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1 | /* Target-dependent code for GDB, the GNU debugger. |
2 | Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000 | |
3 | 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 "frame.h" | |
24 | #include "inferior.h" | |
25 | #include "symtab.h" | |
26 | #include "target.h" | |
27 | #include "gdbcore.h" | |
28 | #include "gdbcmd.h" | |
29 | #include "symfile.h" | |
30 | #include "objfiles.h" | |
31 | ||
9aa1e687 KB |
32 | #include "ppc-tdep.h" |
33 | ||
c877c8e6 KB |
34 | /* The following two instructions are used in the signal trampoline |
35 | code on linux/ppc */ | |
36 | #define INSTR_LI_R0_0x7777 0x38007777 | |
37 | #define INSTR_SC 0x44000002 | |
38 | ||
39 | /* Since the *-tdep.c files are platform independent (i.e, they may be | |
40 | used to build cross platform debuggers), we can't include system | |
41 | headers. Therefore, details concerning the sigcontext structure | |
42 | must be painstakingly rerecorded. What's worse, if these details | |
43 | ever change in the header files, they'll have to be changed here | |
44 | as well. */ | |
45 | ||
46 | /* __SIGNAL_FRAMESIZE from <asm/ptrace.h> */ | |
47 | #define PPC_LINUX_SIGNAL_FRAMESIZE 64 | |
48 | ||
49 | /* From <asm/sigcontext.h>, offsetof(struct sigcontext_struct, regs) == 0x1c */ | |
50 | #define PPC_LINUX_REGS_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x1c) | |
51 | ||
52 | /* From <asm/sigcontext.h>, | |
53 | offsetof(struct sigcontext_struct, handler) == 0x14 */ | |
54 | #define PPC_LINUX_HANDLER_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x14) | |
55 | ||
56 | /* From <asm/ptrace.h>, values for PT_NIP, PT_R1, and PT_LNK */ | |
57 | #define PPC_LINUX_PT_R0 0 | |
58 | #define PPC_LINUX_PT_R1 1 | |
59 | #define PPC_LINUX_PT_R2 2 | |
60 | #define PPC_LINUX_PT_R3 3 | |
61 | #define PPC_LINUX_PT_R4 4 | |
62 | #define PPC_LINUX_PT_R5 5 | |
63 | #define PPC_LINUX_PT_R6 6 | |
64 | #define PPC_LINUX_PT_R7 7 | |
65 | #define PPC_LINUX_PT_R8 8 | |
66 | #define PPC_LINUX_PT_R9 9 | |
67 | #define PPC_LINUX_PT_R10 10 | |
68 | #define PPC_LINUX_PT_R11 11 | |
69 | #define PPC_LINUX_PT_R12 12 | |
70 | #define PPC_LINUX_PT_R13 13 | |
71 | #define PPC_LINUX_PT_R14 14 | |
72 | #define PPC_LINUX_PT_R15 15 | |
73 | #define PPC_LINUX_PT_R16 16 | |
74 | #define PPC_LINUX_PT_R17 17 | |
75 | #define PPC_LINUX_PT_R18 18 | |
76 | #define PPC_LINUX_PT_R19 19 | |
77 | #define PPC_LINUX_PT_R20 20 | |
78 | #define PPC_LINUX_PT_R21 21 | |
79 | #define PPC_LINUX_PT_R22 22 | |
80 | #define PPC_LINUX_PT_R23 23 | |
81 | #define PPC_LINUX_PT_R24 24 | |
82 | #define PPC_LINUX_PT_R25 25 | |
83 | #define PPC_LINUX_PT_R26 26 | |
84 | #define PPC_LINUX_PT_R27 27 | |
85 | #define PPC_LINUX_PT_R28 28 | |
86 | #define PPC_LINUX_PT_R29 29 | |
87 | #define PPC_LINUX_PT_R30 30 | |
88 | #define PPC_LINUX_PT_R31 31 | |
89 | #define PPC_LINUX_PT_NIP 32 | |
90 | #define PPC_LINUX_PT_MSR 33 | |
91 | #define PPC_LINUX_PT_CTR 35 | |
92 | #define PPC_LINUX_PT_LNK 36 | |
93 | #define PPC_LINUX_PT_XER 37 | |
94 | #define PPC_LINUX_PT_CCR 38 | |
95 | #define PPC_LINUX_PT_MQ 39 | |
96 | #define PPC_LINUX_PT_FPR0 48 /* each FP reg occupies 2 slots in this space */ | |
97 | #define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31) | |
98 | #define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1) | |
99 | ||
9aa1e687 | 100 | static int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc); |
50c9bd31 | 101 | |
c877c8e6 KB |
102 | /* Determine if pc is in a signal trampoline... |
103 | ||
104 | Ha! That's not what this does at all. wait_for_inferior in infrun.c | |
