moslab-code/src/l4/pkg/libunwind/lib/build/libunwind-l4.c

#include "elf-image-cache.h"
#include "libunwind-l4.h"
#include "libunwind_i.h"
#include "os-l4.h"

// libunwind uses pipes to validate addresses before local memory accesses,
// however it should not be relevant for remote unwinding.
int pipe (int __pipedes[2])
{
  (void) __pipedes;
  Debug(1, "WARN: Pipe is unimplemented!\n");
  return -1;
}

// Linear search is necessary because l4re binaries do not emit a .eh_frame_hdr section or program header.
static int linear_eh_frame_search(struct elf_image *ei, unsigned long segbase,
                                  unsigned long mapoff, unw_addr_space_t as,
                                  unw_word_t ip, unw_proc_info_t *pi, void *arg)
{
  Elf_W(Shdr) *shdr = elf_w(find_section) (ei, ".eh_frame");
  if (!shdr)
    return -UNW_ENOINFO;

  // eh_frame address in remote process
  Elf_W(Addr) eh_frame_start = shdr->sh_offset + segbase - mapoff;
  Elf_W(Addr) eh_frame_end = eh_frame_start + shdr->sh_size;

  unw_accessors_t *a = unw_get_accessors_int (as);
  int ret = -UNW_ENOINFO;
  unw_word_t addr = eh_frame_start;
  while (addr < eh_frame_end)
    {
      unw_word_t fde_addr = addr;
      if ((ret = dwarf_extract_proc_info_from_fde (as, a, &addr, pi,
                                                   segbase, 0, 0, arg)) < 0)
        return ret;

      if (ip >= pi->start_ip && ip < pi->end_ip)
        {
          addr = fde_addr;
          if ((ret = dwarf_extract_proc_info_from_fde (as, a, &addr, pi,
                                                       segbase, 1, 0, arg)) < 0)
            return ret;

          // Have to manually clear the flags here, as dwarf_extract_proc_info_from_fde does not do it,
          // and thus from a failed dwarf_search_unwind_table run for .debug_frame the UNW_PI_FLAG_DEBUG_FRAME flag might be set,
          // which later breaks CFI program execution.
          pi->flags = 0;

          return UNW_ESUCCESS;
        }
    }
  return ret;
}

static int l4_find_proc_info(unw_addr_space_t as, unw_word_t ip,
                             unw_proc_info_t *pi, int need_unwind_info,
                             void *arg)
{
  l4_unw_data_t *data = arg;

  struct elf_dyn_info edi;
  memset(&edi, 0, sizeof(edi));
  invalidate_edi(&edi);

  /* where it is mapped in virtual memory */
  unsigned long segbase;
  /* offset in the file */
  unsigned long mapoff;
  char path[256];

  if (l4_find_elf(data->rm, ip, &segbase, &mapoff, path, sizeof(path)))
    return -UNW_ENOINFO;

  elf_image_handle_t *elf = get_elf_image(path);
  if (!elf)
    return -UNW_ENOINFO;
  edi.ei = elf->ei;

  int ret = -UNW_ENOINFO;
  if (tdep_find_unwind_table(&edi, as, path, segbase, mapoff, ip) >= 0)
    {
      if (edi.di_cache.format != -1)
        ret = tdep_search_unwind_table (as, ip, &edi.di_cache,
                                        pi, need_unwind_info, arg);

      if (ret == -UNW_ENOINFO && edi.di_debug.format != -1)
        ret = tdep_search_unwind_table (as, ip, &edi.di_debug, pi,
                                        need_unwind_info, arg);

#if UNW_TARGET_ARM
      if (ret == -UNW_ENOINFO && edi.di_arm.format != -1)
        ret = tdep_search_unwind_table (as, ip, &edi.di_arm, pi,
                                        need_unwind_info, arg);
#endif
    }

  // Fall back to lineary searching eh_frame if no binary lookup table (.eh_frame_hdr) or .debug_frame is present,
  // which is what is supported by tdep_find_unwind_table and tdep_search_unwind_table.
  if (ret == -UNW_ENOINFO && edi.di_cache.format == -1)
    ret = linear_eh_frame_search(&edi.ei, segbase, mapoff, as, ip, pi, arg);

  return ret;
}

static int
l4_get_dyn_info_list_addr (unw_addr_space_t as, unw_word_t *dyn_info_list_addr,
                        void *arg)
{
#ifndef UNW_LOCAL_ONLY
# pragma weak _U_dyn_info_list_addr
  if (!_U_dyn_info_list_addr)
    return -UNW_ENOINFO;
#endif
  // Access the `_U_dyn_info_list` from `LOCAL_ONLY` library, i.e. libunwind.so.
  *dyn_info_list_addr = _U_dyn_info_list_addr ();
  return 0;
}

static int l4_access_mem_remote(unw_addr_space_t as, unw_word_t addr,
                                unw_word_t *valp, int write, void *arg)
{
  (void)as;

  l4_unw_data_t *data = arg;
  l4_umword_t val;
  int res = data->remote_mem(addr, &val, write, data->remote_mem_arg);
  if (res >= 0)
    *valp = val;
  return res;
}

static int l4_access_reg(unw_addr_space_t as, unw_regnum_t regnum,
                         unw_word_t *valp, int write, void *arg)
{
  (void)as;

  l4_unw_data_t *data = arg;
  l4_exc_regs_t *regs = data->regs;
  l4_umword_t *reg;

  Debug(16, "reg=%d write=%d\n", regnum, write);

