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faf5f7ad | 1 | /* GNU/Linux on ARM target support. |
4e052eda | 2 | Copyright 1999, 2000, 2001 Free Software Foundation, Inc. |
faf5f7ad SB |
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" | |
c20f6dea SB |
22 | #include "target.h" |
23 | #include "value.h" | |
faf5f7ad | 24 | #include "gdbtypes.h" |
134e61c4 | 25 | #include "floatformat.h" |
2a451106 KB |
26 | #include "gdbcore.h" |
27 | #include "frame.h" | |
4e052eda | 28 | #include "regcache.h" |
faf5f7ad | 29 | |
a52e6aac SB |
30 | /* For arm_linux_skip_solib_resolver. */ |
31 | #include "symtab.h" | |
32 | #include "symfile.h" | |
33 | #include "objfiles.h" | |
34 | ||
faf5f7ad SB |
35 | #ifdef GET_LONGJMP_TARGET |
36 | ||
37 | /* Figure out where the longjmp will land. We expect that we have | |
38 | just entered longjmp and haven't yet altered r0, r1, so the | |
39 | arguments are still in the registers. (A1_REGNUM) points at the | |
40 | jmp_buf structure from which we extract the pc (JB_PC) that we will | |
41 | land at. The pc is copied into ADDR. This routine returns true on | |
42 | success. */ | |
43 | ||
44 | #define LONGJMP_TARGET_SIZE sizeof(int) | |
45 | #define JB_ELEMENT_SIZE sizeof(int) | |
46 | #define JB_SL 18 | |
47 | #define JB_FP 19 | |
48 | #define JB_SP 20 | |
49 | #define JB_PC 21 | |
50 | ||
51 | int | |
52 | arm_get_longjmp_target (CORE_ADDR * pc) | |
53 | { | |
54 | CORE_ADDR jb_addr; | |
55 | char buf[LONGJMP_TARGET_SIZE]; | |
56 | ||
57 | jb_addr = read_register (A1_REGNUM); | |
58 | ||
59 | if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf, | |
60 | LONGJMP_TARGET_SIZE)) | |
61 | return 0; | |
62 | ||
63 | *pc = extract_address (buf, LONGJMP_TARGET_SIZE); | |
64 | return 1; | |
65 | } | |
66 | ||
67 | #endif /* GET_LONGJMP_TARGET */ | |
68 | ||
69 | /* Extract from an array REGBUF containing the (raw) register state | |
70 | a function return value of type TYPE, and copy that, in virtual format, | |
71 | into VALBUF. */ | |
72 | ||
73 | void | |
74 | arm_linux_extract_return_value (struct type *type, | |
75 | char regbuf[REGISTER_BYTES], | |
76 | char *valbuf) | |
77 | { | |
78 | /* ScottB: This needs to be looked at to handle the different | |
79 | floating point emulators on ARM Linux. Right now the code | |
80 | assumes that fetch inferior registers does the right thing for | |
81 | GDB. I suspect this won't handle NWFPE registers correctly, nor | |
82 | will the default ARM version (arm_extract_return_value()). */ | |
83 | ||
84 | int regnum = (TYPE_CODE_FLT == TYPE_CODE (type)) ? F0_REGNUM : A1_REGNUM; | |
85 | memcpy (valbuf, ®buf[REGISTER_BYTE (regnum)], TYPE_LENGTH (type)); | |
86 | } | |
87 | ||
134e61c4 SB |
88 | /* Note: ScottB |
89 | ||
90 | This function does not support passing parameters using the FPA | |
91 | variant of the APCS. It passes any floating point arguments in the | |
92 | general registers and/or on the stack. | |
93 | ||
94 | FIXME: This and arm_push_arguments should be merged. However this | |
95 | function breaks on a little endian host, big endian target | |
96 | using the COFF file format. ELF is ok. | |
97 | ||
98 | ScottB. */ | |
99 | ||
100 | /* Addresses for calling Thumb functions have the bit 0 set. | |
101 | Here are some macros to test, set, or clear bit 0 of addresses. */ | |
102 | #define IS_THUMB_ADDR(addr) ((addr) & 1) | |
