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TOMOYO Linux Cross Reference
Linux/arch/powerpc/kernel/module_64.c

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  1 /*  Kernel module help for PPC64.
  2     Copyright (C) 2001, 2003 Rusty Russell IBM Corporation.
  3 
  4     This program is free software; you can redistribute it and/or modify
  5     it under the terms of the GNU General Public License as published by
  6     the Free Software Foundation; either version 2 of the License, or
  7     (at your option) any later version.
  8 
  9     This program is distributed in the hope that it will be useful,
 10     but WITHOUT ANY WARRANTY; without even the implied warranty of
 11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12     GNU General Public License for more details.
 13 
 14     You should have received a copy of the GNU General Public License
 15     along with this program; if not, write to the Free Software
 16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 17 */
 18 
 19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 20 
 21 #include <linux/module.h>
 22 #include <linux/elf.h>
 23 #include <linux/moduleloader.h>
 24 #include <linux/err.h>
 25 #include <linux/vmalloc.h>
 26 #include <linux/ftrace.h>
 27 #include <linux/bug.h>
 28 #include <linux/uaccess.h>
 29 #include <asm/module.h>
 30 #include <asm/firmware.h>
 31 #include <asm/code-patching.h>
 32 #include <linux/sort.h>
 33 #include <asm/setup.h>
 34 #include <asm/sections.h>
 35 
 36 /* FIXME: We don't do .init separately.  To do this, we'd need to have
 37    a separate r2 value in the init and core section, and stub between
 38    them, too.
 39 
 40    Using a magic allocator which places modules within 32MB solves
 41    this, and makes other things simpler.  Anton?
 42    --RR.  */
 43 
 44 #ifdef PPC64_ELF_ABI_v2
 45 
 46 /* An address is simply the address of the function. */
 47 typedef unsigned long func_desc_t;
 48 
 49 static func_desc_t func_desc(unsigned long addr)
 50 {
 51         return addr;
 52 }
 53 static unsigned long func_addr(unsigned long addr)
 54 {
 55         return addr;
 56 }
 57 static unsigned long stub_func_addr(func_desc_t func)
 58 {
 59         return func;
 60 }
 61 
 62 /* PowerPC64 specific values for the Elf64_Sym st_other field.  */
 63 #define STO_PPC64_LOCAL_BIT     5
 64 #define STO_PPC64_LOCAL_MASK    (7 << STO_PPC64_LOCAL_BIT)
 65 #define PPC64_LOCAL_ENTRY_OFFSET(other)                                 \
 66  (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
 67 
 68 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 69 {
 70         /* sym->st_other indicates offset to local entry point
 71          * (otherwise it will assume r12 is the address of the start
 72          * of function and try to derive r2 from it). */
 73         return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
 74 }
 75 #else
 76 
 77 /* An address is address of the OPD entry, which contains address of fn. */
 78 typedef struct ppc64_opd_entry func_desc_t;
 79 
 80 static func_desc_t func_desc(unsigned long addr)
 81 {
 82         return *(struct ppc64_opd_entry *)addr;
 83 }
 84 static unsigned long func_addr(unsigned long addr)
 85 {
 86         return func_desc(addr).funcaddr;
 87 }
 88 static unsigned long stub_func_addr(func_desc_t func)
 89 {
 90         return func.funcaddr;
 91 }
 92 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 93 {
 94         return 0;
 95 }
 96 
 97 void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 98 {
 99         if (ptr < (void *)mod->arch.start_opd ||
100                         ptr >= (void *)mod->arch.end_opd)
101                 return ptr;
102 
103         return dereference_function_descriptor(ptr);
104 }
105 #endif
106 
107 #define STUB_MAGIC 0x73747562 /* stub */
108 
109 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
110    the kernel itself).  But on PPC64, these need to be used for every
111    jump, actually, to reset r2 (TOC+0x8000). */
112 struct ppc64_stub_entry
113 {
114         /* 28 byte jump instruction sequence (7 instructions). We only
115          * need 6 instructions on ABIv2 but we always allocate 7 so
116          * so we don't have to modify the trampoline load instruction. */
117         u32 jump[7];
118         /* Used by ftrace to identify stubs */
119         u32 magic;
120         /* Data for the above code */
121         func_desc_t funcdata;
122 };
123 
124 /*
125  * PPC64 uses 24 bit jumps, but we need to jump into other modules or
126  * the kernel which may be further.  So we jump to a stub.
