flambda-backend: Fix for stack checks / frame pointers (#2603)

* CI job to test frame pointers with runtime5

* Avoid warning about rewrite_frame_pointers being unused

* Fix frame pointers tests

(cherry picked from commit 4184a7150d754a7d4903566ed5851e2d8f56e8a9)

* Fix for stack checks / frame pointers.

* Backtrace

* Handle non-segfaulting paths...

* Specialized version of ENTER_FUNCTION for caml_raise_stack_overflow_nat.

* Review

---------

Co-authored-by: Mark Shinwell <mshinwell@pm.me>

Author: xclerc

runtime/amd64.S

@@ -548,7 +548,6 @@ ENDFUNCTION(G(caml_call_gc))
 FUNCTION(G(caml_raise_stack_overflow_nat))
 CFI_STARTPROC
         CFI_SIGNAL_FRAME
-        ENTER_FUNCTION
         SAVE_ALL_REGS
         movq    %r15, Caml_state(gc_regs)
         /* We assume that we are always on the OCaml stack at this point.
@@ -558,12 +557,7 @@ CFI_STARTPROC
            in practice this seems most unlikely.  The current situation will
            suffice as this patch is only a temporary measure in any case. */
         SWITCH_OCAML_TO_C
-        C_call (GCALL(caml_raise_stack_overflow))
-        SWITCH_C_TO_OCAML
-        movq    Caml_state(gc_regs), %r15
-        RESTORE_ALL_REGS
-        LEAVE_FUNCTION
-        ret
+        CHECK_STACK_ALIGNMENT; jmp GCALL(caml_raise_stack_overflow)
 CFI_ENDPROC
 ENDFUNCTION(G(caml_raise_stack_overflow_nat))
 

runtime/fiber.c

@@ -749,6 +749,7 @@ void caml_rewrite_exception_stack(struct stack_info *old_stack,
 }
 
 #ifdef WITH_FRAME_POINTERS
+#if defined(STACK_CHECKS_ENABLED)
 /* Update absolute base pointers for new stack */
 static void rewrite_frame_pointers(struct stack_info *old_stack,
     struct stack_info *new_stack)
@@ -803,6 +804,7 @@ static void rewrite_frame_pointers(struct stack_info *old_stack,
 }
 #endif
 #endif
+#endif
 
 int caml_try_realloc_stack(asize_t required_space)
 {

testsuite/tests/frame-pointers/c_call.ml

@@ -6,6 +6,10 @@
  native;
 *)
 
+(* Force -O3 to ensure the "_code" symbols are present (see the
+   reference file). *)
+[@@@ocaml.flambda_o3]
+
 external fp_backtrace : unit -> unit = "fp_backtrace"
 external fp_backtrace_no_alloc : unit -> unit = "fp_backtrace" [@@noalloc]
 external fp_backtrace_many_args : int -> int -> int -> int -> int -> int -> int

testsuite/tests/frame-pointers/c_call.reference

@@ -1,19 +1,19 @@
 fp_backtrace_many_args
 caml_c_call_stack_args
-camlC_call.f
+camlC_call.f_0_1_code
 camlC_call.entry
 caml_program
 caml_start_program
 caml_main/caml_startup
 main
 caml_c_call
-camlC_call.f
+camlC_call.f_0_1_code
 camlC_call.entry
 caml_program
 caml_start_program
 caml_main/caml_startup
 main
-camlC_call.f
+camlC_call.f_0_1_code
 camlC_call.entry
 caml_program
 caml_start_program

testsuite/tests/frame-pointers/exception_handler.ml

@@ -6,6 +6,10 @@
  native;
 *)
 
+(* Force -O3 to ensure the "_code" symbols are present (see the
+   reference file). *)
+[@@@ocaml.flambda_o3]
+
 (* https://github.com/ocaml/ocaml/pull/11031 *)
 external fp_backtrace : unit -> unit = "fp_backtrace" [@@noalloc]
 

testsuite/tests/frame-pointers/exception_handler.reference

@@ -1,26 +1,26 @@
-camlException_handler.handler
-camlException_handler.bare
+camlException_handler.handler_2_7_code
+camlException_handler.bare_4_9_code
 camlException_handler.entry
 caml_program
 caml_start_program
 caml_main/caml_startup
 main
-camlException_handler.handler
-camlException_handler.bare
+camlException_handler.handler_2_7_code
+camlException_handler.bare_4_9_code
 camlException_handler.entry
 caml_program
 caml_start_program
 caml_main/caml_startup
 main
-camlException_handler.handler
-camlException_handler.nested
+camlException_handler.handler_2_7_code
+camlException_handler.nested_3_8_code
 camlException_handler.entry
 caml_program
 caml_start_program
 caml_main/caml_startup
 main
-camlException_handler.handler
-camlException_handler.nested
+camlException_handler.handler_2_7_code
+camlException_handler.nested_3_8_code
 camlException_handler.entry
 caml_program
 caml_start_program