103 | #define MAKE_THUMB_ADDR(addr) ((addr) | 1) | |
104 | #define UNMAKE_THUMB_ADDR(addr) ((addr) & ~1) | |
105 | ||
106 | CORE_ADDR | |
ea7c478f | 107 | arm_linux_push_arguments (int nargs, struct value **args, CORE_ADDR sp, |
134e61c4 SB |
108 | int struct_return, CORE_ADDR struct_addr) |
109 | { | |
110 | char *fp; | |
111 | int argnum, argreg, nstack_size; | |
112 | ||
113 | /* Walk through the list of args and determine how large a temporary | |
114 | stack is required. Need to take care here as structs may be | |
115 | passed on the stack, and we have to to push them. */ | |
116 | nstack_size = -4 * REGISTER_SIZE; /* Some arguments go into A1-A4. */ | |
117 | ||
118 | if (struct_return) /* The struct address goes in A1. */ | |
119 | nstack_size += REGISTER_SIZE; | |
120 | ||
121 | /* Walk through the arguments and add their size to nstack_size. */ | |
122 | for (argnum = 0; argnum < nargs; argnum++) | |
123 | { | |
124 | int len; | |
125 | struct type *arg_type; | |
126 | ||
127 | arg_type = check_typedef (VALUE_TYPE (args[argnum])); | |
128 | len = TYPE_LENGTH (arg_type); | |
129 | ||
130 | /* ANSI C code passes float arguments as integers, K&R code | |
131 | passes float arguments as doubles. Correct for this here. */ | |
132 | if (TYPE_CODE_FLT == TYPE_CODE (arg_type) && REGISTER_SIZE == len) | |
133 | nstack_size += FP_REGISTER_VIRTUAL_SIZE; | |
134 | else | |
135 | nstack_size += len; | |
136 | } | |
137 | ||
138 | /* Allocate room on the stack, and initialize our stack frame | |
139 | pointer. */ | |
140 | fp = NULL; | |
141 | if (nstack_size > 0) | |
142 | { | |
143 | sp -= nstack_size; | |
144 | fp = (char *) sp; | |
145 | } | |
146 | ||
147 | /* Initialize the integer argument register pointer. */ | |
148 | argreg = A1_REGNUM; | |
149 | ||
150 | /* The struct_return pointer occupies the first parameter passing | |
151 | register. */ | |
152 | if (struct_return) | |
153 | write_register (argreg++, struct_addr); | |
154 | ||
155 | /* Process arguments from left to right. Store as many as allowed | |
156 | in the parameter passing registers (A1-A4), and save the rest on | |
157 | the temporary stack. */ | |
158 | for (argnum = 0; argnum < nargs; argnum++) | |
159 | { | |
160 | int len; | |
161 | char *val; | |
162 | double dbl_arg; | |
163 | CORE_ADDR regval; | |
164 | enum type_code typecode; | |
165 | struct type *arg_type, *target_type; | |
166 | ||
167 | arg_type = check_typedef (VALUE_TYPE (args[argnum])); | |
168 | target_type = TYPE_TARGET_TYPE (arg_type); | |
169 | len = TYPE_LENGTH (arg_type); | |
170 | typecode = TYPE_CODE (arg_type); | |
171 | val = (char *) VALUE_CONTENTS (args[argnum]); | |
172 | ||
173 | /* ANSI C code passes float arguments as integers, K&R code | |
174 | passes float arguments as doubles. The .stabs record for | |
175 | for ANSI prototype floating point arguments records the | |
176 | type as FP_INTEGER, while a K&R style (no prototype) | |
177 | .stabs records the type as FP_FLOAT. In this latter case | |
178 | the compiler converts the float arguments to double before | |
179 | calling the function. */ | |
180 | if (TYPE_CODE_FLT == typecode && REGISTER_SIZE == len) | |
181 | { | |
182 | /* Float argument in buffer is in host format. Read it and | |
183 | convert to DOUBLEST, and store it in target double. */ | |
184 | DOUBLEST dblval; | |
185 | ||
186 | len = TARGET_DOUBLE_BIT / TARGET_CHAR_BIT; | |