127  *
128  * For ELFv1 we need to use this to set up the new r2 value (aka TOC
129  * pointer).  For ELFv2 it's the callee's responsibility to set up the
130  * new r2, but for both we need to save the old r2.
131  *
132  * We could simply patch the new r2 value and function pointer into
133  * the stub, but it's significantly shorter to put these values at the
134  * end of the stub code, and patch the stub address (32-bits relative
135  * to the TOC ptr, r2) into the stub.
136  */
137 
138 static u32 ppc64_stub_insns[] = {
139         0x3d620000,                     /* addis   r11,r2, <high> */
140         0x396b0000,                     /* addi    r11,r11, <low> */
141         /* Save current r2 value in magic place on the stack. */
142         0xf8410000|R2_STACK_OFFSET,     /* std     r2,R2_STACK_OFFSET(r1) */
143         0xe98b0020,                     /* ld      r12,32(r11) */
144 #ifdef PPC64_ELF_ABI_v1
145         /* Set up new r2 from function descriptor */
146         0xe84b0028,                     /* ld      r2,40(r11) */
147 #endif
148         0x7d8903a6,                     /* mtctr   r12 */
149         0x4e800420                      /* bctr */
150 };
151 
152 #ifdef CONFIG_DYNAMIC_FTRACE
153 int module_trampoline_target(struct module *mod, unsigned long addr,
154                              unsigned long *target)
155 {
156         struct ppc64_stub_entry *stub;
157         func_desc_t funcdata;
158         u32 magic;
159 
160         if (!within_module_core(addr, mod)) {
161                 pr_err("%s: stub %lx not in module %s\n", __func__, addr, mod->name);
162                 return -EFAULT;
163         }
164 
165         stub = (struct ppc64_stub_entry *)addr;
166 
167         if (probe_kernel_read(&magic, &stub->magic, sizeof(magic))) {
168                 pr_err("%s: fault reading magic for stub %lx for %s\n", __func__, addr, mod->name);
169                 return -EFAULT;
170         }
171 
172         if (magic != STUB_MAGIC) {
173                 pr_err("%s: bad magic for stub %lx for %s\n", __func__, addr, mod->name);
174                 return -EFAULT;
175         }
176 
177         if (probe_kernel_read(&funcdata, &stub->funcdata, sizeof(funcdata))) {
178                 pr_err("%s: fault reading funcdata for stub %lx for %s\n", __func__, addr, mod->name);
179                 return -EFAULT;
180         }
181 
182         *target = stub_func_addr(funcdata);
183 
184         return 0;
185 }
186 #endif
187 
188 /* Count how many different 24-bit relocations (different symbol,
189    different addend) */
190 static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num)
191 {
192         unsigned int i, r_info, r_addend, _count_relocs;
193 
194         /* FIXME: Only count external ones --RR */
195         _count_relocs = 0;
196         r_info = 0;
197         r_addend = 0;
198         for (i = 0; i < num; i++)
199                 /* Only count 24-bit relocs, others don't need stubs */
200                 if (ELF64_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
201                     (r_info != ELF64_R_SYM(rela[i].r_info) ||
202                      r_addend != rela[i].r_addend)) {
203                         _count_relocs++;
204                         r_info = ELF64_R_SYM(rela[i].r_info);
205                         r_addend = rela[i].r_addend;
206                 }
207 
208         return _count_relocs;
209 }
210 
211 static int relacmp(const void *_x, const void *_y)
212 {
213         const Elf64_Rela *x, *y;
214 
215         y = (Elf64_Rela *)_x;
216         x = (Elf64_Rela *)_y;
217 
218         /* Compare the entire r_info (as opposed to ELF64_R_SYM(r_info) only) to
219          * make the comparison cheaper/faster. It won't affect the sorting or
220          * the counting algorithms' performance
221          */
222         if (x->r_info < y->r_info)
223                 return -1;
224         else if (x->r_info > y->r_info)
225                 return 1;
226         else if (x->r_addend < y->r_addend)
227                 return -1;
228         else if (x->r_addend > y->r_addend)
229                 return 1;
230         else
231                 return 0;
232 }
233 
234 static void relaswap(void *_x, void *_y, int size)
235 {
236         uint64_t *x, *y, tmp;
237         int i;
238 
239         y = (uint64_t *)_x;
240         x = (uint64_t *)_y;
241 
242         for (i = 0; i < sizeof(Elf64_Rela) / sizeof(uint64_t); i++) {
243                 tmp = x[i];
244                 x[i] = y[i];
245                 y[i] = tmp;
246         }
247 }
248 
249 /* Get size of potential trampolines required. */
250 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
