1 | /* Create new context. |
2 | Copyright (C) 2002-2018 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Andreas Jaeger <aj@suse.de>, 2002. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either |
9 | version 2.1 of the License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; if not, see |
18 | <http://www.gnu.org/licenses/>. */ |
19 | |
20 | #include <sysdep.h> |
21 | #include <stdarg.h> |
22 | #include <stdint.h> |
23 | #include <ucontext.h> |
24 | |
25 | #include "ucontext_i.h" |
26 | |
27 | /* This implementation can handle any ARGC value but only |
28 | normal integer parameters. |
29 | makecontext sets up a stack and the registers for the |
30 | user context. The stack looks like this: |
31 | +-----------------------+ |
32 | | next context | |
33 | +-----------------------+ |
34 | | parameter 7-n | |
35 | +-----------------------+ |
36 | | trampoline address | |
37 | %rsp -> +-----------------------+ |
38 | |
39 | The registers are set up like this: |
40 | %rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6 |
41 | %rbx : address of next context |
42 | %rsp : stack pointer. |
43 | */ |
44 | |
45 | /* XXX: This implementation currently only handles integer arguments. |
46 | To handle long int and pointer arguments the va_arg arguments needs |
47 | to be changed to long and also the stdlib/tst-setcontext.c file needs |
48 | to be changed to pass long arguments to makecontext. */ |
49 | |
50 | |
51 | void |
52 | __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) |
53 | { |
54 | extern void __start_context (void) attribute_hidden; |
55 | greg_t *sp; |
56 | unsigned int idx_uc_link; |
57 | va_list ap; |
58 | int i; |
59 | |
60 | /* Generate room on stack for parameter if needed and uc_link. */ |
61 | sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp |
62 | + ucp->uc_stack.ss_size); |
63 | sp -= (argc > 6 ? argc - 6 : 0) + 1; |
64 | /* Align stack and make space for trampoline address. */ |
65 | sp = (greg_t *) ((((uintptr_t) sp) & -16L) - 8); |
66 | |
67 | idx_uc_link = (argc > 6 ? argc - 6 : 0) + 1; |
68 | |
69 | /* Setup context ucp. */ |
70 | /* Address to jump to. */ |
71 | ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func; |
72 | /* Setup rbx.*/ |
73 | ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[idx_uc_link]; |
74 | ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp; |
75 | |
76 | /* Setup stack. */ |
77 | sp[0] = (uintptr_t) &__start_context; |
78 | sp[idx_uc_link] = (uintptr_t) ucp->uc_link; |
79 | |
80 | va_start (ap, argc); |
81 | /* Handle arguments. |
82 | |
83 | The standard says the parameters must all be int values. This is |
84 | an historic accident and would be done differently today. For |
85 | x86-64 all integer values are passed as 64-bit values and |
86 | therefore extending the API to copy 64-bit values instead of |
87 | 32-bit ints makes sense. It does not break existing |
88 | functionality and it does not violate the standard which says |
89 | that passing non-int values means undefined behavior. */ |
90 | for (i = 0; i < argc; ++i) |
91 | switch (i) |
92 | { |
93 | case 0: |
94 | ucp->uc_mcontext.gregs[REG_RDI] = va_arg (ap, greg_t); |
95 | break; |
96 | case 1: |
97 | ucp->uc_mcontext.gregs[REG_RSI] = va_arg (ap, greg_t); |
98 | break; |
99 | case 2: |
100 | ucp->uc_mcontext.gregs[REG_RDX] = va_arg (ap, greg_t); |
101 | break; |
102 | case 3: |
103 | ucp->uc_mcontext.gregs[REG_RCX] = va_arg (ap, greg_t); |
104 | break; |
105 | case 4: |
106 | ucp->uc_mcontext.gregs[REG_R8] = va_arg (ap, greg_t); |
107 | break; |
108 | case 5: |
109 | ucp->uc_mcontext.gregs[REG_R9] = va_arg (ap, greg_t); |
110 | break; |
111 | default: |
112 | /* Put value on stack. */ |
113 | sp[i - 5] = va_arg (ap, greg_t); |
114 | break; |
115 | } |
116 | va_end (ap); |
117 | |
118 | } |
119 | |
120 | |
121 | weak_alias (__makecontext, makecontext) |
122 | |