105 | calls IN_SIGTRAMP in order to detect entry into a signal trampoline | |
106 | just after delivery of a signal. But on linux, signal trampolines | |
107 | are used for the return path only. The kernel sets things up so that | |
108 | the signal handler is called directly. | |
109 | ||
110 | If we use in_sigtramp2() in place of in_sigtramp() (see below) | |
111 | we'll (often) end up with stop_pc in the trampoline and prev_pc in | |
112 | the (now exited) handler. The code there will cause a temporary | |
113 | breakpoint to be set on prev_pc which is not very likely to get hit | |
114 | again. | |
115 | ||
116 | If this is confusing, think of it this way... the code in | |
117 | wait_for_inferior() needs to be able to detect entry into a signal | |
118 | trampoline just after a signal is delivered, not after the handler | |
119 | has been run. | |
120 | ||
121 | So, we define in_sigtramp() below to return 1 if the following is | |
122 | true: | |
123 | ||
124 | 1) The previous frame is a real signal trampoline. | |
125 | ||
126 | - and - | |
127 | ||
128 | 2) pc is at the first or second instruction of the corresponding | |
129 | handler. | |
130 | ||
131 | Why the second instruction? It seems that wait_for_inferior() | |
132 | never sees the first instruction when single stepping. When a | |
133 | signal is delivered while stepping, the next instruction that | |
134 | would've been stepped over isn't, instead a signal is delivered and | |
135 | the first instruction of the handler is stepped over instead. That | |
136 | puts us on the second instruction. (I added the test for the | |
137 | first instruction long after the fact, just in case the observed | |
138 | behavior is ever fixed.) | |
139 | ||
140 | IN_SIGTRAMP is called from blockframe.c as well in order to set | |
141 | the signal_handler_caller flag. Because of our strange definition | |
142 | of in_sigtramp below, we can't rely on signal_handler_caller getting | |
143 | set correctly from within blockframe.c. This is why we take pains | |
144 | to set it in init_extra_frame_info(). */ | |
145 | ||
146 | int | |
147 | ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name) | |
148 | { | |
149 | CORE_ADDR lr; | |
150 | CORE_ADDR sp; | |
151 | CORE_ADDR tramp_sp; | |
152 | char buf[4]; | |
153 | CORE_ADDR handler; | |
154 | ||
9aa1e687 | 155 | lr = read_register (PPC_LR_REGNUM); |
c877c8e6 KB |
156 | if (!ppc_linux_at_sigtramp_return_path (lr)) |
157 | return 0; | |
158 | ||
159 | sp = read_register (SP_REGNUM); | |
160 | ||
161 | if (target_read_memory (sp, buf, sizeof (buf)) != 0) | |
162 | return 0; | |
163 | ||
164 | tramp_sp = extract_unsigned_integer (buf, 4); | |
165 | ||
166 | if (target_read_memory (tramp_sp + PPC_LINUX_HANDLER_PTR_OFFSET, buf, | |
167 | sizeof (buf)) != 0) | |
168 | return 0; | |
169 | ||
170 | handler = extract_unsigned_integer (buf, 4); | |
171 | ||
172 | return (pc == handler || pc == handler + 4); | |
173 | } | |
174 | ||
175 | /* | |
176 | * The signal handler trampoline is on the stack and consists of exactly | |
177 | * two instructions. The easiest and most accurate way of determining | |
178 | * whether the pc is in one of these trampolines is by inspecting the | |
179 | * instructions. It'd be faster though if we could find a way to do this | |
180 | * via some simple address comparisons. | |
181 | */ | |
9aa1e687 | 182 | static int |
c877c8e6 KB |
183 | ppc_linux_at_sigtramp_return_path (CORE_ADDR pc) |
184 | { | |
185 | char buf[12]; | |
186 | unsigned long pcinsn; | |
187 | if (target_read_memory (pc - 4, buf, sizeof (buf)) != 0) | |
188 | return 0; | |
189 | ||