187 | floatformat_to_doublest (HOST_FLOAT_FORMAT, val, &dblval); | |
188 | store_floating (&dbl_arg, len, dblval); | |
189 | val = (char *) &dbl_arg; | |
190 | } | |
191 | ||
192 | /* If the argument is a pointer to a function, and it is a Thumb | |
193 | function, set the low bit of the pointer. */ | |
194 | if (TYPE_CODE_PTR == typecode | |
195 | && NULL != target_type | |
196 | && TYPE_CODE_FUNC == TYPE_CODE (target_type)) | |
197 | { | |
198 | CORE_ADDR regval = extract_address (val, len); | |
199 | if (arm_pc_is_thumb (regval)) | |
200 | store_address (val, len, MAKE_THUMB_ADDR (regval)); | |
201 | } | |
202 | ||
203 | /* Copy the argument to general registers or the stack in | |
204 | register-sized pieces. Large arguments are split between | |
205 | registers and stack. */ | |
206 | while (len > 0) | |
207 | { | |
208 | int partial_len = len < REGISTER_SIZE ? len : REGISTER_SIZE; | |
209 | ||
210 | if (argreg <= ARM_LAST_ARG_REGNUM) | |
211 | { | |
212 | /* It's an argument being passed in a general register. */ | |
213 | regval = extract_address (val, partial_len); | |
214 | write_register (argreg++, regval); | |
215 | } | |
216 | else | |
217 | { | |
218 | /* Push the arguments onto the stack. */ | |
219 | write_memory ((CORE_ADDR) fp, val, REGISTER_SIZE); | |
220 | fp += REGISTER_SIZE; | |
221 | } | |
222 | ||
223 | len -= partial_len; | |
224 | val += partial_len; | |
225 | } | |
226 | } | |
227 | ||
228 | /* Return adjusted stack pointer. */ | |
229 | return sp; | |
230 | } | |
231 | ||
f38e884d SB |
232 | /* |
233 | Dynamic Linking on ARM Linux | |
234 | ---------------------------- | |
235 | ||
236 | Note: PLT = procedure linkage table | |
237 | GOT = global offset table | |
238 | ||
239 | As much as possible, ELF dynamic linking defers the resolution of | |
240 | jump/call addresses until the last minute. The technique used is | |
241 | inspired by the i386 ELF design, and is based on the following | |
242 | constraints. | |
243 | ||
244 | 1) The calling technique should not force a change in the assembly | |
245 | code produced for apps; it MAY cause changes in the way assembly | |
246 | code is produced for position independent code (i.e. shared | |
247 | libraries). | |
248 | ||
249 | 2) The technique must be such that all executable areas must not be | |
250 | modified; and any modified areas must not be executed. | |
251 | ||
252 | To do this, there are three steps involved in a typical jump: | |
253 | ||
254 | 1) in the code | |
255 | 2) through the PLT | |
256 | 3) using a pointer from the GOT | |
257 | ||
258 | When the executable or library is first loaded, each GOT entry is | |
259 | initialized to point to the code which implements dynamic name | |
260 | resolution and code finding. This is normally a function in the | |
261 | program interpreter (on ARM Linux this is usually ld-linux.so.2, | |
262 | but it does not have to be). On the first invocation, the function | |
263 | is located and the GOT entry is replaced with the real function | |
264 | address. Subsequent calls go through steps 1, 2 and 3 and end up | |
265 | calling the real code. | |
266 | ||
267 | 1) In the code: | |
268 | ||
269 | b function_call | |
270 | bl function_call | |
271 | ||
272 | This is typical ARM code using the 26 bit relative branch or branch | |
273 | and link instructions. The target of the instruction | |
