1 files changed, 438 insertions, 0 deletions
diff --git a/gdb/jit.c b/gdb/jit.c
new file mode 100644
index 0000000..0c50060
--- /dev/null
+++ b/gdb/jit.c
@@ -0,0 +1,438 @@
+/* Handle JIT code generation in the inferior for GDB, the GNU Debugger.
+
+   Copyright (C) 2009
+   Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+
+#include "jit.h"
+#include "breakpoint.h"
+#include "gdbcore.h"
+#include "observer.h"
+#include "objfiles.h"
+#include "symfile.h"
+#include "symtab.h"
+#include "target.h"
+#include "gdb_stat.h"
+
+static const struct objfile_data *jit_objfile_data;
+
+static const char *const jit_break_name = "__jit_debug_register_code";
+
+static const char *const jit_descriptor_name = "__jit_debug_descriptor";
+
+/* This is the address of the JIT descriptor in the inferior.  */
+
+static CORE_ADDR jit_descriptor_addr = 0;
+
+/* This is a boolean indicating whether we're currently registering code.  This
+   is used to avoid re-entering the registration code.  We want to check for
+   new JITed every time a new object file is loaded, but we want to avoid
+   checking for new code while we're registering object files for JITed code.
+   Therefore, we flip this variable to 1 before registering new object files,
+   and set it to 0 before returning.  */
+
+static int registering_code = 0;
+
+/* Helper cleanup function to clear an integer flag like the one above.  */
+
+static void
+clear_int (void *int_addr)
+{
+  *((int *) int_addr) = 0;
+}
+
+struct target_buffer
+{
+  CORE_ADDR base;
+  size_t size;
+};
+
+/* Openning the file is a no-op.  */
+
+static void *
+mem_bfd_iovec_open (struct bfd *abfd, void *open_closure)
+{
+  return open_closure;
+}
+
+/* Closing the file is just freeing the base/size pair on our side.  */
+
+static int
+mem_bfd_iovec_close (struct bfd *abfd, void *stream)
+{
+  xfree (stream);
+  return 1;
+}
+
+/* For reading the file, we just need to pass through to target_read_memory and
+   fix up the arguments and return values.  */
+
+static file_ptr
+mem_bfd_iovec_pread (struct bfd *abfd, void *stream, void *buf,
+                     file_ptr nbytes, file_ptr offset)
+{
+  int err;
+  struct target_buffer *buffer = (struct target_buffer *) stream;
+
+  /* If this read will read all of the file, limit it to just the rest.  */
+  if (offset + nbytes > buffer->size)
+    nbytes = buffer->size - offset;
+
+  /* If there are no more bytes left, we've reached EOF.  */
+  if (nbytes == 0)
+    return 0;
+
+  err = target_read_memory (buffer->base + offset, (gdb_byte *) buf, nbytes);
+  if (err)
+    return -1;
+
+  return nbytes;
+}
+
+/* For statting the file, we only support the st_size attribute.  */
+
+static int
+mem_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
+{
+  struct target_buffer *buffer = (struct target_buffer*) stream;
+
+  sb->st_size = buffer->size;
+  return 0;
+}
+
+/* Open a BFD from the target's memory.  */
+
+static struct bfd *
+bfd_open_from_target_memory (CORE_ADDR addr, size_t size, char *target)
+{
+  const char *filename = xstrdup ("<in-memory>");
+  struct target_buffer *buffer = xmalloc (sizeof (struct target_buffer));
+
+  buffer->base = addr;
+  buffer->size = size;
+  return bfd_openr_iovec (filename, target,
+                          mem_bfd_iovec_open,
+                          buffer,
+                          mem_bfd_iovec_pread,
+                          mem_bfd_iovec_close,
+                          mem_bfd_iovec_stat);
+}
+
+/* Helper function for reading the global JIT descriptor from remote memory.  */
+
+static void
+jit_read_descriptor (struct jit_descriptor *descriptor)
+{
+  int err;
+  struct type *ptr_type;
+  int ptr_size;
+  int desc_size;
+  gdb_byte *desc_buf;
+  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
+
+  /* Figure out how big the descriptor is on the remote and how to read it.  */
+  ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
+  ptr_size = TYPE_LENGTH (ptr_type);
+  desc_size = 8 + 2 * ptr_size;  /* Two 32-bit ints and two pointers.  */
+  desc_buf = alloca (desc_size);
+
+  /* Read the descriptor.  */
+  err = target_read_memory (jit_descriptor_addr, desc_buf, desc_size);
+  if (err)
+    error (_("Unable to read JIT descriptor from remote memory!"));
+
+  /* Fix the endianness to match the host.  */
+  descriptor->version = extract_unsigned_integer (&desc_buf[0], 4, byte_order);
+  descriptor->action_flag =
+      extract_unsigned_integer (&desc_buf[4], 4, byte_order);
+  descriptor->relevant_entry = extract_typed_address (&desc_buf[8], ptr_type);