251                                     const Elf64_Shdr *sechdrs)
252 {
253         /* One extra reloc so it's always 0-funcaddr terminated */
254         unsigned long relocs = 1;
255         unsigned i;
256 
257         /* Every relocated section... */
258         for (i = 1; i < hdr->e_shnum; i++) {
259                 if (sechdrs[i].sh_type == SHT_RELA) {
260                         pr_debug("Found relocations in section %u\n", i);
261                         pr_debug("Ptr: %p.  Number: %Lu\n",
262                                (void *)sechdrs[i].sh_addr,
263                                sechdrs[i].sh_size / sizeof(Elf64_Rela));
264 
265                         /* Sort the relocation information based on a symbol and
266                          * addend key. This is a stable O(n*log n) complexity
267                          * alogrithm but it will reduce the complexity of
268                          * count_relocs() to linear complexity O(n)
269                          */
270                         sort((void *)sechdrs[i].sh_addr,
271                              sechdrs[i].sh_size / sizeof(Elf64_Rela),
272                              sizeof(Elf64_Rela), relacmp, relaswap);
273 
274                         relocs += count_relocs((void *)sechdrs[i].sh_addr,
275                                                sechdrs[i].sh_size
276                                                / sizeof(Elf64_Rela));
277                 }
278         }
279 
280 #ifdef CONFIG_DYNAMIC_FTRACE
281         /* make the trampoline to the ftrace_caller */
282         relocs++;
283 #endif
284 
285         pr_debug("Looks like a total of %lu stubs, max\n", relocs);
286         return relocs * sizeof(struct ppc64_stub_entry);
287 }
288 
289 /* Still needed for ELFv2, for .TOC. */
290 static void dedotify_versions(struct modversion_info *vers,
291                               unsigned long size)
292 {
293         struct modversion_info *end;
294 
295         for (end = (void *)vers + size; vers < end; vers++)
296                 if (vers->name[0] == '.') {
297                         memmove(vers->name, vers->name+1, strlen(vers->name));
298                 }
299 }
300 
301 /*
302  * Undefined symbols which refer to .funcname, hack to funcname. Make .TOC.
303  * seem to be defined (value set later).
304  */
305 static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
306 {
307         unsigned int i;
308 
309         for (i = 1; i < numsyms; i++) {
310                 if (syms[i].st_shndx == SHN_UNDEF) {
311                         char *name = strtab + syms[i].st_name;
312                         if (name[0] == '.') {
313                                 if (strcmp(name+1, "TOC.") == 0)
314                                         syms[i].st_shndx = SHN_ABS;
315                                 syms[i].st_name++;
316                         }
317                 }
318         }
319 }
320 
321 static Elf64_Sym *find_dot_toc(Elf64_Shdr *sechdrs,
322                                const char *strtab,
323                                unsigned int symindex)
324 {
325         unsigned int i, numsyms;
326         Elf64_Sym *syms;
327 
328         syms = (Elf64_Sym *)sechdrs[symindex].sh_addr;
329         numsyms = sechdrs[symindex].sh_size / sizeof(Elf64_Sym);
330 
331         for (i = 1; i < numsyms; i++) {
332                 if (syms[i].st_shndx == SHN_ABS
333                     && strcmp(strtab + syms[i].st_name, "TOC.") == 0)
334                         return &syms[i];
335         }
336         return NULL;
337 }
338 
339 int module_frob_arch_sections(Elf64_Ehdr *hdr,
340                               Elf64_Shdr *sechdrs,
341                               char *secstrings,
342                               struct module *me)
343 {
344         unsigned int i;
345 
346         /* Find .toc and .stubs sections, symtab and strtab */
347         for (i = 1; i < hdr->e_shnum; i++) {
348                 char *p;
349                 if (strcmp(secstrings + sechdrs[i].sh_name, ".stubs") == 0)
350                         me->arch.stubs_section = i;
351                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".toc") == 0) {
352                         me->arch.toc_section = i;
353                         if (sechdrs[i].sh_addralign < 8)
354                                 sechdrs[i].sh_addralign = 8;
355                 }
356                 else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")==0)
357                         dedotify_versions((void *)hdr + sechdrs[i].sh_offset,
358                                           sechdrs[i].sh_size);
359                 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".opd")) {
