diff options
Diffstat (limited to 'src/pkg/runtime/cgocall.c')
| -rw-r--r-- | src/pkg/runtime/cgocall.c | 246 |
1 files changed, 0 insertions, 246 deletions
diff --git a/src/pkg/runtime/cgocall.c b/src/pkg/runtime/cgocall.c deleted file mode 100644 index 58f287e90..000000000 --- a/src/pkg/runtime/cgocall.c +++ /dev/null @@ -1,246 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -#include "runtime.h" -#include "arch.h" -#include "stack.h" -#include "cgocall.h" - -// Cgo call and callback support. -// -// To call into the C function f from Go, the cgo-generated code calls -// runtime.cgocall(_cgo_Cfunc_f, frame), where _cgo_Cfunc_f is a -// gcc-compiled function written by cgo. -// -// runtime.cgocall (below) locks g to m, calls entersyscall -// so as not to block other goroutines or the garbage collector, -// and then calls runtime.asmcgocall(_cgo_Cfunc_f, frame). -// -// runtime.asmcgocall (in $GOARCH/asm.s) switches to the m->g0 stack -// (assumed to be an operating system-allocated stack, so safe to run -// gcc-compiled code on) and calls _cgo_Cfunc_f(frame). -// -// _cgo_Cfunc_f invokes the actual C function f with arguments -// taken from the frame structure, records the results in the frame, -// and returns to runtime.asmcgocall. -// -// After it regains control, runtime.asmcgocall switches back to the -// original g (m->curg)'s stack and returns to runtime.cgocall. -// -// After it regains control, runtime.cgocall calls exitsyscall, which blocks -// until this m can run Go code without violating the $GOMAXPROCS limit, -// and then unlocks g from m. -// -// The above description skipped over the possibility of the gcc-compiled -// function f calling back into Go. If that happens, we continue down -// the rabbit hole during the execution of f. -// -// To make it possible for gcc-compiled C code to call a Go function p.GoF, -// cgo writes a gcc-compiled function named GoF (not p.GoF, since gcc doesn't -// know about packages). The gcc-compiled C function f calls GoF. -// -// GoF calls crosscall2(_cgoexp_GoF, frame, framesize). Crosscall2 -// (in cgo/$GOOS.S, a gcc-compiled assembly file) is a two-argument -// adapter from the gcc function call ABI to the 6c function call ABI. -// It is called from gcc to call 6c functions. In this case it calls -// _cgoexp_GoF(frame, framesize), still running on m->g0's stack -// and outside the $GOMAXPROCS limit. Thus, this code cannot yet -// call arbitrary Go code directly and must be careful not to allocate -// memory or use up m->g0's stack. -// -// _cgoexp_GoF calls runtime.cgocallback(p.GoF, frame, framesize). -// (The reason for having _cgoexp_GoF instead of writing a crosscall3 -// to make this call directly is that _cgoexp_GoF, because it is compiled -// with 6c instead of gcc, can refer to dotted names like -// runtime.cgocallback and p.GoF.) -// -// runtime.cgocallback (in $GOOS/asm.s) switches from m->g0's -// stack to the original g (m->curg)'s stack, on which it calls -// runtime.cgocallbackg(p.GoF, frame, framesize). -// As part of the stack switch, runtime.cgocallback saves the current -// SP as m->g0->sched.sp, so that any use of m->g0's stack during the -// execution of the callback will be done below the existing stack frames. -// Before overwriting m->g0->sched.sp, it pushes the old value on the -// m->g0 stack, so that it can be restored later. -// -// runtime.cgocallbackg (below) is now running on a real goroutine -// stack (not an m->g0 stack). First it calls runtime.exitsyscall, which will -// block until the $GOMAXPROCS limit allows running this goroutine. -// Once exitsyscall has returned, it is safe to do things like call the memory -// allocator or invoke the Go callback function p.GoF. runtime.cgocallback -// first defers a function to unwind m->g0.sched.sp, so that if p.GoF -// panics, m->g0.sched.sp will be restored to its old