2012-04-27 Sergio Durigan Junior <sergiodj@redhat.com>

	    Tom Tromey  <tromey@redhat.com>
	    Jan Kratochvil  <jan.kratochvil@redhat.com>

	* Makefile.in (SFILES): Add `probe' and `stap-probe'.
	(COMMON_OBS): Likewise.
	(HFILES_NO_SRCDIR): Add `probe'.
	* NEWS: Mention support for static and SystemTap probes.
	* amd64-tdep.c (amd64_init_abi): Initializing proper fields used by
	SystemTap probes' arguments parser.
	* arm-linux-tdep.c: Including headers needed to perform the parsing
	of SystemTap probes' arguments.
	(arm_stap_is_single_operand): New function.
	(arm_stap_parse_special_token): Likewise.
	(arm_linux_init_abi): Initializing proper fields used by SystemTap
	probes' arguments parser.
	* ax-gdb.c (require_rvalue): Removing static declaration.
	(gen_expr): Likewise.
	* ax-gdb.h (gen_expr): Declaring function.
	(require_rvalue): Likewise.
	* breakpoint.c: Include `gdb_regex.h' and `probe.h'.
	(bkpt_probe_breakpoint_ops): New variable.
	(momentary_breakpoint_from_master): Set the `probe' value.
	(add_location_to_breakpoint): Likewise.
	(break_command_1): Using proper breakpoint_ops according to the
	argument passed by the user in the command line.
	(bkpt_probe_insert_location): New function.
	(bkpt_probe_remove_location): Likewise.
	(bkpt_probe_create_sals_from_address): Likewise.
	(bkpt_probe_decode_linespec): Likewise.
	(tracepoint_probe_create_sals_from_address): Likewise.
	(tracepoint_probe_decode_linespec): Likewise.
	(tracepoint_probe_breakpoint_ops): New variable.
	(trace_command): Using proper breakpoint_ops according to the
	argument passed by the user in the command line.
	(initialize_breakpoint_ops): Initializing breakpoint_ops for
	static probes on breakpoints and tracepoints.
	* breakpoint.h (struct bp_location) <probe>: New field.
	* cli-utils.c (skip_spaces_const): New function.
	(extract_arg): Likewise.
	* cli-utils.h (skip_spaces_const): Likewise.
	(extract_arg): Likewise.
	* coffread.c (coff_sym_fns): Add `sym_probe_fns' value.
	* configure.ac: Append `stap-probe.o' to be generated when ELF
	support is present.
	* configure: Regenerate.
	* dbxread.c (aout_sym_fns): Add `sym_probe_fns' value.
	* elfread.c: Include `probe.h' and `arch-utils.h'.
	(probe_key): New variable.
	(elf_get_probes): New function.
	(elf_get_probe_argument_count): Likewise.
	(elf_evaluate_probe_argument): Likewise.
	(elf_compile_to_ax): Likewise.
	(elf_symfile_relocate_probe): Likewise.
	(stap_probe_key_free): Likewise.
	(elf_probe_fns): New variable.
	(elf_sym_fns): Add `sym_probe_fns' value.
	(elf_sym_fns_lazy_psyms): Likewise.
	(elf_sym_fns_gdb_index): Likewise.
	(_initialize_elfread): Initialize objfile cache for static
	probes.
	* gdb_vecs.h (struct probe): New forward declaration.
	(probe_p): New VEC declaration.
	* gdbarch.c: Regenerate.
	* gdbarch.h: Regenerate.
	* gdbarch.sh (stap_integer_prefix): New variable.
	(stap_integer_suffix): Likewise.
	(stap_register_prefix): Likewise.
	(stap_register_suffix): Likewise.
	(stap_register_indirection_prefix): Likewise.
	(stap_register_indirection_suffix): Likewise.
	(stap_gdb_register_prefix): Likewise.
	(stap_gdb_register_suffix): Likewise.
	(stap_is_single_operand): New function.
	(stap_parse_special_token): Likewise.
	(struct stap_parse_info): Forward declaration.
	* i386-tdep.c: Including headers needed to perform the parsing
	of SystemTap probes' arguments.
	(i386_stap_is_single_operand): New function.
	(i386_stap_parse_special_token): Likewise.
	(i386_elf_init_abi): Initializing proper fields used by SystemTap
	probes' arguments parser.
	* i386-tdep.h (i386_stap_is_single_operand): New function.
	(i386_stap_parse_special_token): Likewise.
	* machoread.c (macho_sym_fns): Add `sym_probe_fns' value.
	* mipsread.c (ecoff_sym_fns): Likewise.
	* objfiles.c (objfile_relocate1): Support relocation for static
	probes.
	* parse.c (prefixify_expression): Remove static declaration.
	(initialize_expout): Likewise.
	(reallocate_expout): Likewise.
	* parser-defs.h (initialize_expout): Declare function.
	(reallocate_expout): Likewise.
	(prefixify_expression): Likewise.
	* ppc-linux-tdep.c: Including headers needed to perform the parsing
	of SystemTap probes' arguments.
	(ppc_stap_is_single_operand): New function.
	(ppc_stap_parse_special_token): Likewise.
	(ppc_linux_init_abi): Initializing proper fields used by SystemTap
	probes' arguments parser.
	* probe.c: New file, for generic statically defined probe support.
	* probe.h: Likewise.
	* s390-tdep.c: Including headers needed to perform the parsing of
	SystemTap probes' arguments.
	(s390_stap_is_single_operand): New function.
	(s390_gdbarch_init): Initializing proper fields used by SystemTap
	probes' arguments parser.
	* somread.c (som_sym_fns): Add `sym_probe_fns' value.
	* stap-probe.c: New file, for SystemTap probe support.
	* stap-probe.h: Likewise.
	* symfile.h: Include `gdb_vecs.h'.
	(struct sym_probe_fns): New struct.
	(struct sym_fns) <sym_probe_fns>: New field.
	* symtab.c (init_sal): Initialize `probe' field.
	* symtab.h (struct probe): Forward declaration.
	(struct symtab_and_line) <probe>: New field.
	* tracepoint.c (start_tracing): Adjust semaphore on breakpoints
	locations.
	(stop_tracing): Likewise.
	* xcoffread.c (xcoff_sym_fns): Add `sym_probe_fns' value.

1 files changed, 1558 insertions, 0 deletions

diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
new file mode 100644
index 0000000..13ba281
--- /dev/null
+++ b/gdb/stap-probe.c
@@ -0,0 +1,1558 @@
+/* SystemTap probe support for GDB.
+
+   Copyright (C) 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 "stap-probe.h"
+#include "probe.h"
+#include "vec.h"
+#include "ui-out.h"
+#include "objfiles.h"
+#include "arch-utils.h"
+#include "command.h"
+#include "gdbcmd.h"
+#include "filenames.h"
+#include "value.h"
+#include "exceptions.h"
+#include "ax.h"
+#include "ax-gdb.h"
+#include "complaints.h"
+#include "cli/cli-utils.h"
+#include "linespec.h"
+#include "user-regs.h"
+#include "parser-defs.h"
+#include "language.h"
+#include "elf-bfd.h"
+
+#include <ctype.h>
+
+/* The name of the SystemTap section where we will find information about
+   the probes.  */
+
+#define STAP_BASE_SECTION_NAME ".stapsdt.base"
+
+/* Forward declaration. */
+
+static const struct probe_ops stap_probe_ops;
+
+/* Should we display debug information for the probe's argument expression
+   parsing?  */
+
+static int stap_expression_debug = 0;
+
+/* The various possibilities of bitness defined for a probe's argument.