+  descriptor->first_entry =
+      extract_typed_address (&desc_buf[8 + ptr_size], ptr_type);
+}
+
+/* Helper function for reading a JITed code entry from remote memory.  */
+
+static void
+jit_read_code_entry (CORE_ADDR code_addr, struct jit_code_entry *code_entry)
+{
+  int err;
+  struct type *ptr_type;
+  int ptr_size;
+  int entry_size;
+  gdb_byte *entry_buf;
+  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
+
+  /* Figure out how big the entry is on the remote and how to read it.  */
+  ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
+  ptr_size = TYPE_LENGTH (ptr_type);
+  entry_size = 3 * ptr_size + 8;  /* Three pointers and one 64-bit int.  */
+  entry_buf = alloca (entry_size);
+
+  /* Read the entry.  */
+  err = target_read_memory (code_addr, entry_buf, entry_size);
+  if (err)
+    error (_("Unable to read JIT code entry from remote memory!"));
+
+  /* Fix the endianness to match the host.  */
+  ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
+  code_entry->next_entry = extract_typed_address (&entry_buf[0], ptr_type);
+  code_entry->prev_entry =
+      extract_typed_address (&entry_buf[ptr_size], ptr_type);
+  code_entry->symfile_addr =
+      extract_typed_address (&entry_buf[2 * ptr_size], ptr_type);
+  code_entry->symfile_size =
+      extract_unsigned_integer (&entry_buf[3 * ptr_size], 8, byte_order);
+}
+
+/* This function registers code associated with a JIT code entry.  It uses the
+   pointer and size pair in the entry to read the symbol file from the remote
+   and then calls symbol_file_add_from_local_memory to add it as though it were
+   a symbol file added by the user.  */
+
+static void
+jit_register_code (CORE_ADDR entry_addr, struct jit_code_entry *code_entry)
+{
+  bfd *nbfd;
+  struct section_addr_info *sai;
+  struct bfd_section *sec;
+  struct objfile *objfile;
+  struct cleanup *old_cleanups, *my_cleanups;
+  int i;
+  const struct bfd_arch_info *b;
+  CORE_ADDR *entry_addr_ptr;
+
+  nbfd = bfd_open_from_target_memory (code_entry->symfile_addr,
+                                      code_entry->symfile_size, gnutarget);
+  old_cleanups = make_cleanup_bfd_close (nbfd);
+
+  /* Check the format.  NOTE: This initializes important data that GDB uses!
+     We would segfault later without this line.  */
+  if (!bfd_check_format (nbfd, bfd_object))
+    {
+      printf_unfiltered (_("\
+JITed symbol file is not an object file, ignoring it.\n"));
+      do_cleanups (old_cleanups);
+      return;
+    }
+
+  /* Check bfd arch.  */
+  b = gdbarch_bfd_arch_info (target_gdbarch);
+  if (b->compatible (b, bfd_get_arch_info (nbfd)) != b)
+    warning (_("JITed object file architecture %s is not compatible "
+               "with target architecture %s."), bfd_get_arch_info
+             (nbfd)->printable_name, b->printable_name);
+
+  /* Read the section address information out of the symbol file.  Since the
+     file is generated by the JIT at runtime, it should all of the absolute
+     addresses that we care about.  */
+  sai = alloc_section_addr_info (bfd_count_sections (nbfd));
+  make_cleanup_free_section_addr_info (sai);
+  i = 0;
+  for (sec = nbfd->sections; sec != NULL; sec = sec->next)
+    if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
+      {
+        /* We assume that these virtual addresses are absolute, and do not
+           treat them as offsets.  */
+        sai->other[i].addr = bfd_get_section_vma (nbfd, sec);
+        sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
+        sai->other[i].sectindex = sec->index;
+        ++i;
+      }
+
+  /* Raise this flag while we register code so we won't trigger any
+     re-registration.  */
+  registering_code = 1;
+  my_cleanups = make_cleanup (clear_int, &registering_code);
+
+  /* This call takes ownership of sai.  */
+  objfile = symbol_file_add_from_bfd (nbfd, 0, sai, OBJF_SHARED);
+
+  /* Clear the registering_code flag.  */
+  do_cleanups (my_cleanups);
+
+  /* Remember a mapping from entry_addr to objfile.  */
+  entry_addr_ptr = xmalloc (sizeof (CORE_ADDR));
+  *entry_addr_ptr = entry_addr;
+  set_objfile_data (objfile, jit_objfile_data, entry_addr_ptr);
+
+  discard_cleanups (old_cleanups);
+}
+
+/* This function unregisters JITed code and frees the corresponding objfile.  */
+
+static void
+jit_unregister_code (struct objfile *objfile)
+{
+  free_objfile (objfile);
+}
+
+/* Look up the objfile with this code entry address.  */
+
+static struct objfile *
+jit_find_objf_with_entry_addr (CORE_ADDR entry_addr)
+{
+  struct objfile *objf;
+  CORE_ADDR *objf_entry_addr;
