Separate the procfs tapset

1 files changed, 521 insertions, 0 deletions

diff --git a/tapset-procfs.cxx b/tapset-procfs.cxx
new file mode 100644
index 00000000..3568c3d3
--- /dev/null
+++ b/tapset-procfs.cxx
@@ -0,0 +1,521 @@
+// tapset for procfs
+// Copyright (C) 2005-2009 Red Hat Inc.
+// Copyright (C) 2005-2007 Intel Corporation.
+// Copyright (C) 2008 James.Bottomley@HansenPartnership.com
+//
+// This file is part of systemtap, and is free software.  You can
+// redistribute it and/or modify it under the terms of the GNU General
+// Public License (GPL); either version 2, or (at your option) any
+// later version.
+
+
+#include "session.h"
+#include "tapsets.h"
+#include "translate.h"
+#include "util.h"
+
+#include <cstring>
+#include <string>
+
+
+using namespace std;
+using namespace __gnu_cxx;
+
+
+static string TOK_PROCFS("procfs");
+static string TOK_READ("read");
+static string TOK_WRITE("write");
+
+
+// ------------------------------------------------------------------------
+// procfs file derived probes
+// ------------------------------------------------------------------------
+
+
+struct procfs_derived_probe: public derived_probe
+{
+  string path;
+  bool write;
+  bool target_symbol_seen;
+
+  procfs_derived_probe (systemtap_session &, probe* p, probe_point* l, string ps, bool w);
+  void join_group (systemtap_session& s);
+};
+
+
+struct procfs_probe_set
+{
+  procfs_derived_probe* read_probe;
+  procfs_derived_probe* write_probe;
+
+  procfs_probe_set () : read_probe (NULL), write_probe (NULL) {}
+};
+
+
+struct procfs_derived_probe_group: public generic_dpg<procfs_derived_probe>
+{
+private:
+  map<string, procfs_probe_set*> probes_by_path;
+  typedef map<string, procfs_probe_set*>::iterator p_b_p_iterator;
+  bool has_read_probes;
+  bool has_write_probes;
+
+public:
+  procfs_derived_probe_group () :
+    has_read_probes(false), has_write_probes(false) {}
+
+  void enroll (procfs_derived_probe* probe);
+  void emit_module_decls (systemtap_session& s);
+  void emit_module_init (systemtap_session& s);
+  void emit_module_exit (systemtap_session& s);
+};
+
+
+struct procfs_var_expanding_visitor: public var_expanding_visitor
+{
+  procfs_var_expanding_visitor(systemtap_session& s, const string& pn,
+                               string path, bool write_probe):
+    sess (s), probe_name (pn), path (path), write_probe (write_probe),
+    target_symbol_seen (false) {}
+
+  systemtap_session& sess;
+  string probe_name;
+  string path;
+  bool write_probe;
+  bool target_symbol_seen;
+
+  void visit_target_symbol (target_symbol* e);
+};
+
+
+procfs_derived_probe::procfs_derived_probe (systemtap_session &s, probe* p,
+                                            probe_point* l, string ps, bool w):
+  derived_probe(p, l), path(ps), write(w), target_symbol_seen(false)
+{
+  // Expand local variables in the probe body
+  procfs_var_expanding_visitor v (s, name, path, write);
+  this->body = v.require (this->body);
+  target_symbol_seen = v.target_symbol_seen;
+}
+
+
+void
+procfs_derived_probe::join_group (systemtap_session& s)
+{
+  if (! s.procfs_derived_probes)
+    s.procfs_derived_probes = new procfs_derived_probe_group ();
+  s.procfs_derived_probes->enroll (this);
+}
+
+
+void
+procfs_derived_probe_group::enroll (procfs_derived_probe* p)
+{
+  procfs_probe_set *pset;
+
+  if (probes_by_path.count(p->path) == 0)
+    {
+      pset = new procfs_probe_set;
+      probes_by_path[p->path] = pset;
+    }
+  else
+    {
+      pset = probes_by_path[p->path];
+
+      // You can only specify 1 read and 1 write probe.
