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1 | /* GNU/Linux on ARM native support. |
2 | Copyright 1999 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GDB. | |
5 | ||
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 2 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
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. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with this program; if not, write to the Free Software | |
18 | Foundation, Inc., 59 Temple Place - Suite 330, | |
19 | Boston, MA 02111-1307, USA. */ | |
20 | ||
21 | #include "defs.h" | |
22 | #include "inferior.h" | |
23 | #include "gdbcore.h" | |
24 | #include "gdb_string.h" | |
25 | ||
26 | #include <sys/user.h> | |
27 | #include <sys/ptrace.h> | |
28 | #include <sys/utsname.h> | |
29 | ||
30 | extern int arm_apcs_32; | |
31 | ||
32 | #define typeNone 0x00 | |
33 | #define typeSingle 0x01 | |
34 | #define typeDouble 0x02 | |
35 | #define typeExtended 0x03 | |
36 | #define FPWORDS 28 | |
37 | #define CPSR_REGNUM 16 | |
38 | ||
39 | typedef union tagFPREG | |
40 | { | |
41 | unsigned int fSingle; | |
42 | unsigned int fDouble[2]; | |
43 | unsigned int fExtended[3]; | |
44 | } | |
45 | FPREG; | |
46 | ||
47 | typedef struct tagFPA11 | |
48 | { | |
49 | FPREG fpreg[8]; /* 8 floating point registers */ | |
50 | unsigned int fpsr; /* floating point status register */ | |
51 | unsigned int fpcr; /* floating point control register */ | |
52 | unsigned char fType[8]; /* type of floating point value held in | |
53 | floating point registers. */ | |
54 | int initflag; /* NWFPE initialization flag. */ | |
55 | } | |
56 | FPA11; | |
57 | ||
58 | /* The following variables are used to determine the version of the | |
59 | underlying Linux operating system. Examples: | |
60 | ||
61 | Linux 2.0.35 Linux 2.2.12 | |
62 | os_version = 0x00020023 os_version = 0x0002020c | |
63 | os_major = 2 os_major = 2 | |
64 | os_minor = 0 os_minor = 2 | |
65 | os_release = 35 os_release = 12 | |
66 | ||
67 | Note: os_version = (os_major << 16) | (os_minor << 8) | os_release | |
68 | ||
69 | These are initialized using get_linux_version() from | |
70 | _initialize_arm_linux_nat(). */ | |
71 | ||
72 | static unsigned int os_version, os_major, os_minor, os_release; | |
73 | ||
74 | static void | |
75 | fetch_nw_fpe_single (unsigned int fn, FPA11 * fpa11, unsigned int *pmem) | |
76 | { | |
77 | unsigned int mem[3]; | |
78 | ||
79 | mem[0] = fpa11->fpreg[fn].fSingle; | |
80 | mem[1] = 0; | |
81 | mem[2] = 0; | |
82 | supply_register (F0_REGNUM + fn, (char *) &mem[0]); | |
83 | } | |
84 | ||
85 | static void | |
86 | fetch_nw_fpe_double (unsigned int fn, FPA11 * fpa11, unsigned int *pmem) | |
87 | { | |
88 | unsigned int mem[3]; | |
89 | ||
90 | mem[0] = fpa11->fpreg[fn].fDouble[1]; | |
91 | mem[1] = fpa11->fpreg[fn].fDouble[0]; | |
92 | mem[2] = 0; | |
93 | supply_register (F0_REGNUM + fn, (char *) &mem[0]); | |
94 | } | |
95 | ||
96 | static void | |
97 | fetch_nw_fpe_none (unsigned int fn, FPA11 * fpa11, unsigned int *pmem) | |
98 | { | |
99 | unsigned int mem[3] = | |
100 | {0, 0, 0}; | |
101 | ||
102 | supply_register (F0_REGNUM + fn, (char *) &mem[0]); | |
103 | } | |
104 | ||
105 | static void | |
106 | fetch_nw_fpe_extended (unsigned int fn, FPA11 * fpa11, unsigned int *pmem) | |
107 | { | |
108 | unsigned int mem[3]; | |
109 | ||
110 | mem[0] = fpa11->fpreg[fn].fExtended[0]; /* sign & exponent */ | |
111 | mem[1] = fpa11->fpreg[fn].fExtended[2]; /* ls bits */ | |
112 | mem[2] = fpa11->fpreg[fn].fExtended[1]; /* ms bits */ | |
113 | supply_register (F0_REGNUM + fn, (char *) &mem[0]); | |
114 | } | |
115 | ||
116 | static void | |
117 | store_nw_fpe_single (unsigned int fn, FPA11 * fpa11) | |
118 | { | |
119 | unsigned int mem[3]; | |
