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>

9 files changed, 173 insertions, 2 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.
diff --git a/libdw/Makefile.am b/libdw/Makefile.am
index 6b7834af..4fda33bd 100644
--- a/libdw/Makefile.am
+++ b/libdw/Makefile.am
@@ -63,6 +63,7 @@ libdw_a_SOURCES = dwarf_begin.c dwarf_begin_elf.c dwarf_end.c dwarf_getelf.c \
 		  dwarf_linesrc.c dwarf_lineno.c dwarf_lineaddr.c \
 		  dwarf_linecol.c dwarf_linebeginstatement.c \
 		  dwarf_lineendsequence.c dwarf_lineblock.c \
+		  dwarf_linecontext.c dwarf_linefunctionname.c \
 		  dwarf_lineprologueend.c dwarf_lineepiloguebegin.c \
 		  dwarf_lineisa.c dwarf_linediscriminator.c \
 		  dwarf_lineop_index.c dwarf_line_file.c \
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
   };
 
diff --git a/libdw/dwarf_getsrclines.c b/libdw/dwarf_getsrclines.c
index 8fc48e1d..2c1d7a40 100644
--- a/libdw/dwarf_getsrclines.c
+++ b/libdw/dwarf_getsrclines.c
@@ -93,6 +93,8 @@ struct line_state
   struct linelist *linelist;
   size_t nlinelist;
   unsigned int end_sequence;
+  unsigned int context;
+  unsigned int function_name;
 };
 
 static inline void
@@ -139,6 +141,8 @@ add_new_line (struct line_state *state, struct linelist *new_line)
   SET (epilogue_begin);
   SET (isa);
   SET (discriminator);
+  SET (context);
+  SET (function_name);
 
 #undef SET
 
@@ -161,7 +165,7 @@ read_srclines (Dwarf *dbg,
      the stack.  Stack allocate some entries, only dynamically malloc
      when more than MAX.  */
 #define MAX_STACK_ALLOC 4096
-#define MAX_STACK_LINES MAX_STACK_ALLOC
+#define MAX_STACK_LINES (MAX_STACK_ALLOC / 2)
 #define MAX_STACK_FILES (MAX_STACK_ALLOC / 4)
 #define MAX_STACK_DIRS  (MAX_STACK_ALLOC / 16)
 
@@ -180,7 +184,9 @@ read_srclines (Dwarf *dbg,
       .prologue_end = false,
       .epilogue_begin = false,
       .isa = 0,
-      .discriminator = 0
+      .discriminator = 0,
+      .context = 0,
+      .function_name = 0
     };
 
   /* The dirs normally go on the stack, but if there are too many
@@ -648,6 +654,13 @@ read_srclines (Dwarf *dbg,
 	}
     }
 
+  unsigned int debug_str_offset = 0;
+  if (unlikely (linep == header_start + header_length - 4))
+    {
+      /* CUBINs contain an unsigned 4-byte offset */
+      debug_str_offset = read_4ubyte_unaligned_inc (dbg, linep);
+    }
+
   /* Consistency check.  */
   if (unlikely (linep != header_start + header_length))
     {
@@ -753,6 +766,8 @@ read_srclines (Dwarf *dbg,
 	      state.epilogue_begin = false;
 	      state.isa = 0;
 	      state.discriminator = 0;
+	      state.context = 0;
+	      state.function_name = 0;
 	      break;
 
 	    case DW_LNE_set_address:
@@ -831,6 +846,23 @@ read_srclines (Dwarf *dbg,
 	      get_uleb128 (state.discriminator, linep, lineendp);
 	      break;
 