+      if (p->write && pset->write_probe != NULL)
+        throw semantic_error("only one write procfs probe can exist for procfs path \"" + p->path + "\"");
+      else if (! p->write && pset->read_probe != NULL)
+        throw semantic_error("only one read procfs probe can exist for procfs path \"" + p->path + "\"");
+
+      // XXX: multiple writes should be acceptable
+    }
+
+  if (p->write)
+  {
+    pset->write_probe = p;
+    has_write_probes = true;
+  }
+  else
+  {
+    pset->read_probe = p;
+    has_read_probes = true;
+  }
+}
+
+
+void
+procfs_derived_probe_group::emit_module_decls (systemtap_session& s)
+{
+  if (probes_by_path.empty())
+    return;
+
+  s.op->newline() << "/* ---- procfs probes ---- */";
+  s.op->newline() << "#include \"procfs.c\"";
+
+  // Emit the procfs probe data list
+  s.op->newline() << "static struct stap_procfs_probe {";
+  s.op->newline(1)<< "const char *path;";
+  s.op->newline() << "const char *read_pp;";
+  s.op->newline() << "void (*read_ph) (struct context*);";
+  s.op->newline() << "const char *write_pp;";
+  s.op->newline() << "void (*write_ph) (struct context*);";
+  s.op->newline(-1) << "} stap_procfs_probes[] = {";
+  s.op->indent(1);
+
+  for (p_b_p_iterator it = probes_by_path.begin(); it != probes_by_path.end();
+       it++)
+  {
+      procfs_probe_set *pset = it->second;
+
+      s.op->newline() << "{";
+      s.op->line() << " .path=" << lex_cast_qstring (it->first) << ",";
+
+      if (pset->read_probe != NULL)
+        {
+          s.op->line() << " .read_pp="
+                       << lex_cast_qstring (*pset->read_probe->sole_location())
+                       << ",";
+          s.op->line() << " .read_ph=&" << pset->read_probe->name << ",";
+        }
+      else
+        {
+          s.op->line() << " .read_pp=NULL,";
+          s.op->line() << " .read_ph=NULL,";
+        }
+
+      if (pset->write_probe != NULL)
+        {
+          s.op->line() << " .write_pp="
+                       << lex_cast_qstring (*pset->write_probe->sole_location())
+                       << ",";
+          s.op->line() << " .write_ph=&" << pset->write_probe->name;
+        }
+      else
+        {
+          s.op->line() << " .write_pp=NULL,";
+          s.op->line() << " .write_ph=NULL";
+        }
+      s.op->line() << " },";
+  }
+  s.op->newline(-1) << "};";
+
+  if (has_read_probes)
+    {
+      // Output routine to fill in 'page' with our data.
+      s.op->newline();
+
+      s.op->newline() << "static int _stp_procfs_read(char *page, char **start, off_t off, int count, int *eof, void *data) {";
+
+      s.op->newline(1) << "struct stap_procfs_probe *spp = (struct stap_procfs_probe *)data;";
+      s.op->newline() << "int bytes = 0;";
+      s.op->newline() << "string_t strdata = {'\\0'};";
+
+      common_probe_entryfn_prologue (s.op, "STAP_SESSION_RUNNING", "spp->read_pp");
+
+      s.op->newline() << "if (c->data == NULL)";
+      s.op->newline(1) << "c->data = &strdata;";
+      s.op->newline(-1) << "else {";
+
+      s.op->newline(1) << "if (unlikely (atomic_inc_return (& skipped_count) > MAXSKIPPED)) {";
+      s.op->newline(1) << "atomic_set (& session_state, STAP_SESSION_ERROR);";
+      s.op->newline() << "_stp_exit ();";
+      s.op->newline(-1) << "}";
+      s.op->newline() << "atomic_dec (& c->busy);";
+      s.op->newline() << "goto probe_epilogue;";
+      s.op->newline(-1) << "}";
+
+      // call probe function (which copies data into strdata)
+      s.op->newline() << "(*spp->read_ph) (c);";
+
+      // copy string data into 'page'
+      s.op->newline() << "c->data = NULL;";
+      s.op->newline() << "bytes = strnlen(strdata, MAXSTRINGLEN - 1);";
+      s.op->newline() << "if (off >= bytes)";
+      s.op->newline(1) << "*eof = 1;";
+      s.op->newline(-1) << "else {";
+      s.op->newline(1) << "bytes -= off;";
+      s.op->newline() << "if (bytes > count)";
+      s.op->newline(1) << "bytes = count;";
+      s.op->newline(-1) << "memcpy(page, strdata + off, bytes);";
+      s.op->newline() << "*start = page;";
+      s.op->newline(-1) << "}";
+
+      common_probe_entryfn_epilogue (s.op);
+      s.op->newline() << "return bytes;";
+
+      s.op->newline(-1) << "}";
+    }
+  if (has_write_probes)
+    {
+      s.op->newline() << "static int _stp_procfs_write(struct file *file, const char *buffer, unsigned long count, void *data) {";
+
