1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *  * Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  *  * Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in
12  *    the documentation and/or other materials provided with the
13  *    distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #if !defined(__LP64__) && __mips_isa_rev >= 5
30 #include <sys/prctl.h>
31 #endif
32 
33 #include "linker.h"
34 #include "linker_debug.h"
35 #include "linker_globals.h"
36 #include "linker_phdr.h"
37 #include "linker_relocs.h"
38 #include "linker_reloc_iterators.h"
39 #include "linker_sleb128.h"
40 #include "linker_soinfo.h"
41 
42 template bool soinfo::relocate<plain_reloc_iterator>(const VersionTracker& version_tracker,
43                                                      plain_reloc_iterator&& rel_iterator,
44                                                      const soinfo_list_t& global_group,
45                                                      const soinfo_list_t& local_group);
46 
47 template bool soinfo::relocate<packed_reloc_iterator<sleb128_decoder>>(
48     const VersionTracker& version_tracker,
49     packed_reloc_iterator<sleb128_decoder>&& rel_iterator,
50     const soinfo_list_t& global_group,
51     const soinfo_list_t& local_group);
52 
53 template <typename ElfRelIteratorT>
relocate(const VersionTracker & version_tracker,ElfRelIteratorT && rel_iterator,const soinfo_list_t & global_group,const soinfo_list_t & local_group)54 bool soinfo::relocate(const VersionTracker& version_tracker,
55                       ElfRelIteratorT&& rel_iterator,
56                       const soinfo_list_t& global_group,
57                       const soinfo_list_t& local_group) {
58   for (size_t idx = 0; rel_iterator.has_next(); ++idx) {
59     const auto rel = rel_iterator.next();
60 
61     if (rel == nullptr) {
62       return false;
63     }
64 
65     ElfW(Word) type = ELFW(R_TYPE)(rel->r_info);
66     ElfW(Word) sym = ELFW(R_SYM)(rel->r_info);
67 
68     ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
69     ElfW(Addr) sym_addr = 0;
70     const char* sym_name = nullptr;
71 
72     DEBUG("Processing \"%s\" relocation at index %zd", get_realpath(), idx);
73     if (type == R_GENERIC_NONE) {
74       continue;
75     }
76 
77     const ElfW(Sym)* s = nullptr;
78     soinfo* lsi = nullptr;
79 
80     if (sym != 0) {
81       sym_name = get_string(symtab_[sym].st_name);
82       const version_info* vi = nullptr;
83 
84       if (!lookup_version_info(version_tracker, sym, sym_name, &vi)) {
85         return false;
86       }
87 
88       if (!soinfo_do_lookup(this, sym_name, vi, &lsi, global_group, local_group, &s)) {
89         return false;
90       }
91 
92       if (s == nullptr) {
93         // mips does not support relocation with weak-undefined symbols
94         DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...",
95                sym_name, get_realpath());
96         return false;
97       } else {
98         // We got a definition.
99         sym_addr = lsi->resolve_symbol_address(s);
100       }
101       count_relocation(kRelocSymbol);
102     }
103 
104     switch (type) {
105       case R_MIPS_REL32:
106 #if defined(__LP64__)
107         // MIPS Elf64_Rel entries contain compound relocations
108         // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
109         if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
110             ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
111           DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
112                  type, static_cast<unsigned>(ELF64_R_TYPE2(rel->r_info)),
113                  static_cast<unsigned>(ELF64_R_TYPE3(rel->r_info)), rel, idx);
114           return false;
115         }
116 #endif
117         count_relocation(s == nullptr ? kRelocAbsolute : kRelocRelative);
118         MARK(rel->r_offset);
119         TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
120                    static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
121         if (s != nullptr) {
122           *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
123         } else {
124           *reinterpret_cast<ElfW(Addr)*>(reloc) += load_bias;
125         }
126         break;
127       default:
128         DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
129         return false;
130     }
131   }
132   return true;
133 }
134 
mips_relocate_got(const VersionTracker & version_tracker,const soinfo_list_t & global_group,const soinfo_list_t & local_group)135 bool soinfo::mips_relocate_got(const VersionTracker& version_tracker,
136                                const soinfo_list_t& global_group,
137                                const soinfo_list_t& local_group) {
138   ElfW(Addr)** got = plt_got_;
139   if (got == nullptr) {
140     return true;
141   }
142 
143   // got[0] is the address of the lazy resolver function.
144   // got[1] may be used for a GNU extension.
145   // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
146   // FIXME: maybe this should be in a separate routine?
147   if ((flags_ & FLAG_LINKER) == 0) {
148     size_t g = 0;
149     got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
150     if (reinterpret_cast<intptr_t>(got[g]) < 0) {
151       got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
152     }
153     // Relocate the local GOT entries.
154     for (; g < mips_local_gotno_; g++) {
155       got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + load_bias);
156     }
157   }
158 
159   // Now for the global GOT entries...
160   got = plt_got_ + mips_local_gotno_;
161   for (ElfW(Word) sym = mips_gotsym_; sym < mips_symtabno_; sym++, got++) {
162     // This is an undefined reference... try to locate it.
163     const ElfW(Sym)* local_sym = symtab_ + sym;
164     const char* sym_name = get_string(local_sym->st_name);
165     soinfo* lsi = nullptr;
166     const ElfW(Sym)* s = nullptr;
167 
168     ElfW(Word) st_visibility = (local_sym->st_other & 0x3);
169 
170     if (st_visibility == STV_DEFAULT) {
171       const version_info* vi = nullptr;
172 
173       if (!lookup_version_info(version_tracker, sym, sym_name, &vi)) {
174         return false;
175       }
176 
177       if (!soinfo_do_lookup(this, sym_name, vi, &lsi, global_group, local_group, &s)) {
178         return false;
179       }
180     } else if (st_visibility == STV_PROTECTED) {
181       if (local_sym->st_value == 0) {
182         DL_ERR("%s: invalid symbol \"%s\" (PROTECTED/UNDEFINED) ",
183                get_realpath(), sym_name);
184         return false;
185       }
186       s = local_sym;
187       lsi = this;
188     } else {
189       DL_ERR("%s: invalid symbol \"%s\" visibility: 0x%x",
190              get_realpath(), sym_name, st_visibility);
191       return false;
192     }
193 
194     if (s == nullptr) {
195       // We only allow an undefined symbol if this is a weak reference.
196       if (ELF_ST_BIND(local_sym->st_info) != STB_WEAK) {
197         DL_ERR("%s: cannot locate \"%s\"...", get_realpath(), sym_name);
198         return false;
199       }
200       *got = 0;
201     } else {
202       // FIXME: is this sufficient?
203       // For reference see NetBSD link loader
204       // http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ld.elf_so/arch/mips/mips_reloc.c?rev=1.53&content-type=text/x-cvsweb-markup
205       *got = reinterpret_cast<ElfW(Addr)*>(lsi->resolve_symbol_address(s));
206     }
207   }
208   return true;
209 }
210 
211 #if !defined(__LP64__)
212 
213 // Checks for mips32's various floating point abis.
214 // (Mips64 Android has a single floating point abi and doesn't need any checks)
215 
216 // Linux kernel has declarations similar to the following
217 //   in <linux>/arch/mips/include/asm/elf.h,
218 // but that non-uapi internal header file will never be imported
219 // into bionic's kernel headers.
220 
221 #define PT_MIPS_ABIFLAGS  0x70000003	// is .MIPS.abiflags segment
222 
223 struct mips_elf_abiflags_v0 {
224   uint16_t version;  // version of this structure
225   uint8_t  isa_level, isa_rev, gpr_size, cpr1_size, cpr2_size;
226   uint8_t  fp_abi;  // mips32 ABI variants for floating point
227   uint32_t isa_ext, ases, flags1, flags2;
228 };
229 
230 // Bits of flags1:
231 #define MIPS_AFL_FLAGS1_ODDSPREG 1  // Uses odd-numbered single-prec fp regs
232 
233 // Some values of fp_abi:        via compiler flag:
234 #define MIPS_ABI_FP_DOUBLE 1  // -mdouble-float
235 #define MIPS_ABI_FP_XX     5  // -mfpxx
236 #define MIPS_ABI_FP_64A    7  // -mips32r* -mfp64 -mno-odd-spreg
237 
238 #if __mips_isa_rev >= 5
239 static bool mips_fre_mode_on = false;  // have set FRE=1 mode for process
240 #endif
241 
mips_check_and_adjust_fp_modes()242 bool soinfo::mips_check_and_adjust_fp_modes() {
243   mips_elf_abiflags_v0* abiflags = nullptr;
244   int mips_fpabi;
245 
246   // Find soinfo's optional .MIPS.abiflags segment
247   for (size_t i = 0; i<phnum; ++i) {
248     const ElfW(Phdr)& ph = phdr[i];
249     if (ph.p_type == PT_MIPS_ABIFLAGS) {
250       if (ph.p_filesz < sizeof (mips_elf_abiflags_v0)) {
251         DL_ERR("Corrupt PT_MIPS_ABIFLAGS header found \"%s\"", get_realpath());
252         return false;
253       }
254       abiflags = reinterpret_cast<mips_elf_abiflags_v0*>(ph.p_vaddr + load_bias);
255       break;
256     }
257   }
258 
259   // FP ABI-variant compatibility checks for MIPS o32 ABI
260   if (abiflags == nullptr) {
261     // Old compilers lack the new abiflags section.
262     // These compilers used -mfp32 -mdouble-float -modd-spreg defaults,
263     //   ie FP32 aka DOUBLE, using odd-numbered single-prec regs
264     mips_fpabi = MIPS_ABI_FP_DOUBLE;
265   } else {
266     mips_fpabi = abiflags->fp_abi;
267     if ( (abiflags->flags1 & MIPS_AFL_FLAGS1_ODDSPREG)
268          && (mips_fpabi == MIPS_ABI_FP_XX ||
269              mips_fpabi == MIPS_ABI_FP_64A   ) ) {
270       // Android supports fewer cases than Linux
271       DL_ERR("Unsupported odd-single-prec FloatPt reg uses in \"%s\"",
272              get_realpath());
273       return false;
274     }
275   }
276   if (!(mips_fpabi == MIPS_ABI_FP_DOUBLE ||
277 #if __mips_isa_rev >= 5
278         mips_fpabi == MIPS_ABI_FP_64A    ||
279 #endif
280         mips_fpabi == MIPS_ABI_FP_XX       )) {
281     DL_ERR("Unsupported MIPS32 FloatPt ABI %d found in \"%s\"",
282            mips_fpabi, get_realpath());
283     return false;
284   }
285 
286 #if __mips_isa_rev >= 5
287   // Adjust process's FR Emulation mode, if needed
288   //
289   // On Mips R5 & R6, Android runs continuously in FR=1 64bit-fpreg mode.
290   // NDK mips32 apps compiled with old compilers generate FP32 code
291   //   which expects FR=0 32-bit fp registers.
292   // NDK mips32 apps compiled with newer compilers generate modeless
293   //   FPXX code which runs on both FR=0 and FR=1 modes.
294   // Android itself is compiled in FP64A which requires FR=1 mode.
295   // FP32, FPXX, and FP64A all interlink okay, without dynamic FR mode
296   //   changes during calls.  For details, see
297   //   http://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking
298   // Processes containing FR32 FR=0 code are run via kernel software assist,
299   //   which maps all odd-numbered single-precision reg refs onto the
300   //   upper half of the paired even-numbered double-precision reg.
301   // FRE=1 triggers traps to the kernel's emulator on every single-precision
302   //   fp op (for both odd and even-numbered registers).
303   // Turning on FRE=1 traps is done at most once per process, simultanously
304   //   for all threads of that process, when dlopen discovers FP32 code.
305   // The kernel repacks threads' registers when FRE mode is turn on or off.
306   //   These asynchronous adjustments are wrong if any thread was executing
307   //   FPXX code using odd-numbered single-precision regs.
308   // Current Android compilers default to the -mno-oddspreg option,
309   //   and this requirement is checked by Android's dlopen.
310   //   So FRE can always be safely turned on for FP32, anytime.
311   // Deferred enhancement: Allow loading of odd-spreg FPXX modules.
312 
313   if (mips_fpabi == MIPS_ABI_FP_DOUBLE && !mips_fre_mode_on) {
314     // Turn on FRE mode, which emulates mode-sensitive FR=0 code on FR=1
315     //   register files, by trapping to kernel on refs to single-precision regs
316     if (prctl(PR_SET_FP_MODE, PR_FP_MODE_FR|PR_FP_MODE_FRE)) {
317       DL_ERR("Kernel or cpu failed to set FRE mode required for running \"%s\"",
318              get_realpath());
319       return false;
320     }
321     DL_WARN("Using FRE=1 mode to run \"%s\"", get_realpath());
322     mips_fre_mode_on = true;  // Avoid future redundant mode-switch calls
323     // FRE mode is never turned back off.
324     // Deferred enhancement:
325     //   Reset FRE mode when dlclose() removes all FP32 modules
326   }
327 #else
328   // Android runs continuously in FR=0 32bit-fpreg mode.
329 #endif  // __mips_isa_rev
330   return true;
331 }
332 
333 #endif  // __LP64___
334