274 | (function_call is usually the address of the function to be called. | |
275 | In position independent code, the target of the instruction is | |
276 | actually an entry in the PLT when calling functions in a shared | |
277 | library. Note that this call is identical to a normal function | |
278 | call, only the target differs. | |
279 | ||
280 | 2) In the PLT: | |
281 | ||
282 | The PLT is a synthetic area, created by the linker. It exists in | |
283 | both executables and libraries. It is an array of stubs, one per | |
284 | imported function call. It looks like this: | |
285 | ||
286 | PLT[0]: | |
287 | str lr, [sp, #-4]! @push the return address (lr) | |
288 | ldr lr, [pc, #16] @load from 6 words ahead | |
289 | add lr, pc, lr @form an address for GOT[0] | |
290 | ldr pc, [lr, #8]! @jump to the contents of that addr | |
291 | ||
292 | The return address (lr) is pushed on the stack and used for | |
293 | calculations. The load on the second line loads the lr with | |
294 | &GOT[3] - . - 20. The addition on the third leaves: | |
295 | ||
296 | lr = (&GOT[3] - . - 20) + (. + 8) | |
297 | lr = (&GOT[3] - 12) | |
298 | lr = &GOT[0] | |
299 | ||
300 | On the fourth line, the pc and lr are both updated, so that: | |
301 | ||
302 | pc = GOT[2] | |
303 | lr = &GOT[0] + 8 | |
304 | = &GOT[2] | |
305 | ||
306 | NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little | |
307 | "tight", but allows us to keep all the PLT entries the same size. | |
308 | ||
309 | PLT[n+1]: | |
310 | ldr ip, [pc, #4] @load offset from gotoff | |
311 | add ip, pc, ip @add the offset to the pc | |
312 | ldr pc, [ip] @jump to that address | |
313 | gotoff: .word GOT[n+3] - . | |
314 | ||
315 | The load on the first line, gets an offset from the fourth word of | |
316 | the PLT entry. The add on the second line makes ip = &GOT[n+3], | |
317 | which contains either a pointer to PLT[0] (the fixup trampoline) or | |
318 | a pointer to the actual code. | |
319 | ||
320 | 3) In the GOT: | |
321 | ||
322 | The GOT contains helper pointers for both code (PLT) fixups and | |
323 | data fixups. The first 3 entries of the GOT are special. The next | |
324 | M entries (where M is the number of entries in the PLT) belong to | |
325 | the PLT fixups. The next D (all remaining) entries belong to | |
326 | various data fixups. The actual size of the GOT is 3 + M + D. | |
327 | ||
328 | The GOT is also a synthetic area, created by the linker. It exists | |
329 | in both executables and libraries. When the GOT is first | |
330 | initialized , all the GOT entries relating to PLT fixups are | |
331 | pointing to code back at PLT[0]. | |
332 | ||
333 | The special entries in the GOT are: | |
334 | ||
335 | GOT[0] = linked list pointer used by the dynamic loader | |
336 | GOT[1] = pointer to the reloc table for this module | |
337 | GOT[2] = pointer to the fixup/resolver code | |
338 | ||
339 | The first invocation of function call comes through and uses the | |
340 | fixup/resolver code. On the entry to the fixup/resolver code: | |
341 | ||
342 | ip = &GOT[n+3] | |
343 | lr = &GOT[2] | |
344 | stack[0] = return address (lr) of the function call | |
345 | [r0, r1, r2, r3] are still the arguments to the function call | |
346 | ||
347 | This is enough information for the fixup/resolver code to work | |
348 | with. Before the fixup/resolver code returns, it actually calls | |