190 | /* extract the instruction at the pc */ | |
191 | pcinsn = extract_unsigned_integer (buf + 4, 4); | |
192 | ||
193 | return ( | |
194 | (pcinsn == INSTR_LI_R0_0x7777 | |
195 | && extract_unsigned_integer (buf + 8, 4) == INSTR_SC) | |
196 | || | |
197 | (pcinsn == INSTR_SC | |
198 | && extract_unsigned_integer (buf, 4) == INSTR_LI_R0_0x7777)); | |
199 | } | |
200 | ||
201 | CORE_ADDR | |
202 | ppc_linux_skip_trampoline_code (CORE_ADDR pc) | |
203 | { | |
204 | char buf[4]; | |
205 | struct obj_section *sect; | |
206 | struct objfile *objfile; | |
207 | unsigned long insn; | |
208 | CORE_ADDR plt_start = 0; | |
209 | CORE_ADDR symtab = 0; | |
210 | CORE_ADDR strtab = 0; | |
211 | int num_slots = -1; | |
212 | int reloc_index = -1; | |
213 | CORE_ADDR plt_table; | |
214 | CORE_ADDR reloc; | |
215 | CORE_ADDR sym; | |
216 | long symidx; | |
217 | char symname[1024]; | |
218 | struct minimal_symbol *msymbol; | |
219 | ||
220 | /* Find the section pc is in; return if not in .plt */ | |
221 | sect = find_pc_section (pc); | |
222 | if (!sect || strcmp (sect->the_bfd_section->name, ".plt") != 0) | |
223 | return 0; | |
224 | ||
225 | objfile = sect->objfile; | |
226 | ||
227 | /* Pick up the instruction at pc. It had better be of the | |
228 | form | |
229 | li r11, IDX | |
230 | ||
231 | where IDX is an index into the plt_table. */ | |
232 | ||
233 | if (target_read_memory (pc, buf, 4) != 0) | |
234 | return 0; | |
235 | insn = extract_unsigned_integer (buf, 4); | |
236 | ||
237 | if ((insn & 0xffff0000) != 0x39600000 /* li r11, VAL */ ) | |
238 | return 0; | |
239 | ||
240 | reloc_index = (insn << 16) >> 16; | |
241 | ||
242 | /* Find the objfile that pc is in and obtain the information | |
243 | necessary for finding the symbol name. */ | |
244 | for (sect = objfile->sections; sect < objfile->sections_end; ++sect) | |
245 | { | |
246 | const char *secname = sect->the_bfd_section->name; | |
247 | if (strcmp (secname, ".plt") == 0) | |
248 | plt_start = sect->addr; | |
249 | else if (strcmp (secname, ".rela.plt") == 0) | |
250 | num_slots = ((int) sect->endaddr - (int) sect->addr) / 12; | |
251 | else if (strcmp (secname, ".dynsym") == 0) | |
252 | symtab = sect->addr; | |
253 | else if (strcmp (secname, ".dynstr") == 0) | |
254 | strtab = sect->addr; | |
255 | } | |
256 | ||
257 | /* Make sure we have all the information we need. */ | |
258 | if (plt_start == 0 || num_slots == -1 || symtab == 0 || strtab == 0) | |
259 | return 0; | |
260 | ||
261 | /* Compute the value of the plt table */ | |
262 | plt_table = plt_start + 72 + 8 * num_slots; | |
263 | ||
264 | /* Get address of the relocation entry (Elf32_Rela) */ | |
265 | if (target_read_memory (plt_table + reloc_index, buf, 4) != 0) | |
266 | return 0; | |
267 | reloc = extract_address (buf, 4); | |
268 | ||
269 | sect = find_pc_section (reloc); | |
270 | if (!sect) | |
271 | return 0; | |
272 | ||
273 | if (strcmp (sect->the_bfd_section->name, ".text") == 0) | |
274 | return reloc; | |
275 | ||
276 | /* Now get the r_info field which is the relocation type and symbol | |
277 | index. */ | |
278 | if (target_read_memory (reloc + 4, buf, 4) != 0) | |
279 | return 0; | |
280 | symidx = extract_unsigned_integer (buf, 4); | |
281 | ||
282 | /* Shift out the relocation type leaving just the symbol index */ | |
283 | /* symidx = ELF32_R_SYM(symidx); */ | |
284 | symidx = symidx >> 8; | |
285 | ||
286 | /* compute the address of the symbol */ | |
287 | sym = symtab + symidx * 4; | |
288 | ||
289 | /* Fetch the string table index */ | |
290 | if (target_read_memory (sym, buf, 4) != 0) | |
291 | return 0; | |
292 | symidx = extract_unsigned_integer (buf, 4); | |
