Commit a9ffd048 authored Nov 27, 2020 by Masami Hiramatsu Committed by Arnaldo Carvalho de Melo Nov 27, 2020

perf probe: Change function definition check due to broken DWARF

Since some gcc generates a broken DWARF which lacks DW_AT_declaration
attribute from the subprogram DIE of function prototype.
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060

)

So, in addition to the DW_AT_declaration check, we also check the
subprogram DIE has DW_AT_inline or actual entry pc.

Committer testing:

  # cat /etc/fedora-release
  Fedora release 33 (Thirty Three)
  #

Before:

  # perf test vfs_getname
  78: Use vfs_getname probe to get syscall args filenames             : FAILED!
  79: Check open filename arg using perf trace + vfs_getname          : FAILED!
  81: Add vfs_getname probe to get syscall args filenames             : FAILED!
  #

After:

  # perf test vfs_getname
  78: Use vfs_getname probe to get syscall args filenames             : Ok
  79: Check open filename arg using perf trace + vfs_getname          : Ok
  81: Add vfs_getname probe to get syscall args filenames             : Ok
  #

Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Link: http://lore.kernel.org/lkml/160645613571.2824037.7441351537890235895.stgit@devnote2


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent ab4200c1

tools/perf/util/dwarf-aux.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -356,9 +356,25 @@ bool die_is_signed_type(Dwarf_Die *tp_die)
		bool die_is_func_def(Dwarf_Die *dw_die)
		{
		Dwarf_Attribute attr;
		Dwarf_Addr addr = 0;

		if (dwarf_tag(dw_die) != DW_TAG_subprogram)
		return false;

		if (dwarf_attr(dw_die, DW_AT_declaration, &attr))
		return false;

		return (dwarf_tag(dw_die) == DW_TAG_subprogram &&
		dwarf_attr(dw_die, DW_AT_declaration, &attr) == NULL);
		/*
		* DW_AT_declaration can be lost from function declaration
		* by gcc's bug #97060.
		* So we need to check this subprogram DIE has DW_AT_inline
		* or an entry address.
		*/
		if (!dwarf_attr(dw_die, DW_AT_inline, &attr) &&
		die_entrypc(dw_die, &addr) < 0)
		return false;

		return true;
		}

		/**

tools/perf/util/probe-finder.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1885,8 +1885,7 @@ static int line_range_search_cb(Dwarf_Die sp_die, void data)
		if (lr->file && strtailcmp(lr->file, dwarf_decl_file(sp_die)))
		return DWARF_CB_OK;

		if (die_is_func_def(sp_die) &&
		die_match_name(sp_die, lr->function)) {
		if (die_match_name(sp_die, lr->function) && die_is_func_def(sp_die)) {
		lf->fname = dwarf_decl_file(sp_die);
		dwarf_decl_line(sp_die, &lr->offset);
		pr_debug("fname: %s, lineno:%d\n", lf->fname, lr->offset);

Admin message