1 /* BSD Kernel Data Access Library (libkvm) interface.
2 
3    Copyright 2004 Free Software Foundation, Inc.
4 
5    This file is part of GDB.
6 
7    This program is free software; you can redistribute it and/or modify
8    it under the terms of the GNU General Public License as published by
9    the Free Software Foundation; either version 2 of the License, or
10    (at your option) any later version.
11 
12    This program is distributed in the hope that it will be useful,
13    but WITHOUT ANY WARRANTY; without even the implied warranty of
14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15    GNU General Public License for more details.
16 
17    You should have received a copy of the GNU General Public License
18    along with this program; if not, write to the Free Software
19    Foundation, Inc., 59 Temple Place - Suite 330,
20    Boston, MA 02111-1307, USA.  */
21 
22 #include "defs.h"
23 #include "cli/cli-cmds.h"
24 #include "command.h"
25 #include "frame.h"
26 #include "regcache.h"
27 #include "target.h"
28 #include "value.h"
29 
30 #include "gdb_assert.h"
31 #include <fcntl.h>
32 #include <kvm.h>
33 #include <nlist.h>
34 #include "readline/readline.h"
35 #include <sys/param.h>
36 #include <sys/proc.h>
37 #include <sys/user.h>
38 
39 #include "bsd-kvm.h"
40 
41 /* Kernel memory interface descriptor.  */
42 kvm_t *core_kd;
43 
44 /* Address of process control block.  */
45 struct pcb *bsd_kvm_paddr;
46 
47 /* Pointer to architecture-specific function that reconstructs the
48    register state from PCB and supplies it to REGCACHE.  */
49 int (*bsd_kvm_supply_pcb)(struct regcache *regcache, struct pcb *pcb);
50 
51 /* Target ops for libkvm interface.  */
52 struct target_ops bsd_kvm_ops;
53 
54 static void
bsd_kvm_open(char * filename,int from_tty)55 bsd_kvm_open (char *filename, int from_tty)
56 {
57   char errbuf[_POSIX2_LINE_MAX];
58   char *execfile = NULL;
59   kvm_t *temp_kd;
60 
61   target_preopen (from_tty);
62 
63   if (filename)
64     {
65       char *temp;
66 
67       filename = tilde_expand (filename);
68       if (filename[0] != '/')
69 	{
70 	  temp = concat (current_directory, "/", filename, NULL);
71 	  xfree (filename);
72 	  filename = temp;
73 	}
74     }
75 
76   temp_kd = kvm_openfiles (execfile, filename, NULL, O_RDONLY, errbuf);
77   if (temp_kd == NULL)
78     error ("%s", errbuf);
79 
80   unpush_target (&bsd_kvm_ops);
81   core_kd = temp_kd;
82   push_target (&bsd_kvm_ops);
83 
84   target_fetch_registers (-1);
85 
86   flush_cached_frames ();
87   select_frame (get_current_frame ());
88   print_stack_frame (get_selected_frame (), -1, 1);
89 }
90 
91 static void
bsd_kvm_close(int quitting)92 bsd_kvm_close (int quitting)
93 {
94   if (core_kd)
95     {
96       if (kvm_close (core_kd) == -1)
97 	warning ("%s", kvm_geterr(core_kd));
98       core_kd = NULL;
99     }
100 }
101 
102 static int
bsd_kvm_xfer_memory(CORE_ADDR memaddr,char * myaddr,int len,int write,struct mem_attrib * attrib,struct target_ops * ops)103 bsd_kvm_xfer_memory (CORE_ADDR memaddr, char *myaddr, int len,
104 		    int write, struct mem_attrib *attrib,
105 		    struct target_ops *ops)
106 {
107   if (write)
108     return kvm_write (core_kd, memaddr, myaddr, len);
109   else
110     return kvm_read (core_kd, memaddr, myaddr, len);
111 
112   return -1;
113 }
114 
115 /* Fetch process control block at address PADDR.  */
116 
117 static int
bsd_kvm_fetch_pcb(struct pcb * paddr)118 bsd_kvm_fetch_pcb (struct pcb *paddr)
119 {
120   struct pcb pcb;
121 
122   if (kvm_read (core_kd, (unsigned long) paddr, &pcb, sizeof pcb) == -1)
123     error ("%s", kvm_geterr (core_kd));
124 
125   gdb_assert (bsd_kvm_supply_pcb);
126   return bsd_kvm_supply_pcb (current_regcache, &pcb);
127 }
128 
129 static void
bsd_kvm_fetch_registers(int regnum)130 bsd_kvm_fetch_registers (int regnum)
131 {
132   struct nlist nl[2];
133 
134   if (bsd_kvm_paddr)
135     {
136       bsd_kvm_fetch_pcb (bsd_kvm_paddr);
137       return;
138     }
139 
140   /* On dumping core, BSD kernels store the faulting context (PCB)
141      in the variable "dumppcb".  */
142   memset (nl, 0, sizeof nl);
143   nl[0].n_name = "_dumppcb";
144 
145   if (kvm_nlist (core_kd, nl) == -1)
146     error ("%s", kvm_geterr (core_kd));
147 
148   if (nl[0].n_value != 0)
149     {
150       /* Found dumppcb. If it contains a valid context, return
151 	 immediately.  */
152       if (bsd_kvm_fetch_pcb ((struct pcb *) nl[0].n_value))
153 	return;
154     }
155 
156   /* Traditional BSD kernels have a process proc0 that should always
