[v3] Rebase executable to match relocated base address
Commit Message
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 new base address is read from the Process Environment Block.
gdb/ChangeLog:
2020-03-03 Hannes Domani <ssbssa@yahoo.de>
* windows-tdep.c (windows_solib_create_inferior_hook): New function.
(windows_init_abi): Set and use windows_so_ops.
---
v2:
This version now no longer needs the fake auxv entry.
v3:
- Use of explicit comparison operators.
- Use copy of solib_target_so_ops.
---
gdb/windows-tdep.c | 55 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 54 insertions(+), 1 deletion(-)
Comments
On 2020-03-03 11:22 a.m., Hannes Domani via gdb-patches wrote:
> 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 new base address is read from the Process Environment Block.
>
> gdb/ChangeLog:
>
> 2020-03-03 Hannes Domani <ssbssa@yahoo.de>
>
> * windows-tdep.c (windows_solib_create_inferior_hook): New function.
> (windows_init_abi): Set and use windows_so_ops.
> ---
> v2:
> This version now no longer needs the fake auxv entry.
>
> v3:
> - Use of explicit comparison operators.
> - Use copy of solib_target_so_ops.
Thanks, that version LGTM.
Simon
Am Dienstag, 3. März 2020, 17:58:22 MEZ hat Simon Marchi <simark@simark.ca> Folgendes geschrieben:
> On 2020-03-03 11:22 a.m., Hannes Domani via gdb-patches wrote:
>
> > 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 new base address is read from the Process Environment Block.
> >
> > gdb/ChangeLog:
> >
> > 2020-03-03 Hannes Domani <ssbssa@yahoo.de>
> >
> > * windows-tdep.c (windows_solib_create_inferior_hook): New function.
> > (windows_init_abi): Set and use windows_so_ops.
> > ---
> > v2:
> > This version now no longer needs the fake auxv entry.
> >
> > v3:
> > - Use of explicit comparison operators.
> > - Use copy of solib_target_so_ops.
>
> Thanks, that version LGTM.
Pushed, thanks.
Regards
Hannes Domani
@@ -34,6 +34,9 @@
#include "solib.h"
#include "solib-target.h"
#include "gdbcore.h"
+#include "coff/internal.h"
+#include "libcoff.h"
+#include "solist.h"
/* Windows signal numbers differ between MinGW flavors and between
those and Cygwin. The below enumeration was gleaned from the
@@ -812,6 +815,53 @@ windows_get_siginfo_type (struct gdbarch *gdbarch)
return siginfo_type;
}
+/* Implement the "solib_create_inferior_hook" target_so_ops method. */
+
+static void
+windows_solib_create_inferior_hook (int from_tty)
+{
+ CORE_ADDR exec_base = 0;
+
+ /* Find base address of main executable in
+ TIB->process_environment_block->image_base_address. */
+ struct gdbarch *gdbarch = target_gdbarch ();
+ enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+ int ptr_bytes;
+ int peb_offset; /* Offset of process_environment_block in TIB. */
+ int base_offset; /* Offset of image_base_address in PEB. */
+ if (gdbarch_ptr_bit (gdbarch) == 32)
+ {
+ ptr_bytes = 4;
+ peb_offset = 48;
+ base_offset = 8;
+ }
+ else
+ {
+ ptr_bytes = 8;
+ peb_offset = 96;
+ base_offset = 16;
+ }
+ CORE_ADDR tlb;
+ gdb_byte buf[8];
+ if (target_get_tib_address (inferior_ptid, &tlb)
+ && !target_read_memory (tlb + peb_offset, buf, ptr_bytes))
+ {
+ CORE_ADDR peb = extract_unsigned_integer (buf, ptr_bytes, byte_order);
+ if (!target_read_memory (peb + base_offset, buf, ptr_bytes))
+ exec_base = extract_unsigned_integer (buf, ptr_bytes, byte_order);
+ }
+
+ /* Rebase executable if the base address changed because of ASLR. */
+ if (symfile_objfile != nullptr && exec_base != 0)
+ {
+ CORE_ADDR vmaddr = pe_data (exec_bfd)->pe_opthdr.ImageBase;
+ if (vmaddr != exec_base)
+ objfile_rebase (symfile_objfile, exec_base - vmaddr);
+ }
+}
+
+static struct target_so_ops windows_so_ops;
+
/* To be called from the various GDB_OSABI_CYGWIN handlers for the
various Windows architectures and machine types. */
@@ -830,7 +880,10 @@ windows_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
set_gdbarch_gdb_signal_to_target (gdbarch, windows_gdb_signal_to_target);
- set_solib_ops (gdbarch, &solib_target_so_ops);
+ windows_so_ops = solib_target_so_ops;
+ windows_so_ops.solib_create_inferior_hook
+ = windows_solib_create_inferior_hook;
+ set_solib_ops (gdbarch, &windows_so_ops);
set_gdbarch_get_siginfo_type (gdbarch, windows_get_siginfo_type);
}