/****************************************************************************
 * libs/libc/machine/arm/armv7-a/arch_elf.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <inttypes.h>
#include <stdlib.h>
#include <errno.h>
#include <debug.h>

#include <arch/elf.h>
#include <nuttx/elf.h>

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_checkarch
 *
 * Description:
 *   Given the ELF header in 'hdr', verify that the ELF file is appropriate
 *   for the current, configured architecture.  Every architecture that uses
 *   the ELF loader must provide this function.
 *
 * Input Parameters:
 *   hdr - The ELF header read from the ELF file.
 *
 * Returned Value:
 *   True if the architecture supports this ELF file.
 *
 ****************************************************************************/

bool up_checkarch(FAR const Elf32_Ehdr *ehdr)
{
  /* Make sure it's an ARM executable */

  if (ehdr->e_machine != EM_ARM)
    {
      berr("ERROR: Not for ARM: e_machine=%04x\n", ehdr->e_machine);
      return false;
    }

  /* Make sure that 32-bit objects are supported */

  if (ehdr->e_ident[EI_CLASS] != ELFCLASS32)
    {
      berr("ERROR: Need 32-bit objects: e_ident[EI_CLASS]=%02x\n",
           ehdr->e_ident[EI_CLASS]);
      return false;
    }

  /* Verify endian-ness */

#ifdef CONFIG_ENDIAN_BIG
  if (ehdr->e_ident[EI_DATA] != ELFDATA2MSB)
#else
  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB)
#endif
    {
      berr("ERROR: Wrong endian-ness: e_ident[EI_DATA]=%02x\n",
           ehdr->e_ident[EI_DATA]);
      return false;
    }

  /* Make sure the entry point address is properly aligned */

  if ((ehdr->e_entry & 3) != 0)
    {
      berr("ERROR: Entry point is not properly aligned: %08" PRIx32 "\n",
           ehdr->e_entry);
      return false;
    }

  /* TODO:  Check ABI here. */

  return true;
}

/****************************************************************************
 * Name: up_relocate and up_relocateadd
 *
 * Description:
 *   Perform an architecture-specific ELF relocation.  Every architecture
 *   that uses the ELF loader must provide this function.
 *
 * Input Parameters:
 *   rel - The relocation type
 *   sym - The ELF symbol structure containing the fully resolved value.
 *         There are a few relocation types for a few architectures that do
 *         not require symbol information.  For those, this value will be
 *         NULL.  Implementations of these functions must be able to handle
 *         that case.
 *   addr - The address that requires the relocation.
 *
 * Returned Value:
 *   Zero (OK) if the relocation was successful.  Otherwise, a negated errno
 *   value indicating the cause of the relocation failure.
 *
 ****************************************************************************/

int up_relocate(FAR const Elf32_Rel *rel, FAR const Elf32_Sym *sym,
                uintptr_t addr)
{
  int32_t offset;
  unsigned int relotype;

  /* All relocations except R_ARM_V4BX depend upon having valid symbol
   * information.
   */

  relotype = ELF32_R_TYPE(rel->r_info);
  if (sym == NULL && relotype != R_ARM_NONE && relotype != R_ARM_V4BX)
    {
      return -EINVAL;
    }

  /* Handle the relocation by relocation type */

  switch (relotype)
    {
    case R_ARM_NONE:
      {
        /* No relocation */
      }
      break;

    case R_ARM_PC24:
    case R_ARM_CALL:
    case R_ARM_JUMP24:
      {
        binfo("Performing PC24 [%" PRId32 "] link "
              "at addr %08lx [%08lx] to sym '%p' st_value=%08lx\n",
              ELF32_R_TYPE(rel->r_info), (long)addr,
              (long)(*(uint32_t *)addr),
              sym, (long)sym->st_value);

        offset = (*(uint32_t *)addr & 0x00ffffff) << 2;
        if (offset & 0x02000000)
          {
            offset -= 0x04000000;
          }

        offset += sym->st_value - addr;
        if (offset & 3 || offset < (int32_t) 0xfe000000 ||
            offset >= (int32_t) 0x02000000)
          {
            berr("ERROR: PC24 [%" PRId32 "] relocation out of range, "
                 "offset=%08lx\n",
                 ELF32_R_TYPE(rel->r_info), offset);

            return -EINVAL;
          }

        offset >>= 2;

        *(uint32_t *)addr &= 0xff000000;
        *(uint32_t *)addr |= offset & 0x00ffffff;
      }
      break;

    case R_ARM_ABS32:
    case R_ARM_TARGET1:  /* New ABI:  TARGET1 always treated as ABS32 */
      {
        binfo("Performing ABS32 link "
              "at addr=%08lx [%08lx] to sym=%p st_value=%08lx\n",
              (long)addr, (long)(*(uint32_t *)addr), sym,
              (long)sym->st_value);

        *(uint32_t *)addr += sym->st_value;
      }
      break;

    case R_ARM_V4BX:
      {
        binfo("Performing V4BX link at addr=%08lx [%08lx]\n",
              (long)addr, (long)(*(uint32_t *)addr));

         /* Preserve only Rm and the condition code */

        *(uint32_t *)addr &= 0xf000000f;

        /* Change instruction to 'mov pc, Rm' */

        *(uint32_t *)addr |= 0x01a0f000;
      }
      break;

    case R_ARM_PREL31:
      {
        binfo("Performing PREL31 link "
              "at addr=%08lx [%08lx] to sym=%p st_value=%08lx\n",
              (long)addr, (long)(*(uint32_t *)addr), sym,
              (long)sym->st_value);

        offset            = *(uint32_t *)addr + sym->st_value - addr;
        *(uint32_t *)addr = offset & 0x7fffffff;
      }
      break;

    case R_ARM_MOVW_ABS_NC:
    case R_ARM_MOVT_ABS:
      {
        binfo("Performing MOVx_ABS [%" PRId32 "] link "
              "at addr=%08lx [%08lx] to sym=%p st_value=%08lx\n",
              ELF32_R_TYPE(rel->r_info), (long)addr,
              (long)(*(uint32_t *)addr),
              sym, (long)sym->st_value);

        offset = *(uint32_t *)addr;
        offset = ((offset & 0xf0000) >> 4) | (offset & 0xfff);

        offset += sym->st_value;
        if (ELF32_R_TYPE(rel->r_info) == R_ARM_MOVT_ABS)
          {
            offset >>= 16;
          }

        *(uint32_t *)addr &= 0xfff0f000;
        *(uint32_t *)addr |= ((offset & 0xf000) << 4) | (offset & 0x0fff);
      }
      break;

    default:
      berr("ERROR: Unsupported relocation: %" PRId32 "\n",
           ELF32_R_TYPE(rel->r_info));
      return -EINVAL;
    }

  return OK;
}

int up_relocateadd(FAR const Elf32_Rela *rel, FAR const Elf32_Sym *sym,
                   uintptr_t addr)
{
  berr("ERROR: RELA relocation not supported\n");
  return -ENOSYS;
}