120 | ||
121 | read_register_gen (F0_REGNUM + fn, (char *) &mem[0]); | |
122 | fpa11->fpreg[fn].fSingle = mem[0]; | |
123 | fpa11->fType[fn] = typeSingle; | |
124 | } | |
125 | ||
126 | static void | |
127 | store_nw_fpe_double (unsigned int fn, FPA11 * fpa11) | |
128 | { | |
129 | unsigned int mem[3]; | |
130 | ||
131 | read_register_gen (F0_REGNUM + fn, (char *) &mem[0]); | |
132 | fpa11->fpreg[fn].fDouble[1] = mem[0]; | |
133 | fpa11->fpreg[fn].fDouble[0] = mem[1]; | |
134 | fpa11->fType[fn] = typeDouble; | |
135 | } | |
136 | ||
137 | void | |
138 | store_nw_fpe_extended (unsigned int fn, FPA11 * fpa11) | |
139 | { | |
140 | unsigned int mem[3]; | |
141 | ||
142 | read_register_gen (F0_REGNUM + fn, (char *) &mem[0]); | |
143 | fpa11->fpreg[fn].fExtended[0] = mem[0]; /* sign & exponent */ | |
144 | fpa11->fpreg[fn].fExtended[2] = mem[1]; /* ls bits */ | |
145 | fpa11->fpreg[fn].fExtended[1] = mem[2]; /* ms bits */ | |
146 | fpa11->fType[fn] = typeDouble; | |
147 | } | |
148 | ||
149 | /* Get the whole floating point state of the process and store the | |
150 | floating point stack into registers[]. */ | |
151 | ||
152 | static void | |
153 | fetch_fpregs (void) | |
154 | { | |
155 | int ret, regno; | |
156 | FPA11 fp; | |
157 | ||
158 | /* Read the floating point state. */ | |
159 | ret = ptrace (PT_GETFPREGS, inferior_pid, 0, &fp); | |
160 | if (ret < 0) | |
161 | { | |
162 | warning ("Unable to fetch the floating point state."); | |
163 | return; | |
164 | } | |
165 | ||
166 | /* Fetch fpsr. */ | |
167 | supply_register (FPS_REGNUM, (char *) &fp.fpsr); | |
168 | ||
169 | /* Fetch the floating point registers. */ | |
170 | for (regno = F0_REGNUM; regno <= F7_REGNUM; regno++) | |
171 | { | |
172 | int fn = regno - F0_REGNUM; | |
173 | unsigned int *p = (unsigned int *) ®isters[REGISTER_BYTE (regno)]; | |
174 | ||
175 | switch (fp.fType[fn]) | |
176 | { | |
177 | case typeSingle: | |
178 | fetch_nw_fpe_single (fn, &fp, p); | |
179 | break; | |
180 | ||
181 | case typeDouble: | |
182 | fetch_nw_fpe_double (fn, &fp, p); | |
183 | break; | |
184 | ||
185 | case typeExtended: | |
186 | fetch_nw_fpe_extended (fn, &fp, p); | |
187 | break; | |
188 | ||
189 | default: | |
190 | fetch_nw_fpe_none (fn, &fp, p); | |
191 | } | |
192 | } | |
193 | } | |
194 | ||
195 | /* Save the whole floating point state of the process using | |
196 | the contents from registers[]. */ | |
197 | ||
198 | static void | |
199 | store_fpregs (void) | |
200 | { | |
201 | int ret, regno; | |
202 | unsigned int mem[3]; | |
203 | FPA11 fp; | |
204 | ||
205 | /* Store fpsr. */ | |
206 | if (register_valid[FPS_REGNUM]) | |
207 | read_register_gen (FPS_REGNUM, (char *) &fp.fpsr); | |
208 | ||
209 | /* Store the floating point registers. */ | |
210 | for (regno = F0_REGNUM; regno <= F7_REGNUM; regno++) | |
211 | { | |
212 | if (register_valid[regno]) | |
213 | { | |
214 | unsigned int fn = regno - F0_REGNUM; | |
215 | switch (fp.fType[fn]) | |
216 | { | |
217 | case typeSingle: | |
218 | store_nw_fpe_single (fn, &fp); | |
219 | break; | |
220 | ||
221 | case typeDouble: | |
222 | store_nw_fpe_double (fn, &fp); | |
223 | break; | |
224 | ||
225 | case typeExtended: | |
226 | store_nw_fpe_extended (fn, &fp); | |
227 | break; | |
228 | } | |
229 | } | |
230 | } | |
231 | ||
232 | ret = ptrace (PTRACE_SETFPREGS, inferior_pid, 0, &fp); | |
233 | if (ret < 0) | |
234 | { | |
235 | warning ("Unable to store floating point state."); | |
236 | return; | |
237 | } | |
238 | } | |
239 | ||
240 | /* Fetch all general registers of the process and store into | |
241 | registers[]. */ | |
242 | ||
243 | static void | |
244 | fetch_regs (void) | |
245 | { | |
246 | int ret, regno; | |
247 | struct pt_regs regs; | |
248 | ||