360                         me->arch.start_opd = sechdrs[i].sh_addr;
361                         me->arch.end_opd = sechdrs[i].sh_addr +
362                                            sechdrs[i].sh_size;
363                 }
364 
365                 /* We don't handle .init for the moment: rename to _init */
366                 while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))
367                         p[0] = '_';
368 
369                 if (sechdrs[i].sh_type == SHT_SYMTAB)
370                         dedotify((void *)hdr + sechdrs[i].sh_offset,
371                                  sechdrs[i].sh_size / sizeof(Elf64_Sym),
372                                  (void *)hdr
373                                  + sechdrs[sechdrs[i].sh_link].sh_offset);
374         }
375 
376         if (!me->arch.stubs_section) {
377                 pr_err("%s: doesn't contain .stubs.\n", me->name);
378                 return -ENOEXEC;
379         }
380 
381         /* If we don't have a .toc, just use .stubs.  We need to set r2
382            to some reasonable value in case the module calls out to
383            other functions via a stub, or if a function pointer escapes
384            the module by some means.  */
385         if (!me->arch.toc_section)
386                 me->arch.toc_section = me->arch.stubs_section;
387 
388         /* Override the stubs size */
389         sechdrs[me->arch.stubs_section].sh_size = get_stubs_size(hdr, sechdrs);
390         return 0;
391 }
392 
393 /*
394  * r2 is the TOC pointer: it actually points 0x8000 into the TOC (this gives the
395  * value maximum span in an instruction which uses a signed offset). Round down
396  * to a 256 byte boundary for the odd case where we are setting up r2 without a
397  * .toc section.
398  */
399 static inline unsigned long my_r2(const Elf64_Shdr *sechdrs, struct module *me)
400 {
401         return (sechdrs[me->arch.toc_section].sh_addr & ~0xfful) + 0x8000;
402 }
403 
404 /* Both low and high 16 bits are added as SIGNED additions, so if low
405    16 bits has high bit set, high 16 bits must be adjusted.  These
406    macros do that (stolen from binutils). */
407 #define PPC_LO(v) ((v) & 0xffff)
408 #define PPC_HI(v) (((v) >> 16) & 0xffff)
409 #define PPC_HA(v) PPC_HI ((v) + 0x8000)
410 
411 /* Patch stub to reference function and correct r2 value. */
412 static inline int create_stub(const Elf64_Shdr *sechdrs,
413                               struct ppc64_stub_entry *entry,
414                               unsigned long addr,
415                               struct module *me)
416 {
417         long reladdr;
418 
419         memcpy(entry->jump, ppc64_stub_insns, sizeof(ppc64_stub_insns));
420 
421         /* Stub uses address relative to r2. */
422         reladdr = (unsigned long)entry - my_r2(sechdrs, me);
423         if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
424                 pr_err("%s: Address %p of stub out of range of %p.\n",
425                        me->name, (void *)reladdr, (void *)my_r2);
426                 return 0;
427         }
428         pr_debug("Stub %p get data from reladdr %li\n", entry, reladdr);
429 
430         entry->jump[0] |= PPC_HA(reladdr);
431         entry->jump[1] |= PPC_LO(reladdr);
432         entry->funcdata = func_desc(addr);
433         entry->magic = STUB_MAGIC;
434 
435         return 1;
436 }
437 
438 /* Create stub to jump to function described in this OPD/ptr: we need the
439    stub to set up the TOC ptr (r2) for the function. */
440 static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
441                                    unsigned long addr,
442                                    struct module *me)
443 {
444         struct ppc64_stub_entry *stubs;
445         unsigned int i, num_stubs;
446 
447         num_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*stubs);
448 
449         /* Find this stub, or if that fails, the next avail. entry */
450         stubs = (void *)sechdrs[me->arch.stubs_section].sh_addr;
451         for (i = 0; stub_func_addr(stubs[i].funcdata); i++) {
452                 if (WARN_ON(i >= num_stubs))
453                         return 0;
454 
455                 if (stub_func_addr(stubs[i].funcdata) == func_addr(addr))
456                         return (unsigned long)&stubs[i];
457         }
458 
459         if (!create_stub(sechdrs, &stubs[i], addr, me))
460                 return 0;
461 
462         return (unsigned long)&stubs[i];
463 }
464 
465 #ifdef CC_USING_MPROFILE_KERNEL
466 static bool is_early_mcount_callsite(u32 *instruction)
467 {
468         /*
469          * Check if this is one of the -mprofile-kernel sequences.