157      be present.  The address of proc0's PCB is stored in the variable
158      "proc0paddr".  */
159 
160   memset (nl, 0, sizeof nl);
161   nl[0].n_name = "_proc0paddr";
162 
163   if (kvm_nlist (core_kd, nl) == -1)
164     error ("%s", kvm_geterr (core_kd));
165 
166   if (nl[0].n_value != 0)
167     {
168       struct pcb *paddr;
169 
170       /* Found proc0paddr.  */
171       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
172 	error ("%s", kvm_geterr (core_kd));
173 
174       bsd_kvm_fetch_pcb (paddr);
175       return;
176     }
177 
178 #ifdef HAVE_STRUCT_THREAD_TD_PCB
179   /* In FreeBSD kernels for 5.0-RELEASE and later, the PCB no longer
180      lives in `struct proc' but in `struct thread'.  The `struct
181      thread' for the initial thread for proc0 can be found in the
182      variable "thread0".  */
183 
184   memset (nl, 0, sizeof nl);
185   nl[0].n_name = "_thread0";
186 
187   if (kvm_nlist (core_kd, nl) == -1)
188     error ("%s", kvm_geterr (core_kd));
189 
190   if (nl[0].n_value != 0)
191     {
192       struct pcb *paddr;
193 
194       /* Found thread0.  */
195       nl[0].n_value += offsetof (struct thread, td_pcb);
196       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
197 	error ("%s", kvm_geterr (core_kd));
198 
199       bsd_kvm_fetch_pcb (paddr);
200       return;
201     }
202 #endif
203 
204   error ("Cannot find a valid PCB");
205 }
206 
207 
208 /* Kernel memory interface commands.  */
209 struct cmd_list_element *bsd_kvm_cmdlist;
210 
211 static void
bsd_kvm_cmd(char * arg,int fromtty)212 bsd_kvm_cmd (char *arg, int fromtty)
213 {
214   /* ??? Should this become an alias for "target kvm"?  */
215 }
216 
217 #ifndef HAVE_STRUCT_THREAD_TD_PCB
218 
219 static void
bsd_kvm_proc_cmd(char * arg,int fromtty)220 bsd_kvm_proc_cmd (char *arg, int fromtty)
221 {
222   CORE_ADDR addr;
223 
224   if (arg == NULL)
225     error_no_arg ("proc address");
226 
227   if (core_kd == NULL)
228     error ("No kernel memory image.");
229 
230   addr = parse_and_eval_address (arg);
231   addr += offsetof (struct proc, p_addr);
232 
233   if (kvm_read (core_kd, addr, &bsd_kvm_paddr, sizeof bsd_kvm_paddr) == -1)
234     error ("%s", kvm_geterr (core_kd));
235 
236   target_fetch_registers (-1);
237 
238   flush_cached_frames ();
239   select_frame (get_current_frame ());
240   print_stack_frame (get_selected_frame (), -1, 1);
241 }
242 
243 #endif
244 
245 static void
bsd_kvm_pcb_cmd(char * arg,int fromtty)246 bsd_kvm_pcb_cmd (char *arg, int fromtty)
247 {
248   if (arg == NULL)
249     error_no_arg ("pcb address");
250 
251   if (core_kd == NULL)
252     error ("No kernel memory image.");
253 
254   bsd_kvm_paddr = (struct pcb *) parse_and_eval_address (arg);
255 
256   target_fetch_registers (-1);
257 
258   flush_cached_frames ();
259   select_frame (get_current_frame ());
260   print_stack_frame (get_selected_frame (), -1, 1);
261 }
262 
263 /* Add the libkvm interface to the list of all possible targets and
264    register CUPPLY_PCB as the architecture-specific process control
265    block interpreter.  */
266 
267 void
bsd_kvm_add_target(int (* supply_pcb)(struct regcache *,struct pcb *))268 bsd_kvm_add_target (int (*supply_pcb)(struct regcache *, struct pcb *))
269 {
270   gdb_assert (bsd_kvm_supply_pcb == NULL);
271   bsd_kvm_supply_pcb = supply_pcb;
272 
273   bsd_kvm_ops.to_shortname = "kvm";
274   bsd_kvm_ops.to_longname = "Kernel memory interface";
275   bsd_kvm_ops.to_doc = "Use a kernel virtual memory image as a target.\n\
276 Optionally specify the filename of a core dump.";
277   bsd_kvm_ops.to_open = bsd_kvm_open;
278   bsd_kvm_ops.to_close = bsd_kvm_close;
279   bsd_kvm_ops.to_fetch_registers = bsd_kvm_fetch_registers;
280   bsd_kvm_ops.to_xfer_memory = bsd_kvm_xfer_memory;
281   bsd_kvm_ops.to_stratum = process_stratum;
282   bsd_kvm_ops.to_has_memory = 1;
283   bsd_kvm_ops.to_has_stack = 1;
284   bsd_kvm_ops.to_has_registers = 1;
285   bsd_kvm_ops.to_magic = OPS_MAGIC;
286 
287   add_target (&bsd_kvm_ops);
288 
289   add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, "\
290 Generic command for manipulating the kernel memory interface.",
291 		  &bsd_kvm_cmdlist, "kvm ", 0, &cmdlist);
292 
293 #ifndef HAVE_STRUCT_THREAD_TD_PCB
294   add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
295 	   "Set current context from proc address", &bsd_kvm_cmdlist);
296 #endif
297   add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
298 	   "Set current context from pcb address", &bsd_kvm_cmdlist);
299 }
300