+      s.op->newline(1) << "struct stap_procfs_probe *spp = (struct stap_procfs_probe *)data;";
+      s.op->newline() << "string_t strdata = {'\\0'};";
+
+      common_probe_entryfn_prologue (s.op, "STAP_SESSION_RUNNING", "spp->write_pp");
+
+      s.op->newline() << "if (count > (MAXSTRINGLEN - 1))";
+      s.op->newline(1) << "count = MAXSTRINGLEN - 1;";
+      s.op->newline(-1) << "_stp_copy_from_user(strdata, buffer, count);";
+
+      s.op->newline() << "if (c->data == NULL)";
+      s.op->newline(1) << "c->data = &strdata;";
+      s.op->newline(-1) << "else {";
+
+      s.op->newline(1) << "if (unlikely (atomic_inc_return (& skipped_count) > MAXSKIPPED)) {";
+      s.op->newline(1) << "atomic_set (& session_state, STAP_SESSION_ERROR);";
+      s.op->newline() << "_stp_exit ();";
+      s.op->newline(-1) << "}";
+      s.op->newline() << "atomic_dec (& c->busy);";
+      s.op->newline() << "goto probe_epilogue;";
+      s.op->newline(-1) << "}";
+
+      // call probe function (which copies data out of strdata)
+      s.op->newline() << "(*spp->write_ph) (c);";
+
+      s.op->newline() << "c->data = NULL;";
+      common_probe_entryfn_epilogue (s.op);
+
+      s.op->newline() << "return count;";
+      s.op->newline(-1) << "}";
+    }
+}
+
+
+void
+procfs_derived_probe_group::emit_module_init (systemtap_session& s)
+{
+  if (probes_by_path.empty())
+    return;
+
+  s.op->newline() << "for (i = 0; i < " << probes_by_path.size() << "; i++) {";
+  s.op->newline(1) << "struct stap_procfs_probe *spp = &stap_procfs_probes[i];";
+
+  s.op->newline() << "if (spp->read_pp)";
+  s.op->newline(1) << "probe_point = spp->read_pp;";
+  s.op->newline(-1) << "else";
+  s.op->newline(1) << "probe_point = spp->write_pp;";
+
+  s.op->newline(-1) << "rc = _stp_create_procfs(spp->path, i);";
+
+  s.op->newline() << "if (rc) {";
+  s.op->newline(1) << "_stp_close_procfs();";
+  s.op->newline() << "break;";
+  s.op->newline(-1) << "}";
+
+  if (has_read_probes)
+    {
+      s.op->newline() << "if (spp->read_pp)";
+      s.op->newline(1) << "_stp_procfs_files[i]->read_proc = &_stp_procfs_read;";
+      s.op->newline(-1) << "else";
+      s.op->newline(1) << "_stp_procfs_files[i]->read_proc = NULL;";
+      s.op->indent(-1);
+    }
+  else
+    s.op->newline() << "_stp_procfs_files[i]->read_proc = NULL;";
+
+  if (has_write_probes)
+    {
+      s.op->newline() << "if (spp->write_pp)";
+      s.op->newline(1) << "_stp_procfs_files[i]->write_proc = &_stp_procfs_write;";
+      s.op->newline(-1) << "else";
+      s.op->newline(1) << "_stp_procfs_files[i]->write_proc = NULL;";
+      s.op->indent(-1);
+    }
+  else
+    s.op->newline() << "_stp_procfs_files[i]->write_proc = NULL;";
+
+  s.op->newline() << "_stp_procfs_files[i]->data = spp;";
+  s.op->newline(-1) << "}"; // for loop
+}
+
+
+void
+procfs_derived_probe_group::emit_module_exit (systemtap_session& s)
+{
+  if (probes_by_path.empty())
+    return;
+
+  s.op->newline() << "_stp_close_procfs();";
+}
+
+
+void
+procfs_var_expanding_visitor::visit_target_symbol (target_symbol* e)
+{
+  assert(e->base_name.size() > 0 && e->base_name[0] == '$');
+
+  if (e->base_name != "$value")
+    throw semantic_error ("invalid target symbol for procfs probe, $value expected",
+                          e->tok);
+
+  if (e->components.size() > 0)
+    {
+      switch (e->components[0].first)
+        {
+        case target_symbol::comp_literal_array_index:
+          throw semantic_error("procfs target variable '$value' may not be used as array",
+                               e->tok);
+          break;
+        case target_symbol::comp_struct_member:
+          throw semantic_error("procfs target variable '$value' may not be used as a structure",
+                               e->tok);
+          break;
+        default:
+          throw semantic_error ("invalid use of procfs target variable '$value'",
+                                e->tok);
+          break;
+        }
+    }
+
+  bool lvalue = is_active_lvalue(e);
+  if (write_probe && lvalue)
+    throw semantic_error("procfs $value variable is read-only in a procfs write probe", e->tok);
+  else if (! write_probe && ! lvalue)
+    throw semantic_error("procfs $value variable cannot be read in a procfs read probe", e->tok);
+
+  // Remember that we've seen a target variable.
+  target_symbol_seen = true;
+
+  // Synthesize a function.