293 | ||
294 | /* Fetch the string; we don't know how long it is. Is it possible | |
295 | that the following will fail because we're trying to fetch too | |
296 | much? */ | |
297 | if (target_read_memory (strtab + symidx, symname, sizeof (symname)) != 0) | |
298 | return 0; | |
299 | ||
300 | /* This might not work right if we have multiple symbols with the | |
301 | same name; the only way to really get it right is to perform | |
302 | the same sort of lookup as the dynamic linker. */ | |
303 | msymbol = lookup_minimal_symbol_text (symname, NULL, NULL); | |
304 | if (!msymbol) | |
305 | return 0; | |
306 | ||
307 | return SYMBOL_VALUE_ADDRESS (msymbol); | |
308 | } | |
309 | ||
310 | /* The rs6000 version of FRAME_SAVED_PC will almost work for us. The | |
311 | signal handler details are different, so we'll handle those here | |
312 | and call the rs6000 version to do the rest. */ | |
9aa1e687 | 313 | CORE_ADDR |
c877c8e6 KB |
314 | ppc_linux_frame_saved_pc (struct frame_info *fi) |
315 | { | |
316 | if (fi->signal_handler_caller) | |
317 | { | |
318 | CORE_ADDR regs_addr = | |
50c9bd31 | 319 | read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); |
c877c8e6 KB |
320 | /* return the NIP in the regs array */ |
321 | return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4); | |
322 | } | |
50c9bd31 KB |
323 | else if (fi->next && fi->next->signal_handler_caller) |
324 | { | |
325 | CORE_ADDR regs_addr = | |
326 | read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); | |
327 | /* return LNK in the regs array */ | |
328 | return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4); | |
329 | } | |
330 | else | |
331 | return rs6000_frame_saved_pc (fi); | |
c877c8e6 KB |
332 | } |
333 | ||
334 | void | |
335 | ppc_linux_init_extra_frame_info (int fromleaf, struct frame_info *fi) | |
336 | { | |
337 | rs6000_init_extra_frame_info (fromleaf, fi); | |
338 | ||
339 | if (fi->next != 0) | |
340 | { | |
341 | /* We're called from get_prev_frame_info; check to see if | |
342 | this is a signal frame by looking to see if the pc points | |
343 | at trampoline code */ | |
344 | if (ppc_linux_at_sigtramp_return_path (fi->pc)) | |
345 | fi->signal_handler_caller = 1; | |
346 | else | |
347 | fi->signal_handler_caller = 0; | |
348 | } | |
349 | } | |
350 | ||
351 | int | |
352 | ppc_linux_frameless_function_invocation (struct frame_info *fi) | |
353 | { | |
354 | /* We'll find the wrong thing if we let | |
355 | rs6000_frameless_function_invocation () search for a signal trampoline */ | |
356 | if (ppc_linux_at_sigtramp_return_path (fi->pc)) | |
357 | return 0; | |
358 | else | |
359 | return rs6000_frameless_function_invocation (fi); | |
360 | } | |
361 | ||
362 | void | |
363 | ppc_linux_frame_init_saved_regs (struct frame_info *fi) | |
364 | { | |
365 | if (fi->signal_handler_caller) | |
366 | { | |
367 | CORE_ADDR regs_addr; | |
368 | int i; | |
369 | if (fi->saved_regs) | |
370 | return; | |
371 | ||
372 | frame_saved_regs_zalloc (fi); | |
373 | ||
374 | regs_addr = | |
375 | read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); | |
376 | fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP; | |
9aa1e687 KB |
377 | fi->saved_regs[PPC_PS_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MSR; |
378 | fi->saved_regs[PPC_CR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CCR; | |
379 | fi->saved_regs[PPC_LR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_LNK; | |
380 | fi->saved_regs[PPC_CTR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CTR; | |
381 | fi->saved_regs[PPC_XER_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_XER; | |
