Add -w/--where to show backtraces of traced functions.

- add libunwind as a dep to configure
- add a command line option to show backtraces from traced library functions
- best guess at autoconf stuff, seems to work x86_64 and i686
- NOT TESTED ON ANY OTHER PLATFORMS!

ChangeLog

@@ -1,3 +1,14 @@
+2010-10-31  Joe Damato <ice799@gmail.com>
+
+    * Makefile.am: Add autotool support for libunwind.
+    * configure.ac: Ditto.
+    * common.h: New structure fields for libunwind.
+    * execute_program.c: Initialize libunwind.
+    * proc.c: Ditto.
+    * options.c: New command line option (-w).
+    * options.h: New options parameter for libunwind.
+    * output.c: Use libunwind to do backtraces.
+
 2010-10-18  Petr Machata <pmachata@redhat.com>
 
     * sysdeps/linux-gnu/s390/trace.c: Support 5th argument fetching on s390.

Makefile.am

@@ -28,6 +28,9 @@ libltrace_la_LIBADD = \
 	$(libelf_LIBS) \
 	$(liberty_LIBS) \
 	$(libsupcxx_LIBS) \
+	$(libunwind_LIBS) \
+	$(libunwind_ptrace_LIBS) \
+	$(libunwind_arch_LIBS) \
 	sysdeps/libos.la
 
 

common.h

@@ -1,3 +1,7 @@
+#if defined(HAVE_LIBUNWIND)
+#include <libunwind.h>
+#endif /* defined(HAVE_LIBUNWIND) */
+
 #include <sys/types.h>
 #include <sys/time.h>
 #include <stdio.h>
@@ -186,6 +190,12 @@ struct Process {
 	/* output: */
 	enum tof type_being_displayed;
 
+#if defined(HAVE_LIBUNWIND)
+	/* libunwind address space */
+	unw_addr_space_t unwind_as;
+	void *unwind_priv;
+#endif /* defined(HAVE_LIBUNWIND) */
+
 	Process * next;
 };
 

configure.ac

@@ -62,6 +62,32 @@ AC_CHECK_LIB([supc++], [__cxa_demangle], [
 AC_SUBST(libsupcxx_LIBS)
 
 
+# HAVE_LIBUNWIND
+AC_ARG_WITH(libunwind,
+[  --with-libunwind            Use libunwind frame unwinding support],
+[case "${withval}" in
+  yes)  enable_libunwind=yes ;;
+  no)   enable_libunwind=no ;;
+  *)    AC_MSG_ERROR(bad value ${withval} for GDB with-libunwind option) ;;
+esac],[
+  AC_CHECK_HEADERS(libunwind.h)
+  AC_CHECK_HEADERS(libunwind-ptrace.h)
+  if test x"$ac_cv_header_libunwind_h" = xyes; then
+    enable_libunwind=yes;
+  fi
+])
+
+if test x"$enable_libunwind" = xyes; then
+  AC_CHECK_LIB(unwind, backtrace, libunwind_LIBS=-lunwind, libunwind_LIBS=)
+  AC_SUBST(libunwind_LIBS)
+  AC_CHECK_LIB(unwind-ptrace, _UPT_create, libunwind_ptrace_LIBS=-lunwind-ptrace, libunwind_ptrace_LIBS=)
+  AC_SUBST(libunwind_ptrace_LIBS)
+  AC_CHECK_LIB(unwind-${HOST_CPU}, _U${HOST_CPU}_init_remote, libunwind_arch_LIBS=-lunwind-${HOST_CPU}, libunwind_arch_LIBS=)
+  AC_SUBST(libunwind_arch_LIBS)
+  AC_DEFINE([HAVE_LIBUNWIND], [1], [we have libunwind])
+fi
+
+
 # HAVE_ELF_C_READ_MMAP
 AC_MSG_CHECKING([whether elf_begin accepts ELF_C_READ_MMAP])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <gelf.h>]], [[

execute_program.c

@@ -1,5 +1,9 @@
 #include "config.h"
 
+#if defined(HAVE_LIBUNWIND)
+#include <libunwind-ptrace.h>
+#endif /* defined(HAVE_LIBUNWIND) */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
@@ -87,5 +91,9 @@ execute_program(Process *sp, char **argv) {
 
 	sp->pid = pid;
 
