| /* Create new context. |
| Copyright (C) 2002-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Andreas Jaeger <aj@suse.de>, 2002. |
| |
| The GNU C 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. |
| |
| The GNU C 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 the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <sysdep.h> |
| #include <stdarg.h> |
| #include <stdint.h> |
| #include <ucontext.h> |
| |
| #include "ucontext_i.h" |
| |
| /* This implementation can handle any ARGC value but only |
| normal integer parameters. |
| makecontext sets up a stack and the registers for the |
| user context. The stack looks like this: |
| +-----------------------+ |
| | next context | |
| +-----------------------+ |
| | parameter 7-n | |
| +-----------------------+ |
| | trampoline address | |
| %rsp -> +-----------------------+ |
| |
| The registers are set up like this: |
| %rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6 |
| %rbx : address of next context |
| %rsp : stack pointer. |
| */ |
| |
| /* XXX: This implementation currently only handles integer arguments. |
| To handle long int and pointer arguments the va_arg arguments needs |
| to be changed to long and also the stdlib/tst-setcontext.c file needs |
| to be changed to pass long arguments to makecontext. */ |
| |
| |
| void |
| __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) |
| { |
| extern void __start_context (void) attribute_hidden; |
| greg_t *sp; |
| unsigned int idx_uc_link; |
| va_list ap; |
| int i; |
| |
| /* Generate room on stack for parameter if needed and uc_link. */ |
| sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp |
| + ucp->uc_stack.ss_size); |
| sp -= (argc > 6 ? argc - 6 : 0) + 1; |
| /* Align stack and make space for trampoline address. */ |
| sp = (greg_t *) ((((uintptr_t) sp) & -16L) - 8); |
| |
| idx_uc_link = (argc > 6 ? argc - 6 : 0) + 1; |
| |
| /* Setup context ucp. */ |
| /* Address to jump to. */ |
| ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func; |
| /* Setup rbx.*/ |
| ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[idx_uc_link]; |
| ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp; |
| |
| /* Setup stack. */ |
| sp[0] = (uintptr_t) &__start_context; |
| sp[idx_uc_link] = (uintptr_t) ucp->uc_link; |
| |
| va_start (ap, argc); |
| /* Handle arguments. |
| |
| The standard says the parameters must all be int values. This is |
| an historic accident and would be done differently today. For |
| x86-64 all integer values are passed as 64-bit values and |
| therefore extending the API to copy 64-bit values instead of |
| 32-bit ints makes sense. It does not break existing |
| functionality and it does not violate the standard which says |
| that passing non-int values means undefined behavior. */ |
| for (i = 0; i < argc; ++i) |
| switch (i) |
| { |
| case 0: |
| ucp->uc_mcontext.gregs[REG_RDI] = va_arg (ap, greg_t); |
| break; |
| case 1: |
| ucp->uc_mcontext.gregs[REG_RSI] = va_arg (ap, greg_t); |
| break; |
| case 2: |
| ucp->uc_mcontext.gregs[REG_RDX] = va_arg (ap, greg_t); |
| break; |
| case 3: |
| ucp->uc_mcontext.gregs[REG_RCX] = va_arg (ap, greg_t); |
| break; |
| case 4: |
| ucp->uc_mcontext.gregs[REG_R8] = va_arg (ap, greg_t); |
| break; |
| case 5: |
| ucp->uc_mcontext.gregs[REG_R9] = va_arg (ap, greg_t); |
| break; |
| default: |
| /* Put value on stack. */ |
| sp[i - 5] = va_arg (ap, greg_t); |
| break; |
| } |
| va_end (ap); |
| |
| } |
| |
| |
| weak_alias (__makecontext, makecontext) |