| /* Copyright (C) 2012-2020 Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| GCC 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. |
| |
| Under Section 7 of GPL version 3, you are granted additional |
| permissions described in the GCC Runtime Library Exception, version |
| 3.1, as published by the Free Software Foundation. |
| |
| You should have received a copy of the GNU General Public License and |
| a copy of the GCC Runtime Library Exception along with this program; |
| see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* This file is part of the vtable verification runtime library. It |
| contains our memory allocation and deallocation routines, which we |
| use in order to keep track of the pages in memory in which our sets |
| of valid vtable pointes are stored. (We need to know the pages so |
| we can set the protections on them appropriately). For more |
| information about the vtable verification feature, see the comments |
| in vtv_rts.cc. We use the existing obstack implementation in our |
| memory allocation scheme. */ |
| |
| #include <stdlib.h> |
| #include <unistd.h> |
| #if defined (__CYGWIN__) || defined (__MINGW32__) |
| #include <windows.h> |
| #else |
| #include <sys/mman.h> |
| #endif |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <fcntl.h> |
| #include <stdio.h> |
| |
| #include "vtv_utils.h" |
| #include "vtv_malloc.h" |
| #include "obstack.h" |
| |
| /* The following variables are used only for debugging and performance tuning |
| purposes. Therefore they do not need to be "protected". They cannot be used |
| to attack the vtable verification system and if they become corrupted it will |
| not affect the correctness or security of any of the rest of the vtable |
| verification feature. */ |
| |
| unsigned int num_calls_to_mprotect = 0; |
| unsigned int num_pages_protected = 0; |
| unsigned int long long mprotect_cycles = 0; |
| |
| /* Put the following variables in our ".vtable_map_vars" section so |
| that they are protected. They are explicitly unprotected and |
| protected again by calls to __vtv_unprotect and __vtv_protect */ |
| |
| static struct obstack vtv_obstack VTV_PROTECTED_VAR; |
| static void *current_chunk VTV_PROTECTED_VAR = 0; |
| static size_t current_chunk_size VTV_PROTECTED_VAR = 0; |
| static int malloc_initialized VTV_PROTECTED_VAR = 0; |
| |
| #if defined (__CYGWIN__) || defined (__MINGW32__) |
| //sysconf(_SC_PAGE_SIZE) port |
| long sysconf_SC_PAGE_SIZE() |
| { |
| SYSTEM_INFO si; |
| GetSystemInfo(&si); |
| long pageSize = (long)si.dwPageSize; |
| return pageSize; |
| //return 4096; // standard usermode 32bit pagesize in bytes // FIXME |
| } |
| #endif |
| |
| /* The function goes through and counts all the pages we have allocated |
| so far. It returns the page count. */ |
| |
| int |
| __vtv_count_mmapped_pages (void) |
| { |
| int count = 0; |
| struct _obstack_chunk * ci = (struct _obstack_chunk *) current_chunk; |
| while (ci) |
| { |
| count++; |
| ci = ci->prev; |
| } |
| |
| return count; |
| } |
| |
| /* This function goes through all of the pages we have allocated so |
| far and calls mprotect to change the protections on the pages, |
| according to the value of PROTECTION_FLAG. */ |
| |
| static void |
| change_protections_on_data_chunks (int protection_flag) |
| { |
| struct _obstack_chunk *ci; |
| ci = (struct _obstack_chunk *) current_chunk; |
| |
| while (ci) |
| { |
| /* Initial set up for mprotect call.*/ |
| struct _obstack_chunk *protect_start = ci; |
| size_t chunk_size; |
| size_t total_size; |
| unsigned int num_pages_in_chunk; |
| char *next_page; |
| unsigned long long start, end; |
| int result; |
| |
| |
| /* As long as the next 'chunk' is adjacent to the current one, |
| keep going down the list. */ |
| do |
| { |
| chunk_size = (ci->limit - (char *) ci); |
| total_size = (ci->limit - (char *) protect_start); |
| num_pages_in_chunk = chunk_size / VTV_PAGE_SIZE; |
| if (chunk_size % VTV_PAGE_SIZE > 0) |
| num_pages_in_chunk++; |
| next_page = (char *) ci + (num_pages_in_chunk * VTV_PAGE_SIZE); |
| ci = ci->prev; |
| } while (ci && (char *) ci == next_page); |
| |
| VTV_DEBUG_ASSERT (((unsigned long) protect_start & (VTV_PAGE_SIZE - 1)) |
| == 0); |
| |
