Support software single step on ARM in GDBServer

This patch teaches GDBServer how to software single step on ARM
linux by sharing code with GDB.

The arm_get_next_pcs function in GDB is now shared with GDBServer.  So
that GDBServer can use the function to return the possible addresses of
the next PC.

A proper shared context was also needed so that we could share the code,
this context is described in the arm_get_next_pcs structure.

Testing :

No regressions, tested on ubuntu 14.04 ARMv7 and x86.
With gdbserver-{native,extended} / { -marm -mthumb }

gdb/ChangeLog:

	* Makefile.in (ALL_TARGET_OBS): Append arm-get-next-pcs.o,
	arm-linux.o.
	(ALLDEPFILES): Append arm-get-next-pcs.c, arm-linux.c
	(arm-linux.o): New rule.
	(arm-get-next-pcs.o): New rule.
	* arch/arm-get-next-pcs.c: New file.
	* arch/arm-get-next-pcs.h: New file.
	* arch/arm-linux.h: New file.
	* arch/arm-linux.c: New file.
	* arm.c: Include common-regcache.c.
	(thumb_advance_itstate): Moved from arm-tdep.c.
	(arm_instruction_changes_pc): Likewise.
	(thumb_instruction_changes_pc): Likewise.
	(thumb2_instruction_changes_pc): Likewise.
	(shifted_reg_val): Likewise.
	* arm.h (submask): Move macro from arm-tdep.h
	(bit): Likewise.
	(bits): Likewise.
	(sbits): Likewise.
	(BranchDest): Likewise.
	(thumb_advance_itstate): Moved declaration from arm-tdep.h
	(arm_instruction_changes_pc): Likewise.
	(thumb_instruction_changes_pc): Likewise.
	(thumb2_instruction_changes_pc): Likewise.
	(shifted_reg_val): Likewise.
	* arm-linux-tdep.c: Include arch/arm.h, arch/arm-get-next-pcs.h
	arch/arm-linux.h.
	(arm_linux_get_next_pcs_ops): New struct.
	(ARM_SIGCONTEXT_R0, ARM_UCONTEXT_SIGCONTEXT,
	ARM_OLD_RT_SIGFRAME_SIGINFO, ARM_OLD_RT_SIGFRAME_UCONTEXT,
	ARM_NEW_RT_SIGFRAME_UCONTEXT, ARM_NEW_SIGFRAME_MAGIC): Move stack
	layout defines to arch/arm-linux.h.
	(arm_linux_sigreturn_next_pc_offset): Move to arch/arm-linux.c.
	(arm_linux_software_single_step): Adjust for arm_get_next_pcs
	implementation.
	* arm-tdep.c: Include arch/arm-get-next-pcs.h.
	(arm_get_next_pcs_ops): New struct.
	(submask): Move macro to arm.h.
	(bit): Likewise.
	(bits): Likewise.
	(sbits): Likewise.
	(BranchDest): Likewise.
	(thumb_instruction_changes_pc): Move to arm.c
	(thumb2_instruction_changes_pc): Likewise.
	(arm_instruction_changes_pc): Likewise.
	(shifted_reg_val): Likewise.
	(thumb_advance_itstate): Likewise.
	(thumb_get_next_pc_raw): Move to arm-get-next-pcs.c.
	(arm_get_next_pc_raw): Likewise.
	(arm_get_next_pc): Likewise.
	(thumb_deal_with_atomic_sequence_raw): Likewise.
	(arm_deal_with_atomic_sequence_raw): Likewise.
	(arm_deal_with_atomic_sequence): Likewise.
	(arm_get_next_pcs_read_memory_unsigned_integer): New function.
	(arm_get_next_pcs_addr_bits_remove): Likewise.
	(arm_get_next_pcs_syscall_next_pc): Likewise.
	(arm_get_next_pcs_is_thumb): Likewise.
	(arm_software_single_step): Adjust for arm_get_next_pcs
	implementation.
	* arm-tdep.h: (arm_get_next_pc): Remove declaration.
	(arm_get_next_pcs_read_memory_unsigned_integer):
	New declaration.
	(arm_get_next_pcs_addr_bits_remove): Likewise.
	(arm_get_next_pcs_syscall_next_pc): Likewise.
	(arm_get_next_pcs_is_thumb): Likewise.
	(arm_deal_with_atomic_sequence: Remove declaration.
	* common/gdb_vecs.h: Add CORE_ADDR vector definition.
	* configure.tgt (aarch64*-*-linux): Add arm-get-next-pcs.o,
	arm-linux.o.
	(arm*-wince-pe): Add arm-get-next-pcs.o.
	(arm*-*-linux*): Add arm-get-next-pcs.o, arm-linux.o,
	arm-get-next-pcs.o
	(arm*-*-netbsd*,arm*-*-knetbsd*-gnu): Add arm-get-next-pcs.o.
	(arm*-*-openbsd*): Likewise.
	(arm*-*-symbianelf*): Likewise.
	(arm*-*-*): Likewise.
	* symtab.h: Move CORE_ADDR vector definition to gdb_vecs.h.