470          */
471         if (instruction[-1] == PPC_INST_STD_LR &&
472             instruction[-2] == PPC_INST_MFLR)
473                 return true;
474 
475         if (instruction[-1] == PPC_INST_MFLR)
476                 return true;
477 
478         return false;
479 }
480 
481 /*
482  * In case of _mcount calls, do not save the current callee's TOC (in r2) into
483  * the original caller's stack frame. If we did we would clobber the saved TOC
484  * value of the original caller.
485  */
486 static void squash_toc_save_inst(const char *name, unsigned long addr)
487 {
488         struct ppc64_stub_entry *stub = (struct ppc64_stub_entry *)addr;
489 
490         /* Only for calls to _mcount */
491         if (strcmp("_mcount", name) != 0)
492                 return;
493 
494         stub->jump[2] = PPC_INST_NOP;
495 }
496 #else
497 static void squash_toc_save_inst(const char *name, unsigned long addr) { }
498 
499 /* without -mprofile-kernel, mcount calls are never early */
500 static bool is_early_mcount_callsite(u32 *instruction)
501 {
502         return false;
503 }
504 #endif
505 
506 /* We expect a noop next: if it is, replace it with instruction to
507    restore r2. */
508 static int restore_r2(u32 *instruction, struct module *me)
509 {
510         u32 *prev_insn = instruction - 1;
511 
512         if (is_early_mcount_callsite(prev_insn))
513                 return 1;
514 
515         /*
516          * Make sure the branch isn't a sibling call.  Sibling calls aren't
517          * "link" branches and they don't return, so they don't need the r2
518          * restore afterwards.
519          */
520         if (!instr_is_relative_link_branch(*prev_insn))
521                 return 1;
522 
523         if (*instruction != PPC_INST_NOP) {
524                 pr_err("%s: Expected nop after call, got %08x at %pS\n",
525                         me->name, *instruction, instruction);
526                 return 0;
527         }
528         /* ld r2,R2_STACK_OFFSET(r1) */
529         *instruction = PPC_INST_LD_TOC;
530         return 1;
531 }
532 
533 int apply_relocate_add(Elf64_Shdr *sechdrs,
534                        const char *strtab,
535                        unsigned int symindex,
536                        unsigned int relsec,
537                        struct module *me)
538 {
539         unsigned int i;
540         Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
541         Elf64_Sym *sym;
542         unsigned long *location;
543         unsigned long value;
544 
545         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
546                sechdrs[relsec].sh_info);
547 
548         /* First time we're called, we can fix up .TOC. */
549         if (!me->arch.toc_fixed) {
550                 sym = find_dot_toc(sechdrs, strtab, symindex);
551                 /* It's theoretically possible that a module doesn't want a
552                  * .TOC. so don't fail it just for that. */
553                 if (sym)
554                         sym->st_value = my_r2(sechdrs, me);
555                 me->arch.toc_fixed = true;
556         }
557 
558         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
559                 /* This is where to make the change */
560                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
561                         + rela[i].r_offset;
562                 /* This is the symbol it is referring to */
563                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
564                         + ELF64_R_SYM(rela[i].r_info);
565 
566                 pr_debug("RELOC at %p: %li-type as %s (0x%lx) + %li\n",
567                        location, (long)ELF64_R_TYPE(rela[i].r_info),
568                        strtab + sym->st_name, (unsigned long)sym->st_value,
569                        (long)rela[i].r_addend);
570 
571                 /* `Everything is relative'. */
572                 value = sym->st_value + rela[i].r_addend;
573 
574                 switch (ELF64_R_TYPE(rela[i].r_info)) {
575                 case R_PPC64_ADDR32:
576                         /* Simply set it */
577                         *(u32 *)location = value;
578                         break;
579 
580                 case R_PPC64_ADDR64:
581                         /* Simply set it */
582                         *(unsigned long *)location = value;
583                         break;
584 
585                 case R_PPC64_TOC:
586                         *(unsigned long *)location = my_r2(sechdrs, me);
587                         break;
588 
589                 case R_PPC64_TOC16:
590                         /* Subtract TOC pointer */
591                         value -= my_r2(sechdrs, me);
592                         if (value + 0x8000 > 0xffff) {
593                                 pr_err("%s: bad TOC16 relocation (0x%lx)\n",
594                                        me->name, value);
595                                 return -ENOEXEC;
596                         }