382 | fi->saved_regs[PPC_MQ_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MQ; | |
c877c8e6 | 383 | for (i = 0; i < 32; i++) |
9aa1e687 | 384 | fi->saved_regs[PPC_GP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i; |
c877c8e6 KB |
385 | for (i = 0; i < 32; i++) |
386 | fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i; | |
387 | } | |
388 | else | |
389 | rs6000_frame_init_saved_regs (fi); | |
390 | } | |
391 | ||
392 | CORE_ADDR | |
393 | ppc_linux_frame_chain (struct frame_info *thisframe) | |
394 | { | |
395 | /* Kernel properly constructs the frame chain for the handler */ | |
396 | if (thisframe->signal_handler_caller) | |
397 | return read_memory_integer ((thisframe)->frame, 4); | |
398 | else | |
399 | return rs6000_frame_chain (thisframe); | |
400 | } | |
401 | ||
402 | /* FIXME: Move the following to rs6000-tdep.c (or some other file where | |
403 | it may be used generically by ports which use either the SysV ABI or | |
404 | the EABI */ | |
405 | ||
406 | /* round2 rounds x up to the nearest multiple of s assuming that s is a | |
407 | power of 2 */ | |
408 | ||
409 | #undef round2 | |
410 | #define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s)) | |
411 | ||
412 | /* Pass the arguments in either registers, or in the stack. Using the | |
413 | ppc sysv ABI, the first eight words of the argument list (that might | |
414 | be less than eight parameters if some parameters occupy more than one | |
415 | word) are passed in r3..r10 registers. float and double parameters are | |
416 | passed in fpr's, in addition to that. Rest of the parameters if any | |
417 | are passed in user stack. | |
418 | ||
419 | If the function is returning a structure, then the return address is passed | |
420 | in r3, then the first 7 words of the parametes can be passed in registers, | |
421 | starting from r4. */ | |
422 | ||
423 | CORE_ADDR | |
fba45db2 KB |
424 | ppc_sysv_abi_push_arguments (int nargs, value_ptr *args, CORE_ADDR sp, |
425 | int struct_return, CORE_ADDR struct_addr) | |
c877c8e6 KB |
426 | { |
427 | int argno; | |
428 | int greg, freg; | |
429 | int argstkspace; | |
430 | int structstkspace; | |
431 | int argoffset; | |
432 | int structoffset; | |
433 | value_ptr arg; | |
434 | struct type *type; | |
435 | int len; | |
436 | char old_sp_buf[4]; | |
437 | CORE_ADDR saved_sp; | |
438 | ||
439 | greg = struct_return ? 4 : 3; | |
440 | freg = 1; | |
441 | argstkspace = 0; | |
442 | structstkspace = 0; | |
443 | ||
444 | /* Figure out how much new stack space is required for arguments | |
445 | which don't fit in registers. Unlike the PowerOpen ABI, the | |
446 | SysV ABI doesn't reserve any extra space for parameters which | |
447 | are put in registers. */ | |
448 | for (argno = 0; argno < nargs; argno++) | |
449 | { | |
450 | arg = args[argno]; | |
451 | type = check_typedef (VALUE_TYPE (arg)); | |
452 | len = TYPE_LENGTH (type); | |
453 | ||
454 | if (TYPE_CODE (type) == TYPE_CODE_FLT) | |
455 | { | |
456 | if (freg <= 8) | |
457 | freg++; | |
458 | else | |
459 | { | |
460 | /* SysV ABI converts floats to doubles when placed in | |
461 | memory and requires 8 byte alignment */ | |
462 | if (argstkspace & 0x4) | |
463 | argstkspace += 4; | |
464 | argstkspace += 8; | |
465 | } | |
466 | } | |
467 | else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ | |
468 | { | |
469 | if (greg > 9) | |
470 | { | |
471 | greg = 11; | |
472 | if (argstkspace & 0x4) | |
473 | argstkspace += 4; | |
474 | argstkspace += 8; | |
475 | } | |
476 | else | |
477 | { | |
478 | if ((greg & 1) == 0) | |
479 | greg++; | |
480 | greg += 2; | |
481 | } | |
482 | } | |
