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Diffstat (limited to 'breakpad/linux/memory.h')
| -rw-r--r-- | breakpad/linux/memory.h | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/breakpad/linux/memory.h b/breakpad/linux/memory.h new file mode 100644 index 0000000..e6947a1 --- /dev/null +++ b/breakpad/linux/memory.h @@ -0,0 +1,176 @@ +// Copyright (c) 2009, Google Inc. +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following disclaimer +// in the documentation and/or other materials provided with the +// distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +#ifndef CLIENT_LINUX_HANDLER_MEMORY_H_ +#define CLIENT_LINUX_HANDLER_MEMORY_H_ + +#include <stdint.h> +#include <stdlib.h> +#include <unistd.h> +#include <sys/mman.h> + +#include "breakpad/linux/linux_syscall_support.h" + +namespace google_breakpad { + +// This is very simple allocator which fetches pages from the kernel directly. +// Thus, it can be used even when the heap may be corrupted. +// +// There is no free operation. The pages are only freed when the object is +// destroyed. +class PageAllocator { + public: + PageAllocator() + : page_size_(getpagesize()), + last_(NULL), + current_page_(NULL), + page_offset_(0) { + } + + ~PageAllocator() { + FreeAll(); + } + + void *Alloc(unsigned bytes) { + if (!bytes) + return NULL; + + if (current_page_ && page_size_ - page_offset_ >= bytes) { + uint8_t *const ret = current_page_ + page_offset_; + page_offset_ += bytes; + if (page_offset_ == page_size_) { + page_offset_ = 0; + current_page_ = NULL; + } + + return ret; + } + + const unsigned pages = + (bytes + sizeof(PageHeader) + page_size_ - 1) / page_size_; + uint8_t *const ret = GetNPages(pages); + if (!ret) + return NULL; + + page_offset_ = (page_size_ - (page_size_ * pages - (bytes + sizeof(PageHeader)))) % page_size_; + current_page_ = page_offset_ ? ret + page_size_ * (pages - 1) : NULL; + + return ret + sizeof(PageHeader); + } + + private: + uint8_t *GetNPages(unsigned num_pages) { + void *a = sys_mmap2(NULL, page_size_ * num_pages, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (a == MAP_FAILED) + return NULL; + + struct PageHeader *header = reinterpret_cast<PageHeader*>(a); + header->next = last_; + header->num_pages = num_pages; + last_ = header; + + return reinterpret_cast<uint8_t*>(a); + } + + void FreeAll() { + PageHeader *next; + + for (PageHeader *cur = last_; cur; cur = next) { + next = cur->next; + sys_munmap(cur, cur->num_pages * page_size_); + } + } + + struct PageHeader { + PageHeader *next; // pointer to the start of the next set of pages. + unsigned num_pages; // the number of pages in this set. + }; + + const unsigned page_size_; + PageHeader *last_; + uint8_t *current_page_; + unsigned page_offset_; +}; + +// A wasteful vector is like a normal std::vector, except that it's very much +// simplier and it allocates memory from a PageAllocator. It's wasteful +// because, when resizing, it always allocates a whole new array since the +// PageAllocator doesn't support realloc. +template<class T> +class wasteful_vector { + public: + wasteful_vector(PageAllocator *allocator, unsigned size_hint = 16) + : allocator_(allocator), + a_((T*) allocator->Alloc(sizeof(T) * size_hint)), + allocated_(size_hint), + used_(0) { + } + + void push_back(const T& new_element) { + if (used_ == allocated_) + Realloc(allocated_ * 2); + a_[used_++] = new_element; + } + + size_t size() const { + return used_; + } + + T& operator[](size_t index) { + return a_[index]; + } + + const T& operator[](size_t index) const { + return a_[index]; + } + + private: + void Realloc(unsigned new_size) { + T *new_array = + reinterpret_cast<T*>(allocator_->Alloc(sizeof(T) * new_size)); + memcpy(new_array, a_, used_ * sizeof(T)); + a_ = new_array; + allocated_ = new_size; + } + + PageAllocator *const allocator_; + T *a_; // pointer to an array of |allocated_| elements. + unsigned allocated_; // size of |a_|, in elements. + unsigned used_; // number of used slots in |a_|. +}; + +} // namespace google_breakpad + +inline void* operator new(size_t nbytes, + google_breakpad::PageAllocator& allocator) { + return allocator.Alloc(nbytes); +} + +#endif // CLIENT_LINUX_HANDLER_MEMORY_H_ |