stack_pointer.c

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#include <kernel/cpu/regs.h>
#include <kernel/cpu/stack_pointer.h>
 
#include <kernel/log/log.h>
#include <kernel/mem/vmm.h>
#include <kernel/sched/thread.h>
 
uint64_t stack_pointer_init(stack_pointer_t* stack, uintptr_t maxAddress, uint64_t maxPages)
{
    if (stack == NULL || maxPages == 0 || !VMM_IS_PAGE_ALIGNED(maxAddress))
    {
        errno = EINVAL;
        return ERR;
    }
 
    stack->top = maxAddress;
    stack->bottom = stack->top - (maxPages * PAGE_SIZE);
    if (stack->bottom >= stack->top) // Overflow
    {
        errno = EOVERFLOW;
        return ERR;
    }
    stack->guardTop = stack->bottom;
    stack->guardBottom = stack->guardTop - (STACK_POINTER_GUARD_PAGES * PAGE_SIZE);
    if (stack->guardBottom >= stack->guardTop) // Overflow
    {
        errno = EOVERFLOW;
        return ERR;
    }
    stack->lastPageFault = 0;
 
    return 0;
}
 
uint64_t stack_pointer_init_buffer(stack_pointer_t* stack, void* buffer, uint64_t pages)
{
    if (stack == NULL || buffer == NULL || pages == 0 || !VMM_IS_PAGE_ALIGNED(buffer))
    {
        errno = EINVAL;
        return ERR;
    }
 
    stack->top = (uintptr_t)buffer + pages * PAGE_SIZE;
    stack->bottom = (uintptr_t)buffer;
    if (stack->bottom >= stack->top) // Overflow
    {
        errno = EOVERFLOW;
        return ERR;
    }
    // No guard pages when using a buffer.
    stack->guardTop = stack->bottom;
    stack->guardBottom = stack->bottom;
    stack->lastPageFault = 0;
 
    memset(buffer, 0, pages * PAGE_SIZE);
 
    return 0;
}
 
void stack_pointer_deinit(stack_pointer_t* stack, thread_t* thread)
{
    if (stack == NULL)
    {
        return;
    }
 
    vmm_unmap(&thread->process->space, (void*)stack->bottom, BYTES_TO_PAGES(stack->top - stack->bottom));
 
    stack->top = 0;
    stack->bottom = 0;
    stack->guardTop = 0;
    stack->guardBottom = 0;
    stack->lastPageFault = 0;
}
 
void stack_pointer_deinit_buffer(stack_pointer_t* stack)
{
    if (stack == NULL)
    {
        return;
    }
 
    stack->top = 0;
    stack->bottom = 0;
    stack->guardTop = 0;
    stack->guardBottom = 0;
    stack->lastPageFault = 0;
}
 
bool stack_pointer_is_in_stack(stack_pointer_t* stack, uintptr_t addr, uint64_t length)
{
    if (stack == NULL)
    {
        return false;
    }
 
    uintptr_t endAddr = addr + length;
    if (endAddr < addr)
    {
        return false;
    }
 
    return addr >= stack->bottom && endAddr < stack->top;
}
 
bool stack_pointer_overlaps_guard(stack_pointer_t* stack, uintptr_t addr, uint64_t length)
{
    if (stack == NULL)
    {
        return false;
    }
 
    uintptr_t endAddr = addr + length;
    if (endAddr < addr)
    {
        return false;
    }
 
    return !(endAddr <= stack->guardBottom || addr >= stack->guardTop);
}
 
void stack_pointer_poke(uint64_t offset)
{
    uint64_t rsp = rsp_read();
    for (uint64_t i = 0; i < offset; i += MIN(PAGE_SIZE, offset - i))
    {
        volatile uint8_t dummy;
        dummy = *((uint8_t*)(rsp - i));
    }
}