/* ** GNU Pth - The GNU Portable Threads ** Copyright (c) 1999-2007 Ralf S. Engelschall ** ** This file is part of GNU Pth, a non-preemptive thread scheduling ** library which can be found at http://www.gnu.org/software/pth/. ** ** This library is free software; you can redistribute it and/or ** modify it under the terms of the GNU Lesser General Public ** License as published by the Free Software Foundation; either ** version 2.1 of the License, or (at your option) any later version. ** ** This library is distributed in the hope that it will be useful, ** but WITHOUT ANY WARRANTY; without even the implied warranty of ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ** Lesser General Public License for more details. ** ** You should have received a copy of the GNU Lesser General Public ** License along with this library; if not, write to the Free Software ** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 ** USA, or contact Ralf S. Engelschall . ** ** pth_uctx.c: Pth user-space context handling (stand-alone sub-API) */ /* ``It worries me however, to realize how tough an ass-hole I have had to be, in order to get to stick to the principle of doing things right, rather than "just hack it in".'' -- Poul-Henning Kamp */ #include "pth_p.h" /* user-space context structure */ struct pth_uctx_st { int uc_stack_own; /* whether stack were allocated by us */ char *uc_stack_ptr; /* pointer to start address of stack area */ size_t uc_stack_len; /* size of stack area */ int uc_mctx_set; /* whether uc_mctx is set */ pth_mctx_t uc_mctx; /* saved underlying machine context */ }; /* create user-space context structure */ int pth_uctx_create( pth_uctx_t *puctx) { pth_uctx_t uctx; /* argument sanity checking */ if (puctx == NULL) return pth_error(FALSE, EINVAL); /* allocate the context structure */ if ((uctx = (pth_uctx_t)malloc(sizeof(struct pth_uctx_st))) == NULL) return pth_error(FALSE, errno); /* initialize the context structure */ uctx->uc_stack_own = FALSE; uctx->uc_stack_ptr = NULL; uctx->uc_stack_len = 0; uctx->uc_mctx_set = FALSE; memset((void *)&uctx->uc_mctx, 0, sizeof(pth_mctx_t)); /* pass result to caller */ *puctx = uctx; return TRUE; } /* trampoline context */ typedef struct { pth_mctx_t *mctx_parent; pth_uctx_t uctx_this; pth_uctx_t uctx_after; void (*start_func)(void *); void *start_arg; } pth_uctx_trampoline_t; pth_uctx_trampoline_t pth_uctx_trampoline_ctx; /* trampoline function for pth_uctx_make() */ static void pth_uctx_trampoline(void) { volatile pth_uctx_trampoline_t ctx; /* move context information from global to local storage */ ctx.mctx_parent = pth_uctx_trampoline_ctx.mctx_parent; ctx.uctx_this = pth_uctx_trampoline_ctx.uctx_this; ctx.uctx_after = pth_uctx_trampoline_ctx.uctx_after; ctx.start_func = pth_uctx_trampoline_ctx.start_func; ctx.start_arg = pth_uctx_trampoline_ctx.start_arg; /* switch back to parent */ pth_mctx_switch(&(ctx.uctx_this->uc_mctx), ctx.mctx_parent); /* enter start function */ (*ctx.start_func)(ctx.start_arg); /* switch to successor user-space context */ if (ctx.uctx_after != NULL) pth_mctx_restore(&(ctx.uctx_after->uc_mctx)); /* terminate process (the only reasonable thing to do here) */ exit(0); /* NOTREACHED */ return; } /* make setup of user-space context structure */ int pth_uctx_make( pth_uctx_t uctx, char *sk_addr, size_t sk_size, const sigset_t *sigmask, void (*start_func)(void *), void *start_arg, pth_uctx_t uctx_after) { pth_mctx_t mctx_parent; sigset_t ss; /* argument sanity checking */ if (uctx == NULL || start_func == NULL || sk_size < 16*1024) return pth_error(FALSE, EINVAL); /* configure run-time stack */ if (sk_addr == NULL) { if ((sk_addr = (char *)malloc(sk_size)) == NULL) return pth_error(FALSE, errno); uctx->uc_stack_own = TRUE; } else uctx->uc_stack_own = FALSE; uctx->uc_stack_ptr = sk_addr; uctx->uc_stack_len = sk_size; /* configure the underlying machine context */ if (!pth_mctx_set(&uctx->uc_mctx, pth_uctx_trampoline, uctx->uc_stack_ptr, uctx->uc_stack_ptr+uctx->uc_stack_len)) return pth_error(FALSE, errno); /* move context information into global storage for the trampoline jump */ pth_uctx_trampoline_ctx.mctx_parent = &mctx_parent; pth_uctx_trampoline_ctx.uctx_this = uctx; pth_uctx_trampoline_ctx.uctx_after = uctx_after; pth_uctx_trampoline_ctx.start_func = start_func; pth_uctx_trampoline_ctx.start_arg = start_arg; /* optionally establish temporary signal mask */ if (sigmask != NULL) sigprocmask(SIG_SETMASK, sigmask, &ss); /* perform the trampoline step */ pth_mctx_switch(&mctx_parent, &(uctx->uc_mctx)); /* optionally restore original signal mask */ if (sigmask != NULL) sigprocmask(SIG_SETMASK, &ss, NULL); /* finally flag that the context is now configured */ uctx->uc_mctx_set = TRUE; return TRUE; } /* switch from current to other user-space context */ int pth_uctx_switch( pth_uctx_t uctx_from, pth_uctx_t uctx_to) { /* argument sanity checking */ if (uctx_from == NULL || uctx_to == NULL) return pth_error(FALSE, EINVAL); if (!(uctx_to->uc_mctx_set)) return pth_error(FALSE, EPERM); /* switch underlying machine context */ uctx_from->uc_mctx_set = TRUE; pth_mctx_switch(&(uctx_from->uc_mctx), &(uctx_to->uc_mctx)); return TRUE; } /* destroy user-space context structure */ int pth_uctx_destroy( pth_uctx_t uctx) { /* argument sanity checking */ if (uctx == NULL) return pth_error(FALSE, EINVAL); /* deallocate dynamically allocated stack */ if (uctx->uc_stack_own && uctx->uc_stack_ptr != NULL) free(uctx->uc_stack_ptr); /* deallocate context structure */ free(uctx); return TRUE; }