gdb/gdbserver/ChangeLog:

	* Makefile.in (SFILES): Append arch/arm-linux.c,
	arch/arm-get-next-pcs.c.
	(arm-linux.o): New rule.
	(arm-get-next-pcs.o): New rule.
	* configure.srv (arm*-*-linux*): Add arm-get-next-pcs.o,
	arm-linux.o.
	* linux-aarch32-low.c (arm_abi_breakpoint): Remove macro.  Moved
	to linux-aarch32-low.c.
	(arm_eabi_breakpoint, arm_breakpoint): Likewise.
	(arm_breakpoint_len, thumb_breakpoint): Likewise.
	(thumb_breakpoint_len, thumb2_breakpoint): Likewise.
	(thumb2_breakpoint_len): Likewise.
	(arm_is_thumb_mode): Make non-static.
	* linux-aarch32-low.h (arm_abi_breakpoint): New macro.  Moved
	from linux-aarch32-low.c.
	(arm_eabi_breakpoint, arm_breakpoint): Likewise.
	(arm_breakpoint_len, thumb_breakpoint): Likewise.
	(thumb_breakpoint_len, thumb2_breakpoint): Likewise.
	(thumb2_breakpoint_len): Likewise.
	(arm_is_thumb_mode): New declaration.
	* linux-arm-low.c: Include arch/arm-linux.h
	aarch/arm-get-next-pcs.h, sys/syscall.h.
	(get_next_pcs_ops): New struct.
	(get_next_pcs_addr_bits_remove): New function.
	(get_next_pcs_is_thumb): New function.
	(get_next_pcs_read_memory_unsigned_integer): Likewise.
	(arm_sigreturn_next_pc): Likewise.
	(get_next_pcs_syscall_next_pc): Likewise.
	(arm_gdbserver_get_next_pcs): Likewise.
	(struct linux_target_ops) <arm_gdbserver_get_next_pcs>:
	Initialize.
	* linux-low.h: Move CORE_ADDR vector definition to gdb_vecs.h.
	* server.h: Include gdb_vecs.h.

8 files changed, 216 insertions, 26 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index eab6930..93a8fbe 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,5 +1,41 @@
 2015-12-18  Antoine Tremblay  <antoine.tremblay@ericsson.com>
 
+	* Makefile.in (SFILES): Append arch/arm-linux.c,
+	arch/arm-get-next-pcs.c.
+	(arm-linux.o): New rule.
+	(arm-get-next-pcs.o): New rule.
+	* configure.srv (arm*-*-linux*): Add arm-get-next-pcs.o,
+	arm-linux.o.
+	* linux-aarch32-low.c (arm_abi_breakpoint): Remove macro.  Moved
+	to linux-aarch32-low.c.
+	(arm_eabi_breakpoint, arm_breakpoint): Likewise.
+	(arm_breakpoint_len, thumb_breakpoint): Likewise.
+	(thumb_breakpoint_len, thumb2_breakpoint): Likewise.
+	(thumb2_breakpoint_len): Likewise.
+	(arm_is_thumb_mode): Make non-static.
+	* linux-aarch32-low.h (arm_abi_breakpoint): New macro.  Moved
+	from linux-aarch32-low.c.
+	(arm_eabi_breakpoint, arm_breakpoint): Likewise.
+	(arm_breakpoint_len, thumb_breakpoint): Likewise.
+	(thumb_breakpoint_len, thumb2_breakpoint): Likewise.
+	(thumb2_breakpoint_len): Likewise.
+	(arm_is_thumb_mode): New declaration.
+	* linux-arm-low.c: Include arch/arm-linux.h
+	aarch/arm-get-next-pcs.h, sys/syscall.h.
+	(get_next_pcs_ops): New struct.
+	(get_next_pcs_addr_bits_remove): New function.
+	(get_next_pcs_is_thumb): New function.
+	(get_next_pcs_read_memory_unsigned_integer): Likewise.
+	(arm_sigreturn_next_pc): Likewise.
+	(get_next_pcs_syscall_next_pc): Likewise.
+	(arm_gdbserver_get_next_pcs): Likewise.
+	(struct linux_target_ops) <arm_gdbserver_get_next_pcs>:
+	Initialize.
+	* linux-low.h: Move CORE_ADDR vector definition to gdb_vecs.h.
+	* server.h: Include gdb_vecs.h.
+
+2015-12-18  Antoine Tremblay  <antoine.tremblay@ericsson.com>
+
 	* Makefile.in (SFILES): Append common/common-regcache.c.
 	(OBS): Append common-regcache.o.
 	(common-regcache.o): New rule.
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 82af44c..c72db67 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -181,7 +181,8 @@ SFILES=	$(srcdir)/gdbreplay.c $(srcdir)/inferiors.c $(srcdir)/dll.c \
 	$(srcdir)/common/common-exceptions.c $(srcdir)/symbol.c \
 	$(srcdir)/common/btrace-common.c \
 	$(srcdir)/common/fileio.c $(srcdir)/nat/linux-namespaces.c \
-	$(srcdir)/arch/arm.c $(srcdir)/common/common-regcache.c
+	$(srcdir)/arch/arm.c $(srcdir)/common/common-regcache.c \
+	$(srcdir)/arch/arm-linux.c $(srcdir)/arch/arm-get-next-pcs.c
 
