libdw, readelf: Read inlining info in NVIDIA extended line map

As of CUDA 11.2, NVIDIA added extensions to the line map section
of CUDA binaries to represent inlined functions. These extensions
include

 - two new fields in a line table row to represent inline
   information: context, and functionname,

 - two new DWARF extended opcodes: DW_LNE_NVIDIA_inlined_call,
   DW_LNE_NVIDIA_set_function_name,

 - an additional word in the line table header that indicates
   the offset in the .debug_str function where the function
   names for this line table begin, and

A line table row for an inlined function contains a non-zero "context"
value. The “context” field indicates the index of the line table row
that serves as the call site for an inlined context.

The "functionname" field in a line table row is only meaningful if the
"context" field of the row is non-zero. A meaningful "functionname"
field contains an index into the .debug_str section relative to the
base offset established in the line table header; the position in the
.debug_str section indicates the name of the inlined function.

These extensions resemble the proposed DWARF extensions
(http://dwarfstd.org/ShowIssue.php?issue=140906.1) by Cary Coutant,
but are not identical.

This commit integrates support for handling NVIDIA's extended line
maps into elfutil's libdw library, by adding two functions
dwarf_linecontext and dwarf_linefunctionname, and the readelf
--debug-dump=line command line utility.

Signed-off-by: John M Mellor-Crummey <johnmc@rice.edu>
Signed-off-by: Mark Wielaard <mark@klomp.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 38e6efb2..ca742e6b 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,22 @@
+2021-10-20  John M Mellor-Crummey  <johnmc@rice.edu>
+
+	* dwarf_linecontext.c: New file.
+	* dwarf_linefunctionname.c: Likewise.
+	* Makefile.am (libdw_a_SOURCES): Add dwarf_linecontext.c and
+	dwarf_linefunctionname.c
+	* dwarf.h: Add DW_LNE_NVIDIA_inlined_call and
+	DW_LNE_NVIDIA_set_function_name.
+	* dwarf_getsrclines.c (struct line_state): Add context and
+	function_name fields.
+	(add_new_line): Set context and function_name.
+	(MAX_STACK_LINES): Reduce to MAX_STACK_ALLOC / 2.
+	(read_srclines): Initialize context and function_name.  Try to
+	read debug_str_offset if available.  Handle
+	DW_LNE_NVIDIA_inlined_call and DW_LNE_NVIDIA_set_function_name.
+	* libdw.h (dwarf_linecontext): New declaration.
+	(dwarf_linefunctionname): Likewise.
+	* libdw.map (ELFUTILS_0.186): New section.
+
 2021-11-08  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_begin_elf.c (scn_dwarf_type): New function.