+
+   The relationship is:
+
+   - STAP_ARG_BITNESS_UNDEFINED:  The user hasn't specified the bitness.
+   - STAP_ARG_BITNESS_32BIT_UNSIGNED:  argument string starts with `4@'.
+   - STAP_ARG_BITNESS_32BIT_SIGNED:  argument string starts with `-4@'.
+   - STAP_ARG_BITNESS_64BIT_UNSIGNED:  argument string starts with `8@'.
+   - STAP_ARG_BITNESS_64BIT_SIGNED:  argument string starts with `-8@'.  */
+
+enum stap_arg_bitness
+{
+  STAP_ARG_BITNESS_UNDEFINED,
+  STAP_ARG_BITNESS_32BIT_UNSIGNED,
+  STAP_ARG_BITNESS_32BIT_SIGNED,
+  STAP_ARG_BITNESS_64BIT_UNSIGNED,
+  STAP_ARG_BITNESS_64BIT_SIGNED,
+};
+
+/* The following structure represents a single argument for the probe.  */
+
+struct stap_probe_arg
+{
+  /* The bitness of this argument.  */
+  enum stap_arg_bitness bitness;
+
+  /* The corresponding `struct type *' to the bitness.  */
+  struct type *atype;
+
+  /* The argument converted to an internal GDB expression.  */
+  struct expression *aexpr;
+};
+
+typedef struct stap_probe_arg stap_probe_arg_s;
+DEF_VEC_O (stap_probe_arg_s);
+
+struct stap_probe
+{
+  /* Generic information about the probe.  This shall be the first element
+     of this struct, in order to maintain binary compatibility with the
+     `struct probe' and be able to fully abstract it.  */
+  struct probe p;
+
+  /* If the probe has a semaphore associated, then this is the value of
+     it.  */
+  CORE_ADDR sem_addr;
+
+  unsigned int args_parsed : 1;
+  union
+    {
+      const char *text;
+
+      /* Information about each argument.  This is an array of `stap_probe_arg',
+	 with each entry representing one argument.  */
+      VEC (stap_probe_arg_s) *vec;
+    }
+  args_u;
+};
+
+/* When parsing the arguments, we have to establish different precedences
+   for the various kinds of asm operators.  This enumeration represents those
+   precedences.
+
+   This logic behind this is available at
+   <http://sourceware.org/binutils/docs/as/Infix-Ops.html#Infix-Ops>, or using
+   the command "info '(as)Infix Ops'".  */
+
+enum stap_operand_prec
+{
+  /* Lowest precedence, used for non-recognized operands or for the beginning
+     of the parsing process.  */
+  STAP_OPERAND_PREC_NONE = 0,
+
+  /* Precedence of logical OR.  */
+  STAP_OPERAND_PREC_LOGICAL_OR,
+
+  /* Precedence of logical AND.  */
+  STAP_OPERAND_PREC_LOGICAL_AND,
+
+  /* Precedence of additive (plus, minus) and comparative (equal, less,
+     greater-than, etc) operands.  */
+  STAP_OPERAND_PREC_ADD_CMP,
+
+  /* Precedence of bitwise operands (bitwise OR, XOR, bitwise AND,
+     logical NOT).  */
+  STAP_OPERAND_PREC_BITWISE,
+
+  /* Precedence of multiplicative operands (multiplication, division,
+     remainder, left shift and right shift).  */
+  STAP_OPERAND_PREC_MUL
+};
+
+static void stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
+				   enum stap_operand_prec prec);
+
+static void stap_parse_argument_conditionally (struct stap_parse_info *p);
+
+/* Returns 1 if *S is an operator, zero otherwise.  */
+
+static int stap_is_operator (char op);
+
+static void
+show_stapexpressiondebug (struct ui_file *file, int from_tty,
+			  struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("SystemTap Probe expression debugging is %s.\n"),
+		    value);
+}
+
+/* Returns the operator precedence level of OP, or STAP_OPERAND_PREC_NONE
+   if the operator code was not recognized.  */
+
+static enum stap_operand_prec
+stap_get_operator_prec (enum exp_opcode op)
+{
+  switch (op)
+    {
+    case BINOP_LOGICAL_OR:
+      return STAP_OPERAND_PREC_LOGICAL_OR;
+
+    case BINOP_LOGICAL_AND:
+      return STAP_OPERAND_PREC_LOGICAL_AND;
+
+    case BINOP_ADD:
+    case BINOP_SUB:
+    case BINOP_EQUAL:
+    case BINOP_NOTEQUAL:
+    case BINOP_LESS:
+    case BINOP_LEQ:
+    case BINOP_GTR:
+    case BINOP_GEQ:
+      return STAP_OPERAND_PREC_ADD_CMP;
+
+    case BINOP_BITWISE_IOR:
+    case BINOP_BITWISE_AND:
+    case BINOP_BITWISE_XOR:
+    case UNOP_LOGICAL_NOT:
+      return STAP_OPERAND_PREC_BITWISE;
+
+    case BINOP_MUL:
+    case BINOP_DIV:
+    case BINOP_REM:
+    case BINOP_LSH:
+    case BINOP_RSH:
+      return STAP_OPERAND_PREC_MUL;
+
+    default:
+      return STAP_OPERAND_PREC_NONE;
+    }
+}
+
+/* Given S, read the operator in it and fills the OP pointer with its code.
