NetBSD/lib/libpuffs/callcontext.c

369 lines
8.7 KiB
C

/* $NetBSD: callcontext.c,v 1.30 2018/07/09 00:47:47 christos Exp $ */
/*
* Copyright (c) 2006, 2007, 2008 Antti Kantee. All Rights Reserved.
*
* Development of this software was supported by the
* Research Foundation of Helsinki University of Technology
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#if !defined(lint)
__RCSID("$NetBSD: callcontext.c,v 1.30 2018/07/09 00:47:47 christos Exp $");
#endif /* !lint */
#include <sys/types.h>
#include <sys/mman.h>
#include <assert.h>
#include <errno.h>
#include <puffs.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ucontext.h>
#include <unistd.h>
#include "puffs_priv.h"
#if 0
#define DPRINTF(x) printf x
#else
#define DPRINTF(x)
#endif
/*
* Set the following to 1 to not handle each request on a separate
* stack. This is highly volatile kludge, therefore no external
* interface.
*/
int puffs_fakecc;
/*
* user stuff
*/
/*
* So, we need to get back to where we came from. This can happen in two
* different ways:
* 1) PCC_MLCONT is set, in which case we need to go to the mainloop
* 2) It is not set, and we simply jump to pcc_uc_ret.
*/
void
puffs_cc_yield(struct puffs_cc *pcc)
{
struct puffs_cc *jumpcc;
int rv;
assert(puffs_fakecc == 0);
if ((~pcc->pcc_flags & (PCC_BORROWED|PCC_DONE)) == 0) {
pcc->pcc_flags &= ~(PCC_BORROWED|PCC_DONE);
/*
* see the XXX comment in puffs__cc_cont
*/
puffs__cc_destroy(pcc, 1);
setcontext(&pcc->pcc_uc_ret);
}
pcc->pcc_flags &= ~PCC_BORROWED;
/* romanes eunt domus */
DPRINTF(("puffs_cc_yield: "));
if ((pcc->pcc_flags & PCC_MLCONT) == 0) {
DPRINTF(("no mlcont, pcc %p\n", pcc));
swapcontext(&pcc->pcc_uc, &pcc->pcc_uc_ret);
} else {
DPRINTF(("mlcont, pcc %p\n", pcc));
pcc->pcc_flags &= ~PCC_MLCONT;
rv = puffs__cc_create(pcc->pcc_pu, puffs__theloop, &jumpcc);
if (rv)
abort(); /* p-p-p-pa-pa-panic (XXX: fixme) */
swapcontext(&pcc->pcc_uc, &jumpcc->pcc_uc);
DPRINTF(("puffs_cc_yield: post swap pcc %p\n", pcc));
}
}
/*
* Internal continue routine. This has slightly different semantics.
* We simply make our cc available in the freelist and jump to the
* indicated pcc.
*/
void
puffs__cc_cont(struct puffs_cc *pcc)
{
struct puffs_cc *mycc;
mycc = puffs_cc_getcc(pcc->pcc_pu);
DPRINTF(("puffs__cc_cont: pcc %p, mycc %p\n", pcc, mycc));
/*
* XXX: race between setcontext() and recycle if
* we go multithreaded
*/
puffs__cc_destroy(mycc, 1);
pcc->pcc_flags |= PCC_MLCONT;
setcontext(&pcc->pcc_uc);
}
void
puffs_cc_continue(struct puffs_cc *pcc)
{
/* ramble on */
DPRINTF(("puffs_cc_continue: pcc %p\n", pcc));
if (puffs_fakecc) {
pcc->pcc_func(pcc->pcc_farg);
} else {
swapcontext(&pcc->pcc_uc_ret, &pcc->pcc_uc);
}
}
/*
* "Borrows" pcc, *NOT* called from pcc owner. Acts like continue.
* So the idea is to use this, give something the context back to
* run to completion and then jump back to where ever this was called
* from after the op dispatching is complete (or if the pcc decides to
* yield again).
