1 /* Linux-specific ptrace manipulation routines.
2 Copyright (C) 2012 Free Software Foundation, Inc.
4 This file is part of GDB.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program 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
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
23 #include "gdb_string.h"
26 #include "linux-ptrace.h"
27 #include "linux-procfs.h"
29 #include "gdb_assert.h"
31 /* Find all possible reasons we could fail to attach PID and append these
32 newline terminated reason strings to initialized BUFFER. '\0' termination
33 of BUFFER must be done by the caller. */
36 linux_ptrace_attach_warnings (pid_t pid
, struct buffer
*buffer
)
40 tracerpid
= linux_proc_get_tracerpid (pid
);
42 buffer_xml_printf (buffer
, _("warning: process %d is already traced "
44 (int) pid
, (int) tracerpid
);
46 if (linux_proc_pid_is_zombie (pid
))
47 buffer_xml_printf (buffer
, _("warning: process %d is a zombie "
48 "- the process has already terminated\n"),
54 /* Address of the 'ret' instruction in asm code block below. */
55 extern void (linux_ptrace_test_ret_to_nx_instr
) (void);
65 /* Test broken off-trunk Linux kernel patchset for NX support on i386. It was
66 removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd. */
69 linux_ptrace_test_ret_to_nx (void)
73 gdb_byte
*return_address
, *pc
;
77 return_address
= mmap (NULL
, 2, PROT_READ
| PROT_WRITE
,
78 MAP_PRIVATE
| MAP_ANONYMOUS
, -1, 0);
79 if (return_address
== MAP_FAILED
)
81 warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"),
86 /* Put there 'int3'. */
87 *return_address
= 0xcc;
93 warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"),
98 l
= ptrace (PTRACE_TRACEME
, 0, NULL
, NULL
);
100 warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
104 asm volatile ("pushl %0;"
105 ".globl linux_ptrace_test_ret_to_nx_instr;"
106 "linux_ptrace_test_ret_to_nx_instr:"
108 : : "r" (return_address
) : "%esp", "memory");
109 gdb_assert_not_reached ("asm block did not terminate");
115 got_pid
= waitpid (child
, &status
, 0);
116 gdb_assert (got_pid
== child
);
117 gdb_assert (WIFSTOPPED (status
));
119 /* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */
120 gdb_assert (WSTOPSIG (status
) == SIGTRAP
|| WSTOPSIG (status
) == SIGSEGV
);
123 l
= ptrace (PTRACE_PEEKUSER
, child
, (void *) (uintptr_t) (EIP
* 4), NULL
);
124 gdb_assert (errno
== 0);
125 pc
= (void *) (uintptr_t) l
;
127 if (ptrace (PTRACE_KILL
, child
, NULL
, NULL
) != 0)
128 warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_KILL: %s"),
134 got_pid
= waitpid (child
, &kill_status
, 0);
135 gdb_assert (got_pid
== child
);
136 gdb_assert (WIFSIGNALED (kill_status
));
139 /* + 1 is there as x86* stops after the 'int3' instruction. */
140 if (WSTOPSIG (status
) == SIGTRAP
&& pc
== return_address
+ 1)
146 /* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */
147 if (WSTOPSIG (status
) == SIGSEGV
&& pc
== return_address
)
153 gdb_assert ((void (*) (void)) pc
== &linux_ptrace_test_ret_to_nx_instr
);
155 warning (_("Cannot call inferior functions, you have broken "
156 "Linux kernel i386 NX (non-executable pages) support!"));
157 #endif /* __i386__ */
160 /* Display possible problems on this system. Display them only once per GDB
164 linux_ptrace_init_warnings (void)
166 static int warned
= 0;
172 linux_ptrace_test_ret_to_nx ();