| /* Protect the contiguous chunks so far. */ |
| start = rdtsc (); |
| result = mprotect (protect_start, total_size, protection_flag); |
| end = rdtsc (); |
| mprotect_cycles += end - start; |
| if (result == -1) |
| VTV_error (); |
| num_calls_to_mprotect++; |
| num_pages_protected += (total_size + VTV_PAGE_SIZE - 1)/ VTV_PAGE_SIZE; |
| } |
| |
| #ifdef VTV_DEBUG |
| __vtv_malloc_dump_stats (); |
| #endif |
| } |
| |
| /* This function makes all of our allocated pages read-only. */ |
| |
| void |
| __vtv_malloc_protect (void) |
| { |
| change_protections_on_data_chunks (PROT_READ); |
| } |
| |
| /* This function makes all of our allocated pages read-write. */ |
| |
| void |
| __vtv_malloc_unprotect (void) |
| { |
| change_protections_on_data_chunks (PROT_READ | PROT_WRITE); |
| } |
| |
| /* Allocates a SIZE-sized chunk of memory that is aligned to a page |
| boundary. The amount of memory requested (SIZE) must be a multiple |
| of the page size. Note: We must use mmap to allocate the memory; |
| using malloc here will cause problems. */ |
| |
| static void * |
| obstack_chunk_alloc (size_t size) |
| { |
| /* Increase size to the next multiple of VTV_PAGE_SIZE. */ |
| size = (size + (VTV_PAGE_SIZE - 1)) & (~(VTV_PAGE_SIZE - 1)); |
| VTV_DEBUG_ASSERT ((size & (VTV_PAGE_SIZE - 1)) == 0); |
| void *allocated; |
| |
| #if defined (__CYGWIN__) || defined (__MINGW32__) |
| if ((allocated = VirtualAlloc(NULL, size, MEM_RESERVE|MEM_COMMIT, |
| PAGE_READWRITE)) == 0) |
| #else |
| if ((allocated = mmap (NULL, size, PROT_READ | PROT_WRITE, |
| MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)) == 0) |
| #endif |
| VTV_error (); |
| |
| VTV_DEBUG_ASSERT (((unsigned long) allocated & (VTV_PAGE_SIZE - 1)) == 0); |
| |
| current_chunk = allocated; |
| current_chunk_size = size; |
| return allocated; |
| } |
| |
| static void |
| obstack_chunk_free (void *) |
| { |
| /* Do nothing. For our purposes there should be very little |
| de-allocation. */ |
| } |
| |
| /* This function sets up and initializes the obstack pieces for our |
| memory allocation scheme. */ |
| |
| void |
| __vtv_malloc_init (void) |
| { |
| /* Make sure we only execute the main body of this function ONCE. */ |
| if (malloc_initialized) |
| return; |
| |
| #if defined (__CYGWIN__) || defined (__MINGW32__) |
| if (VTV_PAGE_SIZE != sysconf_SC_PAGE_SIZE()) |
| #else |
| if (VTV_PAGE_SIZE != sysconf (_SC_PAGE_SIZE)) |
| #endif |
| VTV_error (); |
| |
| /* We guarantee that the obstack alloc failed handler will never be |
| called because in case the allocation of the chunk fails, it will |
| never return */ |
| obstack_alloc_failed_handler = NULL; |
| |
| obstack_specify_allocation (&vtv_obstack, VTV_PAGE_SIZE, sizeof (long), |
| obstack_chunk_alloc, obstack_chunk_free); |
| malloc_initialized = 1; |
| } |
| |
| /* This is our external interface for the memory allocation. SIZE is |
| the requested number of bytes to be allocated/ */ |
| |
| void * |
| __vtv_malloc (size_t size) |
| { |
| return obstack_alloc (&vtv_obstack, size); |
| } |
| |
| |
| /* This is our external interface for memory deallocation. */ |
| |
| void |
| __vtv_free (void *) |
| { |
| /* Do nothing. We dont care about recovering unneded memory at this |
| time. */ |
| } |
| |
| |
| /* This is a debugging function tat collects statistics about our |
| memory allocation. */ |
| void |
| __vtv_malloc_stats (void) |
| { |
| int count = 0; |
| struct _obstack_chunk * ci = (struct _obstack_chunk *) current_chunk; |
| while (ci) |
| { |
| count++; |
| ci = ci->prev; |
| } |
| fprintf (stderr, |
| "__vtv_malloc_stats:\n Page Size = %lu bytes\n " |
| "Number of pages = %d\n", static_cast<unsigned long>(VTV_PAGE_SIZE), |
| count); |
| } |
| |
| /* This is a debugging function. It writes out our memory allocation |
| statistics to a log file. */ |
| |
| void |
| __vtv_malloc_dump_stats (void) |
| { |
| static int fd = -1; |
| |
| if (fd == -1) |
| fd = __vtv_open_log ("vtv_mem_protection.log"); |
| if (fd == -1) |
| return; |
| |
| int count = 0; |
| struct _obstack_chunk * ci = (struct _obstack_chunk *) current_chunk; |
| while (ci) |
| { |
| count++; |
| ci = ci->prev; |
| } |
| |
| __vtv_add_to_log (fd, "__vtv_malloc_protect protected=%d pages\n", count); |
| } |