Prevent traps after rsp modification

gdb/nacl-tdep.c

 /* Target-dependent code for NaCl.
 
    Copyright (C) 2001, 2003-2012 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 "amd64-linux-tdep.h"
 #include "i386-linux-tdep.h"
 #include "linux-tdep.h"
 #include "amd64-tdep.h"
 #include "nacl-manifest.h"
 #include "symtab.h"
 #include "solib-svr4.h"
 #include "frame.h"
 #include "osabi.h"
+#include "disasm.h"
+#include "breakpoint.h"
+#include "target.h"
 
 static void
 nacl_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
   /* NaCl uses SVR4-style shared libraries.  */
   set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
   set_solib_svr4_map_so_name (gdbarch, nacl_manifest_find);
   set_gdbarch_process_record (gdbarch, i386_process_record);
 }
 
@@ skipping 52 matching lines @@
       lmo.l_addr_offset = 0;
       lmo.l_name_offset = 8;
       lmo.l_ld_offset = 12;
       lmo.l_next_offset = 16;
       lmo.l_prev_offset = 20;
     }
 
   return lmp;
 }
 
+static CORE_ADDR
+amd64_nacl_skip_rsp_sandboxing (CORE_ADDR addr)
+{
+  gdb_byte buf[3];
+  if (target_read_memory (addr, buf, sizeof(buf)) == 0)
+    {
+      /* 4c 01 fc    add  %r15,%rsp  */
+      if (buf[0] == 0x4c && buf[1] == 0x01 && buf[2] == 0xfc)
+        {
+          return addr + 3;
+        }
+    }
+  return addr;
+}
+
+static CORE_ADDR
+amd64_nacl_adjust_breakpoint_address (struct gdbarch *gdbarch, CORE_ADDR addr)
+{
+  return amd64_nacl_skip_rsp_sandboxing (addr);
+}
+
+static int
+amd64_nacl_software_single_step (struct frame_info *frame)
+{
+  struct gdbarch *gdbarch;
+  CORE_ADDR pc;
+  CORE_ADDR bp_pc;
+
+  gdbarch = get_frame_arch (frame);
+  pc = get_frame_register_unsigned (frame, gdbarch_pc_regnum (gdbarch));
+
+  /* Check if next instruction is rsp sandboxing.  If yes, assume current
+     instruction is rsp modification.  */
+  pc += gdb_insn_length (gdbarch, pc);
+  bp_pc = amd64_nacl_skip_rsp_sandboxing (pc);
+  if (bp_pc != pc)
+    {
+      insert_single_step_breakpoint (gdbarch,
+                                     get_frame_address_space (frame),
+                                     bp_pc);
+      return 1;
+    }
+
+  return 0;
+}
+
 static void
 amd64_nacl_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   linux_init_abi (info, gdbarch);
   amd64_init_abi (info, gdbarch);
   tdep->tdesc = tdesc_amd64_linux;
   set_solib_svr4_fetch_link_map_offsets (gdbarch,
                                          amd64_nacl_fetch_link_map_offsets);
   nacl_init_abi (info, gdbarch);
@@ skipping 11 matching lines @@
 
   /* TODO(eaeltsin): we might use address size instead of pointer size to
      distinguish between i386 and x86_64...  At least address size is not
      a property of the data model.  */
   set_gdbarch_addr_bit (gdbarch, 64);
 
   /* How to extract addresses from registers.  */
   set_gdbarch_addr_bits_remove (gdbarch, amd64_nacl_addr_bits_remove);
   set_gdbarch_unwind_pc (gdbarch, amd64_nacl_unwind_pc);
   set_gdbarch_unwind_sp (gdbarch, amd64_nacl_unwind_sp);
+
+  /* Where to set breakpoints.  */
+  set_gdbarch_adjust_breakpoint_address (gdbarch,
+                                         amd64_nacl_adjust_breakpoint_address);
+  set_gdbarch_software_single_step (gdbarch, amd64_nacl_software_single_step);
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */
 extern void _initialize_nacl_tdep (void);
 
 void
 _initialize_nacl_tdep (void)
 {
   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
                           GDB_OSABI_NACL, amd64_nacl_init_abi);
 
   gdbarch_register_osabi (bfd_arch_i386, 0,
                           GDB_OSABI_NACL, i386_nacl_init_abi);
 }