+#if defined(HAVE_LIBUNWIND)
+	sp->unwind_priv = _UPT_create(pid);
+#endif /* defined(HAVE_LIBUNWIND) */
+
 	return;
 }

options.c

@@ -100,6 +100,9 @@ usage(void) {
 		"  -T                  show the time spent inside each call.\n"
 		"  -u USERNAME         run command with the userid, groupid of username.\n"
 		"  -V, --version       output version information and exit.\n"
+#if defined(HAVE_LIBUNWIND)
+		"  -w=NR, --where=NR   print backtrace showing NR stack frames at most.\n"
+#endif /* defined(HAVE_LIBUNWIND) */
 		"  -x NAME             treat the global NAME like a library subroutine.\n"
 #ifdef PLT_REINITALISATION_BP
 		"  -X NAME             same as -x; and PLT's will be initialized by here.\n"
@@ -183,6 +186,9 @@ process_options(int argc, char **argv) {
 	options.output = stderr;
 	options.no_plt = 0;
 	options.no_signals = 0;
+#if defined(HAVE_LIBUNWIND)
+	options.bt_depth = -1;
+#endif /* defined(HAVE_LIBUNWIND) */
 
 	guess_cols();
 
@@ -204,13 +210,20 @@ process_options(int argc, char **argv) {
 			{"version", 0, 0, 'V'},
 			{"no-plt", 0, 0, 'g'},
 			{"no-signals", 0, 0, 'b'},
+#if defined(HAVE_LIBUNWIND)
+			{"where", 1, 0, 'w'},
+#endif /* defined(HAVE_LIBUNWIND) */
 			{0, 0, 0, 0}
 		};
 		c = getopt_long(argc, argv, "+cfhiLrStTVgb"
 # ifdef USE_DEMANGLE
 				"C"
 # endif
+#if defined(HAVE_LIBUNWIND)
+				"a:A:D:e:F:l:n:o:p:s:u:x:X:w:", long_options,
+#else /* !defined(HAVE_LIBUNWIND) */
 				"a:A:D:e:F:l:n:o:p:s:u:x:X:", long_options,
+#endif
 				&option_index);
 		if (c == -1) {
 			break;
@@ -313,6 +326,11 @@ process_options(int argc, char **argv) {
 		case 'n':
 			options.indent = atoi(optarg);
 			break;
+#if defined(HAVE_LIBUNWIND)
+		case 'w':
+			options.bt_depth = atoi(optarg);
+			break;
+#endif /* defined(HAVE_LIBUNWIND) */
 		case 'o':
 			options.output = fopen(optarg, "w");
 			if (!options.output) {

options.h

@@ -16,6 +16,9 @@ struct options_t {
 	int follow;     /* trace child processes */
 	int no_plt;     /* set bps on PLT entries */
 	int no_signals; /* don't print signals */
+#if defined(HAVE_LIBUNWIND)
+	int bt_depth;	 /* how may levels of stack frames to show */
+#endif /* defined(HAVE_LIBUNWIND) */
 };
 extern struct options_t options;
 

output.c

@@ -297,6 +297,28 @@ output_right(enum tof type, Process *proc, char *function_name) {
 			(int)current_time_spent.tv_usec);
 	}
 	fprintf(options.output, "\n");
+
+#if defined(HAVE_LIBUNWIND)
+	if (options.bt_depth > 0) {
+		unw_cursor_t cursor;
+		unw_word_t ip, sp;
+		int unwind_depth = options.bt_depth;
+		char fn_name[100];
+
+		unw_init_remote(&cursor, proc->unwind_as, proc->unwind_priv);
+		while (unwind_depth) {
+			unw_get_reg(&cursor, UNW_REG_IP, &ip);
+			unw_get_reg(&cursor, UNW_REG_SP, &sp);
+			unw_get_proc_name(&cursor, fn_name, 100, NULL);
+			fprintf(options.output, "\t\t\t%s (ip = 0x%lx)\n", fn_name, (long) ip);
+			if (unw_step(&cursor) <= 0)
+				break;
+			unwind_depth--;
+		}
+		fprintf(options.output, "\n");
+	}
+#endif /* defined(HAVE_LIBUNWIND) */
+
 	current_proc = 0;
 	current_column = 0;
 }

proc.c

@@ -1,3 +1,10 @@
+#include "config.h"
+
+#if defined(HAVE_LIBUNWIND)
+#include <libunwind.h>
+#include <libunwind-ptrace.h>
+#endif /* defined(HAVE_LIBUNWIND) */
+
 #include <sys/types.h>
 #include <string.h>
 #include <stdio.h>
@@ -18,11 +25,21 @@ open_program(char *filename, pid_t pid) {
 	proc->breakpoints_enabled = -1;
 	if (pid) {
 		proc->pid = pid;
+#if defined(HAVE_LIBUNWIND)
+		proc->unwind_priv = _UPT_create(pid);
+	} else {
+		proc->unwind_priv = NULL;
+#endif /* defined(HAVE_LIBUNWIND) */
 	}
+
 	breakpoints_init(proc);
 
 	proc->next = list_of_processes;
 	list_of_processes = proc;
+
+#if defined(HAVE_LIBUNWIND)
+	proc->unwind_as = unw_create_addr_space(&_UPT_accessors, 0);
+#endif /* defined(HAVE_LIBUNWIND) */
 	return proc;
 }