From dad58090c6b195675a7039b380736b5b476fda0a Mon Sep 17 00:00:00 2001
From: Xavier Leroy <xavier.leroy@inria.fr>
Date: Mon, 27 Jun 2016 04:52:48 -0400
Subject: [PATCH] s390x.S: fix errors related to stack backtraces

caml_raise_exception: set caml_backtrace_pos = 0, this is not a reraise

caml_ml_array_bound_error: save SP before decrementing it, otherwise
it doesn't match the frame descriptor generated by ocamlopt

Cleanup: no need to set caml_return_address to 0 on return, that was
useful a long time ago but no longer is.
---
 asmrun/s390x.S | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/asmrun/s390x.S b/asmrun/s390x.S
index 175ea6a08..0e8ebf30c 100644
--- a/asmrun/s390x.S
+++ b/asmrun/s390x.S
@@ -110,6 +110,7 @@ caml_call_gc:
         .type   caml_c_call, @function
 caml_c_call:
         Storeglobal(%r15, caml_bottom_of_stack)
+.L101:
     /* Save return address */
         ldgr    %f15, %r14
     /* Get ready to call C function (address in r7) */
@@ -125,10 +126,6 @@ caml_c_call:
     /* Reload allocation pointer and allocation limit*/
         Loadglobal(%r11, caml_young_ptr)
         Loadglobal(%r10, caml_young_limit)
-    /* Say we are back into OCaml code */
-        lgfi   %r0, 0
-        Storeglobal(%r0, caml_last_return_address)
-
     /* Return to caller */
         br %r14
 
@@ -181,7 +178,7 @@ caml_reraise_exn:
         .globl  caml_raise_exception
         .type   caml_raise_exception, @function
 caml_raise_exception:
-        Loadglobal32(0, caml_backtrace_active)
+        Loadglobal32(%r0, caml_backtrace_active)
         cgfi    %r0, 0
         jne    .L112
 .L113:
@@ -189,9 +186,6 @@ caml_raise_exception:
         Loadglobal(%r15, caml_exception_pointer)
         Loadglobal(%r11, caml_young_ptr)
         Loadglobal(%r10, caml_young_limit)
-    /* Say we are back into OCaml code */
-        lgfi   %r0, 0
-        Storeglobal(%r0, caml_last_return_address)
     /* Pop trap frame */
         lg      %r1, 0(%r15)
         lg      %r13, 8(%r15)
@@ -199,7 +193,9 @@ caml_raise_exception:
     /* Branch to handler */
         br      %r1;
 .L112:
-        ldgr    %f15,%r2        /* preserve exn bucket in callee-save reg */
+        lgfi      %r0, 0
+        Storeglobal32(%r0, caml_backtrace_pos)
+	ldgr    %f15,%r2        /* preserve exn bucket in callee-save reg */
                                 /* arg1: exception bucket, already in r2 */
         Loadglobal(%r3, caml_last_return_address) /* arg2: PC of raise */
         Loadglobal(%r4, caml_bottom_of_stack)     /* arg3: SP of raise */
@@ -335,9 +331,12 @@ caml_callback3_exn:
         .globl  caml_ml_array_bound_error
         .type   caml_ml_array_bound_error, @function
 caml_ml_array_bound_error:
+	/* Save return address before decrementing SP, otherwise
+	   the frame descriptor for the call site is not correct */
+        Storeglobal(%r15, caml_bottom_of_stack)
         lay     %r15, -160(%r15)    /* Reserve stack space for C call */
         larl    %r7, caml_array_bound_error
-        j       caml_c_call
+        j       .L101
         .globl  caml_system__code_end
 caml_system__code_end: