/* Copyright (C) 2007-2010 The Android Open Source Project ** ** This software is licensed under the terms of the GNU General Public ** License version 2, as published by the Free Software Foundation, and ** may be copied, distributed, and modified under those terms. ** ** This program is distributed in the hope that it will be useful, ** but WITHOUT ANY WARRANTY; without even the implied warranty of ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ** GNU General Public License for more details. */ /* * Contains implementation of memory checking framework in the emulator. */ #include "qemu-queue.h" #include "qemu_file.h" #include "elff_api.h" #include "memcheck.h" #include "memcheck_proc_management.h" #include "memcheck_util.h" #include "memcheck_logging.h" // ============================================================================= // Global data // ============================================================================= /* Controls what messages from the guest should be printed to emulator's * stdout. This variable holds a combinations of TRACE_LIBC_XXX flags. */ uint32_t trace_flags = 0; /* Global flag, indicating whether or not memchecking has been enabled * for the current emulator session. 1 means that memchecking has been enabled, * 0 means that memchecking has not been enabled. */ int memcheck_enabled = 0; /* Global flag, indicating whether or not __ld/__stx_mmu should be instrumented * for checking for access violations. If read / write access violation check * has been disabled by -memcheck flags, there is no need to instrument mmu * routines and waste performance. * 1 means that instrumenting is required, 0 means that instrumenting is not * required. */ int memcheck_instrument_mmu = 0; /* Global flag, indicating whether or not memchecker is collecting call stack. * 1 - call stack is being collected, 0 means that stack is not being * collected. */ int memcheck_watch_call_stack = 1; // ============================================================================= // Static routines. // ============================================================================= /* Prints invalid pointer access violation information. * Param: * proc - Process that caused access violation. * ptr - Pointer that caused access violation. * routine - If 1, access violation has occurred in 'free' routine. * If 2, access violation has occurred in 'realloc' routine. */ static void av_invalid_pointer(ProcDesc* proc, target_ulong ptr, int routine) { if (trace_flags & TRACE_CHECK_INVALID_PTR_ENABLED) { printf("memcheck: Access violation is detected in process %s[pid=%u]:\n" " INVALID POINTER 0x%08X is used in '%s' operation.\n" " Allocation descriptor for this pointer has not been found in the\n" " allocation map for the process. Most likely, this is an attempt\n" " to %s a pointer that has been freed.\n", proc->image_path, proc->pid, ptr, routine == 1 ? "free" : "realloc", routine == 1 ? "free" : "reallocate"); } } /* Prints read / write access violation information. * Param: * proc - Process that caused access violation. * desc - Allocation descriptor for the violation. * addr - Address at which vilation has occurred. * data_size - Size of data accessed at the 'addr'. * val - If access violation has occurred at write operation, this parameter * contains value that's being written to 'addr'. For read violation this * parameter is not used. * retaddr - Code address (in TB) where access violation has occurred. * is_read - If 1, access violation has occurred when memory at 'addr' has been * read. If 0, access violation has occurred when memory was written. */ static void av_access_violation(ProcDesc* proc, MallocDescEx* desc, target_ulong addr, uint32_t data_size, uint64_t val, target_ulong retaddr, int is_read) { target_ulong vaddr; Elf_AddressInfo elff_info; ELFF_HANDLE elff_handle = NULL; desc->malloc_desc.av_count++; if ((is_read && !(trace_flags & TRACE_CHECK_READ_VIOLATION_ENABLED)) || (!is_read && !(trace_flags & TRACE_CHECK_WRITE_VIOLATION_ENABLED))) { return; } /* Convert host address to guest address. */ vaddr = memcheck_tpc_to_gpc(retaddr); printf("memcheck: Access violation is detected in process %s[pid=%u]:\n", proc->image_path, proc->pid); /* Obtain routine, filename / line info for the address. */ const MMRangeDesc* rdesc = procdesc_get_range_desc(proc, vaddr); if (rdesc != NULL) { int elff_res; printf(" In module %s at address 0x%08X\n", rdesc->path, vaddr); elff_res = memcheck_get_address_info(vaddr, rdesc, &elff_info, &elff_handle); if (elff_res == 0) { printf(" In routine %s in %s/%s:%u\n", elff_info.routine_name, elff_info.dir_name, elff_info.file_name, elff_info.line_number); if (elff_info.inline_stack != NULL) { const Elf_InlineInfo* inl = elff_info.inline_stack; int index = 0; for (; inl[index].routine_name != NULL; index++) { char align[64]; size_t set_align = 4 + index * 2; if (set_align >= sizeof(align)) { set_align = sizeof(align) -1; } memset(align, ' ', set_align); align[set_align] = '\0'; printf("%s", align); if (inl[index].inlined_in_file == NULL) { printf("inlined to %s in unknown location\n", inl[index].routine_name); } else { printf("inlined to %s in %s/%s:%u\n", inl[index].routine_name, inl[index].inlined_in_file_dir, inl[index].inlined_in_file, inl[index].inlined_at_line); } } } elff_free_pc_address_info(elff_handle, &elff_info); elff_close(elff_handle); } else if (elff_res == 1) { printf(" Unable to obtain routine information. Symbols file is not found.\n"); } else { printf(" Unable to obtain routine information.\n" " Symbols file doesn't contain debugging information for address 0x%08X.\n", mmrangedesc_get_module_offset(rdesc, vaddr)); } } else { printf(" In unknown module at address 0x%08X\n", vaddr); } printf(" Process attempts to %s %u bytes %s address 0x%08X\n", is_read ? "read" : "write", data_size, is_read ? "from" : "to", addr); printf(" Accessed range belongs to the %s guarding area of allocated block.\n", addr < (target_ulong)mallocdesc_get_user_ptr(&desc->malloc_desc) ? "prefix" : "suffix"); printf(" Allocation descriptor for this violation:\n"); memcheck_dump_malloc_desc(desc, 1, 0); } /* Validates access to a guest address. * Param: * addr - Virtual address in the guest space where memory is accessed. * data_size - Size of the accessed data. * proc_ptr - Upon exit from this routine contains pointer to the process * descriptor for the current process, or NULL, if no such descriptor has * been found. * desc_ptr - Upon exit from this routine contains pointer to the allocation * descriptor matching given address range, or NULL, if allocation * descriptor for the validated memory range has not been found. * Return: * 0 if access to the given guest address range doesn't violate anything, or * 1 if given guest address range doesn't match any entry in the current * process allocation descriptors map, or * -1 if a violation has been detected. */ static int memcheck_common_access_validation(target_ulong addr, uint32_t data_size, ProcDesc** proc_ptr, MallocDescEx** desc_ptr) { MallocDescEx* desc; target_ulong validating_range_end; target_ulong user_range_end; ProcDesc* proc = get_current_process(); *proc_ptr = proc; if (proc == NULL) { *desc_ptr = NULL; return 1; } desc = procdesc_find_malloc_for_range(proc, addr, data_size); *desc_ptr = desc; if (desc == NULL) { return 1; } /* Verify that validating address range doesn't start before the address * available to the user. */ if (addr < mallocdesc_get_user_ptr(&desc->malloc_desc)) { // Stepped on the prefix guarding area. return -1; } validating_range_end = addr + data_size; user_range_end = mallocdesc_get_user_alloc_end(&desc->malloc_desc); /* Verify that validating address range ends inside the user block. * We may step on the suffix guarding area because of alignment issue. * For example, the application code reads last byte in the allocated block * with something like this: * * char last_byte_value = *(char*)last_byte_address; * * and this code got compiled into something like this: * * mov eax, [last_byte_address]; * mov [last_byte_value], al; * * In this case we will catch a read from the suffix area, even though * there were no errors in the code. So, in order to prevent such "false * negative" alarms, lets "forgive" this violation. * There is one bad thing about this "forgivness" though, as it may very * well be, that in real life some of these "out of bound" bytes will cross * page boundaries, marching into a page that has not been mapped to the * process. */ if (validating_range_end <= user_range_end) { // Validating address range is fully contained inside the user block. return 0; } /* Lets see if this AV is caused by an alignment issue.*/ if ((validating_range_end - user_range_end) < data_size) { /* Could be an alignment. */ return 0; } return -1; } /* Checks if process has allocation descriptors for pages defined by a buffer. * Param: * addr - Starting address of a buffer. * buf_size - Buffer size. * Return: * 1 if process has allocations descriptors for pages defined by a buffer, or * 0 if pages containing given buffer don't have any memory allocations in * them. */ static inline int procdesc_contains_allocs(ProcDesc* proc, target_ulong addr, uint32_t buf_size) { if (proc != NULL) { // Beginning of the page containing last byte in range. const target_ulong end_page = (addr + buf_size - 1) & TARGET_PAGE_MASK; // Adjust beginning of the range to the beginning of the page. addr &= TARGET_PAGE_MASK; // Total size of range to check for descriptors. buf_size = end_page - addr + TARGET_PAGE_SIZE + 1; return procdesc_find_malloc_for_range(proc, addr, buf_size) ? 1 : 0; } else { return 0; } } // ============================================================================= // Memchecker API. // ============================================================================= void memcheck_init(const char* tracing_flags) { if (*tracing_flags == '0') { // Memchecker is disabled. return; } else if (*tracing_flags == '1') { // Set default tracing. trace_flags = TRACE_CHECK_LEAK_ENABLED | TRACE_CHECK_READ_VIOLATION_ENABLED | TRACE_CHECK_INVALID_PTR_ENABLED | TRACE_CHECK_WRITE_VIOLATION_ENABLED; } // Parse -memcheck option params, converting them into tracing flags. while (*tracing_flags) { switch (*tracing_flags) { case 'A': // Enable all emulator's tracing messages. trace_flags |= TRACE_ALL_ENABLED; break; case 'F': // Enable fork() tracing. trace_flags |= TRACE_PROC_FORK_ENABLED; break; case 'S': // Enable guest process staring tracing. trace_flags |= TRACE_PROC_START_ENABLED; break; case 'E': // Enable guest process exiting tracing. trace_flags |= TRACE_PROC_EXIT_ENABLED; break; case 'C': // Enable clone() tracing. trace_flags |= TRACE_PROC_CLONE_ENABLED; break; case 'N': // Enable new PID allocation tracing. trace_flags |= TRACE_PROC_NEW_PID_ENABLED; break; case 'B': // Enable libc.so initialization tracing. trace_flags |= TRACE_PROC_LIBC_INIT_ENABLED; break; case 'L': // Enable memory leaks tracing. trace_flags |= TRACE_CHECK_LEAK_ENABLED; break; case 'I': // Enable invalid free / realloc pointer tracing. trace_flags |= TRACE_CHECK_INVALID_PTR_ENABLED; break; case 'R': // Enable reading violations tracing. trace_flags |= TRACE_CHECK_READ_VIOLATION_ENABLED; break; case 'W': // Enable writing violations tracing. trace_flags |= TRACE_CHECK_WRITE_VIOLATION_ENABLED; break; case 'M': // Enable module mapping tracing. trace_flags |= TRACE_PROC_MMAP_ENABLED; break; default: break; } if (trace_flags == TRACE_ALL_ENABLED) { break; } tracing_flags++; } /* Lets see if we need to instrument MMU, injecting memory access checking. * We instrument MMU only if we monitor read, or write memory access. */ if (trace_flags & (TRACE_CHECK_READ_VIOLATION_ENABLED | TRACE_CHECK_WRITE_VIOLATION_ENABLED)) { memcheck_instrument_mmu = 1; } else { memcheck_instrument_mmu = 0; } memcheck_init_proc_management(); /* Lets check env. variables needed for memory checking. */ if (getenv("ANDROID_PROJECT_OUT") == NULL) { printf("memcheck: Missing ANDROID_PROJECT_OUT environment variable, that is used\n" "to calculate path to symbol files.\n"); } // Always set this flag at the very end of the initialization! memcheck_enabled = 1; } void memcheck_guest_libc_initialized(uint32_t pid) { ProcDesc* proc = get_process_from_pid(pid); if (proc == NULL) { ME("memcheck: Unable to obtain process for libc_init pid=%u", pid); return; } proc->flags |= PROC_FLAG_LIBC_INITIALIZED; /* When process initializes its own libc.so instance, it means that now * it has fresh heap. So, at this point we must get rid of all entries * (inherited and transition) that were collected in this process' * allocation descriptors map. */ procdesc_empty_alloc_map(proc); T(PROC_LIBC_INIT, "memcheck: libc.so has been initialized for %s[pid=%u]\n", proc->image_path, proc->pid); } void memcheck_guest_alloc(target_ulong guest_address) { MallocDescEx desc; MallocDescEx replaced; RBTMapResult insert_res; ProcDesc* proc; ThreadDesc* thread; uint32_t indx; // Copy allocation descriptor from guest to emulator. memcheck_get_malloc_descriptor(&desc.malloc_desc, guest_address); desc.flags = 0; desc.call_stack = NULL; desc.call_stack_count = 0; proc = get_process_from_pid(desc.malloc_desc.allocator_pid); if (proc == NULL) { ME("memcheck: Unable to obtain process for allocation pid=%u", desc.malloc_desc.allocator_pid); memcheck_fail_alloc(guest_address); return; } if (!procdesc_is_executing(proc)) { desc.flags |= MDESC_FLAG_TRANSITION_ENTRY; } /* Copy thread's calling stack to the allocation descriptor. */ thread = get_current_thread(); desc.call_stack_count = thread->call_stack_count; if (desc.call_stack_count) { desc.call_stack = qemu_malloc(desc.call_stack_count * sizeof(target_ulong)); if (desc.call_stack == NULL) { ME("memcheck: Unable to allocate %u bytes for the calling stack", desc.call_stack_count * sizeof(target_ulong)); return; } } /* Thread's calling stack is in descending order (i.e. first entry in the * thread's stack is the most distant routine from the current one). On the * other hand, we keep calling stack entries in allocation descriptor in * assending order. */ for (indx = 0; indx < thread->call_stack_count; indx++) { desc.call_stack[indx] = thread->call_stack[thread->call_stack_count - 1 - indx].call_address; } // Save malloc descriptor in the map. insert_res = procdesc_add_malloc(proc, &desc, &replaced); if (insert_res == RBT_MAP_RESULT_ENTRY_INSERTED) { // Invalidate TLB cache for the allocated block. if (memcheck_instrument_mmu) { invalidate_tlb_cache(desc.malloc_desc.ptr, mallocdesc_get_alloc_end(&desc.malloc_desc)); } } else if (insert_res == RBT_MAP_RESULT_ENTRY_REPLACED) { /* We don't expect to have another entry in the map that matches * inserting entry. This is an error condition for us, indicating * that we somehow lost track of memory allocations. */ ME("memcheck: Duplicate allocation blocks:"); if (VERBOSE_CHECK(memcheck)) { printf(" New block:\n"); memcheck_dump_malloc_desc(&desc, 1, 1); printf(" Replaced block:\n"); memcheck_dump_malloc_desc(&replaced, 1, 1); } if (replaced.call_stack != NULL) { qemu_free(replaced.call_stack); } } else { ME("memcheck: Unable to insert an entry to the allocation map:"); if (VERBOSE_CHECK(memcheck)) { memcheck_dump_malloc_desc(&desc, 1, 1); } memcheck_fail_alloc(guest_address); return; } } void memcheck_guest_free(target_ulong guest_address) { MallocFree desc; MallocDescEx pulled; int pull_res; ProcDesc* proc; // Copy free descriptor from guest to emulator. memcheck_get_free_descriptor(&desc, guest_address); proc = get_process_from_pid(desc.free_pid); if (proc == NULL) { ME("memcheck: Unable to obtain process for pid=%u on free", desc.free_pid); memcheck_fail_free(guest_address); return; } // Pull matching entry from the map. pull_res = procdesc_pull_malloc(proc, desc.ptr, &pulled); if (pull_res) { av_invalid_pointer(proc, desc.ptr, 1); memcheck_fail_free(guest_address); return; } // Make sure that ptr has expected value if (desc.ptr != mallocdesc_get_user_ptr(&pulled.malloc_desc)) { if (trace_flags & TRACE_CHECK_INVALID_PTR_ENABLED) { printf("memcheck: Access violation is detected in process %s[pid=%u]:\n", proc->image_path, proc->pid); printf(" INVALID POINTER 0x%08X is used in 'free' operation.\n" " This pointer is unexpected for 'free' operation, as allocation\n" " descriptor found for this pointer in the process' allocation map\n" " suggests that 0x%08X is the pointer to be used to free this block.\n" " Allocation descriptor matching the pointer:\n", desc.ptr, (uint32_t)mallocdesc_get_user_ptr(&pulled.malloc_desc)); memcheck_dump_malloc_desc(&pulled, 1, 0); } } if (pulled.call_stack != NULL) { qemu_free(pulled.call_stack); } } void memcheck_guest_query_malloc(target_ulong guest_address) { MallocDescQuery qdesc; MallocDescEx* found; ProcDesc* proc; // Copy free descriptor from guest to emulator. memcheck_get_query_descriptor(&qdesc, guest_address); proc = get_process_from_pid(qdesc.query_pid); if (proc == NULL) { ME("memcheck: Unable to obtain process for pid=%u on query_%s", qdesc.query_pid, qdesc.routine == 1 ? "free" : "realloc"); memcheck_fail_query(guest_address); return; } // Find allocation entry for the given address. found = procdesc_find_malloc(proc, qdesc.ptr); if (found == NULL) { av_invalid_pointer(proc, qdesc.ptr, qdesc.routine); memcheck_fail_query(guest_address); return; } // Copy allocation descriptor back to the guest's space. memcheck_set_malloc_descriptor(qdesc.desc, &found->malloc_desc); } void memcheck_guest_print_str(target_ulong str) { char str_copy[4096]; memcheck_get_guest_string(str_copy, str, sizeof(str_copy)); printf("%s", str_copy); } /* Validates read operations, detected in __ldx_mmu routine. * This routine is called from __ldx_mmu wrapper implemented in * softmmu_template.h on condition that loading is occurring from user memory. * Param: * addr - Virtual address in the guest space where memory is read. * data_size - Size of the read. * retaddr - Code address (in TB) that accesses memory. * Return: * 1 if TLB record for the accessed page should be invalidated in order to * ensure that subsequent attempts to access data in this page will cause * __ld/stx_mmu to be used. If memchecker is no longer interested in monitoring * access to this page, this routine returns 0. */ int memcheck_validate_ld(target_ulong addr, uint32_t data_size, target_ulong retaddr) { ProcDesc* proc; MallocDescEx* desc; int res = memcheck_common_access_validation(addr, data_size, &proc, &desc); if (res == -1) { av_access_violation(proc, desc, addr, data_size, 0, retaddr, 1); return 1; } /* Even though descriptor for the given address range has not been found, * we need to make sure that pages containing the given address range * don't contain other descriptors. */ return res ? procdesc_contains_allocs(proc, addr, data_size) : 0; } /* Validates write operations, detected in __stx_mmu routine. * This routine is called from __stx_mmu wrapper implemented in * softmmu_template.h on condition that storing is occurring from user memory. * Param: * addr - Virtual address in the guest space where memory is written. * data_size - Size of the write. * value - Value to be written. Note that we typecast all values to 64 bits, * since this will fit all data sizes. * retaddr - Code address (in TB) that accesses memory. * Return: * 1 if TLB record for the accessed page should be invalidated in order to * ensure that subsequent attempts to access data in this page will cause * __ld/stx_mmu to be used. If memchecker is no longer interested in monitoring * access to this page, this routine returns 0. */ int memcheck_validate_st(target_ulong addr, uint32_t data_size, uint64_t value, target_ulong retaddr) { MallocDescEx* desc; ProcDesc* proc; int res = memcheck_common_access_validation(addr, data_size, &proc, &desc); if (res == -1) { av_access_violation(proc, desc, addr, data_size, value, retaddr, 0); return 1; } /* Even though descriptor for the given address range has not been found, * we need to make sure that pages containing the given address range * don't contain other descriptors. */ return res ? procdesc_contains_allocs(proc, addr, data_size) : 0; } /* Checks if given address range in the context of the current process is under * surveillance. * Param: * addr - Starting address of a range. * size - Range size. * Return: * boolean: 1 if address range contains memory that require access violation * detection, or 0 if given address range is in no interest to the memchecker. */ int memcheck_is_checked(target_ulong addr, uint32_t size) { return procdesc_contains_allocs(get_current_process(), addr, size) ? 1 : 0; }