349 | the requested function and repairs &GOT[n+3]. */ | |
350 | ||
a52e6aac SB |
351 | /* Find the minimal symbol named NAME, and return both the minsym |
352 | struct and its objfile. This probably ought to be in minsym.c, but | |
353 | everything there is trying to deal with things like C++ and | |
354 | SOFUN_ADDRESS_MAYBE_TURQUOISE, ... Since this is so simple, it may | |
355 | be considered too special-purpose for general consumption. */ | |
356 | ||
357 | static struct minimal_symbol * | |
358 | find_minsym_and_objfile (char *name, struct objfile **objfile_p) | |
359 | { | |
360 | struct objfile *objfile; | |
361 | ||
362 | ALL_OBJFILES (objfile) | |
363 | { | |
364 | struct minimal_symbol *msym; | |
365 | ||
366 | ALL_OBJFILE_MSYMBOLS (objfile, msym) | |
367 | { | |
368 | if (SYMBOL_NAME (msym) | |
369 | && STREQ (SYMBOL_NAME (msym), name)) | |
370 | { | |
371 | *objfile_p = objfile; | |
372 | return msym; | |
373 | } | |
374 | } | |
375 | } | |
376 | ||
377 | return 0; | |
378 | } | |
379 | ||
380 | ||
381 | static CORE_ADDR | |
382 | skip_hurd_resolver (CORE_ADDR pc) | |
383 | { | |
384 | /* The HURD dynamic linker is part of the GNU C library, so many | |
385 | GNU/Linux distributions use it. (All ELF versions, as far as I | |
386 | know.) An unresolved PLT entry points to "_dl_runtime_resolve", | |
387 | which calls "fixup" to patch the PLT, and then passes control to | |
388 | the function. | |
389 | ||
390 | We look for the symbol `_dl_runtime_resolve', and find `fixup' in | |
391 | the same objfile. If we are at the entry point of `fixup', then | |
392 | we set a breakpoint at the return address (at the top of the | |
393 | stack), and continue. | |
394 | ||
395 | It's kind of gross to do all these checks every time we're | |
396 | called, since they don't change once the executable has gotten | |
397 | started. But this is only a temporary hack --- upcoming versions | |
398 | of Linux will provide a portable, efficient interface for | |
399 | debugging programs that use shared libraries. */ | |
400 | ||
401 | struct objfile *objfile; | |
402 | struct minimal_symbol *resolver | |
403 | = find_minsym_and_objfile ("_dl_runtime_resolve", &objfile); | |
404 | ||
405 | if (resolver) | |
406 | { | |
407 | struct minimal_symbol *fixup | |
408 | = lookup_minimal_symbol ("fixup", 0, objfile); | |
409 | ||
410 | if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc) | |
411 | return (SAVED_PC_AFTER_CALL (get_current_frame ())); | |
412 | } | |
413 | ||
414 | return 0; | |
415 | } | |
416 | ||
417 | /* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c. | |
418 | This function: | |
419 | 1) decides whether a PLT has sent us into the linker to resolve | |
420 | a function reference, and | |
421 | 2) if so, tells us where to set a temporary breakpoint that will | |
422 | trigger when the dynamic linker is done. */ | |
423 | ||
f38e884d | 424 | CORE_ADDR |
a52e6aac | 425 | arm_linux_skip_solib_resolver (CORE_ADDR pc) |
f38e884d | 426 | { |
a52e6aac SB |
427 | CORE_ADDR result; |
428 | ||
429 | /* Plug in functions for other kinds of resolvers here. */ | |
430 | result = skip_hurd_resolver (pc); | |
e1d6e81f | 431 | |
a52e6aac SB |
432 | if (result) |
433 | return result; | |
a52e6aac | 434 | |
f38e884d SB |
435 | return 0; |
436 | } | |
437 | ||
2a451106 KB |
438 | /* The constants below were determined by examining the following files |
