Add backtrace to kdesktop_lock exception handler

3 files changed, 349 insertions, 2 deletions

diff --git a/kdesktop/lock/CMakeLists.txt b/kdesktop/lock/CMakeLists.txt
index caa655f59..6694f4315 100644
--- a/kdesktop/lock/CMakeLists.txt
+++ b/kdesktop/lock/CMakeLists.txt
@@ -32,11 +32,11 @@ set( target kdesktop_lock )
 
 set( ${target}_SRCS
   lockprocess.cc lockdlg.cc infodlg.cc querydlg.cc sakdlg.cc
-  securedlg.cc autologout.cc main.cc
+  securedlg.cc autologout.cc main.cc backtrace_symbols.c
 )
 
 tde_add_executable( ${target} AUTOMOC
   SOURCES ${${target}_SRCS}
-  LINK kdesktopsettings-static dmctl-static kio-shared Xext ${GL_LIBRARY} "${LINKER_IMMEDIATE_BINDING_FLAGS}"
+  LINK kdesktopsettings-static dmctl-static kio-shared Xext bfd ${GL_LIBRARY} "${LINKER_IMMEDIATE_BINDING_FLAGS}"
   DESTINATION ${BIN_INSTALL_DIR}
 )
diff --git a/kdesktop/lock/backtrace_symbols.c b/kdesktop/lock/backtrace_symbols.c
new file mode 100644
index 000000000..69aa2d740
--- /dev/null
+++ b/kdesktop/lock/backtrace_symbols.c
@@ -0,0 +1,325 @@
+/*
+  A hacky replacement for backtrace_symbols in glibc
+
+  backtrace_symbols in glibc looks up symbols using dladdr which is limited in
+  the symbols that it sees. libbacktracesymbols opens the executable and shared
+  libraries using libbfd and will look up backtrace information using the symbol
+  table and the dwarf line information.
+
+  It may make more sense for this program to use libelf instead of libbfd.
+  However, I have not investigated that yet.
+
+  Derived from addr2line.c from GNU Binutils by Jeff Muizelaar
+
+  Copyright 2007 Jeff Muizelaar
+  Copyright 2012 Timothy Pearson
+*/
+
+/* addr2line.c -- convert addresses to line number and function name
+   Copyright 1997, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+   Contributed by Ulrich Lauther <Ulrich.Lauther@mchp.siemens.de>
+
+   This file was part of GNU Binutils.
+
+   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 2, 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, write to the Free Software
+   Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+#define fatal(a, b) exit(1)
+#define bfd_fatal(a) exit(1)
+#define bfd_nonfatal(a) exit(1)
+#define list_matching_formats(a) exit(1)
+
+/* 2 characters for each byte, plus 1 each for 0, x, and NULL */
+#define PTRSTR_LEN (sizeof(void *) * 2 + 3)
+#define true 1
+#define false 0
+
+#define _GNU_SOURCE
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <execinfo.h>
+#include <bfd.h>
+#include <libiberty.h>
+#include <dlfcn.h>
+#include <link.h>
+#include <demangle.h>
+
+
+static asymbol **syms;		/* Symbol table.  */
+
+/* 150 isn't special; it's just an arbitrary non-ASCII char value.  */
+#define OPTION_DEMANGLER	(150)
+
+static void slurp_symtab(bfd * abfd);
+static void find_address_in_section(bfd *abfd, asection *section, void *data);
+
+/* Read in the symbol table.  */
+
+static void slurp_symtab(bfd * abfd)
+{
+	long symcount;
+	unsigned int size;
+
+	if ((bfd_get_file_flags(abfd) & HAS_SYMS) == 0)
+		return;
+
+	symcount = (long)bfd_read_minisymbols(abfd, false, (void**) & syms, &size);
+	if (symcount == 0)
+		symcount = bfd_read_minisymbols(abfd, true /* dynamic */ ,
+						(void**) & syms, &size);
+
+	if (symcount < 0)
+		bfd_fatal(bfd_get_filename(abfd));
+}
+
+/* These global variables are used to pass information between