 DEPFILES = @GDBSERVER_DEPFILES@
 
@@ -592,6 +593,12 @@ common-regcache.o: ../common/common-regcache.c
 arm.o: ../arch/arm.c
 	$(COMPILE) $<
 	$(POSTCOMPILE)
+arm-linux.o: ../arch/arm-linux.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
+arm-get-next-pcs.o: ../arch/arm-get-next-pcs.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
 
 # Native object files rules from ../nat
 
diff --git a/gdb/gdbserver/configure.srv b/gdb/gdbserver/configure.srv
index 6dfd6e0..5f5112e 100644
--- a/gdb/gdbserver/configure.srv
+++ b/gdb/gdbserver/configure.srv
@@ -72,6 +72,8 @@ case "${target}" in
 			srv_tgtobj="$srv_linux_obj linux-arm-low.o"
 			srv_tgtobj="$srv_tgtobj linux-aarch32-low.o"
 			srv_tgtobj="${srv_tgtobj} arm.o"
+			srv_tgtobj="${srv_tgtobj} arm-linux.o"
+			srv_tgtobj="${srv_tgtobj} arm-get-next-pcs.o"
 			srv_xmlfiles="arm-with-iwmmxt.xml"
 			srv_xmlfiles="${srv_xmlfiles} arm-with-vfpv2.xml"
 			srv_xmlfiles="${srv_xmlfiles} arm-with-vfpv3.xml"
diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c
index 930e73a..bbef721 100644
--- a/gdb/gdbserver/linux-aarch32-low.c
+++ b/gdb/gdbserver/linux-aarch32-low.c
@@ -137,30 +137,9 @@ struct regs_info regs_info_aarch32 =
     &aarch32_regsets_info
   };
 
-/* Correct in either endianness.  */
-#define arm_abi_breakpoint 0xef9f0001UL
-
-/* For new EABI binaries.  We recognize it regardless of which ABI
-   is used for gdbserver, so single threaded debugging should work
-   OK, but for multi-threaded debugging we only insert the current
-   ABI's breakpoint instruction.  For now at least.  */
-#define arm_eabi_breakpoint 0xe7f001f0UL
-
-#if (defined __ARM_EABI__ || defined __aarch64__)
-static const unsigned long arm_breakpoint = arm_eabi_breakpoint;
-#else
-static const unsigned long arm_breakpoint = arm_abi_breakpoint;
-#endif
-
-#define arm_breakpoint_len 4
-static const unsigned short thumb_breakpoint = 0xde01;
-#define thumb_breakpoint_len 2
-static const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
-#define thumb2_breakpoint_len 4
-
 /* Returns 1 if the current instruction set is thumb, 0 otherwise.  */
 
