Add a "fork" of musl as //fusl.

fusl/src/thread/powerpc/syscall_cp.s

+.global __cp_begin
+.hidden __cp_begin
+.global __cp_end
+.hidden __cp_end
+.global __cp_cancel
+.hidden __cp_cancel
+.hidden __cancel
+.global __syscall_cp_asm
+.hidden __syscall_cp_asm
+
+#r0: volatile. may be modified during linkage.
+#r1: stack frame: 16 byte alignment.
+#r2: tls/thread pointer on pp32
+#r3,r4: return values, first args
+#r5-r10: args
+#r11-r12: volatile. may be modified during linkage
+#r13: "small data area" pointer
+#r14 - r30: local vars
+#r31: local or environment pointer
+
+#r1, r14-31: belong to the caller, must be saved and restored
+#r0, r3-r12, ctr, xer: volatile, not preserved
+#r0,r11,r12: may be altered by cross-module call, 
+#"a func cannot depend on that these regs have the values placed by the caller"
+
+#the fields CR2,CR2,CR4 of the cond reg must be preserved
+#LR (link reg) shall contain the funcs return address
+        .text
+        .type   __syscall_cp_asm,%function
+__syscall_cp_asm:
+        # at enter: r3 = pointer to self->cancel, r4: syscall no, r5: first arg, r6: 2nd, r7: 3rd, r8: 4th, r9: 5th, r10: 6th
+__cp_begin:
+        # r3 holds first argument, its a pointer to self->cancel. 
+        # we must compare the dereferenced value with 0 and jump to __cancel if its not
+        
+        lwz 0, 0(3) #deref pointer into r0
+        
+        cmpwi cr7, 0, 0 #compare r0 with 0, store result in cr7. 
+        beq+ cr7, 1f #jump to label 1 if r0 was 0
+        
+        b __cp_cancel #else call cancel
+1:
+        #ok, the cancel flag was not set
+        # syscall: number goes to r0, the rest 3-8
+        mr      0, 4                  # put the system call number into r0
+        mr      3, 5                  # Shift the arguments: arg1
+        mr      4, 6                  # arg2
+        mr      5, 7                  # arg3
+        mr      6, 8                  # arg4
+        mr      7, 9                  # arg5
+        mr      8, 10                  # arg6
+        sc
+__cp_end:
+        bnslr+ # return if no summary overflow. 
+        #else negate result.
+        neg 3, 3
+        blr
+__cp_cancel:
+        b __cancel