+
+  ALL_OBJFILES (objf)
+    {
+      objf_entry_addr = (CORE_ADDR *) objfile_data (objf, jit_objfile_data);
+      if (objf_entry_addr != NULL && *objf_entry_addr == entry_addr)
+        return objf;
+    }
+  return NULL;
+}
+
+void
+jit_inferior_created_hook (void)
+{
+  struct minimal_symbol *reg_symbol;
+  struct minimal_symbol *desc_symbol;
+  CORE_ADDR reg_addr;
+  struct jit_descriptor descriptor;
+  struct jit_code_entry cur_entry;
+  CORE_ADDR cur_entry_addr;
+  struct cleanup *old_cleanups;
+
+  /* When we register code, GDB resets its breakpoints in case symbols have
+     changed.  That in turn calls this handler, which makes us look for new
+     code again.  To avoid being re-entered, we check this flag.  */
+  if (registering_code)
+    return;
+
+  /* Lookup the registration symbol.  If it is missing, then we assume we are
+     not attached to a JIT.  */
+  reg_symbol = lookup_minimal_symbol (jit_break_name, NULL, NULL);
+  if (reg_symbol == NULL)
+    return;
+  reg_addr = SYMBOL_VALUE_ADDRESS (reg_symbol);
+  if (reg_addr == 0)
+    return;
+
+  /* Lookup the descriptor symbol and cache the addr.  If it is missing, we
+     assume we are not attached to a JIT and return early.  */
+  desc_symbol = lookup_minimal_symbol (jit_descriptor_name, NULL, NULL);
+  if (desc_symbol == NULL)
+    return;
+  jit_descriptor_addr = SYMBOL_VALUE_ADDRESS (desc_symbol);
+  if (jit_descriptor_addr == 0)
+    return;
+
+  /* Read the descriptor so we can check the version number and load any already
+     JITed functions.  */
+  jit_read_descriptor (&descriptor);
+
+  /* Check that the version number agrees with that we support.  */
+  if (descriptor.version != 1)
+    error (_("Unsupported JIT protocol version in descriptor!"));
+
+  /* Put a breakpoint in the registration symbol.  */
+  create_jit_event_breakpoint (target_gdbarch, reg_addr);
+
+  /* If we've attached to a running program, we need to check the descriptor to
+     register any functions that were already generated.  */
+  for (cur_entry_addr = descriptor.first_entry;
+       cur_entry_addr != 0;
+       cur_entry_addr = cur_entry.next_entry)
+    {
+      jit_read_code_entry (cur_entry_addr, &cur_entry);
+
+      /* This hook may be called many times during setup, so make sure we don't
+         add the same symbol file twice.  */
+      if (jit_find_objf_with_entry_addr (cur_entry_addr) != NULL)
+        continue;
+
+      jit_register_code (cur_entry_addr, &cur_entry);
+    }
+}
+
+/* Wrapper to match the observer function pointer prototype.  */
+
+static void
+jit_inferior_created_hook1 (struct target_ops *objfile, int from_tty)
+{
+  jit_inferior_created_hook ();
+}
+
+/* This function cleans up any code entries left over when the inferior exits.
+   We get left over code when the inferior exits without unregistering its code,
+   for example when it crashes.  */
+
+static void
+jit_inferior_exit_hook (int pid)
+{
+  struct objfile *objf;
+  struct objfile *temp;
+
+  /* We need to reset the descriptor addr so that next time we load up the
+     inferior we look for it again.  */
+  jit_descriptor_addr = 0;
+
+  ALL_OBJFILES_SAFE (objf, temp)
+    if (objfile_data (objf, jit_objfile_data) != NULL)
+      jit_unregister_code (objf);
+}
+
+void
+jit_event_handler (void)
+{
+  struct jit_descriptor descriptor;
+  struct jit_code_entry code_entry;
+  CORE_ADDR entry_addr;
+  struct objfile *objf;
+
+  /* Read the descriptor from remote memory.  */
+  jit_read_descriptor (&descriptor);
+  entry_addr = descriptor.relevant_entry;
+
+  /* Do the corresponding action. */
+  switch (descriptor.action_flag)
+    {
+    case JIT_NOACTION:
+      break;
+    case JIT_REGISTER:
+      jit_read_code_entry (entry_addr, &code_entry);
+      jit_register_code (entry_addr, &code_entry);
+      break;
+    case JIT_UNREGISTER:
+      objf = jit_find_objf_with_entry_addr (entry_addr);
+      if (objf == NULL)
+        printf_unfiltered ("Unable to find JITed code entry at address: %p\n",
+                           (void *) entry_addr);
+      else
+        jit_unregister_code (objf);
+
+      break;
+    default:
+      error (_("Unknown action_flag value in JIT descriptor!"));
+      break;
+    }
+}
+
+/* Provide a prototype to silence -Wmissing-prototypes.  */
+
+extern void _initialize_jit (void);
+
+void
+_initialize_jit (void)
+{
+  observer_attach_inferior_created (jit_inferior_created_hook1);
+  observer_attach_inferior_exit (jit_inferior_exit_hook);
+  jit_objfile_data = register_objfile_data ();
+}