 }

src/system/kernel/arch/x86/64/thread.cpp

@@ -376,6 +376,7 @@ arch_setup_signal_frame(Thread* thread, struct sigaction* action,
 		+ (addr_t)commPageAddress;
 	clear_ac();
 	frame->di = (addr_t)userSignalFrameData;
+	frame->flags &= ~(uint64)(X86_EFLAGS_TRAP | X86_EFLAGS_DIRECTION);
 
 	return B_OK;
 }