+   Return 1 on success, zero if the operator was not recognized.  */
+
+static int
+stap_get_opcode (const char **s, enum exp_opcode *op)
+{
+  const char c = **s;
+  int ret = 1;
+
+  *s += 1;
+
+  switch (c)
+    {
+    case '*':
+      *op = BINOP_MUL;
+      break;
+
+    case '/':
+      *op = BINOP_DIV;
+      break;
+
+    case '%':
+      *op = BINOP_REM;
+    break;
+
+    case '<':
+      *op = BINOP_LESS;
+      if (**s == '<')
+	{
+	  *s += 1;
+	  *op = BINOP_LSH;
+	}
+      else if (**s == '=')
+	{
+	  *s += 1;
+	  *op = BINOP_LEQ;
+	}
+      else if (**s == '>')
+	{
+	  *s += 1;
+	  *op = BINOP_NOTEQUAL;
+	}
+    break;
+
+    case '>':
+      *op = BINOP_GTR;
+      if (**s == '>')
+	{
+	  *s += 1;
+	  *op = BINOP_RSH;
+	}
+      else if (**s == '=')
+	{
+	  *s += 1;
+	  *op = BINOP_GEQ;
+	}
+    break;
+
+    case '|':
+      *op = BINOP_BITWISE_IOR;
+      if (**s == '|')
+	{
+	  *s += 1;
+	  *op = BINOP_LOGICAL_OR;
+	}
+    break;
+
+    case '&':
+      *op = BINOP_BITWISE_AND;
+      if (**s == '&')
+	{
+	  *s += 1;
+	  *op = BINOP_LOGICAL_AND;
+	}
+    break;
+
+    case '^':
+      *op = BINOP_BITWISE_XOR;
+      break;
+
+    case '!':
+      *op = UNOP_LOGICAL_NOT;
+      break;
+
+    case '+':
+      *op = BINOP_ADD;
+      break;
+
+    case '-':
+      *op = BINOP_SUB;
+      break;
+
+    case '=':
+      if (**s != '=')
+	{
+	  ret = 0;
+	  break;
+	}
+      *op = BINOP_EQUAL;
+      break;
+
+    default:
+      /* We didn't find any operator.  */
+      *s -= 1;
+      return 0;
+    }
+
+  return ret;
+}
+
+/* Given the bitness of the argument, represented by B, return the
+   corresponding `struct type *'.  */
+
+static struct type *
+stap_get_expected_argument_type (struct gdbarch *gdbarch,
+				 enum stap_arg_bitness b)
+{
+  switch (b)
+    {
+    case STAP_ARG_BITNESS_UNDEFINED:
+      if (gdbarch_addr_bit (gdbarch) == 32)
+	return builtin_type (gdbarch)->builtin_uint32;
+      else
+	return builtin_type (gdbarch)->builtin_uint64;
+
+    case STAP_ARG_BITNESS_32BIT_SIGNED:
+      return builtin_type (gdbarch)->builtin_int32;
+
+    case STAP_ARG_BITNESS_32BIT_UNSIGNED:
+      return builtin_type (gdbarch)->builtin_uint32;
+
+    case STAP_ARG_BITNESS_64BIT_SIGNED:
+      return builtin_type (gdbarch)->builtin_int64;
+
+    case STAP_ARG_BITNESS_64BIT_UNSIGNED:
+      return builtin_type (gdbarch)->builtin_uint64;
+
+    default:
+      internal_error (__FILE__, __LINE__,
+		      _("Undefined bitness for probe."));
+      break;
+    }
+}
+
+/* Function responsible for parsing a register operand according to
+   SystemTap parlance.  Assuming:
+
+   RP  = register prefix
+   RS  = register suffix
+   RIP = register indirection prefix
+   RIS = register indirection suffix
+   
+   Then a register operand can be:
+   
+   [RIP] [RP] REGISTER [RS] [RIS]
+
+   This function takes care of a register's indirection, displacement and
+   direct access.  It also takes into consideration the fact that some
+   registers are named differently inside and outside GDB, e.g., PPC's
+   general-purpose registers are represented by integers in the assembly
+   language (e.g., `15' is the 15th general-purpose register), but inside
+   GDB they have a prefix (the letter `r') appended.  */
+
+static void
+stap_parse_register_operand (struct stap_parse_info *p)
+{
+  /* Simple flag to indicate whether we have seen a minus signal before
+     certain number.  */
+  int got_minus = 0;
+
+  /* Flags to indicate whether this register access is being displaced and/or
+     indirected.  */
+  int disp_p = 0, indirect_p = 0;
+  struct gdbarch *gdbarch = p->gdbarch;
+
+  /* Needed to generate the register name as a part of an expression.  */
+  struct stoken str;
+
+  /* Variables used to extract the register name from the probe's
+     argument.  */
+  const char *start;
+  char *regname;
+  int len;
+
+  /* Prefixes for the parser.  */
+  const char *reg_prefix = gdbarch_stap_register_prefix (gdbarch);
+  const char *reg_ind_prefix
+    = gdbarch_stap_register_indirection_prefix (gdbarch);
+  const char *gdb_reg_prefix = gdbarch_stap_gdb_register_prefix (gdbarch);
+  int reg_prefix_len = reg_prefix ? strlen (reg_prefix) : 0;
+  int reg_ind_prefix_len = reg_ind_prefix ? strlen (reg_ind_prefix) : 0;
+  int gdb_reg_prefix_len = gdb_reg_prefix ? strlen (gdb_reg_prefix) : 0;
+
+  /* Suffixes for the parser.  */
+  const char *reg_suffix = gdbarch_stap_register_suffix (gdbarch);
+  const char *reg_ind_suffix
+    = gdbarch_stap_register_indirection_suffix (gdbarch);
+  const char *gdb_reg_suffix = gdbarch_stap_gdb_register_suffix (gdbarch);
+  int reg_suffix_len = reg_suffix ? strlen (reg_suffix) : 0;
+  int reg_ind_suffix_len = reg_ind_suffix ? strlen (reg_ind_suffix) : 0;
+  int gdb_reg_suffix_len = gdb_reg_suffix ? strlen (gdb_reg_suffix) : 0;
+
+  /* Checking for a displacement argument.  */
+  if (*p->arg == '+')
+    {
+      /* If it's a plus sign, we don't need to do anything, just advance the
+	 pointer.  */
+      ++p->arg;
+    }
+
+  if (*p->arg == '-')
+    {
+      got_minus = 1;
+      ++p->arg;
+    }
+
+  if (isdigit (*p->arg))
+    {
+      /* The value of the displacement.  */
+      long displacement;
+
+      disp_p = 1;
+      displacement = strtol (p->arg, (char **) &p->arg, 10);
+
+      /* Generating the expression for the displacement.  */
+      write_exp_elt_opcode (OP_LONG);
+      write_exp_elt_type (builtin_type (gdbarch)->builtin_long);
+      write_exp_elt_longcst (displacement);
+      write_exp_elt_opcode (OP_LONG);
+      if (got_minus)
+	write_exp_elt_opcode (UNOP_NEG);
+    }
+
+  /* Getting rid of register indirection prefix.  */
+  if (reg_ind_prefix
+      && strncmp (p->arg, reg_ind_prefix, reg_ind_prefix_len) == 0)
+    {
+      indirect_p = 1;
+      p->arg += reg_ind_prefix_len;
+    }
+
+  if (disp_p && !indirect_p)
+    error (_("Invalid register displacement syntax on expression `%s'."),
+	   p->saved_arg);
+
+  /* Getting rid of register prefix.  */
+  if (reg_prefix && strncmp (p->arg, reg_prefix, reg_prefix_len) == 0)
+    p->arg += reg_prefix_len;
+
+  /* Now we should have only the register name.  Let's extract it and get
+     the associated number.  */
+  start = p->arg;
+
+  /* We assume the register name is composed by letters and numbers.  */
+  while (isalnum (*p->arg))
+    ++p->arg;
+
+  len = p->arg - start;
+
+  regname = alloca (len + gdb_reg_prefix_len + gdb_reg_suffix_len + 1);
+  regname[0] = '\0';
+
+  /* We only add the GDB's register prefix/suffix if we are dealing with
+     a numeric register.  */
+  if (gdb_reg_prefix && isdigit (*start))
+    {
+      strncpy (regname, gdb_reg_prefix, gdb_reg_prefix_len);
+      strncpy (regname + gdb_reg_prefix_len, start, len);
+
+      if (gdb_reg_suffix)
+	strncpy (regname + gdb_reg_prefix_len + len,
+		 gdb_reg_suffix, gdb_reg_suffix_len);
+
+      len += gdb_reg_prefix_len + gdb_reg_suffix_len;
+    }
+  else
+    strncpy (regname, start, len);
+
+  regname[len] = '\0';
+
+  /* Is this a valid register name?  */
+  if (user_reg_map_name_to_regnum (gdbarch, regname, len) == -1)
+    error (_("Invalid register name `%s' on expression `%s'."),
+	   regname, p->saved_arg);
+
+  write_exp_elt_opcode (OP_REGISTER);
+  str.ptr = regname;
+  str.length = len;
+  write_exp_string (str);
+  write_exp_elt_opcode (OP_REGISTER);
+
+  if (indirect_p)
+    {
+      if (disp_p)
+	write_exp_elt_opcode (BINOP_ADD);
+
+      /* Casting to the expected type.  */
+      write_exp_elt_opcode (UNOP_CAST);
+      write_exp_elt_type (lookup_pointer_type (p->arg_type));
+      write_exp_elt_opcode (UNOP_CAST);
+
+      write_exp_elt_opcode (UNOP_IND);
+    }
+
+  /* Getting rid of the register name suffix.  */
+  if (reg_suffix)
+    {
+      if (strncmp (p->arg, reg_suffix, reg_suffix_len) != 0)
+	error (_("Missing register name suffix `%s' on expression `%s'."),
+	       reg_suffix, p->saved_arg);
+
+      p->arg += reg_suffix_len;
+    }
+
+  /* Getting rid of the register indirection suffix.  */
+  if (indirect_p && reg_ind_suffix)
+    {
+      if (strncmp (p->arg, reg_ind_suffix, reg_ind_suffix_len) != 0)
+	error (_("Missing indirection suffix `%s' on expression `%s'."),
+	       reg_ind_suffix, p->saved_arg);
+
+      p->arg += reg_ind_suffix_len;
+    }
+}
+
+/* This function is responsible for parsing a single operand.