-static int
+int
 arm_is_thumb_mode (void)
 {
   struct regcache *regcache = get_thread_regcache (current_thread, 1);
diff --git a/gdb/gdbserver/linux-aarch32-low.h b/gdb/gdbserver/linux-aarch32-low.h
index 0afddc8..d452894 100644
--- a/gdb/gdbserver/linux-aarch32-low.h
+++ b/gdb/gdbserver/linux-aarch32-low.h
@@ -15,6 +15,27 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+/* Correct in either endianness.  */
+#define arm_abi_breakpoint 0xef9f0001UL
+
+/* For new EABI binaries.  We recognize it regardless of which ABI
+   is used for gdbserver, so single threaded debugging should work
+   OK, but for multi-threaded debugging we only insert the current
+   ABI's breakpoint instruction.  For now at least.  */
+#define arm_eabi_breakpoint 0xe7f001f0UL
+
+#ifndef __ARM_EABI__
+static const unsigned long arm_breakpoint = arm_abi_breakpoint;
+#else
+static const unsigned long arm_breakpoint = arm_eabi_breakpoint;
+#endif
+
+#define arm_breakpoint_len 4
+static const unsigned short thumb_breakpoint = 0xde01;
+#define thumb_breakpoint_len 2
+static const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
+#define thumb2_breakpoint_len 4
+
 extern struct regs_info regs_info_aarch32;
 
 void arm_fill_gregset (struct regcache *regcache, void *buf);
@@ -31,4 +52,6 @@ int arm_breakpoint_at (CORE_ADDR where);
 void initialize_low_arch_aarch32 (void);
 
 void init_registers_arm_with_neon (void);
+int arm_is_thumb_mode (void);
+
 extern const struct target_desc *tdesc_arm_with_neon;
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index 2e8cd6d..af6df7f 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -19,6 +19,8 @@
 #include "server.h"
 #include "linux-low.h"
 #include "arch/arm.h"
+#include "arch/arm-linux.h"
+#include "arch/arm-get-next-pcs.h"
 #include "linux-aarch32-low.h"
 
 #include <sys/uio.h>
@@ -29,6 +31,7 @@
 #endif
 #include "nat/gdb_ptrace.h"
 #include <signal.h>
+#include <sys/syscall.h>
 
 /* Defined in auto-generated files.  */
 void init_registers_arm (void);
@@ -136,6 +139,27 @@ static int arm_regmap[] = {
   64
 };
 
+/* Forward declarations needed for get_next_pcs ops.  */
+static ULONGEST get_next_pcs_read_memory_unsigned_integer (CORE_ADDR memaddr,
+							   int len,
+							   int byte_order);
+
+static CORE_ADDR get_next_pcs_addr_bits_remove (struct arm_get_next_pcs *self,
+						CORE_ADDR val);
+
+static CORE_ADDR get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self,
+					       CORE_ADDR pc);
+
+static int get_next_pcs_is_thumb (struct arm_get_next_pcs *self);
+
+/* get_next_pcs operations.  */
+static struct arm_get_next_pcs_ops get_next_pcs_ops = {
+  get_next_pcs_read_memory_unsigned_integer,
+  get_next_pcs_syscall_next_pc,
+  get_next_pcs_addr_bits_remove,
+  get_next_pcs_is_thumb
+};
+
 static int
 arm_cannot_store_register (int regno)
 {
@@ -198,6 +222,13 @@ arm_fill_vfpregset (struct regcache *regcache, void *buf)
   arm_fill_vfpregset_num (regcache, buf, num);
 }
 
+/* Wrapper of UNMAKE_THUMB_ADDR for get_next_pcs.  */
+static CORE_ADDR
+get_next_pcs_addr_bits_remove (struct arm_get_next_pcs *self, CORE_ADDR val)
+{
+  return UNMAKE_THUMB_ADDR (val);
+}
+
 static void
 arm_store_vfpregset (struct regcache *regcache, const void *buf)
 {
@@ -233,6 +264,27 @@ arm_set_pc (struct regcache *regcache, CORE_ADDR pc)
   supply_register_by_name (regcache, "pc", &newpc);
 }
 
+/* Wrapper of arm_is_thumb_mode for get_next_pcs.  */
+static int
+get_next_pcs_is_thumb (struct arm_get_next_pcs *self)
+{
+  return arm_is_thumb_mode ();
+}
+
+/* Read memory from the inferiror.
+   BYTE_ORDER is ignored and there to keep compatiblity with GDB's
+   read_memory_unsigned_integer. */
+static ULONGEST
+get_next_pcs_read_memory_unsigned_integer (CORE_ADDR memaddr,
+					   int len,
+					   int byte_order)
+{
+  ULONGEST res;
+
+  (*the_target->read_memory) (memaddr, (unsigned char *) &res, len);
+  return res;
+}
+
 /* Fetch the thread-local storage pointer for libthread_db.  */
 
 ps_err_e
@@ -717,6 +769,77 @@ arm_prepare_to_resume (struct lwp_info *lwp)
       }
 }
 
