loader_stage1.c


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#include <stddef.h>
#include <stdint.h>
#include <global.h>

#define STAGE2_ADDR ((volatile char*) 0x4000)

// There's one tricky thing about managing executable's own code.
// Mainly, symbols are visible to c code as extern chars, but the actual
// values are their adresses... see the code below
extern char
  __stage2_start,
  __stage2_end,
  __stage2_size;

__attribute__((section(".text.stage1main")))
void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
{
  // stage2 of the bootloader is part of executable;
  // copy it over to it's destination place
  // TODO implement a memcpy() somewhere and use it instead of loops
  for (size_t i = 0; i < (size_t) &__stage2_size; i++)
    STAGE2_ADDR[i] = (&__stage2_start)[i];

  // jump to stage2
  ((void(*)(uint32_t, uint32_t, uint32_t))STAGE2_ADDR)(r0, r1, atags);
}