249 | ret = ptrace (PTRACE_GETREGS, inferior_pid, 0, ®s); | |
250 | if (ret < 0) | |
251 | { | |
252 | warning ("Unable to fetch general registers."); | |
253 | return; | |
254 | } | |
255 | ||
256 | for (regno = A1_REGNUM; regno < PC_REGNUM; regno++) | |
257 | supply_register (regno, (char *) ®s.uregs[regno]); | |
258 | ||
259 | if (arm_apcs_32) | |
260 | supply_register (PS_REGNUM, (char *) ®s.uregs[CPSR_REGNUM]); | |
261 | else | |
262 | supply_register (PS_REGNUM, (char *) ®s.uregs[PC_REGNUM]); | |
263 | ||
264 | regs.uregs[PC_REGNUM] = ADDR_BITS_REMOVE (regs.uregs[PC_REGNUM]); | |
265 | supply_register (PC_REGNUM, (char *) ®s.uregs[PC_REGNUM]); | |
266 | } | |
267 | ||
268 | /* Store all general registers of the process from the values in | |
269 | registers[]. */ | |
270 | ||
271 | static void | |
272 | store_regs (void) | |
273 | { | |
274 | int ret, regno; | |
275 | struct pt_regs regs; | |
276 | ||
277 | ret = ptrace (PTRACE_GETREGS, inferior_pid, 0, ®s); | |
278 | if (ret < 0) | |
279 | { | |
280 | warning ("Unable to fetch general registers."); | |
281 | return; | |
282 | } | |
283 | ||
284 | for (regno = A1_REGNUM; regno <= PC_REGNUM; regno++) | |
285 | { | |
286 | if (register_valid[regno]) | |
287 | read_register_gen (regno, (char *) ®s.uregs[regno]); | |
288 | } | |
289 | ||
290 | ret = ptrace (PTRACE_SETREGS, inferior_pid, 0, ®s); | |
291 | ||
292 | if (ret < 0) | |
293 | { | |
294 | warning ("Unable to store general registers."); | |
295 | return; | |
296 | } | |
297 | } | |
298 | ||
299 | /* Fetch registers from the child process. Fetch all registers if | |
300 | regno == -1, otherwise fetch all general registers or all floating | |
301 | point registers depending upon the value of regno. */ | |
302 | ||
303 | void | |
304 | fetch_inferior_registers (int regno) | |
305 | { | |
306 | if ((regno < F0_REGNUM) || (regno > FPS_REGNUM)) | |
307 | fetch_regs (); | |
308 | ||
309 | if (((regno >= F0_REGNUM) && (regno <= FPS_REGNUM)) || (regno == -1)) | |
310 | fetch_fpregs (); | |
311 | } | |
312 | ||
313 | /* Store registers back into the inferior. Store all registers if | |
314 | regno == -1, otherwise store all general registers or all floating | |
315 | point registers depending upon the value of regno. */ | |
316 | ||
317 | void | |
318 | store_inferior_registers (int regno) | |
319 | { | |
320 | if ((regno < F0_REGNUM) || (regno > FPS_REGNUM)) | |
321 | store_regs (); | |
322 | ||
323 | if (((regno >= F0_REGNUM) && (regno <= FPS_REGNUM)) || (regno == -1)) | |
324 | store_fpregs (); | |
325 | } | |
326 | ||
327 | #ifdef GET_LONGJMP_TARGET | |
328 | ||
329 | /* Figure out where the longjmp will land. We expect that we have | |
330 | just entered longjmp and haven't yet altered r0, r1, so the | |
331 | arguments are still in the registers. (A1_REGNUM) points at the | |
332 | jmp_buf structure from which we extract the pc (JB_PC) that we will | |
333 | land at. The pc is copied into ADDR. This routine returns true on | |
334 | success. */ | |
335 | ||
336 | #define LONGJMP_TARGET_SIZE sizeof(int) | |
337 | #define JB_ELEMENT_SIZE sizeof(int) | |
338 | #define JB_SL 18 | |
339 | #define JB_FP 19 | |
340 | #define JB_SP 20 | |
341 | #define JB_PC 21 | |
342 | ||
343 | int | |
344 | arm_get_longjmp_target (CORE_ADDR * pc) | |
345 | { | |
346 | CORE_ADDR jb_addr; | |
347 | char buf[LONGJMP_TARGET_SIZE]; | |
348 | ||
349 | jb_addr = read_register (A1_REGNUM); | |
350 | ||
351 | if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf, | |
352 | LONGJMP_TARGET_SIZE)) | |
353 | return 0; | |
354 | ||
355 | *pc = extract_address (buf, LONGJMP_TARGET_SIZE); | |
356 | return 1; | |
357 | } | |
358 | ||
359 | #endif /* GET_LONGJMP_TARGET */ | |
360 | ||
361 | /* | |
362 | Dynamic Linking on ARM Linux | |
363 | ---------------------------- | |