+	    case DW_LNE_NVIDIA_inlined_call:
+	      if (unlikely (linep >= lineendp))
+		goto invalid_data;
+	      get_uleb128 (state.context, linep, lineendp);
+	      if (unlikely (linep >= lineendp))
+		goto invalid_data;
+	      get_uleb128 (state.function_name, linep, lineendp);
+	      state.function_name += debug_str_offset;
+	      break;
+
+	    case DW_LNE_NVIDIA_set_function_name:
+	      if (unlikely (linep >= lineendp))
+		goto invalid_data;
+	      get_uleb128 (state.function_name, linep, lineendp);
+	      state.function_name += debug_str_offset;
+	      break;
+
 	    default:
 	      /* Unknown, ignore it.  */
 	      if (unlikely ((size_t) (lineendp - (linep - 1)) < len))
diff --git a/libdw/dwarf_linecontext.c b/libdw/dwarf_linecontext.c
new file mode 100644
index 00000000..84572e22
--- /dev/null
+++ b/libdw/dwarf_linecontext.c
@@ -0,0 +1,45 @@
+/* Return context in line.
+   This file is part of elfutils.
+   Written by John Mellor-Crummey <johnmc@rice.edu>, 2021.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at
+       your option) any later version
+
+   or both in parallel, as here.
+
+   elfutils 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 copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "libdwP.h"
+
+
+Dwarf_Line*
+dwarf_linecontext (Dwarf_Lines* lines, Dwarf_Line *line)
+{
+  if (lines == NULL || line == NULL)
+    return NULL;
+  if (line->context == 0 || line->context >= lines->nlines)
+    return NULL;
+
+  return lines->info + (line->context - 1);
+}
diff --git a/libdw/dwarf_linefunctionname.c b/libdw/dwarf_linefunctionname.c
new file mode 100644
index 00000000..e194d212
--- /dev/null
+++ b/libdw/dwarf_linefunctionname.c
@@ -0,0 +1,52 @@
+/* Return function name in line.
+   This file is part of elfutils.
+   Written by John Mellor-Crummey <johnmc@rice.edu>, 2021.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at
+       your option) any later version
+
+   or both in parallel, as here.
+
+   elfutils 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 copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <string.h>
+#include "libdwP.h"
+
+
+const char *
+dwarf_linefunctionname (Dwarf *dbg, Dwarf_Line *line)
+{
+  if (dbg == NULL || line == NULL)
+    return NULL;
+  if (line->context == 0)
+    return NULL;
+
+  Elf_Data *str_data = dbg->sectiondata[IDX_debug_str];
+  if (str_data == NULL || line->function_name >= str_data->d_size
+      || memchr (str_data->d_buf + line->function_name, '\0',
+		 str_data->d_size - line->function_name) == NULL)
+    return NULL;
+
+  return (char *) str_data->d_buf + line->function_name;
+}
diff --git a/libdw/libdw.h b/libdw/libdw.h
index 77174d28..64d1689a 100644
--- a/libdw/libdw.h
+++ b/libdw/libdw.h
@@ -701,6 +701,15 @@ extern int dwarf_linediscriminator (Dwarf_Line *line, unsigned int *discp)
 extern const char *dwarf_linesrc (Dwarf_Line *line,
 				  Dwarf_Word *mtime, Dwarf_Word *length);
 
+/* Return the caller of this line if inlined.  If not inlined,
+   return NULL.  */
+extern Dwarf_Line *dwarf_linecontext (Dwarf_Lines *lines, Dwarf_Line *line);
+
+/* Return the function name in this line record. If this line is
+   inlined, this is the name of the function that was inlined. If this line
+   is not inlined, return NULL.  */
+extern const char *dwarf_linefunctionname (Dwarf *dbg, Dwarf_Line *line);
+
 /* Return file information.  The returned string is NULL when
    an error occurred, or the file path.  The file path is either absolute
    or relative to the compilation directory.  See dwarf_decl_file.  */
diff --git a/libdw/libdw.map b/libdw/libdw.map
index 8ab0a2a0..4f530378 100644
--- a/libdw/libdw.map
+++ b/libdw/libdw.map
@@ -360,3 +360,9 @@ ELFUTILS_0.177 {
     # presume that NULL is only returned on error (otherwise ELF_K_NONE).
     dwelf_elf_begin;
 } ELFUTILS_0.175;
+
+ELFUTILS_0.186 {
+  global:
+    dwarf_linecontext;
+    dwarf_linefunctionname;
+} ELFUTILS_0.177;
diff --git a/libdw/libdwP.h b/libdw/libdwP.h
index 48f3a943..360ad01a 100644
--- a/libdw/libdwP.h
+++ b/libdw/libdwP.h
@@ -303,6 +303,9 @@ struct Dwarf_Line_s
   unsigned int op_index:8;
   unsigned int isa:8;
   unsigned int discriminator:24;
+  /* These are currently only used for the NVIDIA extensions.  */
+  unsigned int context;
+  unsigned int function_name;
 };
 
 struct Dwarf_Lines_s