+
+   A single operand can be:
+
+      - an unary operation (e.g., `-5', `~2', or even with subexpressions
+        like `-(2 + 1)')
+      - a register displacement, which will be treated as a register
+        operand (e.g., `-4(%eax)' on x86)
+      - a numeric constant, or
+      - a register operand (see function `stap_parse_register_operand')
+
+   The function also calls special-handling functions to deal with
+   unrecognized operands, allowing arch-specific parsers to be
+   created.  */
+
+static void
+stap_parse_single_operand (struct stap_parse_info *p)
+{
+  struct gdbarch *gdbarch = p->gdbarch;
+
+  /* Prefixes for the parser.  */
+  const char *const_prefix = gdbarch_stap_integer_prefix (gdbarch);
+  const char *reg_prefix = gdbarch_stap_register_prefix (gdbarch);
+  const char *reg_ind_prefix
+    = gdbarch_stap_register_indirection_prefix (gdbarch);
+  int const_prefix_len = const_prefix ? strlen (const_prefix) : 0;
+  int reg_prefix_len = reg_prefix ? strlen (reg_prefix) : 0;
+  int reg_ind_prefix_len = reg_ind_prefix ? strlen (reg_ind_prefix) : 0;
+
+  /* Suffixes for the parser.  */
+  const char *const_suffix = gdbarch_stap_integer_suffix (gdbarch);
+  const char *reg_suffix = gdbarch_stap_register_suffix (gdbarch);
+  const char *reg_ind_suffix
+    = gdbarch_stap_register_indirection_suffix (gdbarch);
+  int const_suffix_len = const_suffix ? strlen (const_suffix) : 0;
+  int reg_suffix_len = reg_suffix ? strlen (reg_suffix) : 0;
+  int reg_ind_suffix_len = reg_ind_suffix ? strlen (reg_ind_suffix) : 0;
+
+  /* We first try to parse this token as a "special token".  */
+  if (gdbarch_stap_parse_special_token_p (gdbarch))
+    {
+      int ret = gdbarch_stap_parse_special_token (gdbarch, p);
+
+      if (ret)
+	{
+	  /* If the return value of the above function is not zero,
+	     it means it successfully parsed the special token.
+
+	     If it is NULL, we try to parse it using our method.  */
+	  return;
+	}
+    }
+
+  if (*p->arg == '-' || *p->arg == '~' || *p->arg == '+')
+    {
+      char c = *p->arg;
+      int number;
+
+      /* We use this variable to do a lookahead.  */
+      const char *tmp = p->arg;
+
+      ++tmp;
+
+      /* This is an unary operation.  Here is a list of allowed tokens
+	 here:
+
+	 - numeric literal;
+	 - number (from register displacement)
+	 - subexpression (beginning with `(')
+
+	 We handle the register displacement here, and the other cases
+	 recursively.  */
+      if (p->inside_paren_p)
+	tmp = skip_spaces_const (tmp);
+
+      if (isdigit (*tmp))
+	number = strtol (tmp, (char **) &tmp, 10);
+
+      if (!reg_ind_prefix
+	  || strncmp (tmp, reg_ind_prefix, reg_ind_prefix_len) != 0)
+	{
+	  /* This is not a displacement.  We skip the operator, and deal
+	     with it later.  */
+	  ++p->arg;
+	  stap_parse_argument_conditionally (p);
+	  if (c == '-')
+	    write_exp_elt_opcode (UNOP_NEG);
+	  else if (c == '~')
+	    write_exp_elt_opcode (UNOP_COMPLEMENT);
+	}
+      else
+	{
+	  /* If we are here, it means it is a displacement.  The only
+	     operations allowed here are `-' and `+'.  */
+	  if (c == '~')
+	    error (_("Invalid operator `%c' for register displacement "
+		     "on expression `%s'."), c, p->saved_arg);
+
+	  stap_parse_register_operand (p);
+	}
+    }
+  else if (isdigit (*p->arg))
+    {
+      /* A temporary variable, needed for lookahead.  */
+      const char *tmp = p->arg;
+      long number;
+
+      /* We can be dealing with a numeric constant (if `const_prefix' is
+	 NULL), or with a register displacement.  */
+      number = strtol (tmp, (char **) &tmp, 10);
+
+      if (p->inside_paren_p)
+	tmp = skip_spaces_const (tmp);
+      if (!const_prefix && reg_ind_prefix
+	  && strncmp (tmp, reg_ind_prefix, reg_ind_prefix_len) != 0)
+	{
+	  /* We are dealing with a numeric constant.  */
+	  write_exp_elt_opcode (OP_LONG);
+	  write_exp_elt_type (builtin_type (gdbarch)->builtin_long);
+	  write_exp_elt_longcst (number);
+	  write_exp_elt_opcode (OP_LONG);
+
+	  p->arg = tmp;
+
+	  if (const_suffix)
+	    {
+	      if (strncmp (p->arg, const_suffix, const_suffix_len) == 0)
+		p->arg += const_suffix_len;
+	      else
+		error (_("Invalid constant suffix on expression `%s'."),
+		       p->saved_arg);
+	    }
+	}
+      else if (reg_ind_prefix
+	       && strncmp (tmp, reg_ind_prefix, reg_ind_prefix_len) == 0)
+	stap_parse_register_operand (p);
+      else
+	error (_("Unknown numeric token on expression `%s'."),
+	       p->saved_arg);
+    }
+  else if (const_prefix
+	   && strncmp (p->arg, const_prefix, const_prefix_len) == 0)
+    {
+      /* We are dealing with a numeric constant.  */
+      long number;
+
+      p->arg += const_prefix_len;
+      number = strtol (p->arg, (char **) &p->arg, 10);
+
+      write_exp_elt_opcode (OP_LONG);
+      write_exp_elt_type (builtin_type (gdbarch)->builtin_long);
+      write_exp_elt_longcst (number);
+      write_exp_elt_opcode (OP_LONG);
+
+      if (const_suffix)
+	{
+	  if (strncmp (p->arg, const_suffix, const_suffix_len) == 0)
+	    p->arg += const_suffix_len;
+	  else
+	    error (_("Invalid constant suffix on expression `%s'."),
+		   p->saved_arg);
+	}
+    }
+  else if ((reg_prefix
+	    && strncmp (p->arg, reg_prefix, reg_prefix_len) == 0)
+	   || (reg_ind_prefix
+	       && strncmp (p->arg, reg_ind_prefix, reg_ind_prefix_len) == 0))
+    stap_parse_register_operand (p);
+  else
+    error (_("Operator `%c' not recognized on expression `%s'."),
+	   *p->arg, p->saved_arg);
+}
+
+/* This function parses an argument conditionally, based on single or
+   non-single operands.  A non-single operand would be a parenthesized
+   expression (e.g., `(2 + 1)'), and a single operand is anything that
+   starts with `-', `~', `+' (i.e., unary operators), a digit, or
+   something recognized by `gdbarch_stap_is_single_operand'.  */
+
+static void
+stap_parse_argument_conditionally (struct stap_parse_info *p)
+{
+  if (*p->arg == '-' || *p->arg == '~' || *p->arg == '+' /* Unary.  */
+      || isdigit (*p->arg)
+      || gdbarch_stap_is_single_operand (p->gdbarch, p->arg))
+    stap_parse_single_operand (p);
+  else if (*p->arg == '(')
+    {
+      /* We are dealing with a parenthesized operand.  It means we
+	 have to parse it as it was a separate expression, without
+	 left-side or precedence.  */
+      ++p->arg;
+      p->arg = skip_spaces_const (p->arg);
+      ++p->inside_paren_p;
+
+      stap_parse_argument_1 (p, 0, STAP_OPERAND_PREC_NONE);
+
+      --p->inside_paren_p;
+      if (*p->arg != ')')
+	error (_("Missign close-paren on expression `%s'."),
+	       p->saved_arg);
+
+      ++p->arg;
+      if (p->inside_paren_p)
+	p->arg = skip_spaces_const (p->arg);
+    }
+  else
+    error (_("Cannot parse expression `%s'."), p->saved_arg);
+}
+
+/* Helper function for `stap_parse_argument'.  Please, see its comments to
+   better understand what this function does.  */
+
+static void
+stap_parse_argument_1 (struct stap_parse_info *p, int has_lhs,
+		       enum stap_operand_prec prec)
+{
+  /* This is an operator-precedence parser.