+   translate_addresses and find_address_in_section.  */
+
+static bfd_vma pc;
+static const char *filename;
+static const char *functionname;
+static unsigned int line;
+static int found;
+
+/* Look for an address in a section.  This is called via
+   bfd_map_over_sections.  */
+
+static void find_address_in_section(bfd *abfd, asection *section, void *data __attribute__ ((__unused__)) )
+{
+	bfd_vma vma;
+	bfd_size_type size;
+
+	if (found)
+		return;
+
+	if ((bfd_get_section_flags(abfd, section) & SEC_ALLOC) == 0)
+		return;
+
+	vma = bfd_get_section_vma(abfd, section);
+	if (pc < vma)
+		return;
+
+	size = bfd_section_size(abfd, section);
+	if (pc >= vma + size)
+		return;
+
+	found = bfd_find_nearest_line(abfd, section, syms, pc - vma,
+				      &filename, &functionname, &line);
+}
+
+/* Read hexadecimal addresses from stdin, translate into
+   file_name:line_number and optionally function name.  */
+
+enum { Count, Print };
+
+static char** translate_addresses_buf(bfd * abfd, bfd_vma *addr, int naddr)
+{
+	int naddr_orig = naddr;
+	char b;
+	int total  = 0;
+	int state;
+	char *buf = &b;
+	int len = 0;
+	char **ret_buf = NULL;
+
+	/* iterate over the formating twice.
+	 * the first time we count how much space we need
+	 * the second time we do the actual printing */
+	for (state=Count; state<=Print; state++) {
+		if (state == Print) {
+			ret_buf = (char**)malloc(total + sizeof(char*)*naddr);
+			buf = (char*)(ret_buf + naddr);
+			len = total;
+		}
+		while (naddr) {
+			if (state == Print)
+				ret_buf[naddr-1] = buf;
+			pc = addr[naddr-1];
+	
+			found = false;
+			bfd_map_over_sections(abfd, find_address_in_section,
+			(PTR) NULL);
+	
+			if (!found) {
+				total += snprintf(buf, len, "[0x%llx] \?\?() \?\?:0",(long long unsigned int) addr[naddr-1]) + 1;
+			} else {
+				const char *name;
+	
+				name = functionname;
+				if (name == NULL || *name == '\0')
+					name = "??";
+				if (filename != NULL) {
+					const char *h;
+	
+					h = strrchr(filename, '/');
+					if (h != NULL)
+						filename = h + 1;
+				}
+	
+				char* funcname = cplus_demangle(name, DMGL_AUTO);
+				if (funcname) {
+					// demangling succeeded
+					total += snprintf(buf, len, "%s:%u\t%s()", filename ? filename : "??", line, funcname) + 1;
+				}
+				else {
+					// demangling failed
+					total += snprintf(buf, len, "%s:%u\t%s()", filename ? filename : "??", line, name) + 1;
+				}
+			}
+			if (state == Print) {
+				/* set buf just past the end of string */
+				buf = buf + total + 1;
+			}
+			naddr--;
+		}
+		naddr = naddr_orig;
+	}
+	return ret_buf;
+}
+/* Process a file.  */
+
+static char **process_file(const char *file_name, bfd_vma *addr, int naddr)
+{
+	bfd *abfd;
+	char **matching;
+	char **ret_buf;
+
+	abfd = bfd_openr(file_name, NULL);
+
+	if (abfd == NULL)
+		bfd_fatal(file_name);
+
+	if (bfd_check_format(abfd, bfd_archive))
+		fatal("%s: can not get addresses from archive", file_name);
+
+	if (!bfd_check_format_matches(abfd, bfd_object, &matching)) {
+		bfd_nonfatal(bfd_get_filename(abfd));
+		if (bfd_get_error() ==
+		    bfd_error_file_ambiguously_recognized) {
+			list_matching_formats(matching);
+			free(matching);
+		}
+		xexit(1);
+	}
+
+	slurp_symtab(abfd);
+
+	ret_buf = translate_addresses_buf(abfd, addr, naddr);
+
+	if (syms != NULL) {
+		free(syms);
+		syms = NULL;
+	}
+
+	bfd_close(abfd);
+	return ret_buf;
+}
+
+#define MAX_DEPTH 16
