Add $argN context variables on per-process-syscall probes

6 files changed, 103 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index cb5a6f4b..df495cab 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2008-09-09  Masami Hiramatsu  <mhiramat@redhat.com>
 
+	* stapprobes.5.in: Added a description about $argN.
+	* NEWS: Ditto.
+	* tapsets.cxx (utrace_var_expanding_copy_visitor): Added
+	visit_target_symbol_arg() and visit_target_symbol_syscall().
+	(visit_target_symbol_arg): New function for handling $argN.
+	(visit_target_symbol_syscall): New function for handling $syscall.
+	(visit_target_symbol): Use visit_target_symbol_arg() and
+	visit_target_symbol_syscall().
+
+2008-09-09  Masami Hiramatsu  <mhiramat@redhat.com>
+
 	* stapprobes.5.in : Added a line for $name context variable.
 	* translate.cxx (c_unparser::emit_common_header): Add marker_name and
 	marker_format fields to context.
diff --git a/NEWS b/NEWS
index c7ddce45..b48870e2 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,9 @@
 * What's new
 
+- Additional context variables are available on user-space syscall probes.
+  - $argN ($arg1, $arg2, ... $arg6) in process(PATH_OR_PID).syscall
+    gives you the argument of the system call.
+
 - Target process mode (stap -c CMD or -x PID) now implicitly restricts all
   "process.*" probes to the given child process.  (It does not affect
   kernel.* or other probe types.)  The CMD string is now executed directly,
diff --git a/stapprobes.5.in b/stapprobes.5.in
index ecc6956c..6e8c3ff2 100644
--- a/stapprobes.5.in
+++ b/stapprobes.5.in
@@ -421,8 +421,13 @@ probe gets called when a thread described by PID or PATH dies.
 A
 .B .syscall
 probe gets called when a thread described by PID or PATH makes a
-system call.  The system call number is available in the "$syscall"
-context variable.
+system call.  The system call number is available in the
+.BR $syscall
+context variable, and the first 6 arguments of the system call
+are available in the
+.BR $argN
+(ex. $arg1, $arg2, ...) context variable.
+
 A
 .B .syscall.return
 probe gets called when a thread described by PID or PATH returns from a
diff --git a/tapset/ChangeLog b/tapset/ChangeLog
index d3117620..5a08ac63 100644
--- a/tapset/ChangeLog
+++ b/tapset/ChangeLog
@@ -1,5 +1,9 @@
 2008-09-09  Masami Hiramatsu  <mhiramat@redhat.com>
 
+	* utrace.stp: Added _utrace_syscall_arg().
+
+2008-09-09  Masami Hiramatsu  <mhiramat@redhat.com>
+
 	* marker.stp : New file, including marker context variable accessors.
 
 2008-09-01  Frank Ch. Eigler  <fche@elastic.org>
diff --git a/tapset/utrace.stp b/tapset/utrace.stp
index 3831ca3c..2b661573 100644
--- a/tapset/utrace.stp
+++ b/tapset/utrace.stp
@@ -5,7 +5,10 @@
 #include "syscall.h"
 %}
 
-
 function _utrace_syscall_nr:long () %{
    THIS->__retvalue = __stp_user_syscall_nr(CONTEXT->regs); /* pure */
 %}
+
+function _utrace_syscall_arg:long (n:long) %{
+   THIS->__retvalue = *__stp_user_syscall_arg(current, CONTEXT->regs, (int)THIS->n); /* pure */
+%}
diff --git a/tapsets.cxx b/tapsets.cxx
index 4774c0f6..5941339c 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -5846,6 +5846,8 @@ struct utrace_var_expanding_copy_visitor: public var_expanding_copy_visitor
   enum utrace_derived_probe_flags flags;
   bool target_symbol_seen;
 
+  void visit_target_symbol_arg (target_symbol* e);
+  void visit_target_symbol_syscall (target_symbol* e);
   void visit_target_symbol (target_symbol* e);
 };
 
@@ -5923,18 +5925,61 @@ utrace_derived_probe::join_group (systemtap_session& s)
 
 
 void
-utrace_var_expanding_copy_visitor::visit_target_symbol (target_symbol* e)
+utrace_var_expanding_copy_visitor::visit_target_symbol_arg (target_symbol* e)
 {
-  assert(e->base_name.size() > 0 && e->base_name[0] == '$');
+  string argnum_s = e->base_name.substr(4,e->base_name.length()-4);
+  int argnum = atoi (argnum_s.c_str());
 