#ifdef ARCH_arm
  if (regnum >= UNW_ARM_R0 && regnum <= UNW_ARM_R12)
    reg = &regs->r[regnum];
  else if (regnum == UNW_TDEP_SP)
    reg = &regs->sp;
  else if (regnum == UNW_ARM_R14)
    reg = &regs->ulr;
  else if (regnum == UNW_TDEP_IP)
    reg = &regs->pc;
  else
    {
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    }
#elif defined(ARCH_arm64)
  if (regnum >= UNW_AARCH64_X0 && regnum <= UNW_AARCH64_X30)
    reg = &regs->r[regnum - UNW_AARCH64_X0];
  else if(regnum == UNW_AARCH64_SP)
    reg = &regs->sp;
  else if(regnum == UNW_AARCH64_PC)
    reg = &regs->pc;
  else
    {
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    }
#elif defined(ARCH_x86)
  switch (regnum)
    {
    case UNW_X86_EAX:
      reg = &regs->eax;
      break;
    case UNW_X86_EDX:
      reg = &regs->edx;
      break;
    case UNW_X86_ECX:
      reg = &regs->ecx;
      break;
    case UNW_X86_EBX:
      reg = &regs->ebx;
      break;
    case UNW_X86_ESI:
      reg = &regs->esi;
      break;
    case UNW_X86_EDI:
      reg = &regs->edi;
      break;
    case UNW_X86_EBP:
      reg = &regs->ebp;
      break;
    case UNW_X86_ESP:
      reg = &regs->sp;
      break;
    case UNW_X86_EIP:
      reg = &regs->ip;
      break;
    case UNW_X86_EFLAGS:
      reg = &regs->flags;
      break;
    case UNW_X86_TRAPNO:
      reg = &regs->trapno;
      break;
    default:
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    };
#elif defined(ARCH_amd64)
  switch (regnum)
    {
    case UNW_X86_64_RAX:
      reg = &regs->rax;
      break;
    case UNW_X86_64_RDX:
      reg = &regs->rdx;
      break;
    case UNW_X86_64_RCX:
      reg = &regs->rcx;
      break;
    case UNW_X86_64_RBX:
      reg = &regs->rbx;
      break;
    case UNW_X86_64_RSI:
      reg = &regs->rsi;
      break;
    case UNW_X86_64_RDI:
      reg = &regs->rdi;
      break;
    case UNW_X86_64_RBP:
      reg = &regs->rbp;
      break;
    case UNW_X86_64_RSP:
      reg = &regs->sp;
      break;
    case UNW_X86_64_RIP:
      reg = &regs->ip;
      break;
    case UNW_X86_64_R8:
      reg = &regs->r8;
      break;
    case UNW_X86_64_R9:
      reg = &regs->r9;
      break;
    case UNW_X86_64_R10:
      reg = &regs->r10;
      break;
    case UNW_X86_64_R11:
      reg = &regs->r11;
      break;
    case UNW_X86_64_R12:
      reg = &regs->r12;
      break;
    case UNW_X86_64_R13:
      reg = &regs->r13;
      break;
    case UNW_X86_64_R14:
      reg = &regs->r14;
      break;
    case UNW_X86_64_R15:
      reg = &regs->r15;
      break;
    default:
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    };
#elif defined(ARCH_riscv)
  if (regnum == UNW_RISCV_X0)
    {
      if (!write)
        *valp = 0;
      return 0;
    }
  else if (regnum >= UNW_RISCV_X1 && regnum <= UNW_RISCV_X31)
    reg = &regs->r[regnum - UNW_RISCV_X1];
  else if(regnum == UNW_RISCV_PC)
    reg = &regs->pc;
  else
    {
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    }
#elif defined(ARCH_ppc32)
  if (regnum >= UNW_PPC32_R0 && regnum <= UNW_PPC32_R31)
    reg = &regs->r[regnum - UNW_PPC32_R0];
  else
    {
      printf("Unknown/unhandled regnum %d\n", regnum);
      return -UNW_EBADREG;
    }
#elif defined(ARCH_sparc)
  printf("Unknown/unhandled regnum %d\n", regnum);
  return -UNW_EBADREG;
#elif defined(ARCH_mips)
  printf("Unknown/unhandled regnum %d\n", regnum);
  return -UNW_EBADREG;
#else
#error libunwind: Add missing architecture support
#endif

  if (write)
    *reg = *valp;
  else
    *valp = *reg;

  Debug(16, "reg %d = 0x%lx\n", regnum, *valp);

  return 0;
}

static int l4_access_fpreg(unw_addr_space_t as, unw_regnum_t regnum,
                           unw_fpreg_t *fwalp, int write, void *arg)
{
  (void)as; (void)regnum; (void)fwalp; (void)write; (void)arg;
  printf("l4_access_fpreg(regnum=%d, write=%d): Not implemented\n",
         regnum, write);
  return -UNW_EINVAL;
}

static int l4_resume(unw_addr_space_t as, unw_cursor_t *cp, void *arg)
{
  (void)as; (void)cp; (void)arg;
  printf("l4_resume(): Not implemented\n");
  return -UNW_EINVAL;
}

static int l4_get_proc_name(unw_addr_space_t as, unw_word_t addr, char *bufp,
                            size_t buf_len, unw_word_t *offp, void *arg)
{
  l4_unw_data_t *data = arg;
  return elf_w(get_proc_name) (as, l4_to_pid(data->rm), addr, bufp, buf_len, offp);
}

unw_accessors_t l4_unw_accessors =
  {
    .find_proc_info         = l4_find_proc_info,
    .put_unwind_info        = dwarf_put_unwind_info,
    .get_dyn_info_list_addr = l4_get_dyn_info_list_addr,
    .access_mem             = l4_access_mem_remote,
    .access_reg             = l4_access_reg,
    .access_fpreg           = l4_access_fpreg,
    .resume                 = l4_resume,
    .get_proc_name          = l4_get_proc_name,
  };