Permalink
Cannot retrieve contributors at this time
Name already in use
A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
glibc/sysdeps/unix/sysv/linux/x86_64/makecontext.c
Go to fileThis commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
121 lines (102 sloc)
3.84 KB
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/* Create new context. | |
Copyright (C) 2002-2016 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); | |
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) |