597                         *((uint16_t *) location)
598                                 = (*((uint16_t *) location) & ~0xffff)
599                                 | (value & 0xffff);
600                         break;
601 
602                 case R_PPC64_TOC16_LO:
603                         /* Subtract TOC pointer */
604                         value -= my_r2(sechdrs, me);
605                         *((uint16_t *) location)
606                                 = (*((uint16_t *) location) & ~0xffff)
607                                 | (value & 0xffff);
608                         break;
609 
610                 case R_PPC64_TOC16_DS:
611                         /* Subtract TOC pointer */
612                         value -= my_r2(sechdrs, me);
613                         if ((value & 3) != 0 || value + 0x8000 > 0xffff) {
614                                 pr_err("%s: bad TOC16_DS relocation (0x%lx)\n",
615                                        me->name, value);
616                                 return -ENOEXEC;
617                         }
618                         *((uint16_t *) location)
619                                 = (*((uint16_t *) location) & ~0xfffc)
620                                 | (value & 0xfffc);
621                         break;
622 
623                 case R_PPC64_TOC16_LO_DS:
624                         /* Subtract TOC pointer */
625                         value -= my_r2(sechdrs, me);
626                         if ((value & 3) != 0) {
627                                 pr_err("%s: bad TOC16_LO_DS relocation (0x%lx)\n",
628                                        me->name, value);
629                                 return -ENOEXEC;
630                         }
631                         *((uint16_t *) location)
632                                 = (*((uint16_t *) location) & ~0xfffc)
633                                 | (value & 0xfffc);
634                         break;
635 
636                 case R_PPC64_TOC16_HA:
637                         /* Subtract TOC pointer */
638                         value -= my_r2(sechdrs, me);
639                         value = ((value + 0x8000) >> 16);
640                         *((uint16_t *) location)
641                                 = (*((uint16_t *) location) & ~0xffff)
642                                 | (value & 0xffff);
643                         break;
644 
645                 case R_PPC_REL24:
646                         /* FIXME: Handle weak symbols here --RR */
647                         if (sym->st_shndx == SHN_UNDEF ||
648                             sym->st_shndx == SHN_LIVEPATCH) {
649                                 /* External: go via stub */
650                                 value = stub_for_addr(sechdrs, value, me);
651                                 if (!value)
652                                         return -ENOENT;
653                                 if (!restore_r2((u32 *)location + 1, me))
654                                         return -ENOEXEC;
655 
656                                 squash_toc_save_inst(strtab + sym->st_name, value);
657                         } else
658                                 value += local_entry_offset(sym);
659 
660                         /* Convert value to relative */
661                         value -= (unsigned long)location;
662                         if (value + 0x2000000 > 0x3ffffff || (value & 3) != 0){
663                                 pr_err("%s: REL24 %li out of range!\n",
664                                        me->name, (long int)value);
665                                 return -ENOEXEC;
666                         }
667 
668                         /* Only replace bits 2 through 26 */
669                         *(uint32_t *)location
670                                 = (*(uint32_t *)location & ~0x03fffffc)
671                                 | (value & 0x03fffffc);
672                         break;
673 
674                 case R_PPC64_REL64:
675                         /* 64 bits relative (used by features fixups) */
676                         *location = value - (unsigned long)location;
677                         break;
678 
679                 case R_PPC64_REL32:
680                         /* 32 bits relative (used by relative exception tables) */
681                         *(u32 *)location = value - (unsigned long)location;
682                         break;
683 
684                 case R_PPC64_TOCSAVE:
685                         /*
686                          * Marker reloc indicates we don't have to save r2.
687                          * That would only save us one instruction, so ignore
688                          * it.
689                          */
690                         break;
691 
692                 case R_PPC64_ENTRY:
693                         /*
694                          * Optimize ELFv2 large code model entry point if
695                          * the TOC is within 2GB range of current location.