+
+     We work with left- and right-sides of expressions, and
+     parse them depending on the precedence of the operators
+     we find.  */
+
+  if (p->inside_paren_p)
+    p->arg = skip_spaces_const (p->arg);
+
+  if (!has_lhs)
+    {
+      /* We were called without a left-side, either because this is the
+	 first call, or because we were called to parse a parenthesized
+	 expression.  It doesn't really matter; we have to parse the
+	 left-side in order to continue the process.  */
+      stap_parse_argument_conditionally (p);
+    }
+
+  /* Start to parse the right-side, and to "join" left and right sides
+     depending on the operation specified.
+
+     This loop shall continue until we run out of characters in the input,
+     or until we find a close-parenthesis, which means that we've reached
+     the end of a sub-expression.  */
+  while (p->arg && *p->arg && *p->arg != ')' && !isspace (*p->arg))
+    {
+      const char *tmp_exp_buf;
+      enum exp_opcode opcode;
+      enum stap_operand_prec cur_prec;
+
+      if (!stap_is_operator (*p->arg))
+	error (_("Invalid operator `%c' on expression `%s'."), *p->arg,
+	       p->saved_arg);
+
+      /* We have to save the current value of the expression buffer because
+	 the `stap_get_opcode' modifies it in order to get the current
+	 operator.  If this operator's precedence is lower than PREC, we
+	 should return and not advance the expression buffer pointer.  */
+      tmp_exp_buf = p->arg;
+      stap_get_opcode (&tmp_exp_buf, &opcode);
+
+      cur_prec = stap_get_operator_prec (opcode);
+      if (cur_prec < prec)
+	{
+	  /* If the precedence of the operator that we are seeing now is
+	     lower than the precedence of the first operator seen before
+	     this parsing process began, it means we should stop parsing
+	     and return.  */
+	  break;
+	}
+
+      p->arg = tmp_exp_buf;
+      if (p->inside_paren_p)
+	p->arg = skip_spaces_const (p->arg);
+
+      /* Parse the right-side of the expression.  */
+      stap_parse_argument_conditionally (p);
+
+      /* While we still have operators, try to parse another
+	 right-side, but using the current right-side as a left-side.  */
+      while (*p->arg && stap_is_operator (*p->arg))
+	{
+	  enum exp_opcode lookahead_opcode;
+	  enum stap_operand_prec lookahead_prec;
+
+	  /* Saving the current expression buffer position.  The explanation
+	     is the same as above.  */
+	  tmp_exp_buf = p->arg;
+	  stap_get_opcode (&tmp_exp_buf, &lookahead_opcode);
+	  lookahead_prec = stap_get_operator_prec (lookahead_opcode);
+
+	  if (lookahead_prec <= prec)
+	    {
+	      /* If we are dealing with an operator whose precedence is lower
+		 than the first one, just abandon the attempt.  */
+	      break;
+	    }
+
+	  /* Parse the right-side of the expression, but since we already
+	     have a left-side at this point, set `has_lhs' to 1.  */
+	  stap_parse_argument_1 (p, 1, lookahead_prec);
+	}
+
+      write_exp_elt_opcode (opcode);
+    }
+}
+
+/* Parse a probe's argument.
+
+   Assuming that:
+
+   LP = literal integer prefix
+   LS = literal integer suffix
+
+   RP = register prefix
+   RS = register suffix
+
+   RIP = register indirection prefix
+   RIS = register indirection suffix
+
+   This routine assumes that arguments' tokens are of the form:
+
+   - [LP] NUMBER [LS]
+   - [RP] REGISTER [RS]
+   - [RIP] [RP] REGISTER [RS] [RIS]
+   - If we find a number without LP, we try to parse it as a literal integer
+   constant (if LP == NULL), or as a register displacement.
+   - We count parenthesis, and only skip whitespaces if we are inside them.
+   - If we find an operator, we skip it.
+
+   This function can also call a special function that will try to match
+   unknown tokens.  It will return 1 if the argument has been parsed
+   successfully, or zero otherwise.  */
+
+static struct expression *
+stap_parse_argument (const char **arg, struct type *atype,
+		     struct gdbarch *gdbarch)
+{
+  struct stap_parse_info p;
+  volatile struct gdb_exception e;
+  struct cleanup *back_to;
+
+  /* We need to initialize the expression buffer, in order to begin
+     our parsing efforts.  The language here does not matter, since we
+     are using our own parser.  */
+  initialize_expout (10, current_language, gdbarch);
+  back_to = make_cleanup (free_current_contents, &expout);
+
+  p.saved_arg = *arg;
+  p.arg = *arg;
+  p.arg_type = atype;
+  p.gdbarch = gdbarch;
+  p.inside_paren_p = 0;
+
+  stap_parse_argument_1 (&p, 0, STAP_OPERAND_PREC_NONE);
+
+  discard_cleanups (back_to);
+
+  gdb_assert (p.inside_paren_p == 0);
+
+  /* Casting the final expression to the appropriate type.  */
+  write_exp_elt_opcode (UNOP_CAST);
+  write_exp_elt_type (atype);
+  write_exp_elt_opcode (UNOP_CAST);
+
+  reallocate_expout ();
+
+  p.arg = skip_spaces_const (p.arg);
+  *arg = p.arg;
+
+  return expout;
+}
+
+/* Function which parses an argument string from PROBE, correctly splitting
+   the arguments and storing their information in properly ways.