+
+struct file_match {
+	const char *file;
+	void *address;
+	void *base;
+	void *hdr;
+};
+
+static int find_matching_file(struct dl_phdr_info *info,
+		size_t size, void *data)
+{
+	struct file_match *match = data;
+	/* This code is modeled from Gfind_proc_info-lsb.c:callback() from libunwind */
+	long n;
+	const ElfW(Phdr) *phdr;
+	ElfW(Addr) load_base = info->dlpi_addr;
+	phdr = info->dlpi_phdr;
+	for (n = info->dlpi_phnum; --n >= 0; phdr++) {
+		if (phdr->p_type == PT_LOAD) {
+			ElfW(Addr) vaddr = phdr->p_vaddr + load_base;
+			if (match->address >= (void*)vaddr && match->address < (void*)(vaddr + phdr->p_memsz)) {
+				/* we found a match */
+				match->file = info->dlpi_name;
+				match->base = (void*)info->dlpi_addr;
+			}
+		}
+	}
+	return 0;
+}
+
+char **backtrace_symbols(void *const *buffer, int size)
+{
+	int stack_depth = size - 1;
+	int x,y;
+	/* discard calling function */
+	int total = 0;
+
+	char ***locations;
+	char **final;
+	char *f_strings;
+
+	locations = (char***)malloc(sizeof(char**) * (stack_depth+1));
+
+	bfd_init();
+	for(x=stack_depth, y=0; x>=0; x--, y++){
+		struct file_match match = { .address = buffer[x] };
+		char **ret_buf;
+		bfd_vma addr;
+		dl_iterate_phdr(find_matching_file, &match);
+		addr = buffer[x] - match.base;
+		if (match.file && strlen(match.file))
+			ret_buf = process_file(match.file, &addr, 1);
+		else
+			ret_buf = process_file("/proc/self/exe", &addr, 1);
+		locations[x] = ret_buf;
+		total += strlen(ret_buf[0]) + 1;
+	}
+
+	/* allocate the array of char* we are going to return and extra space for
+	 * all of the strings */
+	final = (char**)malloc(total + (stack_depth + 1) * sizeof(char*));
+	/* get a pointer to the extra space */
+	f_strings = (char*)(final + stack_depth + 1);
+
+	/* fill in all of strings and pointers */
+	for(x=stack_depth; x>=0; x--){
+		strcpy(f_strings, locations[x][0]);
+		free(locations[x]);
+		final[x] = f_strings;
+		f_strings += strlen(f_strings) + 1;
+	}
+
+	free(locations);
+
+	return final;
+}
+
+void
+backtrace_symbols_fd(void *const *buffer, int size, int fd)
+{
+        int j;
+        char **strings;
+
+        strings = backtrace_symbols(buffer, size);
+        if (strings == NULL) {
+		perror("backtrace_symbols");
+		exit(EXIT_FAILURE);
+        }
+
+        for (j = 0; j < size; j++)
+		printf("%s\n", strings[j]);
+
+        free(strings);
+}
+
diff --git a/kdesktop/lock/lockprocess.cc b/kdesktop/lock/lockprocess.cc
index 3c37090a6..70836c26c 100644
--- a/kdesktop/lock/lockprocess.cc
+++ b/kdesktop/lock/lockprocess.cc
@@ -18,6 +18,8 @@
 
 #include <config.h>
 
+#include <execinfo.h>
+
 #include "lockprocess.h"
 #include "lockdlg.h"
 #include "infodlg.h"
@@ -129,9 +131,29 @@ static Window gVRootData = 0;
 static Atom   gXA_VROOT;
 static Atom   gXA_SCREENSAVER_VERSION;
 
+void print_trace()
+{
+	void *array[10];
+	size_t size;
+	char **strings;
+	size_t i;
+
+	size = backtrace (array, 10);
+	strings = backtrace_symbols (array, size);
+
+	printf ("[kdesktop_lock] Obtained %zd stack frames.\n\r", size);
+
+	for (i = 0; i < size; i++) {
+		printf ("[kdesktop_lock] %s\n\r", strings[i]);
+	}
+
+	free (strings);
+}
+
 static void segv_handler(int)
 {
 	printf("[kdesktop_lock] WARNING: A fatal exception was encountered.  Trapping and ignoring it so as not to compromise desktop security...\n\r");
+	print_trace();
 	sleep(1);
 }