elfloader-arm.c

#include <stdlib.h>
#include <malloc.h>
#include <loader/elfloader-arch-otf.h>

#if 0
#include <stdio.h>
#define PRINTF(...) printf(__VA_ARGS__)
#else
#define PRINTF(...) do {} while (0)
#endif

#define ELF32_R_TYPE(info)      ((unsigned char)(info))

/* Supported relocations */

#define R_ARM_ABS32     2
#define R_ARM_THM_CALL  10

/* Adapted from elfloader-avr.c */

int
elfloader_arch_relocate(int input_fd,
                        struct elfloader_output *output,
                        unsigned int sectionoffset,
                        char *sectionaddr,
                        struct elf32_rela *rela, char *addr)
{
  unsigned int type;

  type = ELF32_R_TYPE(rela->r_info);

  cfs_seek(input_fd, sectionoffset + rela->r_offset, CFS_SEEK_SET);

/*   PRINTF("elfloader_arch_relocate: type %d\n", type); */
/*   PRINTF("Addr: %p, Addend: %ld\n",   addr, rela->r_addend); */
  switch(type) {
  case R_ARM_ABS32:
    {
      int32_t addend;
      cfs_read(input_fd, (char*)&addend, 4);
      addr += addend;
      elfloader_output_write_segment(output,(char*) &addr, 4);
      PRINTF("%p: addr: %p\n", sectionaddr +rela->r_offset,
             addr);
    }
    break;
  case R_ARM_THM_CALL:
    {
      uint16_t instr[2];
      int32_t offset;
      char *base;
      cfs_read(input_fd, (char*)instr, 4);
      /* Ignore the addend since it will be zero for calls to symbols,
         and I can't think of a case when doing a relative call to
         a non-symbol position */
      base = sectionaddr + (rela->r_offset + 4);

      if (((instr[1]) & 0xe800) == 0xe800) {
        /* BL or BLX */
        if (((uint32_t)addr) & 0x1) {
          /* BL */
          instr[1] |= 0x1800;
        } else {
#if defined(__ARM_ARCH_4T__)
          return ELFLOADER_UNHANDLED_RELOC;
#else
          /* BLX */
          instr[1] &= ~0x1800;
          instr[1] |= 0x0800;
#endif
        }
      }
      /* Adjust address for BLX */
      if ((instr[1] & 0x1800) == 0x0800) {
        addr = (char*)((((uint32_t)addr) & 0xfffffffd)
                       | (((uint32_t)base) & 0x00000002));
      }
      offset = addr -  (sectionaddr + (rela->r_offset + 4));
      if (offset < -(1<<22) || offset >= (1<<22)) {
        PRINTF("elfloader-arm.c: offset %d too large for relative call\n",
               (int)offset);
      }
    /*   PRINTF("%p: %04x %04x  offset: %d addr: %p\n", sectionaddr +rela->r_offset, instr[0], instr[1], (int)offset, addr);  */
      instr[0] = (instr[0] & 0xf800) | ((offset>>12)&0x07ff);
      instr[1] = (instr[1] & 0xf800) | ((offset>>1)&0x07ff);
      elfloader_output_write_segment(output, (char*)instr, 4);
  /*     PRINTF("cfs_write: %04x %04x\n",instr[0], instr[1]);  */
    }
    break;
    
  default:
    PRINTF("elfloader-arm.c: unsupported relocation type %d\n", type);
    return ELFLOADER_UNHANDLED_RELOC;
  }
  return ELFLOADER_OK;
}