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 <[email protected]>
Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/libdw/dwarf.h b/libdw/dwarf.h
index 19a4be96..3ce7f236 100644
--- a/libdw/dwarf.h
+++ b/libdw/dwarf.h
@@ -844,6 +844,10 @@ enum
     DW_LNE_set_discriminator = 4,
 
     DW_LNE_lo_user = 128,
+
+    DW_LNE_NVIDIA_inlined_call = 144,
+    DW_LNE_NVIDIA_set_function_name = 145,
+
     DW_LNE_hi_user = 255
   };