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/*
* Memory Mapping Allocator
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/internal/mmap_mem.h>
#include <vector>
#include <cstring>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#ifndef MAP_FAILED
#define MAP_FAILED -1
#endif
namespace Botan {
namespace {
/*
* MemoryMapping_Allocator Exception
*/
class BOTAN_DLL MemoryMapping_Failed : public Exception
{
public:
MemoryMapping_Failed(const std::string& msg) :
Exception("MemoryMapping_Allocator: " + msg) {}
};
}
/*
* Memory Map a File into Memory
*/
void* MemoryMapping_Allocator::alloc_block(size_t n)
{
class TemporaryFile
{
public:
int get_fd() const { return fd; }
TemporaryFile(const std::string& base)
{
const std::string mkstemp_template = base + "XXXXXX";
std::vector<char> filepath(mkstemp_template.begin(),
mkstemp_template.end());
filepath.push_back(0); // add terminating NULL
mode_t old_umask = ::umask(077);
fd = ::mkstemp(&filepath[0]);
::umask(old_umask);
if(fd == -1)
throw MemoryMapping_Failed("Temporary file allocation failed");
if(::unlink(&filepath[0]) != 0)
throw MemoryMapping_Failed("Could not unlink temporary file");
}
~TemporaryFile()
{
/*
* We can safely close here, because post-mmap the file
* will continue to exist until the mmap is unmapped from
* our address space upon deallocation (or process exit).
*/
if(fd != -1 && ::close(fd) == -1)
throw MemoryMapping_Failed("Could not close file");
}
private:
int fd;
};
TemporaryFile file("/tmp/botan_");
if(file.get_fd() == -1)
throw MemoryMapping_Failed("Could not create file");
std::vector<byte> zeros(4096);
size_t remaining = n;
while(remaining)
{
const size_t write_try = std::min(zeros.size(), remaining);
ssize_t wrote_got = ::write(file.get_fd(),
&zeros[0],
write_try);
if(wrote_got == -1 && errno != EINTR)
throw MemoryMapping_Failed("Could not write to file");
remaining -= wrote_got;
}
#ifndef MAP_NOSYNC
#define MAP_NOSYNC 0
#endif
void* ptr = ::mmap(0, n,
PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_NOSYNC,
file.get_fd(), 0);
if(ptr == static_cast<void*>(MAP_FAILED))
throw MemoryMapping_Failed("Could not map file");
return ptr;
}
/*
* Remove a Memory Mapping
*/
void MemoryMapping_Allocator::dealloc_block(void* ptr, size_t n)
{
if(ptr == nullptr)
return;
const byte PATTERNS[] = { 0x00, 0xF5, 0x5A, 0xAF, 0x00 };
for(size_t i = 0; i != sizeof(PATTERNS); ++i)
{
std::memset(ptr, PATTERNS[i], n);
if(::msync((char*)ptr, n, MS_SYNC))
throw MemoryMapping_Failed("Sync operation failed");
}
if(::munmap((char*)ptr, n))
throw MemoryMapping_Failed("Could not unmap file");
}
}
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