+  functiondecl *fdecl = new functiondecl;
+  fdecl->tok = e->tok;
+  embeddedcode *ec = new embeddedcode;
+  ec->tok = e->tok;
+
+  string fname = (string(lvalue ? "_procfs_value_set" : "_procfs_value_get")
+                  + "_" + lex_cast<string>(tick++));
+  string locvalue = "CONTEXT->data";
+
+  if (! lvalue)
+    ec->code = string("strlcpy (THIS->__retvalue, ") + locvalue
+      + string(", MAXSTRINGLEN); /* pure */");
+  else
+    ec->code = string("strlcpy (") + locvalue
+      + string(", THIS->value, MAXSTRINGLEN);");
+
+  fdecl->name = fname;
+  fdecl->body = ec;
+  fdecl->type = pe_string;
+
+  if (lvalue)
+    {
+      // Modify the fdecl so it carries a single pe_string formal
+      // argument called "value".
+
+      vardecl *v = new vardecl;
+      v->type = pe_string;
+      v->name = "value";
+      v->tok = e->tok;
+      fdecl->formal_args.push_back(v);
+    }
+  sess.functions[fdecl->name]=fdecl;
+
+  // Synthesize a functioncall.
+  functioncall* n = new functioncall;
+  n->tok = e->tok;
+  n->function = fname;
+  n->referent = 0; // NB: must not resolve yet, to ensure inclusion in session
+
+  if (lvalue)
+    {
+      // Provide the functioncall to our parent, so that it can be
+      // used to substitute for the assignment node immediately above
+      // us.
+      assert(!target_symbol_setter_functioncalls.empty());
+      *(target_symbol_setter_functioncalls.top()) = n;
+    }
+
+  provide (n);
+}
+
+
+struct procfs_builder: public derived_probe_builder
+{
+  procfs_builder() {}
+  virtual void build(systemtap_session & sess,
+                     probe * base,
+                     probe_point * location,
+                     literal_map_t const & parameters,
+                     vector<derived_probe *> & finished_results);
+};
+
+
+void
+procfs_builder::build(systemtap_session & sess,
+                      probe * base,
+                      probe_point * location,
+                      literal_map_t const & parameters,
+                      vector<derived_probe *> & finished_results)
+{
+  string path;
+  bool has_procfs = get_param(parameters, TOK_PROCFS, path);
+  bool has_read = (parameters.find(TOK_READ) != parameters.end());
+  bool has_write = (parameters.find(TOK_WRITE) != parameters.end());
+
+  // If no procfs path, default to "command".  The runtime will do
+  // this for us, but if we don't do it here, we'll think the
+  // following 2 probes are attached to different paths:
+  //
+  //   probe procfs("command").read {}"
+  //   probe procfs.write {}
+
+  if (! has_procfs)
+    path = "command";
+  // If we have a path, we need to validate it.
+  else
+    {
+      string::size_type start_pos, end_pos;
+      string component;
+      start_pos = 0;
+      while ((end_pos = path.find('/', start_pos)) != string::npos)
+        {
+          // Make sure it doesn't start with '/'.
+          if (end_pos == 0)
+            throw semantic_error ("procfs path cannot start with a '/'",
+                                  location->tok);
+
+          component = path.substr(start_pos, end_pos - start_pos);
+          // Make sure it isn't empty.
+          if (component.size() == 0)
+            throw semantic_error ("procfs path component cannot be empty",
+                                  location->tok);
+          // Make sure it isn't relative.
+          else if (component == "." || component == "..")
+            throw semantic_error ("procfs path cannot be relative (and contain '.' or '..')", location->tok);
+
+          start_pos = end_pos + 1;
+        }
+      component = path.substr(start_pos);
+      // Make sure it doesn't end with '/'.
+      if (component.size() == 0)
+        throw semantic_error ("procfs path cannot end with a '/'", location->tok);
+      // Make sure it isn't relative.
+      else if (component == "." || component == "..")
+        throw semantic_error ("procfs path cannot be relative (and contain '.' or '..')", location->tok);
+    }
+
+  if (!(has_read ^ has_write))
+    throw semantic_error ("need read/write component", location->tok);
+
+  finished_results.push_back(new procfs_derived_probe(sess, base, location,
+                                                      path, has_write));
+}
+
+
+void
+register_tapset_procfs(systemtap_session& s)
+{
+  match_node* root = s.pattern_root;
+  derived_probe_builder *builder = new procfs_builder();
+
+  root->bind(TOK_PROCFS)->bind(TOK_READ)->bind(builder);
+  root->bind_str(TOK_PROCFS)->bind(TOK_READ)->bind(builder);
+  root->bind(TOK_PROCFS)->bind(TOK_WRITE)->bind(builder);
+  root->bind_str(TOK_PROCFS)->bind(TOK_WRITE)->bind(builder);
+}
+
+
+
+/* vim: set sw=2 ts=8 cino=>4,n-2,{2,^-2,t0,(0,u0,w1,M1 : */