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/**
* @file init.c
* riscv64 'bootstrap', move actual kernel into place and jump to virtual
* memory.
*/
#include <apos/types.h>
#include <apos/attrs.h>
#include <apos/utils.h>
#include <apos/vmem.h>
#include <arch/vmem.h>
#include "../kernel/csr.h"
/** Temporary virtual memory space.
* Assume 64bit riscv for now.
*/
struct vmem *root_branch;
/**
* Create page table entry.
* Copy from \ref arch/riscv64/kernel/vmem.c.
*
* @param a Virtual address.
* @param f PTE flags.
*/
#define to_pte(a, f) (((a) >> 12) << 10 | (f))
/** Jump into virtual memory. */
static void init_bootmem()
{
size_t flags = VM_V | VM_X | VM_R | VM_W;
extern char *__init_start;
root_branch = (struct vmem *)align_down(
(uintptr_t)&__init_start - SZ_4K, SZ_4K);
/* direct mapping (temp) */
for (size_t i = 0; i < CSTACK_PAGE; ++i)
root_branch->leaf[i] = (struct vmem *)to_pte(SZ_1G * i, flags);
/* kernel (also sort of direct mapping) */
flags |= VM_G;
for (size_t i = KSTART_PAGE; i < IO_PAGE; ++i)
root_branch->leaf[i] = (struct vmem *)to_pte(
RAM_BASE + SZ_1G * (i - 256), flags);
/* kernel IO, map to 0 for now, will be updated in the future */
root_branch->leaf[IO_PAGE] = (struct vmem *)to_pte(0, flags);
csr_write(CSR_SATP, SATP_MODE_Sv39 | ((uintptr_t)root_branch >> 12));
}
/** Relocate kernel proper. */
static void move_kernel()
{
extern char *__init_end;
extern char *__kernel_size;
unsigned long sz = (unsigned long)&__kernel_size;
char *src = (char *)&__init_end;
char *dst = (char *)VM_KERN;
for (size_t i = 0; i < sz; ++i)
dst[i] = src[i];
}
/**
* Convert an existing physical address in a register to a virtual address.
* There is probably an easier way to do this, but this seems to work alright.
*
* @param reg Register to modify.
*/
#define __va_reg(reg) \
{ \
vm_t reg = 0; \
__asm__ ("mv %0, " QUOTE(reg) : "=r" (reg)::); \
reg = (vm_t)__va(reg); \
__asm__ ("mv " QUOTE(reg) ", %0" ::"rK" (reg) :); \
}
/**
* Main driver for the init loader.
*
* @param fdt Global FDT pointer, provided by bootloader.
*/
void init(void *fdt)
{
extern char *__init_end;
extern void jump_to_kernel(void *k, void *fdt);
init_bootmem();
move_kernel();
__va_reg(sp);
__va_reg(fp);
__va_reg(gp);
jump_to_kernel((void *)VM_KERN, __va(fdt));
}
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