[PING^2] [PATCH] Rebase executable to match relocated base address

["Hannes Domani via gdb-patches" <gdb-patches at sourceware dot org>]

Ping.

Am Samstag, 8. Februar 2020, 17:37:03 MEZ hat Hannes Domani <ssbssa@yahoo.de> Folgendes geschrieben:

> Ping.
>
> Am Samstag, 25. Januar 2020, 17:47:19 MEZ hat Hannes Domani via gdb-patches <gdb-patches@sourceware.org> Folgendes geschrieben:
>
> > Compared to the [RFC], only Tom's noticed coding style problems were
> > fixed.
> >
> > binutils 2.34 will have an improved -dynamicbase (so far this only
> > worked with some workarounds for executables), so the rebasing problem
> > might get more relevant in the future.
> >
> >
> > Windows executables linked with -dynamicbase get a new base address
> > when loaded, which makes debugging impossible if the executable isn't
> > also rebased in gdb.
> >
> > The transfer of the new base address is done via a fake auxv entry,
> > so it's working with gdbserver as well.
> >
> > gdb/ChangeLog:
> >
> > 2020-01-25  Hannes Domani  <ssbssa@yahoo.de>
> >
> >     * windows-nat.c (windows_nat_target::get_windows_debug_event):
> >     Set current_exec_base.
> >     (windows_xfer_auxv): New function.
> >     (windows_nat_target::xfer_partial): Call windows_xfer_auxv.
> >     * windows-tdep.c (windows_solib_create_inferior_hook): New function.
> >     (windows_init_abi): Use windows_solib_create_inferior_hook.
> >
> > gdb/gdbserver/ChangeLog:
> >
> > 2020-01-25  Hannes Domani  <ssbssa@yahoo.de>
> >
> >     * win32-low.c (get_child_debug_event): Set current_exec_base.
> >     (win32_read_auxv): New function.
> > ---
> > gdb/gdbserver/win32-low.c | 35 ++++++++++++++++++++++++++++++++++-
> > gdb/windows-nat.c        | 38 ++++++++++++++++++++++++++++++++++++++
> > gdb/windows-tdep.c        | 20 ++++++++++++++++++++
> > 3 files changed, 92 insertions(+), 1 deletion(-)
> >
> > diff --git a/gdb/gdbserver/win32-low.c b/gdb/gdbserver/win32-low.c
> > index 2c4a9b1074..2f6fe5785e 100644
> > --- a/gdb/gdbserver/win32-low.c
> > +++ b/gdb/gdbserver/win32-low.c
> > @@ -75,6 +75,7 @@ static int attaching = 0;
> > static HANDLE current_process_handle = NULL;
> > static DWORD current_process_id = 0;
> > static DWORD main_thread_id = 0;
> > +static CORE_ADDR current_exec_base;    /* Executable base address */
> > static enum gdb_signal last_sig = GDB_SIGNAL_0;
> >
> > /* The current debug event from WaitForDebugEvent.  */
> > @@ -1486,6 +1487,8 @@ get_child_debug_event (struct target_waitstatus *ourstatus)
> >
> >       current_process_handle = current_event.u.CreateProcessInfo.hProcess;
> >       main_thread_id = current_event.dwThreadId;
> > +      current_exec_base
> > +    = (CORE_ADDR) current_event.u.CreateProcessInfo.lpBaseOfImage;
> >
> >       /* Add the main thread.  */
> >       child_add_thread (current_event.dwProcessId,
> > @@ -1713,6 +1716,36 @@ win32_request_interrupt (void)
> >   soft_interrupt_requested = 1;
> > }
> >
> > +/* Windows does not have auxv, but this creates a fake AT_ENTRY entry
> > +  which is the base address of the executable.  */
> > +
> > +static int
> > +win32_read_auxv (CORE_ADDR offset, unsigned char *myaddr, unsigned int len)
> > +{
> > +  size_t buf[4];
> > +
> > +  if (!myaddr)
> > +    return -1;
> > +
> > +  if (offset > sizeof (buf))
> > +    return -1;
> > +
> > +  if (offset == sizeof (buf))
> > +    return 0;
> > +
> > +  if (offset + len > sizeof (buf))
> > +    len = sizeof (buf) - offset;
> > +
> > +  buf[0] = 9; /* AT_ENTRY */
> > +  buf[1] = current_exec_base;
> > +  buf[2] = 0; /* AT_NULL */
> > +  buf[3] = 0;
> > +
> > +  memcpy (myaddr, (char *) buf + offset, len);
> > +
> > +  return len;
> > +}
> > +
> > #ifdef _WIN32_WCE
> > int
> > win32_error_to_fileio_error (DWORD err)
> > @@ -1814,7 +1847,7 @@ static process_stratum_target win32_target_ops = {
> >   win32_write_inferior_memory,
> >   NULL, /* lookup_symbols */
> >   win32_request_interrupt,
> > -  NULL, /* read_auxv */
> > +  win32_read_auxv,
> >   win32_supports_z_point_type,
> >   win32_insert_point,
> >   win32_remove_point,
> > diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
