From: Dodji Seketeli Date: Thu, 13 Aug 2015 13:59:41 +0000 (+0200) Subject: Fix finding split debug info files not located by the build-id mechanism X-Git-Tag: elfutils-0.164~48 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b901b5e742e03d781fe9b6ecf030d6d297948018;p=thirdparty%2Felfutils.git Fix finding split debug info files not located by the build-id mechanism [This bug has been found by using elfutils in the context of libabigail. The initial bug report is https://sourceware.org/bugzilla/show_bug.cgi?id=18792. The interesting comments start at is https://sourceware.org/bugzilla/show_bug.cgi?id=18792#c4] suppose we have a debug info file that is located at a /prefix1/usr/lib/debug/prefix2/libfoo.so. Suppose also that the debug info describes a binary that is located at /prefix1/prefix2/libfoo.so Suppose the debug_link property inside the binary /prefix1/prefix2/libfoo.so correctly contains the string "libfoo.so" that designates the name of the debug info file. The problem is, when find_debuginfo_in_path() is called with its file_name parameter set to "/prefix1/prefix2/libfoo.so" and mod->dwfl->callbacks->debuginfo_path set to "/prefix1/lib/debug/", it fails to locate the debug info file libfoo.so under "/prefix1/usr/lib/debug/prefix2/". This patch fixes the issue by making find_debuginfo_in_path() try all the sub-strings of "/prefix1/prefix2/libfoo.so "under" "/prefix1/usr/lib/debug/", to find libfoo.so. That is, it tries, in order: - /prefix1/usr/lib/debug/prefix1/prefix2/libfoo.so - /prefix1/usr/lib/debug/prefix2/libfoo.so <-- and boom, it finds it! Note that the patch tries the variations between the two candidates above too. The patch uses a goto. I dislike gotos like anyone else, but then here, not using this would imply a bigger change of the logic of that function. So I am proposing the scheme based on the goto instead. * libdwfl/find-debuginfo.c (find_debuginfo_in_path): Try to locate the debug info file named debuglink_file under mod->dwfl->callbacks->debuginfo_path, by looking at the set of sub-trees under mod->dwfl->callbacks->debuginfo_path which is common to the set of non-absolute parent trees of file_name. https://bugzilla.redhat.com/show_bug.cgi?id=1253367 Signed-off-by: Dodji Seketeli Signed-off-by: Mark Wielaard --- diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog index 5059be6d2..3e36aa757 100644 --- a/libdwfl/ChangeLog +++ b/libdwfl/ChangeLog @@ -1,3 +1,12 @@ +2015-08-14 Dodji Seketeli + + * find-debuginfo.c (find_debuginfo_in_path): Try to locate the + debug info file named debuglink_file under + mod->dwfl->callbacks->debuginfo_path, by looking at + the set of sub-trees under mod->dwfl->callbacks->debuginfo_path + which is common to the set of non-absolute parent trees of + file_name. + 2015-06-18 Mark Wielaard * find-debuginfo.c (try_open): Free fname on all failure paths. diff --git a/libdwfl/find-debuginfo.c b/libdwfl/find-debuginfo.c index 1faa494d8..6b8d1ac4b 100644 --- a/libdwfl/find-debuginfo.c +++ b/libdwfl/find-debuginfo.c @@ -252,7 +252,15 @@ find_debuginfo_in_path (Dwfl_Module *mod, const char *file_name, dir = p; if (mod->dw == NULL) { - subdir = file_dirname + 1; + subdir = file_dirname; + /* We want to explore all sub-subdirs. Chop off one slash + at a time. */ + explore_dir: + subdir = strchr (subdir, '/'); + if (subdir != NULL) + subdir = subdir + 1; + if (subdir && *subdir == 0) + continue; file = debuglink_file; } else @@ -292,6 +300,9 @@ find_debuginfo_in_path (Dwfl_Module *mod, const char *file_name, } break; } + /* If possible try again with a sub-subdir. */ + if (mod->dw == NULL && subdir) + goto explore_dir; continue; default: goto fail_free; diff --git a/libdwfl/libdwfl.h b/libdwfl/libdwfl.h index 2bb4f455a..1098c833e 100644 --- a/libdwfl/libdwfl.h +++ b/libdwfl/libdwfl.h @@ -275,12 +275,14 @@ extern int dwfl_module_build_id (Dwfl_Module *mod, In searches for debuginfo by name, if the remainder of the element is empty, the directory containing the main file is tried; if it's an absolute path name, the absolute directory path - containing the main file is taken as a subdirectory of this path; - a relative path name is taken as a subdirectory of the directory - containing the main file. Hence for /bin/ls, the default string - ":.debug:/usr/lib/debug" says to look in /bin, then /bin/.debug, - then /usr/lib/debug/bin, for the file name in the .gnu_debuglink - section (or "ls.debug" if none was found). */ + (and any subdirectory of that path) containing the main file is + taken as a subdirectory of this path; a relative path name is taken + as a subdirectory of the directory containing the main file. + Hence for /usr/bin/ls, the default string ":.debug:/usr/lib/debug" + says to look in /usr/bin, then /usr/bin/.debug, then the path subdirs + under /usr/lib/debug, in the order /usr/lib/debug/usr/bin, then + /usr/lib/debug/bin, and finally /usr/lib/debug, for the file name in + the .gnu_debuglink section (or "ls.debug" if none was found). */ /* Standard find_elf callback function working solely on build ID. This can be tried first by any find_elf callback, to use the