/*
* Create a new user context of given size
*/
static struct User_Context *Create_User_Context(ulong_t size) {
struct User_Context *context;
int index;
/* Size must be a multiple of the page size */
size = Round_Up_To_Page(size);
if (userDebug)
Print("Size of user memory == %lu (%lx) (%lu pages)\n", size, size,
size / PAGE_SIZE);
/* Allocate memory for the user context */
Disable_Interrupts();
context = (struct User_Context *)Malloc(sizeof(*context));
if (context != 0)
context->memory = Malloc(size);
Enable_Interrupts();
if (context == 0 || context->memory == 0)
goto fail;
/*
* Fill user memory with zeroes;
* leaving it uninitialized is a potential security flaw
*/
memset(context->memory, '\0', size);
context->size = size;
/* Allocate an LDT descriptor for the user context */
context->ldtDescriptor = Allocate_Segment_Descriptor();
if (context->ldtDescriptor == 0)
goto fail;
if (userDebug)
Print("Allocated descriptor %d for LDT\n",
Get_Descriptor_Index(context->ldtDescriptor));
Init_LDT_Descriptor(context->ldtDescriptor, context->ldt,
NUM_USER_LDT_ENTRIES);
index = Get_Descriptor_Index(context->ldtDescriptor);
context->ldtSelector = Selector(KERNEL_PRIVILEGE, true, index);
/* Initialize code and data segments within the LDT */
Init_Code_Segment_Descriptor(&context->ldt[0],
(ulong_t) context->memory,
size / PAGE_SIZE, USER_PRIVILEGE);
Init_Data_Segment_Descriptor(&context->ldt[1],
(ulong_t) context->memory,
size / PAGE_SIZE, USER_PRIVILEGE);
context->csSelector = Selector(USER_PRIVILEGE, false, 0);
context->dsSelector = Selector(USER_PRIVILEGE, false, 1);
/* Nobody is using this user context yet */
context->refCount = 0;
/* Initialize background flag */
context->backgrounded = 0;
/* Initialize all semaphore flags to 0 */
int sem_ind;
for (sem_ind = 0; sem_ind < MAX_SEM_SIZE; sem_ind++) {
context->sem_flags[sem_ind] = 0;
}
/* Success! */
return context;
fail:
/* We failed; release any allocated memory */
Disable_Interrupts();
if (context != 0) {
if (context->memory != 0)
Free(context->memory);
Free(context);
}
Enable_Interrupts();
return 0;
}
static int Spawn_Program(char *exeFileData, struct Exe_Format *exeFormat)
{
struct Segment_Descriptor* desc;
unsigned long virtSize;
unsigned short codeSelector, dataSelector;
int i;
ulong_t maxva = 0;
/* Find maximum virtual address */
for (i = 0; i < exeFormat->numSegments; ++i) {
struct Exe_Segment *segment = &exeFormat->segmentList[i];
ulong_t topva = segment->startAddress + segment->sizeInMemory;
if (topva > maxva)
maxva = topva;
}
/* setup some memory space for the program */
virtSize = Round_Up_To_Page(maxva) + 4096; /* leave some slack for stack */
virtSpace = Malloc(virtSize);
memset((char *) virtSpace, '\0', virtSize);
/* Load segment data into memory */
for (i = 0; i < exeFormat->numSegments; ++i) {
struct Exe_Segment *segment = &exeFormat->segmentList[i];
memcpy(virtSpace + segment->startAddress,
exeFileData + segment->offsetInFile,
segment->lengthInFile);
}
/* allocate and init descriptors and selectors for code and data */
// Kernel code segment.
desc = Allocate_Segment_Descriptor();
Init_Code_Segment_Descriptor(
desc,
(unsigned long)virtSpace, // base address
(virtSize/PAGE_SIZE)+10, // num pages
0 // privilege level (0 == kernel)
);
codeSelector = Selector( 0, true, Get_Descriptor_Index( desc ) );
// Kernel data segment.
desc = Allocate_Segment_Descriptor();
Init_Data_Segment_Descriptor(
desc,
(unsigned long)virtSpace, // base address
(virtSize/PAGE_SIZE)+10, // num pages
0 // privilege level (0 == kernel)
);
dataSelector = Selector( 0, true, Get_Descriptor_Index( desc ) );
Install_Interrupt_Handler( 0x90, &Printrap_Handler );
if (lprogdebug)
{
Print("Spawn_Program(): all structures are set up\n");
Print(" virtSpace = %x\n", (unsigned int) virtSpace);
Print(" virtSize = %x\n", (unsigned int) virtSize);
Print(" codeSelector = %x\n", codeSelector);
Print(" dataSelector = %x\n", dataSelector);
Print("Now calling Trampoline()... \n");
}
Trampoline(codeSelector, dataSelector, exeFormat->entryAddr);
return 0;
}
/*
* Load a user executable into memory by creating a User_Context
* data structure.
