src/rt/rust_upcall.cpp

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*
  Upcalls

  These are runtime functions that the compiler knows about and generates
  calls to. They are called on the Rust stack and, in most cases, immediately
  switch to the C stack.
 */

#include "rust_globals.h"
#include "rust_util.h"

//Unwinding ABI declarations.
typedef int _Unwind_Reason_Code;
typedef int _Unwind_Action;

struct _Unwind_Context;
struct _Unwind_Exception;

typedef void (*CDECL stack_switch_shim)(void*);

/**********************************************************************
 * Switches to the C-stack and invokes |fn_ptr|, passing |args| as argument.
 * This is used by the C compiler to call foreign functions and by other
 * upcalls to switch to the C stack.  The return value is passed through a
 * field in the args parameter. This upcall is specifically for switching
 * to the shim functions generated by rustc.
 */
extern "C" CDECL void
upcall_call_shim_on_c_stack(void *args, void *fn_ptr) {
    stack_switch_shim f = (stack_switch_shim)fn_ptr;
    f(args);
}

/*
 * The opposite of above. Starts on a C stack and switches to the Rust
 * stack. This is the only upcall that runs from the C stack.
 */
extern "C" CDECL void
upcall_call_shim_on_rust_stack(void *args, void *fn_ptr) {
    // There's no task. Call the function and hope for the best
    stack_switch_shim f = (stack_switch_shim)fn_ptr;
    f(args);
}

/**********************************************************************/

#ifdef __SEH__
#  define PERSONALITY_FUNC __gxx_personality_seh0
#else
#  ifdef __USING_SJLJ_EXCEPTIONS__
#    define PERSONALITY_FUNC __gxx_personality_sjlj
#  else
#    define PERSONALITY_FUNC __gxx_personality_v0
#  endif
#endif

extern "C" _Unwind_Reason_Code
PERSONALITY_FUNC(int version,
                     _Unwind_Action actions,
                     uint64_t exception_class,
                     _Unwind_Exception *ue_header,
                     _Unwind_Context *context);

struct s_rust_personality_args {
    _Unwind_Reason_Code retval;
    int version;
    _Unwind_Action actions;
    uint64_t exception_class;
    _Unwind_Exception *ue_header;
    _Unwind_Context *context;
};

extern "C" void
upcall_s_rust_personality(s_rust_personality_args *args) {
    args->retval = PERSONALITY_FUNC(args->version,
                                    args->actions,
                                    args->exception_class,
                                    args->ue_header,
                                    args->context);
}

/**
   The exception handling personality function. It figures
   out what to do with each landing pad. Just a stack-switching
   wrapper around the C++ personality function.
*/
extern "C" _Unwind_Reason_Code
upcall_rust_personality(int version,
                        _Unwind_Action actions,
                        uint64_t exception_class,
                        _Unwind_Exception *ue_header,
                        _Unwind_Context *context) {
    s_rust_personality_args args = {(_Unwind_Reason_Code)0,
                                    version, actions, exception_class,
                                    ue_header, context};
    upcall_s_rust_personality(&args);
    return args.retval;
}

// NB: This needs to be blazing fast. Don't switch stacks
extern "C" CDECL void *
upcall_new_stack(size_t stk_sz, void *args_addr, size_t args_sz) {
    assert(false && "newsched shouldn't be growing the stack");
    return NULL;
}

// NB: This needs to be blazing fast. Don't switch stacks
extern "C" CDECL void
upcall_del_stack() {
    assert(false && "newsched shouldn't be growing the stack");
}

// Landing pads need to call this to insert the
// correct limit into TLS.
// NB: This must run on the Rust stack because it
// needs to acquire the value of the stack pointer
extern "C" CDECL void
upcall_reset_stack_limit() {
}

//
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//