483 | else | |
484 | { | |
485 | if (len > 4 | |
486 | || TYPE_CODE (type) == TYPE_CODE_STRUCT | |
487 | || TYPE_CODE (type) == TYPE_CODE_UNION) | |
488 | { | |
489 | /* Rounding to the nearest multiple of 8 may not be necessary, | |
490 | but it is safe. Particularly since we don't know the | |
491 | field types of the structure */ | |
492 | structstkspace += round2 (len, 8); | |
493 | } | |
494 | if (greg <= 10) | |
495 | greg++; | |
496 | else | |
497 | argstkspace += 4; | |
498 | } | |
499 | } | |
500 | ||
501 | /* Get current SP location */ | |
502 | saved_sp = read_sp (); | |
503 | ||
504 | sp -= argstkspace + structstkspace; | |
505 | ||
506 | /* Allocate space for backchain and callee's saved lr */ | |
507 | sp -= 8; | |
508 | ||
509 | /* Make sure that we maintain 16 byte alignment */ | |
510 | sp &= ~0x0f; | |
511 | ||
512 | /* Update %sp before proceeding any further */ | |
513 | write_register (SP_REGNUM, sp); | |
514 | ||
515 | /* write the backchain */ | |
516 | store_address (old_sp_buf, 4, saved_sp); | |
517 | write_memory (sp, old_sp_buf, 4); | |
518 | ||
519 | argoffset = 8; | |
520 | structoffset = argoffset + argstkspace; | |
521 | freg = 1; | |
522 | greg = 3; | |
482ca3f5 KB |
523 | /* Fill in r3 with the return structure, if any */ |
524 | if (struct_return) | |
525 | { | |
526 | char val_buf[4]; | |
527 | store_address (val_buf, 4, struct_addr); | |
528 | memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); | |
529 | greg++; | |
530 | } | |
c877c8e6 KB |
531 | /* Now fill in the registers and stack... */ |
532 | for (argno = 0; argno < nargs; argno++) | |
533 | { | |
534 | arg = args[argno]; | |
535 | type = check_typedef (VALUE_TYPE (arg)); | |
536 | len = TYPE_LENGTH (type); | |
537 | ||
538 | if (TYPE_CODE (type) == TYPE_CODE_FLT) | |
539 | { | |
540 | if (freg <= 8) | |
541 | { | |
542 | if (len > 8) | |
543 | printf_unfiltered ( | |
544 | "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno); | |
545 | memcpy (®isters[REGISTER_BYTE (FP0_REGNUM + freg)], | |
546 | VALUE_CONTENTS (arg), len); | |
547 | freg++; | |
548 | } | |
549 | else | |
550 | { | |
551 | /* SysV ABI converts floats to doubles when placed in | |
552 | memory and requires 8 byte alignment */ | |
553 | /* FIXME: Convert floats to doubles */ | |
554 | if (argoffset & 0x4) | |
555 | argoffset += 4; | |
556 | write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); | |
557 | argoffset += 8; | |
558 | } | |
559 | } | |
560 | else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ | |
561 | { | |
562 | if (greg > 9) | |
563 | { | |
564 | greg = 11; | |
565 | if (argoffset & 0x4) | |
566 | argoffset += 4; | |
567 | write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); | |
568 | argoffset += 8; | |
569 | } | |
570 | else | |
571 | { | |
572 | if ((greg & 1) == 0) | |
573 | greg++; | |
574 | ||
575 | memcpy (®isters[REGISTER_BYTE (greg)], | |
576 | VALUE_CONTENTS (arg), 4); | |
577 | memcpy (®isters[REGISTER_BYTE (greg + 1)], | |
578 | VALUE_CONTENTS (arg) + 4, 4); | |
579 | greg += 2; | |
580 | } | |
581 | } | |
582 | else | |
583 | { | |
584 | char val_buf[4]; | |
585 | if (len > 4 | |
586 | || TYPE_CODE (type) == TYPE_CODE_STRUCT | |
587 | || TYPE_CODE (type) == TYPE_CODE_UNION) | |
588 | { | |
589 | write_memory (sp + structoffset, VALUE_CONTENTS (arg), len); | |
590 | store_address (val_buf, 4, sp + structoffset); | |
591 | structoffset += round2 (len, 8); | |
592 | } | |
593 | else | |
594 | { | |
595 | memset (val_buf, 0, 4); | |
596 | memcpy (val_buf, VALUE_CONTENTS (arg), len); | |
597 | } | |
598 | if (greg <= 10) | |
599 | { | |