696                          */
697                         value = my_r2(sechdrs, me) - (unsigned long)location;
698                         if (value + 0x80008000 > 0xffffffff)
699                                 break;
700                         /*
701                          * Check for the large code model prolog sequence:
702                          *      ld r2, ...(r12)
703                          *      add r2, r2, r12
704                          */
705                         if ((((uint32_t *)location)[0] & ~0xfffc)
706                             != 0xe84c0000)
707                                 break;
708                         if (((uint32_t *)location)[1] != 0x7c426214)
709                                 break;
710                         /*
711                          * If found, replace it with:
712                          *      addis r2, r12, (.TOC.-func)@ha
713                          *      addi r2, r12, (.TOC.-func)@l
714                          */
715                         ((uint32_t *)location)[0] = 0x3c4c0000 + PPC_HA(value);
716                         ((uint32_t *)location)[1] = 0x38420000 + PPC_LO(value);
717                         break;
718 
719                 case R_PPC64_REL16_HA:
720                         /* Subtract location pointer */
721                         value -= (unsigned long)location;
722                         value = ((value + 0x8000) >> 16);
723                         *((uint16_t *) location)
724                                 = (*((uint16_t *) location) & ~0xffff)
725                                 | (value & 0xffff);
726                         break;
727 
728                 case R_PPC64_REL16_LO:
729                         /* Subtract location pointer */
730                         value -= (unsigned long)location;
731                         *((uint16_t *) location)
732                                 = (*((uint16_t *) location) & ~0xffff)
733                                 | (value & 0xffff);
734                         break;
735 
736                 default:
737                         pr_err("%s: Unknown ADD relocation: %lu\n",
738                                me->name,
739                                (unsigned long)ELF64_R_TYPE(rela[i].r_info));
740                         return -ENOEXEC;
741                 }
742         }
743 
744         return 0;
745 }
746 
747 #ifdef CONFIG_DYNAMIC_FTRACE
748 
749 #ifdef CC_USING_MPROFILE_KERNEL
750 
751 #define PACATOC offsetof(struct paca_struct, kernel_toc)
752 
753 /*
754  * For mprofile-kernel we use a special stub for ftrace_caller() because we
755  * can't rely on r2 containing this module's TOC when we enter the stub.
756  *
757  * That can happen if the function calling us didn't need to use the toc. In
758  * that case it won't have setup r2, and the r2 value will be either the
759  * kernel's toc, or possibly another modules toc.
760  *
761  * To deal with that this stub uses the kernel toc, which is always accessible
762  * via the paca (in r13). The target (ftrace_caller()) is responsible for
763  * saving and restoring the toc before returning.
764  */
765 static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
766 {
767         struct ppc64_stub_entry *entry;
768         unsigned int i, num_stubs;
769         static u32 stub_insns[] = {
770                 0xe98d0000 | PACATOC,   /* ld      r12,PACATOC(r13)     */
771                 0x3d8c0000,             /* addis   r12,r12,<high>       */
772                 0x398c0000,             /* addi    r12,r12,<low>        */
773                 0x7d8903a6,             /* mtctr   r12                  */
774                 0x4e800420,             /* bctr                         */
775         };
776         long reladdr;
777 
778         num_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*entry);
779 
780         /* Find the next available stub entry */
781         entry = (void *)sechdrs[me->arch.stubs_section].sh_addr;
782         for (i = 0; i < num_stubs && stub_func_addr(entry->funcdata); i++, entry++);
783 
784         if (i >= num_stubs) {
785                 pr_err("%s: Unable to find a free slot for ftrace stub.\n", me->name);
786                 return 0;
787         }
788 
789         memcpy(entry->jump, stub_insns, sizeof(stub_insns));
790 
791         /* Stub uses address relative to kernel toc (from the paca) */
792         reladdr = (unsigned long)ftrace_caller - kernel_toc_addr();
793         if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
794                 pr_err("%s: Address of ftrace_caller out of range of kernel_toc.\n", me->name);
795                 return 0;
796         }
797 
798         entry->jump[1] |= PPC_HA(reladdr);
799         entry->jump[2] |= PPC_LO(reladdr);
800 
801         /* Eventhough we don't use funcdata in the stub, it's needed elsewhere. */
802         entry->funcdata = func_desc((unsigned long)ftrace_caller);
803         entry->magic = STUB_MAGIC;
804 
805         return (unsigned long)entry;
806 }
807 #else
808 static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
809 {
810         return stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me);
811 }
812 #endif
813 
814 int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
815 {
816         mod->arch.toc = my_r2(sechdrs, mod);
817         mod->arch.tramp = create_ftrace_stub(sechdrs, mod);
818 
819         if (!mod->arch.tramp)
820                 return -ENOENT;
821 
822         return 0;
823 }
824 #endif
825 

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