-  if (flags != UDPF_SYSCALL && flags != UDPF_SYSCALL_RETURN)
-    throw semantic_error ("only \"process(PATH_OR_PID).syscall\" and \"process(PATH_OR_PID).syscall.return\" probes support target symbols",
-			  e->tok);
+  if (flags != UDPF_SYSCALL)
+    throw semantic_error ("only \"process(PATH_OR_PID).syscall\" support $argN.", e->tok);
 
-  if (e->base_name != "$syscall")
-    throw semantic_error ("invalid target symbol for utrace probe, $syscall expected",
-			  e->tok);
+  if (e->components.size() > 0)
+    {
+      switch (e->components[0].first)
+	{
+	case target_symbol::comp_literal_array_index:
+	  throw semantic_error("utrace target variable '$argN' may not be used as array",
+			       e->tok);
+	  break;
+	case target_symbol::comp_struct_member:
+	  throw semantic_error("utrace target variable '$argN' may not be used as a structure",
+			       e->tok);
+	  break;
+	default:
+	  throw semantic_error ("invalid use of utrace target variable '$argN'",
+				e->tok);
+	  break;
+	}
+    }
+
+  // FIXME: max argnument number should not be hardcoded.
+  if (argnum < 1 || argnum > 6)
+    throw semantic_error ("invalid syscall argument number (1-6)", e->tok);
+
+  bool lvalue = is_active_lvalue(e);
+  if (lvalue)
+    throw semantic_error("utrace '$argN' variable is read-only", e->tok);
 
+  // Remember that we've seen a target variable.
+  target_symbol_seen = true;
+
+  // We're going to substitute a synthesized '_utrace_syscall_arg'
+  // function call for the '$argN' reference.
+  functioncall* n = new functioncall;
+  n->tok = e->tok;
+  n->function = "_utrace_syscall_arg";
+  n->referent = 0; // NB: must not resolve yet, to ensure inclusion in session
+
+  literal_number *num = new literal_number(argnum - 1);
+  num->tok = e->tok;
+  n->args.push_back(num);
+
+  provide <functioncall*> (this, n);
+}
+
+void
+utrace_var_expanding_copy_visitor::visit_target_symbol_syscall (target_symbol* e)
+{
   if (e->components.size() > 0)
     {
       switch (e->components[0].first)
@@ -5956,12 +6001,12 @@ utrace_var_expanding_copy_visitor::visit_target_symbol (target_symbol* e)
 
   bool lvalue = is_active_lvalue(e);
   if (lvalue)
-    throw semantic_error("utrace $syscall variable is read-only", e->tok);
+    throw semantic_error("utrace '$syscall' variable is read-only", e->tok);
 
   // Remember that we've seen a target variable.
   target_symbol_seen = true;
 
-  // We're going to substitute a synthesized '_syscall_nr_get'
+  // We're going to substitute a synthesized '_utrace_syscall_nr'
   // function call for the '$syscall' reference.
   functioncall* n = new functioncall;
   n->tok = e->tok;
@@ -5971,6 +6016,24 @@ utrace_var_expanding_copy_visitor::visit_target_symbol (target_symbol* e)
   provide <functioncall*> (this, n);
 }
 
+void
+utrace_var_expanding_copy_visitor::visit_target_symbol (target_symbol* e)
+{
+  assert(e->base_name.size() > 0 && e->base_name[0] == '$');
+
+  if (flags != UDPF_SYSCALL && flags != UDPF_SYSCALL_RETURN)
+    throw semantic_error ("only \"process(PATH_OR_PID).syscall\" and \"process(PATH_OR_PID).syscall.return\" probes support target symbols",
+			  e->tok);
+
+  if (e->base_name.substr(0,4) == "$arg")
+    visit_target_symbol_arg(e);
+  else if (e->base_name == "$syscall")
+    visit_target_symbol_syscall(e);
+  else
+    throw semantic_error ("invalid target symbol for utrace probe, $syscall or $argN expected",
+			  e->tok);
+}
+
 
 struct utrace_builder: public derived_probe_builder
 {