364 | ||
365 | Note: PLT = procedure linkage table | |
366 | GOT = global offset table | |
367 | ||
368 | As much as possible, ELF dynamic linking defers the resolution of | |
369 | jump/call addresses until the last minute. The technique used is | |
370 | inspired by the i386 ELF design, and is based on the following | |
371 | constraints. | |
372 | ||
373 | 1) The calling technique should not force a change in the assembly | |
374 | code produced for apps; it MAY cause changes in the way assembly | |
375 | code is produced for position independent code (i.e. shared | |
376 | libraries). | |
377 | ||
378 | 2) The technique must be such that all executable areas must not be | |
379 | modified; and any modified areas must not be executed. | |
380 | ||
381 | To do this, there are three steps involved in a typical jump: | |
382 | ||
383 | 1) in the code | |
384 | 2) through the PLT | |
385 | 3) using a pointer from the GOT | |
386 | ||
387 | When the executable or library is first loaded, each GOT entry is | |
388 | initialized to point to the code which implements dynamic name | |
389 | resolution and code finding. This is normally a function in the | |
390 | program interpreter (on ARM Linux this is usually ld-linux.so.2, | |
391 | but it does not have to be). On the first invocation, the function | |
392 | is located and the GOT entry is replaced with the real function | |
393 | address. Subsequent calls go through steps 1, 2 and 3 and end up | |
394 | calling the real code. | |
395 | ||
396 | 1) In the code: | |
397 | ||
398 | b function_call | |
399 | bl function_call | |
400 | ||
401 | This is typical ARM code using the 26 bit relative branch or branch | |
402 | and link instructions. The target of the instruction | |
403 | (function_call is usually the address of the function to be called. | |
404 | In position independent code, the target of the instruction is | |
405 | actually an entry in the PLT when calling functions in a shared | |
406 | library. Note that this call is identical to a normal function | |
407 | call, only the target differs. | |
408 | ||
409 | 2) In the PLT: | |
410 | ||
411 | The PLT is a synthetic area, created by the linker. It exists in | |
412 | both executables and libraries. It is an array of stubs, one per | |
413 | imported function call. It looks like this: | |
414 | ||
415 | PLT[0]: | |
416 | str lr, [sp, #-4]! @push the return address (lr) | |
417 | ldr lr, [pc, #16] @load from 6 words ahead | |
418 | add lr, pc, lr @form an address for GOT[0] | |
419 | ldr pc, [lr, #8]! @jump to the contents of that addr | |
420 | ||
421 | The return address (lr) is pushed on the stack and used for | |
422 | calculations. The load on the second line loads the lr with | |
423 | &GOT[3] - . - 20. The addition on the third leaves: | |
424 | ||
425 | lr = (&GOT[3] - . - 20) + (. + 8) | |
426 | lr = (&GOT[3] - 12) | |
427 | lr = &GOT[0] | |
428 | ||
429 | On the fourth line, the pc and lr are both updated, so that: | |
430 | ||
431 | pc = GOT[2] | |
432 | lr = &GOT[0] + 8 | |
433 | = &GOT[2] | |
434 | ||
435 | NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little | |
436 | "tight", but allows us to keep all the PLT entries the same size. | |
437 | ||
438 | PLT[n+1]: | |
439 | ldr ip, [pc, #4] @load offset from gotoff | |
440 | add ip, pc, ip @add the offset to the pc | |
441 | ldr pc, [ip] @jump to that address | |
442 | gotoff: .word GOT[n+3] - . | |
443 | ||
444 | The load on the first line, gets an offset from the fourth word of | |
445 | the PLT entry. The add on the second line makes ip = &GOT[n+3], | |
446 | which contains either a pointer to PLT[0] (the fixup trampoline) or | |
447 | a pointer to the actual code. | |
448 | ||
449 | 3) In the GOT: | |