+
+   Consider the following argument string (x86 syntax):
+
+   `4@%eax 4@$10'
+
+   We have two arguments, `%eax' and `$10', both with 32-bit unsigned bitness.
+   This function basically handles them, properly filling some structures with
+   this information.  */
+
+static void
+stap_parse_probe_arguments (struct stap_probe *probe, struct objfile *objfile)
+{
+  const char *cur;
+  struct gdbarch *gdbarch = get_objfile_arch (objfile);
+
+  gdb_assert (!probe->args_parsed);
+  cur = probe->args_u.text;
+  probe->args_parsed = 1;
+  probe->args_u.vec = NULL;
+
+  if (!cur || !*cur || *cur == ':')
+    return;
+
+  while (*cur)
+    {
+      struct stap_probe_arg arg;
+      enum stap_arg_bitness b;
+      int got_minus = 0;
+      struct expression *expr;
+
+      memset (&arg, 0, sizeof (arg));
+
+      /* We expect to find something like:
+
+	 N@OP
+
+	 Where `N' can be [+,-][4,8].  This is not mandatory, so
+	 we check it here.  If we don't find it, go to the next
+	 state.  */
+      if ((*cur == '-' && cur[1] && cur[2] != '@')
+	  && cur[1] != '@')
+	arg.bitness = STAP_ARG_BITNESS_UNDEFINED;
+      else
+	{
+	  if (*cur == '-')
+	    {
+	      /* Discard the `-'.  */
+	      ++cur;
+	      got_minus = 1;
+	    }
+
+	  if (*cur == '4')
+	    b = (got_minus ? STAP_ARG_BITNESS_32BIT_SIGNED
+		 : STAP_ARG_BITNESS_32BIT_UNSIGNED);
+	  else if (*cur == '8')
+	    b = (got_minus ? STAP_ARG_BITNESS_64BIT_SIGNED
+		 : STAP_ARG_BITNESS_64BIT_UNSIGNED);
+	  else
+	    {
+	      /* We have an error, because we don't expect anything
+		 except 4 and 8.  */
+	      complaint (&symfile_complaints,
+			 _("unrecognized bitness `%c' for probe `%s'"),
+			 *cur, probe->p.name);
+	      return;
+	    }
+
+	  arg.bitness = b;
+	  arg.atype = stap_get_expected_argument_type (gdbarch, b);
+
+	  /* Discard the number and the `@' sign.  */
+	  cur += 2;
+	}
+
+      expr = stap_parse_argument (&cur, arg.atype, gdbarch);
+
+      if (stap_expression_debug)
+	dump_raw_expression (expr, gdb_stdlog,
+			     "before conversion to prefix form");
+
+      prefixify_expression (expr);
+
+      if (stap_expression_debug)
+	dump_prefix_expression (expr, gdb_stdlog);
+
+      arg.aexpr = expr;
+
+      /* Start it over again.  */
+      cur = skip_spaces_const (cur);
+
+      VEC_safe_push (stap_probe_arg_s, probe->args_u.vec, &arg);
+    }
+}
+
+/* Given PROBE, returns the number of arguments present in that probe's
+   argument string.  */
+
+static unsigned
+stap_get_probe_argument_count (struct probe *probe_generic,
+			       struct objfile *objfile)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  if (!probe->args_parsed)
+    stap_parse_probe_arguments (probe, objfile);
+
+  gdb_assert (probe->args_parsed);
+  return VEC_length (stap_probe_arg_s, probe->args_u.vec);
+}
+
+/* Return 1 if OP is a valid operator inside a probe argument, or zero
+   otherwise.  */
+
+static int
+stap_is_operator (char op)
+{
+  return (op == '+' || op == '-' || op == '*' || op == '/'
+	  || op == '>' || op == '<' || op == '!' || op == '^'
+	  || op == '|' || op == '&' || op == '%' || op == '=');
+}
+
+static struct stap_probe_arg *
+stap_get_arg (struct stap_probe *probe, struct objfile *objfile, unsigned n)
+{
+  if (!probe->args_parsed)
+    stap_parse_probe_arguments (probe, objfile);
+
+  return VEC_index (stap_probe_arg_s, probe->args_u.vec, n);
+}
+
+/* Evaluate the probe's argument N (indexed from 0), returning a value
+   corresponding to it.  Assertion is thrown if N does not exist.  */
+
+static struct value *
+stap_evaluate_probe_argument (struct probe *probe_generic,
+			      struct objfile *objfile, unsigned n)
+{
+  struct stap_probe *stap_probe = (struct stap_probe *) probe_generic;
+  struct stap_probe_arg *arg;
+  int pos = 0;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  arg = stap_get_arg (stap_probe, objfile, n);
+  return evaluate_subexp_standard (arg->atype, arg->aexpr, &pos, EVAL_NORMAL);
+}
+
+/* Compile the probe's argument N (indexed from 0) to agent expression.
+   Assertion is thrown if N does not exist.  */
+
+static void
+stap_compile_to_ax (struct probe *probe_generic, struct objfile *objfile,
+		    struct agent_expr *expr, struct axs_value *value,
+		    unsigned n)
+{
+  struct stap_probe *stap_probe = (struct stap_probe *) probe_generic;
+  struct stap_probe_arg *arg;
+  union exp_element *pc;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  arg = stap_get_arg (stap_probe, objfile, n);
+
+  pc = arg->aexpr->elts;
+  gen_expr (arg->aexpr, &pc, expr, value);
+
+  require_rvalue (expr, value);
+  value->type = arg->atype;
+}
+
+/* Destroy (free) the data related to PROBE.  PROBE memory itself is not feed
+   as it is allocated from OBJFILE_OBSTACK.  */
+
+static void
+stap_probe_destroy (struct probe *probe_generic)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  if (probe->args_parsed)
+    {
+      struct stap_probe_arg *arg;
+      int ix;
+
+      for (ix = 0; VEC_iterate (stap_probe_arg_s, probe->args_u.vec, ix, arg);
+	   ++ix)
+	xfree (arg->aexpr);
+      VEC_free (stap_probe_arg_s, probe->args_u.vec);
+    }
+}
+
+
+
+/* This is called to compute the value of one of the $_probe_arg*
+   convenience variables.  */
+
+static struct value *
+compute_probe_arg (struct gdbarch *arch, struct internalvar *ivar,
+		   void *data)
+{
+  struct frame_info *frame = get_selected_frame (_("No frame selected"));
+  CORE_ADDR pc = get_frame_pc (frame);
+  int sel = (int) (uintptr_t) data;
+  struct objfile *objfile;
+  struct probe *pc_probe;
+  unsigned n_args;
+
+  /* SEL == -1 means "_probe_argc".  */
+  gdb_assert (sel >= -1);
+
+  pc_probe = find_probe_by_pc (pc, &objfile);
+  if (pc_probe == NULL)
+    error (_("No SystemTap probe at PC %s"), core_addr_to_string (pc));
+
+  n_args
+    = objfile->sf->sym_probe_fns->sym_get_probe_argument_count (objfile,
+								pc_probe);
+  if (sel == -1)
+    return value_from_longest (builtin_type (arch)->builtin_int, n_args);
+
+  if (sel >= n_args)
+    error (_("Invalid probe argument %d -- probe has %u arguments available"),
+	   sel, n_args);
+
+  return objfile->sf->sym_probe_fns->sym_evaluate_probe_argument (objfile,
+								  pc_probe,
+								  sel);
+}
+
+/* This is called to compile one of the $_probe_arg* convenience
+   variables into an agent expression.  */
+
+static void
+compile_probe_arg (struct internalvar *ivar, struct agent_expr *expr,
+		   struct axs_value *value, void *data)
+{
+  CORE_ADDR pc = expr->scope;
+  int sel = (int) (uintptr_t) data;