> > index 366c98fbf3..459bb10fe9 100644
> > --- a/gdb/windows-nat.c
> > +++ b/gdb/windows-nat.c
> > @@ -236,6 +236,7 @@ static DEBUG_EVENT current_event;    /* The current debug event from
> >                       WaitForDebugEvent */
> > static HANDLE current_process_handle;    /* Currently executing process */
> > static windows_thread_info *current_thread;    /* Info on currently selected thread */
> > +static CORE_ADDR current_exec_base;    /* Executable base address */
> >
> > /* Counts of things.  */
> > static int exception_count = 0;
> > @@ -1604,6 +1605,8 @@ windows_nat_target::get_windows_debug_event (int pid,
> >     break;
> >
> >       current_process_handle = current_event.u.CreateProcessInfo.hProcess;
> > +      current_exec_base
> > +    = (CORE_ADDR) current_event.u.CreateProcessInfo.lpBaseOfImage;
> >       /* Add the main thread.  */
> >       th = windows_add_thread
> >         (ptid_t (current_event.dwProcessId, 0,
> > @@ -2996,6 +2999,38 @@ windows_xfer_shared_libraries (struct target_ops *ops,
> >   return len != 0 ? TARGET_XFER_OK : TARGET_XFER_EOF;
> > }
> >
> > +/* Windows does not have auxv, but this creates a fake AT_ENTRY entry
> > +  which is the base address of the executable.  */
> > +
> > +static enum target_xfer_status
> > +windows_xfer_auxv (gdb_byte *readbuf, ULONGEST offset, ULONGEST len,
> > +          ULONGEST *xfered_len)
> > +{
> > +  CORE_ADDR buf[4];
> > +
> > +  if (!readbuf)
> > +    return TARGET_XFER_E_IO;
> > +
> > +  if (offset > sizeof (buf))
> > +    return TARGET_XFER_E_IO;
> > +
> > +  if (offset == sizeof (buf))
> > +    return TARGET_XFER_EOF;
> > +
> > +  if (offset + len > sizeof (buf))
> > +    len = sizeof (buf) - offset;
> > +
> > +  buf[0] = 9; /* AT_ENTRY */
> > +  buf[1] = current_exec_base;
> > +  buf[2] = 0; /* AT_NULL */
> > +  buf[3] = 0;
> > +
> > +  memcpy (readbuf, (char *) buf + offset, len);
> > +  *xfered_len = len;
> > +
> > +  return TARGET_XFER_OK;
> > +}
> > +
> > enum target_xfer_status
> > windows_nat_target::xfer_partial (enum target_object object,
> >                   const char *annex, gdb_byte *readbuf,
> > @@ -3011,6 +3046,9 @@ windows_nat_target::xfer_partial (enum target_object object,
> >       return windows_xfer_shared_libraries (this, object, annex, readbuf,
> >                         writebuf, offset, len, xfered_len);
> >
> > +    case TARGET_OBJECT_AUXV:
> > +      return windows_xfer_auxv (readbuf, offset, len, xfered_len);
> > +
> >     default:
> >       if (beneath () == NULL)
> >     {
> > diff --git a/gdb/windows-tdep.c b/gdb/windows-tdep.c
> > index 6c9632d035..fd491e8e67 100644
> > --- a/gdb/windows-tdep.c
> > +++ b/gdb/windows-tdep.c
> > @@ -34,6 +34,10 @@
> > #include "solib.h"
> > #include "solib-target.h"
> > #include "gdbcore.h"
> > +#include "coff/internal.h"
> > +#include "libcoff.h"
> > +#include "solist.h"
> > +#include "auxv.h"
> >
> > /* Windows signal numbers differ between MinGW flavors and between
> >     those and Cygwin.  The below enumeration was gleaned from the
> > @@ -656,6 +660,20 @@ windows_gdb_signal_to_target (struct gdbarch *gdbarch, enum gdb_signal signal)
> >   return -1;
> > }
> >
> > +static void
> > +windows_solib_create_inferior_hook (int from_tty)
> > +{
> > +  CORE_ADDR exec_base;
> > +  /* 9 -> AT_ENTRY */
> > +  if (target_auxv_search (current_top_target (), 9, &exec_base) == 1
> > +      && exec_base && symfile_objfile)
> > +    {
> > +      CORE_ADDR vmaddr = pe_data (exec_bfd)->pe_opthdr.ImageBase;
> > +      if (vmaddr != exec_base)
> > +    objfile_rebase (symfile_objfile, exec_base - vmaddr);
> > +    }
> > +}
> > +
> > /* To be called from the various GDB_OSABI_CYGWIN handlers for the
> >     various Windows architectures and machine types.  */
> >
> > @@ -674,6 +692,8 @@ windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
> >
> >   set_gdbarch_gdb_signal_to_target (gdbarch, windows_gdb_signal_to_target);
> >
> > +  solib_target_so_ops.solib_create_inferior_hook
> > +    = windows_solib_create_inferior_hook;
> >   set_solib_ops (gdbarch, &solib_target_so_ops);
> > }
> >
> > --
> > 2.25.0