*/
void
puffs__goto(struct puffs_cc *loanpcc)
{
loanpcc->pcc_flags |= PCC_BORROWED;
swapcontext(&loanpcc->pcc_uc_ret, &loanpcc->pcc_uc);
}
void
puffs_cc_schedule(struct puffs_cc *pcc)
{
struct puffs_usermount *pu = pcc->pcc_pu;
assert(pu->pu_state & PU_INLOOP);
TAILQ_INSERT_TAIL(&pu->pu_sched, pcc, pcc_schedent);
}
int
puffs_cc_getcaller(struct puffs_cc *pcc, pid_t *pid, lwpid_t *lid)
{
if ((pcc->pcc_flags & PCC_HASCALLER) == 0) {
errno = ESRCH;
return -1;
}
if (pid)
*pid = pcc->pcc_pid;
if (lid)
*lid = pcc->pcc_lid;
return 0;
}
static struct puffs_cc fakecc;
static struct puffs_cc *
slowccalloc(struct puffs_usermount *pu)
{
struct puffs_cc *volatile pcc;
void *sp;
size_t stacksize = 1<<pu->pu_cc_stackshift;
const long psize = sysconf(_SC_PAGESIZE);
if (puffs_fakecc)
return &fakecc;
sp = mmap(NULL, stacksize, PROT_READ|PROT_WRITE,
MAP_ANON|MAP_PRIVATE|MAP_ALIGNED(pu->pu_cc_stackshift), -1, 0);
if (sp == MAP_FAILED)
return NULL;
pcc = sp;
memset(pcc, 0, sizeof(struct puffs_cc));
#ifndef __MACHINE_STACK_GROWS_UP
mprotect((uint8_t *)sp + psize, (size_t)psize, PROT_NONE);
#else
mprotect((uint8_t *)sp + stacksize - psize, (size_t)psize, PROT_NONE);
#endif
/* initialize both ucontext's */
if (getcontext(&pcc->pcc_uc) == -1) {
munmap(pcc, stacksize);
return NULL;
}
if (getcontext(&pcc->pcc_uc_ret) == -1) {
munmap(pcc, stacksize);
return NULL;
}
return pcc;
}
int
puffs__cc_create(struct puffs_usermount *pu, puffs_ccfunc func,
struct puffs_cc **pccp)
{
struct puffs_cc *pcc;
size_t stacksize = 1<<pu->pu_cc_stackshift;
stack_t *st;
/* Do we have a cached copy? */
if (pu->pu_cc_nstored == 0) {
pcc = slowccalloc(pu);
if (pcc == NULL)
return -1;
pcc->pcc_pu = pu;
DPRINTF(("puffs__cc_create: allocated pcc %p\n", pcc));
} else {
pcc = LIST_FIRST(&pu->pu_ccmagazin);
assert(pcc != NULL);
LIST_REMOVE(pcc, pcc_rope);
pu->pu_cc_nstored--;
DPRINTF(("puffs__cc_create: magazin pcc %p\n", pcc));
}
assert(pcc->pcc_pu == pu);
if (puffs_fakecc) {
pcc->pcc_func = func;
pcc->pcc_farg = pcc;
} else {
const long psize = sysconf(_SC_PAGESIZE);
/* link context */
pcc->pcc_uc.uc_link = &pcc->pcc_uc_ret;
/* setup stack
*
* XXX: I guess this should theoretically be preserved by
* swapcontext(). However, it gets lost. So reinit it.
*/
st = &pcc->pcc_uc.uc_stack;
st->ss_sp = ((uint8_t *)(void *)pcc) + psize;
st->ss_size = stacksize - psize;
st->ss_flags = 0;
/*
* Give us an initial context to jump to.
*
* Our manual page says that portable code shouldn't
* rely on being able to pass pointers through makecontext().
* kjk says that NetBSD code doesn't need to worry about this.
* uwe says it would be like putting a "keep away from
* children" sign on a box of toys.
*/
makecontext(&pcc->pcc_uc, (void *)func, 1, (uintptr_t)pcc);
}
*pccp = pcc;
return 0;
}
void
puffs__cc_setcaller(struct puffs_cc *pcc, pid_t pid, lwpid_t lid)
{
pcc->pcc_pid = pid;
pcc->pcc_lid = lid;
pcc->pcc_flags |= PCC_HASCALLER;
}
static void
cc_free(struct puffs_cc *pcc)
{
struct puffs_usermount *pu = pcc->pcc_pu;
size_t stacksize = 1<<pu->pu_cc_stackshift;
DPRINTF(("invalidating pcc %p\n", pcc));
assert(!puffs_fakecc);
munmap(pcc, stacksize);
}
void
puffs__cc_destroy(struct puffs_cc *pcc, int nonuke)
{
struct puffs_usermount *pu = pcc->pcc_pu;
pcc->pcc_flags &= ~PCC_HASCALLER;
assert(pcc->pcc_flags == 0);
assert(!puffs_fakecc);
/* not over limit? stuff away in the store, otherwise nuke */
if (nonuke || pu->pu_cc_nstored < PUFFS_CCMAXSTORE) {
pcc->pcc_pb = NULL;
DPRINTF(("puffs__cc_destroy: storing pcc %p\n", pcc));
LIST_INSERT_HEAD(&pu->pu_ccmagazin, pcc, pcc_rope);
pu->pu_cc_nstored++;
} else {
cc_free(pcc);
}
}
void
puffs__cc_exit(struct puffs_usermount *pu)
{
struct puffs_cc *pcc;
while ((pcc = LIST_FIRST(&pu->pu_ccmagazin)) != NULL) {
LIST_REMOVE(pcc, pcc_rope);
cc_free(pcc);
}
}
struct puffs_cc *
puffs_cc_getcc(struct puffs_usermount *pu)
{
size_t stacksize = 1<<pu->pu_cc_stackshift;
uintptr_t bottom;
if (puffs_fakecc)
return &fakecc;
bottom = ((uintptr_t)&bottom) & ~(stacksize-1);
return (struct puffs_cc *)bottom;
}
int
puffs__cc_savemain(struct puffs_usermount *pu)
{
if (puffs_fakecc)
return 0;
PU_CLRSFLAG(pu, PU_MAINRESTORE);
return getcontext(&pu->pu_mainctx);
}
int
puffs__cc_restoremain(struct puffs_usermount *pu)
{
if (puffs_fakecc)
return 0;
puffs__cc_destroy(puffs_cc_getcc(pu), 1);
PU_SETSFLAG(pu, PU_MAINRESTORE);
return setcontext(&pu->pu_mainctx);
}