450 | ||
451 | The GOT contains helper pointers for both code (PLT) fixups and | |
452 | data fixups. The first 3 entries of the GOT are special. The next | |
453 | M entries (where M is the number of entries in the PLT) belong to | |
454 | the PLT fixups. The next D (all remaining) entries belong to | |
455 | various data fixups. The actual size of the GOT is 3 + M + D. | |
456 | ||
457 | The GOT is also a synthetic area, created by the linker. It exists | |
458 | in both executables and libraries. When the GOT is first | |
459 | initialized , all the GOT entries relating to PLT fixups are | |
460 | pointing to code back at PLT[0]. | |
461 | ||
462 | The special entries in the GOT are: | |
463 | ||
464 | GOT[0] = linked list pointer used by the dynamic loader | |
465 | GOT[1] = pointer to the reloc table for this module | |
466 | GOT[2] = pointer to the fixup/resolver code | |
467 | ||
468 | The first invocation of function call comes through and uses the | |
469 | fixup/resolver code. On the entry to the fixup/resolver code: | |
470 | ||
471 | ip = &GOT[n+3] | |
472 | lr = &GOT[2] | |
473 | stack[0] = return address (lr) of the function call | |
474 | [r0, r1, r2, r3] are still the arguments to the function call | |
475 | ||
476 | This is enough information for the fixup/resolver code to work | |
477 | with. Before the fixup/resolver code returns, it actually calls | |
478 | the requested function and repairs &GOT[n+3]. */ | |
479 | ||
480 | CORE_ADDR | |
481 | arm_skip_solib_resolver (CORE_ADDR pc) | |
482 | { | |
483 | /* FIXME */ | |
484 | return 0; | |
485 | } | |
486 | ||
487 | int | |
488 | arm_linux_register_u_addr (int blockend, int regnum) | |
489 | { | |
490 | return blockend + REGISTER_BYTE (regnum); | |
491 | } | |
492 | ||
493 | int | |
494 | arm_linux_kernel_u_size (void) | |
495 | { | |
496 | return (sizeof (struct user)); | |
497 | } | |
498 | ||
499 | /* Extract from an array REGBUF containing the (raw) register state | |
500 | a function return value of type TYPE, and copy that, in virtual format, | |
501 | into VALBUF. */ | |
502 | ||
503 | void | |
504 | arm_linux_extract_return_value (struct type *type, | |
505 | char regbuf[REGISTER_BYTES], | |
506 | char *valbuf) | |
507 | { | |
508 | /* ScottB: This needs to be looked at to handle the different | |
509 | floating point emulators on ARM Linux. Right now the code | |
510 | assumes that fetch inferior registers does the right thing for | |
511 | GDB. I suspect this won't handle NWFPE registers correctly, nor | |
512 | will the default ARM version (arm_extract_return_value()). */ | |
513 | ||
514 | int regnum = (TYPE_CODE_FLT == TYPE_CODE (type)) ? F0_REGNUM : A1_REGNUM; | |
515 | memcpy (valbuf, ®buf[REGISTER_BYTE (regnum)], TYPE_LENGTH (type)); | |
516 | } | |
517 | ||
518 | static unsigned int | |
519 | get_linux_version (unsigned int *vmajor, | |
520 | unsigned int *vminor, | |
521 | unsigned int *vrelease) | |
522 | { | |
523 | struct utsname info; | |
524 | char *pmajor, *pminor, *prelease, *tail; | |
525 | ||
526 | if (-1 == uname (&info)) | |
527 | { | |
528 | warning ("Unable to determine Linux version."); | |
529 | return -1; | |
530 | } | |
531 | ||
532 | pmajor = strtok (info.release, "."); | |
533 | pminor = strtok (NULL, "."); | |
534 | prelease = strtok (NULL, "."); | |
535 | ||
536 | *vmajor = (unsigned int) strtoul (pmajor, &tail, 0); | |
537 | *vminor = (unsigned int) strtoul (pminor, &tail, 0); | |
538 | *vrelease = (unsigned int) strtoul (prelease, &tail, 0); | |
539 | ||
540 | return ((*vmajor << 16) | (*vminor << 8) | *vrelease); | |
541 | } | |
542 | ||
543 | void | |
544 | _initialize_arm_linux_nat (void) | |
545 | { | |
546 | os_version = get_linux_version (&os_major, &os_minor, &os_release); | |
547 | } |