Fix delivery of unhandled effect exceptions on s390x (ocaml#12486)

Delivery of Effect.Unhandled and Effect.Continuation_already_resumed (through caml_raise_unhandled_effect and caml_raise_continuation_already_resumed respectively) should not assume anything about the stack it runs on and thus should not bypass the first few instructions of caml_c_call.
dustanddreams · Sep 4, 2023 · 9a83067 · 9a83067
1 parent 221c769
commit 9a83067
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diff --git a/Changes b/Changes
@@ -331,6 +331,9 @@ Working version
 - #12949: open shadowing mistriggers
   (Gabriel Scherer, review by Florian Angeletti, report by Andreas Rossberg)
 
+- #12486: Fix delivery of unhandled effect exceptions on s390x
+  (Miod Vallat, report by Jan Midtgaard)
+
 OCaml 5.1.0
 ---------------
 

diff --git a/runtime/s390x.S b/runtime/s390x.S
@@ -753,7 +753,7 @@ LBL(112):
         SWITCH_OCAML_STACKS(%r9, %r8)
     /* No parent stack. Raise Unhandled. */
         LEA_VAR(caml_raise_unhandled_effect, ADDITIONAL_ARG)
-        brcl    15, LBL(caml_c_call)
+        brcl    15, GCALL(caml_c_call)
 CFI_ENDPROC
 ENDFUNCTION(G(caml_perform))
 
@@ -795,7 +795,7 @@ LBL(caml_resume_1):
         br      %r5
 LBL(caml_resume_2):
         LEA_VAR(caml_raise_continuation_already_resumed, ADDITIONAL_ARG)
-        brcl    15, LBL(caml_c_call)
+        brcl    15, G(caml_c_call)
 CFI_ENDPROC
 ENDFUNCTION(G(caml_resume))
 
@@ -891,6 +891,8 @@ CFI_STARTPROC
         CFI_OFFSET(14, -168)
         ENTER_FUNCTION
         LEA_VAR(caml_array_bound_error_asm, ADDITIONAL_ARG)
+    /* Note the following jumps in the middle of caml_c_call, since stack
+       has already been adjusted. */
         brcl    15, LBL(caml_c_call)
 CFI_ENDPROC
 ENDFUNCTION(G(caml_ml_array_bound_error))