439 | in the linux kernel sources: | |
440 | ||
441 | arch/arm/kernel/signal.c | |
442 | - see SWI_SYS_SIGRETURN and SWI_SYS_RT_SIGRETURN | |
443 | include/asm-arm/unistd.h | |
444 | - see __NR_sigreturn, __NR_rt_sigreturn, and __NR_SYSCALL_BASE */ | |
445 | ||
446 | #define ARM_LINUX_SIGRETURN_INSTR 0xef900077 | |
447 | #define ARM_LINUX_RT_SIGRETURN_INSTR 0xef9000ad | |
448 | ||
449 | /* arm_linux_in_sigtramp determines if PC points at one of the | |
450 | instructions which cause control to return to the Linux kernel upon | |
451 | return from a signal handler. FUNC_NAME is unused. */ | |
452 | ||
453 | int | |
454 | arm_linux_in_sigtramp (CORE_ADDR pc, char *func_name) | |
455 | { | |
456 | unsigned long inst; | |
457 | ||
458 | inst = read_memory_integer (pc, 4); | |
459 | ||
460 | return (inst == ARM_LINUX_SIGRETURN_INSTR | |
461 | || inst == ARM_LINUX_RT_SIGRETURN_INSTR); | |
462 | ||
463 | } | |
464 | ||
465 | /* arm_linux_sigcontext_register_address returns the address in the | |
466 | sigcontext of register REGNO given a stack pointer value SP and | |
467 | program counter value PC. The value 0 is returned if PC is not | |
468 | pointing at one of the signal return instructions or if REGNO is | |
469 | not saved in the sigcontext struct. */ | |
470 | ||
471 | CORE_ADDR | |
472 | arm_linux_sigcontext_register_address (CORE_ADDR sp, CORE_ADDR pc, int regno) | |
473 | { | |
474 | unsigned long inst; | |
475 | CORE_ADDR reg_addr = 0; | |
476 | ||
477 | inst = read_memory_integer (pc, 4); | |
478 | ||
479 | if (inst == ARM_LINUX_SIGRETURN_INSTR || inst == ARM_LINUX_RT_SIGRETURN_INSTR) | |
480 | { | |
481 | CORE_ADDR sigcontext_addr; | |
482 | ||
483 | /* The sigcontext structure is at different places for the two | |
484 | signal return instructions. For ARM_LINUX_SIGRETURN_INSTR, | |
485 | it starts at the SP value. For ARM_LINUX_RT_SIGRETURN_INSTR, | |
486 | it is at SP+8. For the latter instruction, it may also be | |
487 | the case that the address of this structure may be determined | |
488 | by reading the 4 bytes at SP, but I'm not convinced this is | |
489 | reliable. | |
490 | ||
491 | In any event, these magic constants (0 and 8) may be | |
492 | determined by examining struct sigframe and struct | |
493 | rt_sigframe in arch/arm/kernel/signal.c in the Linux kernel | |
494 | sources. */ | |
495 | ||
496 | if (inst == ARM_LINUX_RT_SIGRETURN_INSTR) | |
497 | sigcontext_addr = sp + 8; | |
498 | else /* inst == ARM_LINUX_SIGRETURN_INSTR */ | |
499 | sigcontext_addr = sp + 0; | |
500 | ||
501 | /* The layout of the sigcontext structure for ARM GNU/Linux is | |
502 | in include/asm-arm/sigcontext.h in the Linux kernel sources. | |
503 | ||
504 | There are three 4-byte fields which precede the saved r0 | |
505 | field. (This accounts for the 12 in the code below.) The | |
506 | sixteen registers (4 bytes per field) follow in order. The | |
507 | PSR value follows the sixteen registers which accounts for | |
508 | the constant 19 below. */ | |
509 | ||
510 | if (0 <= regno && regno <= PC_REGNUM) | |
511 | reg_addr = sigcontext_addr + 12 + (4 * regno); | |
512 | else if (regno == PS_REGNUM) | |
513 | reg_addr = sigcontext_addr + 19 * 4; | |
514 | } | |
515 | ||
516 | return reg_addr; | |
517 | } | |
518 | ||
faf5f7ad SB |
519 | void |
520 | _initialize_arm_linux_tdep (void) | |
521 | { | |
522 | } |