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sortix--sortix/kernel/copy.cpp
2014-12-02 15:35:50 +01:00

240 lines
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C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2012, 2014.
This file is part of Sortix.
Sortix 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 of the License, or (at your option) any later
version.
Sortix 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.
You should have received a copy of the GNU General Public License along with
Sortix. If not, see <http://www.gnu.org/licenses/>.
copy.cpp
The context for io operations: who made it, how should data be copied, etc.
*******************************************************************************/
#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <string.h>
#include <sortix/mman.h>
#include <sortix/kernel/copy.h>
#include <sortix/kernel/kernel.h>
#include <sortix/kernel/kthread.h>
#include <sortix/kernel/process.h>
#include <sortix/kernel/segment.h>
#include <sortix/kernel/string.h>
// NOTE: The copy-from-user-space functions are specially made such that they
// guarantee the relevant memory exist and are unchanged during the copy
// operation. They do not protect against another thread concurrently
// modifying the memory, but the functions cope in that case and just
// transfer whatever memory they see in that case, they don't malfunction.
// TODO: We could check the page tables for extra safely.
namespace Sortix {
static bool IsInProgressAddressSpace(Process* process)
{
addr_t current_address_space;
#if defined(__i386__)
asm ( "mov %%cr3, %0" : "=r"(current_address_space) );
#elif defined(__x86_64__)
asm ( "mov %%cr3, %0" : "=r"(current_address_space) );
#else
#warning "You should set current_address_space for safety"
current_address_space = process->addrspace;
#endif
return current_address_space == process->addrspace;
}
static struct segment* FindSegment(Process* process, uintptr_t addr)
{
for ( size_t i = 0; i < process->segments_used; i++ )
{
struct segment* segment = &process->segments[i];
if ( addr < segment->addr )
continue;
if ( segment->addr + segment->size <= addr )
continue;
return segment;
}
return NULL;
}
bool CopyToUser(void* userdst_ptr, const void* ksrc_ptr, size_t count)
{
uintptr_t userdst = (uintptr_t) userdst_ptr;
uintptr_t ksrc = (uintptr_t) ksrc_ptr;
bool result = true;
Process* process = CurrentProcess();
assert(IsInProgressAddressSpace(process));
kthread_mutex_lock(&process->segment_lock);
while ( count )
{
struct segment* segment = FindSegment(process, userdst);
if ( !segment || !(segment->prot & PROT_WRITE) )
{
errno = EFAULT;
result = false;
break;
}
size_t amount = count;
size_t segment_available = segment->addr + segment->size - userdst;
if ( segment_available < amount )
amount = segment_available;
memcpy((void*) userdst, (const void*) ksrc, amount);
userdst += amount;
ksrc += amount;
count -= amount;
}
kthread_mutex_unlock(&process->segment_lock);
return result;
}
bool CopyFromUser(void* kdst_ptr, const void* usersrc_ptr, size_t count)
{
uintptr_t kdst = (uintptr_t) kdst_ptr;
uintptr_t usersrc = (uintptr_t) usersrc_ptr;
bool result = true;
Process* process = CurrentProcess();
assert(IsInProgressAddressSpace(process));
kthread_mutex_lock(&process->segment_lock);
while ( count )
{
struct segment* segment = FindSegment(process, usersrc);
if ( !segment || !(segment->prot & PROT_READ) )
{
errno = EFAULT;
result = false;
break;
}
size_t amount = count;
size_t segment_available = segment->addr + segment->size - usersrc;
if ( segment_available < amount )
amount = segment_available;
memcpy((void*) kdst, (const void*) usersrc, amount);
kdst += amount;
usersrc += amount;
count -= amount;
}
kthread_mutex_unlock(&process->segment_lock);
return result;
}
bool CopyToKernel(void* kdst, const void* ksrc, size_t count)
{
memcpy(kdst, ksrc, count);
return true;
}
bool CopyFromKernel(void* kdst, const void* ksrc, size_t count)
{
memcpy(kdst, ksrc, count);
return true;
}
bool ZeroKernel(void* kdst, size_t count)
{
// TODO: We could check the page tables for extra safely.
memset(kdst, 0, count);
return true;
}
bool ZeroUser(void* userdst_ptr, size_t count)
{
uintptr_t userdst = (uintptr_t) userdst_ptr;
bool result = true;
Process* process = CurrentProcess();
assert(IsInProgressAddressSpace(process));
kthread_mutex_lock(&process->segment_lock);
while ( count )
{
struct segment* segment = FindSegment(process, userdst);
if ( !segment || !(segment->prot & PROT_WRITE) )
{
errno = EFAULT;
result = false;
break;
}
size_t amount = count;
size_t segment_available = segment->addr + segment->size - userdst;
if ( segment_available < amount )
amount = segment_available;
memset((void*) userdst, 0, amount);
userdst += amount;
count -= amount;
}
kthread_mutex_unlock(&process->segment_lock);
return result;
}
// NOTE: No overflow can happen here because the user can't make an infinitely
// long string spanning the entire address space because the user can't
// control the entire address space.
char* GetStringFromUser(const char* usersrc_str)
{
uintptr_t usersrc = (uintptr_t) usersrc_str;
size_t result_length = 0;
Process* process = CurrentProcess();
assert(IsInProgressAddressSpace(process));
kthread_mutex_lock(&process->segment_lock);
while ( true )
{
uintptr_t current_at = usersrc + result_length;
struct segment* segment = FindSegment(process, current_at);
if ( !segment || !(segment->prot & PROT_READ) )
{
kthread_mutex_unlock(&process->segment_lock);
return errno = EFAULT, (char*) NULL;
}
size_t segment_available = segment->addr + segment->size - current_at;
volatile const char* str = (volatile const char*) current_at;
size_t length = 0;
for ( ; length < segment_available; length++ )
{
char c = str[length];
if ( c == '\0' )
break;
length++;
}
result_length += length;
if ( length < segment_available )
break;
}
char* result = new char[result_length + 1];
if ( !result )
{
kthread_mutex_unlock(&process->segment_lock);
return (char*) NULL;
}
memcpy(result, (const char*) usersrc, result_length);
result[result_length] = '\0';
// We have transferred a bunch of bytes from user-space and appended a zero
// byte. This is a string. If no concurrent threads were modifying the
// memory, this is the intended string. If the memory was modified, we got
// potential garbage followed by a NUL byte. This is a string, but probably
// not what was intended. If the garbage itself had a premature unexpected
// NUL byte, that's okay, the garbage string just got truncated.
kthread_mutex_unlock(&process->segment_lock);
return result;
}
} // namespace Sortix