value: the m->g0 stack -// and the m->curg stack will be unwound in lock step. -// Then it calls p.GoF. Finally it pops but does not execute the deferred -// function, calls runtime.entersyscall, and returns to runtime.cgocallback. -// -// After it regains control, runtime.cgocallback switches back to -// m->g0's stack (the pointer is still in m->g0.sched.sp), restores the old -// m->g0.sched.sp value from the stack, and returns to _cgoexp_GoF. -// -// _cgoexp_GoF immediately returns to crosscall2, which restores the -// callee-save registers for gcc and returns to GoF, which returns to f. - -void *initcgo; /* filled in by dynamic linker when Cgo is available */ -int64 ncgocall; - -static void unlockm(void); -static void unwindm(void); - -// Call from Go to C. - -void -runtime·cgocall(void (*fn)(void*), void *arg) -{ - Defer *d; - - if(!runtime·iscgo) - runtime·throw("cgocall unavailable"); - - if(fn == 0) - runtime·throw("cgocall nil"); - - ncgocall++; - - /* - * Lock g to m to ensure we stay on the same stack if we do a - * cgo callback. - */ - d = nil; - if(m->lockedg == nil) { - m->lockedg = g; - g->lockedm = m; - - // Add entry to defer stack in case of panic. - d = runtime·malloc(sizeof(*d)); - d->fn = (byte*)unlockm; - d->siz = 0; - d->link = g->defer; - d->argp = (void*)-1; // unused because unwindm never recovers - g->defer = d; - } - - /* - * Announce we are entering a system call - * so that the scheduler knows to create another - * M to run goroutines while we are in the - * foreign code. - * - * The call to asmcgocall is guaranteed not to - * split the stack and does not allocate memory, - * so it is safe to call while "in a system call", outside - * the $GOMAXPROCS accounting. - */ - runtime·entersyscall(); - runtime·asmcgocall(fn, arg); - runtime·exitsyscall(); - - if(d != nil) { - if(g->defer != d || d->fn != (byte*)unlockm) - runtime·throw("runtime: bad defer entry in cgocallback"); - g->defer = d->link; - runtime·free(d); - unlockm(); - } -} - -static void -unlockm(void) -{ - m->lockedg = nil; - g->lockedm = nil; -} - -void -runtime·Cgocalls(int64 ret) -{ - ret = ncgocall; - FLUSH(&ret); -} - -// Helper functions for cgo code. - -void (*_cgo_malloc)(void*); -void (*_cgo_free)(void*); - -void* -runtime·cmalloc(uintptr n) -{ - struct { - uint64 n; - void *ret; - } a; - - a.n = n; - a.ret = nil; - runtime·cgocall(_cgo_malloc, &a); - return a.ret; -} - -void -runtime·cfree(void *p) -{ - runtime·cgocall(_cgo_free, p); -} - -// Call from C back to Go. - -void -runtime·cgocallbackg(void (*fn)(void), void *arg, uintptr argsize) -{ - Defer *d; - - if(g != m->curg) - runtime·throw("runtime: bad g in cgocallback"); - - runtime·exitsyscall(); // coming out of cgo call - - // Add entry to defer stack in case of panic. - d = runtime·malloc(sizeof(*d)); - d->fn = (byte*)unwindm; - d->siz = 0; - d->link = g->defer; - d->argp = (void*)-1; // unused because unwindm never recovers - g->defer = d; - - // Invoke callback. - reflect·call((byte*)fn, arg, argsize); - - // Pop defer. - // Do not unwind m->g0->sched.sp. - // Our caller, cgocallback, will do that. - if(g->defer != d || d->fn != (byte*)unwindm) - runtime·throw("runtime: bad defer entry in cgocallback"); - g->defer = d->link; - runtime·free(d); - - runtime·entersyscall(); // going back to cgo call -} - -static void -unwindm(void) -{ - // Restore sp saved by cgocallback during - // unwind of g's stack (see comment at top of file). - switch(thechar){ - default: - runtime·throw("runtime: unwindm not implemented"); - case '8': - case '6': - m->g0->sched.sp = *(void**)m->g0->sched.sp; - break; - } -} - -void -runtime·badcgocallback(void) // called from assembly -{ - runtime·throw("runtime: misaligned stack in cgocallback"); -} - -void -runtime·cgounimpl(void) // called from (incomplete) assembly -{ - runtime·throw("runtime: cgo not implemented"); -} |