+/* Find the next pc for a sigreturn or rt_sigreturn syscall.
+   See arm-linux.h for stack layout details.  */
+static CORE_ADDR
+arm_sigreturn_next_pc (struct regcache *regcache, int svc_number)
+{
+  unsigned long sp;
+  unsigned long sp_data;
+  /* Offset of PC register.  */
+  int pc_offset = 0;
+  CORE_ADDR next_pc = 0;
+
+  gdb_assert (svc_number == __NR_sigreturn || svc_number == __NR_rt_sigreturn);
+
+  collect_register_by_name (regcache, "sp", &sp);
+  (*the_target->read_memory) (sp, (unsigned char *) &sp_data, 4);
+
+  pc_offset = arm_linux_sigreturn_next_pc_offset
+    (sp, sp_data, svc_number, __NR_sigreturn == svc_number ? 1 : 0);
+
+  (*the_target->read_memory) (sp + pc_offset, (unsigned char *) &next_pc, 4);
+
+  return next_pc;
+}
+
+/* When PC is at a syscall instruction, return the PC of the next
+   instruction to be executed.  */
+static CORE_ADDR
+get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self, CORE_ADDR pc)
+{
+  CORE_ADDR next_pc = 0;
+  int is_thumb = arm_is_thumb_mode ();
+  ULONGEST svc_number = 0;
+  struct regcache *regcache = self->regcache;
+
+  if (is_thumb)
+    {
+      collect_register (regcache, 7, &svc_number);
+      next_pc = pc + 2;
+    }
+  else
+    {
+      unsigned long this_instr;
+      unsigned long svc_operand;
+
+      (*the_target->read_memory) (pc, (unsigned char *) &this_instr, 4);
+      svc_operand = (0x00ffffff & this_instr);
+
+      if (svc_operand)  /* OABI.  */
+	{
+	  svc_number = svc_operand - 0x900000;
+	}
+      else /* EABI.  */
+	{
+	  collect_register (regcache, 7, &svc_number);
+	}
+
+      next_pc = pc + 4;
+    }
+
+  /* This is a sigreturn or sigreturn_rt syscall.  */
+  if (svc_number == __NR_sigreturn || svc_number == __NR_rt_sigreturn)
+    {
+      next_pc = arm_sigreturn_next_pc (regcache, svc_number);
+    }
+
+  /* Addresses for calling Thumb functions have the bit 0 set.  */
+  if (is_thumb)
+    next_pc = MAKE_THUMB_ADDR (next_pc);
+
+  return next_pc;
+}
 
 static int
 arm_get_hwcap (unsigned long *valp)
@@ -806,6 +929,27 @@ arm_arch_setup (void)
     have_ptrace_getregset = 0;
 }
 
+/* Fetch the next possible PCs after the current instruction executes.  */
+
+static VEC (CORE_ADDR) *
+arm_gdbserver_get_next_pcs (CORE_ADDR pc, struct regcache *regcache)
+{
+  struct arm_get_next_pcs next_pcs_ctx;
+  VEC (CORE_ADDR) *next_pcs = NULL;
+
+  arm_get_next_pcs_ctor (&next_pcs_ctx,
+			 &get_next_pcs_ops,
+			 /* Byte order is ignored assumed as host.  */
+			 0,
+			 0,
+			 (const gdb_byte *) &thumb2_breakpoint,
+			 regcache);
+
+  next_pcs = arm_get_next_pcs (&next_pcs_ctx, pc);
+
+  return next_pcs;
+}
+
 /* Support for hardware single step.  */
 
 static int
@@ -871,7 +1015,7 @@ struct linux_target_ops the_low_target = {
   arm_set_pc,
   arm_breakpoint_kind_from_pc,
   arm_sw_breakpoint_from_kind,
-  NULL, /* get_next_pcs */
+  arm_gdbserver_get_next_pcs,
   0,
   arm_breakpoint_at,
   arm_supports_z_point_type,
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index cd455a8..8eaad3e 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -124,8 +124,6 @@ struct process_info_private
 
 struct lwp_info;
 
-DEF_VEC_I (CORE_ADDR);
-
 struct linux_target_ops
 {
   /* Architecture-specific setup.  */
diff --git a/gdb/gdbserver/server.h b/gdb/gdbserver/server.h
index 18095f2..498367c 100644
--- a/gdb/gdbserver/server.h
+++ b/gdb/gdbserver/server.h
@@ -123,6 +123,7 @@ extern void discard_queued_stop_replies (ptid_t ptid);
 
 #include "utils.h"
 #include "debug.h"
+#include "gdb_vecs.h"
 
 /* Maximum number of bytes to read/write at once.  The value here
    is chosen to fill up a packet (the headers account for the 32).  */