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Re: [PING^2] [PATCH] Rebase executable to match relocated base address
- From: "Hannes Domani via gdb-patches" <gdb-patches at sourceware dot org>
- To: Gdb-patches <gdb-patches at sourceware dot org>
- Date: Sun, 1 Mar 2020 11:25:43 +0000 (UTC)
- Subject: Re: [PING^2] [PATCH] Rebase executable to match relocated base address
- References: <1893806852.4098891.1583060010697.ref@mail.yahoo.com> <1893806852.4098891.1583060010697@mail.yahoo.com>
- Reply-to: Hannes Domani <ssbssa at yahoo dot de>
Please ignore this one, I pinged the v1 by mistake.
> Am Sonntag, 1. März 2020, 12:20:36 MEZ hat Hannes Domani via gdb-patches <gdb-patches@sourceware.org> Folgendes geschrieben:
>
> 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