600 | *(int *) ®isters[REGISTER_BYTE (greg)] = 0; | |
601 | memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); | |
602 | greg++; | |
603 | } | |
604 | else | |
605 | { | |
606 | write_memory (sp + argoffset, val_buf, 4); | |
607 | argoffset += 4; | |
608 | } | |
609 | } | |
610 | } | |
611 | ||
612 | target_store_registers (-1); | |
613 | return sp; | |
614 | } | |
482ca3f5 | 615 | |
122a33de KB |
616 | /* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint |
617 | in much the same fashion as memory_remove_breakpoint in mem-break.c, | |
618 | but is careful not to write back the previous contents if the code | |
619 | in question has changed in between inserting the breakpoint and | |
620 | removing it. | |
621 | ||
622 | Here is the problem that we're trying to solve... | |
623 | ||
624 | Once upon a time, before introducing this function to remove | |
625 | breakpoints from the inferior, setting a breakpoint on a shared | |
626 | library function prior to running the program would not work | |
627 | properly. In order to understand the problem, it is first | |
628 | necessary to understand a little bit about dynamic linking on | |
629 | this platform. | |
630 | ||
631 | A call to a shared library function is accomplished via a bl | |
632 | (branch-and-link) instruction whose branch target is an entry | |
633 | in the procedure linkage table (PLT). The PLT in the object | |
634 | file is uninitialized. To gdb, prior to running the program, the | |
635 | entries in the PLT are all zeros. | |
636 | ||
637 | Once the program starts running, the shared libraries are loaded | |
638 | and the procedure linkage table is initialized, but the entries in | |
639 | the table are not (necessarily) resolved. Once a function is | |
640 | actually called, the code in the PLT is hit and the function is | |
641 | resolved. In order to better illustrate this, an example is in | |
642 | order; the following example is from the gdb testsuite. | |
643 | ||
644 | We start the program shmain. | |
645 | ||
646 | [kev@arroyo testsuite]$ ../gdb gdb.base/shmain | |
647 | [...] | |
648 | ||
649 | We place two breakpoints, one on shr1 and the other on main. | |
650 | ||
651 | (gdb) b shr1 | |
652 | Breakpoint 1 at 0x100409d4 | |
653 | (gdb) b main | |
654 | Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44. | |
655 | ||
656 | Examine the instruction (and the immediatly following instruction) | |
657 | upon which the breakpoint was placed. Note that the PLT entry | |
658 | for shr1 contains zeros. | |
659 | ||
660 | (gdb) x/2i 0x100409d4 | |
661 | 0x100409d4 <shr1>: .long 0x0 | |
662 | 0x100409d8 <shr1+4>: .long 0x0 | |
663 | ||
664 | Now run 'til main. | |
665 | ||
666 | (gdb) r | |
667 | Starting program: gdb.base/shmain | |
668 | Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19. | |
669 | ||
670 | Breakpoint 2, main () | |
671 | at gdb.base/shmain.c:44 | |
672 | 44 g = 1; | |
673 | ||
674 | Examine the PLT again. Note that the loading of the shared | |
675 | library has initialized the PLT to code which loads a constant | |
676 | (which I think is an index into the GOT) into r11 and then | |
677 | branchs a short distance to the code which actually does the | |
678 | resolving. | |
679 | ||
680 | (gdb) x/2i 0x100409d4 | |
681 | 0x100409d4 <shr1>: li r11,4 | |
682 | 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> | |
683 | (gdb) c | |
684 | Continuing. | |
685 | ||
686 | Breakpoint 1, shr1 (x=1) | |
687 | at gdb.base/shr1.c:19 | |
688 | 19 l = 1; | |
689 | ||
690 | Now we've hit the breakpoint at shr1. (The breakpoint was | |
691 | reset from the PLT entry to the actual shr1 function after the | |
