Commit 1cefe14424

Andrew Kelley <andrew@ziglang.org>
2019-09-16 20:22:32
update clone on arm32 to latest musl implementation
See musl commit 05870abeaac0588fb9115cfd11f96880a0af2108 by Rich Felker. Commit message from musl reproduced here: fix code path where child function returns in arm __clone built as thumb mov lr,pc is not a valid way to save the return address in thumb mode since it omits the thumb bit. use a chain of bl and bx to emulate blx. this could be avoided by converting to a .S file with preprocessor conditions to use blx if available, but the time cost here is dominated by the syscall anyway. while making this change, also remove the remnants of support for pre-bx ISA levels. commit 9f290a49bf9ee247d540d3c83875288a7991699c removed the hack from the parent code paths, but left the unnecessary code in the child. keeping it would require rewriting two code paths rather than one, and is useless for reasons described in that commit.
master
1 parent cddd6b4
Changed files (1)
std
special
c.zig
std/special/c.zig
@@ -258,16 +258,11 @@ nakedcc fn clone() void {
             \\    bx lr
             \\
             \\1:  mov r0,r6
-            \\    tst r5,#1
-            \\    bne 1f
-            \\    mov lr,pc
-            \\    mov pc,r5
+            \\    bl 3f
             \\2:  mov r7,#1
             \\    svc 0
-            \\
-            \\1:  mov lr,pc
-            \\    bx r5
             \\    b 2b
+            \\3:  bx r5
         );
     } else {
         @compileError("Implement clone() for this arch.");