+  struct objfile *objfile;
+  struct probe *pc_probe;
+  int n_probes;
+
+  /* SEL == -1 means "_probe_argc".  */
+  gdb_assert (sel >= -1);
+
+  pc_probe = find_probe_by_pc (pc, &objfile);
+  if (pc_probe == NULL)
+    error (_("No SystemTap probe at PC %s"), core_addr_to_string (pc));
+
+  n_probes
+    = objfile->sf->sym_probe_fns->sym_get_probe_argument_count (objfile,
+								pc_probe);
+  if (sel == -1)
+    {
+      value->kind = axs_rvalue;
+      value->type = builtin_type (expr->gdbarch)->builtin_int;
+      ax_const_l (expr, n_probes);
+      return;
+    }
+
+  gdb_assert (sel >= 0);
+  if (sel >= n_probes)
+    error (_("Invalid probe argument %d -- probe has %d arguments available"),
+	   sel, n_probes);
+
+  objfile->sf->sym_probe_fns->sym_compile_to_ax (objfile, pc_probe,
+						 expr, value, sel);
+}
+
+
+
+/* Set or clear a SystemTap semaphore.  ADDRESS is the semaphore's
+   address.  SET is zero if the semaphore should be cleared, or one
+   if it should be set.  This is a helper function for `stap_semaphore_down'
+   and `stap_semaphore_up'.  */
+
+static void
+stap_modify_semaphore (CORE_ADDR address, int set, struct gdbarch *gdbarch)
+{
+  gdb_byte bytes[sizeof (LONGEST)];
+  /* The ABI specifies "unsigned short".  */
+  struct type *type = builtin_type (gdbarch)->builtin_unsigned_short;
+  ULONGEST value;
+
+  if (address == 0)
+    return;
+
+  /* Swallow errors.  */
+  if (target_read_memory (address, bytes, TYPE_LENGTH (type)) != 0)
+    {
+      warning (_("Could not read the value of a SystemTap semaphore."));
+      return;
+    }
+
+  value = extract_unsigned_integer (bytes, TYPE_LENGTH (type),
+				    gdbarch_byte_order (gdbarch));
+  /* Note that we explicitly don't worry about overflow or
+     underflow.  */
+  if (set)
+    ++value;
+  else
+    --value;
+
+  store_unsigned_integer (bytes, TYPE_LENGTH (type),
+			  gdbarch_byte_order (gdbarch), value);
+
+  if (target_write_memory (address, bytes, TYPE_LENGTH (type)) != 0)
+    warning (_("Could not write the value of a SystemTap semaphore."));
+}
+
+/* Set a SystemTap semaphore.  SEM is the semaphore's address.  Semaphores
+   act as reference counters, so calls to this function must be paired with
+   calls to `stap_semaphore_down'.
+
+   This function and `stap_semaphore_down' race with another tool changing
+   the probes, but that is too rare to care.  */
+
+static void
+stap_set_semaphore (struct probe *probe_generic, struct gdbarch *gdbarch)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  stap_modify_semaphore (probe->sem_addr, 1, gdbarch);
+}
+
+/* Clear a SystemTap semaphore.  SEM is the semaphore's address.  */
+
+static void
+stap_clear_semaphore (struct probe *probe_generic, struct gdbarch *gdbarch)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  stap_modify_semaphore (probe->sem_addr, 0, gdbarch);
+}
+
+/* Implementation of `$_probe_arg*' set of variables.  */
+
+static const struct internalvar_funcs probe_funcs =
+{
+  compute_probe_arg,
+  compile_probe_arg,
+  NULL
+};
+
+/* Helper function that parses the information contained in a
+   SystemTap's probe.  Basically, the information consists in:
+
+   - Probe's PC address;
+   - Link-time section address of `.stapsdt.base' section;
+   - Link-time address of the semaphore variable, or ZERO if the
+     probe doesn't have an associated semaphore;
+   - Probe's provider name;
+   - Probe's name;
+   - Probe's argument format
+   
+   This function returns 1 if the handling was successful, and zero
+   otherwise.  */
+
+static void
+handle_stap_probe (struct objfile *objfile, struct sdt_note *el,
+		   VEC (probe_p) **probesp, CORE_ADDR base)
+{
+  bfd *abfd = objfile->obfd;
+  int size = bfd_get_arch_size (abfd) / 8;
+  struct gdbarch *gdbarch = get_objfile_arch (objfile);
+  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
+  CORE_ADDR base_ref;
+  const char *probe_args = NULL;
+  struct stap_probe *ret;
+
+  ret = obstack_alloc (&objfile->objfile_obstack, sizeof (*ret));
+  ret->p.pops = &stap_probe_ops;
+
+  /* Provider and the name of the probe.  */
+  ret->p.provider = &el->data[3 * size];
+  ret->p.name = memchr (ret->p.provider, '\0',
+			(char *) el->data + el->size - ret->p.provider);
+  /* Making sure there is a name.  */
+  if (!ret->p.name)
+    {
+      complaint (&symfile_complaints, _("corrupt probe name when "
+					"reading `%s'"), objfile->name);
+
+      /* There is no way to use a probe without a name or a provider, so
+	 returning zero here makes sense.  */
+      return;
+    }
+  else
+    ++ret->p.name;
+
+  /* Retrieving the probe's address.  */
+  ret->p.address = extract_typed_address (&el->data[0], ptr_type);
+
+  /* Link-time sh_addr of `.stapsdt.base' section.  */
+  base_ref = extract_typed_address (&el->data[size], ptr_type);
+
+  /* Semaphore address.  */
+  ret->sem_addr = extract_typed_address (&el->data[2 * size], ptr_type);
+
+  ret->p.address += (ANOFFSET (objfile->section_offsets,
+			       SECT_OFF_TEXT (objfile))
+		     + base - base_ref);
+  if (ret->sem_addr)
+    ret->sem_addr += (ANOFFSET (objfile->section_offsets,
+				SECT_OFF_DATA (objfile))
+		      + base - base_ref);
+
+  /* Arguments.  We can only extract the argument format if there is a valid
+     name for this probe.  */
+  probe_args = memchr (ret->p.name, '\0',
+		       (char *) el->data + el->size - ret->p.name);
+
+  if (probe_args != NULL)
+    ++probe_args;
+
+  if (probe_args == NULL || (memchr (probe_args, '\0',
+				     (char *) el->data + el->size - ret->p.name)
+			     != el->data + el->size - 1))
+    {
+      complaint (&symfile_complaints, _("corrupt probe argument when "
+					"reading `%s'"), objfile->name);
+      /* If the argument string is NULL, it means some problem happened with
+	 it.  So we return 0.  */
+      return;
+    }
+
+  ret->args_parsed = 0;
+  ret->args_u.text = (void *) probe_args;
+
+  /* Successfully created probe.  */
+  VEC_safe_push (probe_p, *probesp, (struct probe *) ret);
+}
+
+/* Helper function which tries to find the base address of the SystemTap
+   base section named STAP_BASE_SECTION_NAME.  */
+
+static void
+get_stap_base_address_1 (bfd *abfd, asection *sect, void *obj)
+{
+  asection **ret = obj;
+
+  if ((sect->flags & (SEC_DATA | SEC_ALLOC | SEC_HAS_CONTENTS))
+      && sect->name && !strcmp (sect->name, STAP_BASE_SECTION_NAME))
+    *ret = sect;
+}
+
+/* Helper function which iterates over every section in the BFD file,
+   trying to find the base address of the SystemTap base section.