692 | shared library was loaded.) Note that the PLT entry has been | |
693 | resolved to contain a branch that takes us directly to shr1. | |
694 | (The real one, not the PLT entry.) | |
695 | ||
696 | (gdb) x/2i 0x100409d4 | |
697 | 0x100409d4 <shr1>: b 0xffaf76c <shr1> | |
698 | 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> | |
699 | ||
700 | The thing to note here is that the PLT entry for shr1 has been | |
701 | changed twice. | |
702 | ||
703 | Now the problem should be obvious. GDB places a breakpoint (a | |
704 | trap instruction) on the zero value of the PLT entry for shr1. | |
705 | Later on, after the shared library had been loaded and the PLT | |
706 | initialized, GDB gets a signal indicating this fact and attempts | |
707 | (as it always does when it stops) to remove all the breakpoints. | |
708 | ||
709 | The breakpoint removal was causing the former contents (a zero | |
710 | word) to be written back to the now initialized PLT entry thus | |
711 | destroying a portion of the initialization that had occurred only a | |
712 | short time ago. When execution continued, the zero word would be | |
713 | executed as an instruction an an illegal instruction trap was | |
714 | generated instead. (0 is not a legal instruction.) | |
715 | ||
716 | The fix for this problem was fairly straightforward. The function | |
717 | memory_remove_breakpoint from mem-break.c was copied to this file, | |
718 | modified slightly, and renamed to ppc_linux_memory_remove_breakpoint. | |
719 | In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new | |
720 | function. | |
721 | ||
722 | The differences between ppc_linux_memory_remove_breakpoint () and | |
723 | memory_remove_breakpoint () are minor. All that the former does | |
724 | that the latter does not is check to make sure that the breakpoint | |
725 | location actually contains a breakpoint (trap instruction) prior | |
726 | to attempting to write back the old contents. If it does contain | |
727 | a trap instruction, we allow the old contents to be written back. | |
728 | Otherwise, we silently do nothing. | |
729 | ||
730 | The big question is whether memory_remove_breakpoint () should be | |
731 | changed to have the same functionality. The downside is that more | |
732 | traffic is generated for remote targets since we'll have an extra | |
733 | fetch of a memory word each time a breakpoint is removed. | |
734 | ||
735 | For the time being, we'll leave this self-modifying-code-friendly | |
736 | version in ppc-linux-tdep.c, but it ought to be migrated somewhere | |
737 | else in the event that some other platform has similar needs with | |
738 | regard to removing breakpoints in some potentially self modifying | |
739 | code. */ | |
482ca3f5 KB |
740 | int |
741 | ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache) | |
742 | { | |
743 | unsigned char *bp; | |
744 | int val; | |
745 | int bplen; | |
746 | char old_contents[BREAKPOINT_MAX]; | |
747 | ||
748 | /* Determine appropriate breakpoint contents and size for this address. */ | |
749 | bp = BREAKPOINT_FROM_PC (&addr, &bplen); | |
750 | if (bp == NULL) | |
751 | error ("Software breakpoints not implemented for this target."); | |
752 | ||
753 | val = target_read_memory (addr, old_contents, bplen); | |
754 | ||
755 | /* If our breakpoint is no longer at the address, this means that the | |
756 | program modified the code on us, so it is wrong to put back the | |
757 | old value */ | |
758 | if (val == 0 && memcmp (bp, old_contents, bplen) == 0) | |
759 | val = target_write_memory (addr, contents_cache, bplen); | |
760 | ||
761 | return val; | |
762 | } |