* Params:
* exeFileData - a buffer containing the executable to load
* exeFileLength - number of bytes in exeFileData
* exeFormat - parsed ELF segment information describing how to
* load the executable's text and data segments, and the
* code entry point address
* command - string containing the complete command to be executed:
* this should be used to create the argument block for the
* process
* pUserContext - reference to the pointer where the User_Context
* should be stored
*
* Returns:
* 0 if successful, or an error code (< 0) if unsuccessful
*/
int Load_User_Program(char *exeFileData, ulong_t exeFileLength,
struct Exe_Format *exeFormat, const char *command,
struct User_Context **pUserContext)
{
/*
* Hints:
* ok - Determine where in memory each executable segment will be placed
* ok - Determine size of argument block and where it memory it will
* be placed
* - Copy each executable segment into memory
* - Format argument block in memory
* - In the created User_Context object, set code entry point
* address, argument block address, and initial kernel stack pointer
* address
*/
int i;
ulong_t size;
ulong_t maxva = 0;
unsigned numArgs;
ulong_t argBlockSize;
/* calculates arg block length */
Get_Argument_Block_Size(command, &numArgs, &argBlockSize);
/* Find maximum virtual address */
for (i = 0; i < exeFormat->numSegments; ++i) {
struct Exe_Segment *segment = &exeFormat->segmentList[i];
ulong_t topva = segment->startAddress + segment->sizeInMemory;
if (topva > maxva)
maxva = topva;
}
/* calculates memory size for the program, the stack and the args */
size = Round_Up_To_Page(maxva) + Round_Up_To_Page(DEFAULT_USER_STACK_SIZE + argBlockSize);
/* creates the user context */
if( (*pUserContext = Create_User_Context(size)) == 0 )
return -1;
/* Load segment data into memory */
for (i = 0; i < exeFormat->numSegments; ++i) {
struct Exe_Segment *segment = &exeFormat->segmentList[i];
memcpy((*pUserContext)->memory + segment->startAddress,
exeFileData + segment->offsetInFile,
segment->lengthInFile);
}
/* copy the args just after the data segment */
struct Exe_Segment *segment = &exeFormat->segmentList[1];
int userAddress = segment->startAddress + segment->lengthInFile;
Print("%.8x\n", userAddress);
Format_Argument_Block( (*pUserContext)->memory + userAddress, numArgs, userAddress, command);
/* to show some part of the code */
// memDump((*pUserContext)->memory + userAddress, 0x6c + 0x20);
/* allocate the LDT descriptor in the GDT */
(*pUserContext)->ldtDescriptor = Allocate_Segment_Descriptor();
Init_LDT_Descriptor(
(*pUserContext)->ldtDescriptor,
(*pUserContext)->ldt,
NUM_USER_LDT_ENTRIES);
/* the LDT selector */
(*pUserContext)->ldtSelector = Selector(
KERNEL_PRIVILEGE,
true, /* in the GDT */
Get_Descriptor_Index( (*pUserContext)->ldtDescriptor ));
/* code descriptor */
Init_Code_Segment_Descriptor(
&(*pUserContext)->ldt[0],
(ulong_t)(*pUserContext)->memory , // base address
((*pUserContext)->size/PAGE_SIZE)+10, // FIXME is ok??? num pages
USER_PRIVILEGE
);
(*pUserContext)->csSelector = Selector(
USER_PRIVILEGE,
false, /* LDT */
0 ); /* descriptor index */
/* data descriptor */
Init_Data_Segment_Descriptor(
&(*pUserContext)->ldt[1],
(ulong_t)(*pUserContext)->memory , // base address
((*pUserContext)->size/PAGE_SIZE)+10, // FIXME is ok??? num pages
USER_PRIVILEGE
);
(*pUserContext)->dsSelector = Selector(
USER_PRIVILEGE,
false, /* LDT */
1 ); /* descriptor index */
/* entry point */
(*pUserContext)->entryAddr = exeFormat->entryAddr;
/* Address of argument block in user memory */
(*pUserContext)->argBlockAddr = userAddress;
(*pUserContext)->stackPointerAddr = (*pUserContext)->size;
/* Initial stack pointer */
// TODO stackPointerAddr;
/*
* May use this in future to allow multiple threads
* in the same user context
*
* int refCount;
*
*/
/* for debuging */
Print("virt Space: From %p to %p\n", (*pUserContext)->memory, (*pUserContext)->memory + (*pUserContext)->size);
Print("%.8lX\n", (*pUserContext)->size);
//Print("codeSelector=%08x,DataSelector=%08x\n", (*pUserContext)->csSelector,
// (*pUserContext)->dsSelector);
//j memDump((*pUserContext)->memory+0x24f0,0x100);
// memDump((void*)(*pUserContext),0x100);
return 0;
}