+   Returns 1 if found (setting BASE to the proper value), zero otherwise.  */
+
+static int
+get_stap_base_address (bfd *obfd, bfd_vma *base)
+{
+  asection *ret = NULL;
+
+  bfd_map_over_sections (obfd, get_stap_base_address_1, (void *) &ret);
+
+  if (!ret)
+    {
+      complaint (&symfile_complaints, _("could not obtain base address for "
+					"SystemTap section on objfile `%s'."),
+		 obfd->filename);
+      return 0;
+    }
+
+  if (base)
+    *base = ret->vma;
+
+  return 1;
+}
+
+/* Helper function for `elf_get_probes', which gathers information about all
+   SystemTap probes from OBJFILE.  */
+
+static void
+stap_get_probes (VEC (probe_p) **probesp, struct objfile *objfile)
+{
+  /* If we are here, then this is the first time we are parsing the
+     SystemTap probe's information.  We basically have to count how many
+     probes the objfile has, and then fill in the necessary information
+     for each one.  */
+  bfd *obfd = objfile->obfd;
+  bfd_vma base;
+  struct sdt_note *iter;
+  unsigned save_probesp_len = VEC_length (probe_p, *probesp);
+
+  if (!elf_tdata (obfd)->sdt_note_head)
+    {
+      /* There isn't any probe here.  */
+      return;
+    }
+
+  if (!get_stap_base_address (obfd, &base))
+    {
+      /* There was an error finding the base address for the section.
+	 Just return NULL.  */
+      return;
+    }
+
+  /* Parsing each probe's information.  */
+  for (iter = elf_tdata (obfd)->sdt_note_head; iter; iter = iter->next)
+    {
+      /* We first have to handle all the information about the
+	 probe which is present in the section.  */
+      handle_stap_probe (objfile, iter, probesp, base);
+    }
+
+  if (save_probesp_len == VEC_length (probe_p, *probesp))
+    {
+      /* If we are here, it means we have failed to parse every known
+	 probe.  */
+      complaint (&symfile_complaints, _("could not parse SystemTap probe(s) "
+					"from inferior"));
+      return;
+    }
+}
+
+static void
+stap_relocate (struct probe *probe_generic, CORE_ADDR delta)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  probe->p.address += delta;
+  if (probe->sem_addr)
+    probe->sem_addr += delta;
+}
+
+static int
+stap_probe_is_linespec (const char **linespecp)
+{
+  static const char *const keywords[] = { "-pstap", "-probe-stap", NULL };
+
+  return probe_is_linespec_by_keyword (linespecp, keywords);
+}
+
+static void
+stap_gen_info_probes_table_header (VEC (info_probe_column_s) **heads)
+{
+  info_probe_column_s stap_probe_column;
+
+  stap_probe_column.field_name = "semaphore";
+  stap_probe_column.print_name = _("Semaphore");
+
+  VEC_safe_push (info_probe_column_s, *heads, &stap_probe_column);
+}
+
+static void
+stap_gen_info_probes_table_values (struct probe *probe_generic,
+				   struct objfile *objfile,
+				   VEC (const_char_ptr) **ret)
+{
+  struct stap_probe *probe = (struct stap_probe *) probe_generic;
+  struct gdbarch *gdbarch = get_objfile_arch (objfile);
+  const char *val = NULL;
+
+  gdb_assert (probe_generic->pops == &stap_probe_ops);
+
+  if (probe->sem_addr)
+    val = print_core_address (gdbarch, probe->sem_addr);
+
+  VEC_safe_push (const_char_ptr, *ret, val);
+}
+
+/* SystemTap probe_ops.  */
+
+static const struct probe_ops stap_probe_ops =
+{
+  stap_probe_is_linespec,
+  stap_get_probes,
+  stap_relocate,
+  stap_get_probe_argument_count,
+  stap_evaluate_probe_argument,
+  stap_compile_to_ax,
+  stap_set_semaphore,
+  stap_clear_semaphore,
+  stap_probe_destroy,
+  stap_gen_info_probes_table_header,
+  stap_gen_info_probes_table_values,
+};
+
+/* Implementation of the `info probes stap' command.  */
+
+static void
+info_probes_stap_command (char *arg, int from_tty)
+{
+  info_probes_for_ops (arg, from_tty, &stap_probe_ops);
+}
+
+void _initialize_stap_probe (void);
+
+void
+_initialize_stap_probe (void)
+{
+  VEC_safe_push (probe_ops_cp, all_probe_ops, &stap_probe_ops);
+
+  add_setshow_zinteger_cmd ("stap-expression", class_maintenance,
+			    &stap_expression_debug,
+			    _("Set SystemTap expression debugging."),
+			    _("Show SystemTap expression debugging."),
+			    _("When non-zero, the internal representation "
+			      "of SystemTap expressions will be printed."),
+			    NULL,
+			    show_stapexpressiondebug,
+			    &setdebuglist, &showdebuglist);
+
+  create_internalvar_type_lazy ("_probe_argc", &probe_funcs,
+				(void *) (uintptr_t) -1);
+  create_internalvar_type_lazy ("_probe_arg0", &probe_funcs,
+				(void *) (uintptr_t) 0);
+  create_internalvar_type_lazy ("_probe_arg1", &probe_funcs,
+				(void *) (uintptr_t) 1);
+  create_internalvar_type_lazy ("_probe_arg2", &probe_funcs,
+				(void *) (uintptr_t) 2);
+  create_internalvar_type_lazy ("_probe_arg3", &probe_funcs,
+				(void *) (uintptr_t) 3);
+  create_internalvar_type_lazy ("_probe_arg4", &probe_funcs,
+				(void *) (uintptr_t) 4);
+  create_internalvar_type_lazy ("_probe_arg5", &probe_funcs,
+				(void *) (uintptr_t) 5);
+  create_internalvar_type_lazy ("_probe_arg6", &probe_funcs,
+				(void *) (uintptr_t) 6);
+  create_internalvar_type_lazy ("_probe_arg7", &probe_funcs,
+				(void *) (uintptr_t) 7);
+  create_internalvar_type_lazy ("_probe_arg8", &probe_funcs,
+				(void *) (uintptr_t) 8);
+  create_internalvar_type_lazy ("_probe_arg9", &probe_funcs,
+				(void *) (uintptr_t) 9);
+  create_internalvar_type_lazy ("_probe_arg10", &probe_funcs,
+				(void *) (uintptr_t) 10);
+  create_internalvar_type_lazy ("_probe_arg11", &probe_funcs,
+				(void *) (uintptr_t) 11);
+
+  add_cmd ("stap", class_info, info_probes_stap_command,
+	   _("\
+Show information about SystemTap static probes.\n\
+Usage: info probes stap [PROVIDER [NAME [OBJECT]]]\n\
+Each argument is a regular expression, used to select probes.\n\
+PROVIDER matches probe provider names.\n\
+NAME matches the probe names.\n\
+OBJECT matches the executable or shared library name."),
+	   info_probes_cmdlist_get ());
+
+}