PR4186: cross-architecture probe building

* main.cxx (main): Add 'a:' and 'B:' options.
* session.h (kbuildflags): New place to store -B args.
* testsuite/systemtap.base/cmd_parse.exp: Test them lightly.
* buildrun.cxx (run_make_cmd): Use "--no-print-directory"
  rather than ">/dev/null" in kbuild invocations.  Pass
  '-a' and '-B' flags along.
* hash.cxx (find_script_hash): Add them.
* NEWS, stap.1.in: Mention this.

7 files changed, 69 insertions, 7 deletions

diff --git a/NEWS b/NEWS
index f07acd9f..a7843979 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,14 @@
 * What's new
 
+- It is now possible to cross-compile systemtap scripts for foreign
+  architectures, using the new '-a ARCH' and '-B OPT=VALUE' flags.
+  For example, put arm-linux-gcc etc. into your $PATH, and point
+  systemtap at the target kernel build tree with:
+     stap -a arm -B CROSS_COMPILE=arm-linux- -r /build/tree  [...]
+  The -B option is passed to kbuild make.  -r identifies the already
+  configured/built kernel tree and -a its architecture (kbuild ARCH=...).
+  Systemtap will infer -p4.
+
 - It is now possible to define multiple probe aliases with the same name.
   A probe will expand to all matching aliases.
 	probe foo = bar { }
diff --git a/buildrun.cxx b/buildrun.cxx
index 1820002d..69cc5a66 100644
--- a/buildrun.cxx
+++ b/buildrun.cxx
@@ -59,9 +59,9 @@ run_make_cmd(systemtap_session& s, string& make_cmd)
   if (s.verbose > 2)
     make_cmd += " V=1";
   else if (s.verbose > 1)
-    make_cmd += " >/dev/null";
+    make_cmd += " --no-print-directory";
   else
-    make_cmd += " -s >/dev/null";
+    make_cmd += " -s --no-print-directory";
 
   return stap_system (s.verbose, make_cmd);
 }
@@ -222,8 +222,17 @@ compile_pass (systemtap_session& s)
 
   // Run make
   string make_cmd = string("make")
-    + string (" -C \"") + module_dir + string("\"");
-  make_cmd += string(" M=\"") + s.tmpdir + string("\" modules");
+    + string (" -C \"") + module_dir + string("\""); // XXX: lex_cast_qstring?
+  make_cmd += string(" M=\"") + s.tmpdir + string("\"");
+
+  // Add architecture
+  make_cmd += string(" ARCH=") + lex_cast_qstring(s.architecture);
+
+  // Add any custom kbuild flags
+  for (unsigned k=0; k<s.kbuildflags.size(); k++)
+    make_cmd += string(" ") + lex_cast_qstring(s.kbuildflags[k]);
+
+  make_cmd += string (" modules");
 
   rc = run_make_cmd(s, make_cmd);
 
diff --git a/hash.cxx b/hash.cxx
index eac22f48..6e798f81 100644
--- a/hash.cxx
+++ b/hash.cxx
@@ -190,6 +190,9 @@ find_script_hash (systemtap_session& s, const string& script, const hash &base)
   for (unsigned i = 0; i < s.macros.size(); i++)
     h.add(s.macros[i]);
 
+  for (unsigned i = 0; i < s.kbuildflags.size(); i++)
+    h.add(s.kbuildflags[i]);
+
   // -d MODULE
   for (set<string>::iterator it = s.unwindsym_modules.begin();
        it != s.unwindsym_modules.end();
diff --git a/main.cxx b/main.cxx
index 15447efc..d62c2fac 100644
--- a/main.cxx
+++ b/main.cxx
@@ -106,11 +106,13 @@ usage (systemtap_session& s, int exitcode)
     clog << "              " << s.include_path[i] << endl;
   clog
     << "   -D NM=VAL  emit macro definition into generated C code" << endl
+    << "   -B NM=VAL  pass option to kbuild make" << endl
     << "   -R DIR     look in DIR for runtime, instead of" << endl
     << "              " << s.runtime_path << endl
     << "   -r DIR     cross-compile to kernel with given build tree; or else" << endl
     << "   -r RELEASE cross-compile to kernel /lib/modules/RELEASE/build, instead of" << endl
     << "              " << s.kernel_build_tree << endl
+    << "   -a ARCH    cross-compile to given architecture, instead of " << s.architecture << endl
     << "   -m MODULE  set probe module name, instead of " << endl
     << "              " << s.module_name << endl
     << "   -o FILE    send script output to file, instead of stdout. This supports" << endl
@@ -590,8 +592,8 @@ main (int argc, char * const argv [])
         { "unprivileged", 0, &long_opt, LONG_OPT_UNPRIVILEGED },
         { NULL, 0, NULL, 0 }
       };
-      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:m:kgPc:x:D:bs:uqwl:d:L:FS:",
-                                                          long_options, NULL);
+      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:a:m:kgPc:x:D:bs:uqwl:d:L:FS:B:",
+                             long_options, NULL);
       if (grc < 0)
         break;
       switch (grc)
@@ -711,6 +713,10 @@ main (int argc, char * const argv [])
           setup_kernel_release(s, optarg);
           break;
 
+        case 'a':
+          s.architecture = string(optarg);
+          break;
+
         case 'k':
           s.keep_tmpdir = true;
           s.use_cache = false; /* User wants to keep a usable build tree. */
@@ -792,6 +798,10 @@ main (int argc, char * const argv [])
           s.load_only = true;
 	  break;
 
+	case 'B':
+          s.kbuildflags.push_back (string (optarg));
+	  break;
+
         case 0:
           switch (long_opt)
             {
diff --git a/session.h b/session.h
index ea914425..24e6ae80 100644
--- a/session.h
+++ b/session.h
@@ -83,6 +83,7 @@ struct systemtap_session
   std::vector<std::string> include_path;
   std::vector<std::string> macros;
   std::vector<std::string> args;
+  std::vector<std::string> kbuildflags;
   std::string kernel_release;
   std::string kernel_base_release;
   std::string kernel_build_tree;
diff --git a/stap.1.in b/stap.1.in
index a45c90a6..fc72cf32 100644
--- a/stap.1.in
+++ b/stap.1.in
@@ -153,6 +153,10 @@ description of pass 2 for details.
 Add the given C preprocessor directive to the module Makefile.  These can
 be used to override limit parameters described below.
 .TP
+.BI \-B " NAME=VALUE"
+Add the given make directive to the kernel module build's make invocation.
+These can be used to add or override kconfig options.
+.TP
 .BI \-R " DIR"
 Look for the systemtap runtime sources in the given directory.
 .TP
diff --git a/testsuite/systemtap.base/cmd_parse.exp b/testsuite/systemtap.base/cmd_parse.exp
index 7f5f70d9..8824e6c4 100644
--- a/testsuite/systemtap.base/cmd_parse.exp
+++ b/testsuite/systemtap.base/cmd_parse.exp
@@ -1,5 +1,5 @@
 if {![installtest_p]} {
-    for {set i 0} { $i < 8} {incr i} {
+    for {set i 0} { $i < 16} {incr i} {
         untested cmd_parse$i
     }
     return
@@ -129,3 +129,29 @@ expect {
     eof { fail "cmd_parse14: eof" }
 }
 wait;catch {close}
+
+set uname [exec uname -r]
+spawn sh -c "stap -m do_not_cache_me -B kernelrelease -p4 -e 'probe begin {exit()}'"
+# the \r below is meant to match the "kernelrelease" output, as distinct from
+# any possible auxiliary make verbosity.
+expect {
+    -re "$uname\r" { pass "cmd_parse15" }
+    timeout { fail "cmd_parse15: timeout" }
+    eof { fail "cmd_parse15: eof" }
+}
+wait;catch {close}
+
+set uname [exec uname -m]
+spawn sh -c "stap -m do_not_cache_me -a $uname -p4 -e 'probe begin {exit()}'"
+# the \r below is meant to match the "kernelrelease" output, as distinct from
+# any possible auxiliary make verbosity.
+expect {
+    -re "do_not_cache_me.ko\r" { pass "cmd_parse16" }
+    timeout { fail "cmd_parse16: timeout" }
+    eof { fail "cmd_parse16: eof" }
+}
+wait;catch {close}
+
+
+# NB: when adding extra tests here, increment the ![installtest_p]
+# loop count too at the top.