[binutils-gdb] gdb/jit: fix jit-reader linetable integrity

[Andrew Burgess]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d3685ec080cc5bfb9646cdc1f5ddda0c3da92b76

commit d3685ec080cc5bfb9646cdc1f5ddda0c3da92b76
Author: Yang Liu <liuyang22@iscas.ac.cn>
Date:   Mon Dec 23 00:33:30 2024 +0800

    gdb/jit: fix jit-reader linetable integrity
    
    The custom linetable functionality in GDB's JIT Interface has been broken
    since commit 1acc9dca423f78e44553928f0de839b618c13766.
    
    In that commit, linetables were made independent from the objfile, which
    requires objfile->section_offsets to be initialized. However, section_offsets
    were never initialized in objfiles generated by GDB's JIT Interface
    with custom jit-readers, leading to GDB crashes when stepping into JITed code
    blocks with the following command already executed:
    
      jit-reader-load libmygdbjitreader.so
    
    This patch fixes the issue by initializing the minimum section_offsets required
    for linetable parsing procedures.
    
    A minimal test is included.  The test sets up some very simple line
    table information, which is enough to trigger the bug.  However, the
    line table information is crafted such that none of the line table
    entries will end up being displayed in GDB's output when the test is
    run, as such, none of the expected output actually changes.
    
    It might be nice in the future to extend some of the jit tests to
    actually test hitting line table entries added via the jit reader.
    
    Approved-By: Tom Tromey <tom@tromey.com>

Diff:
---
 gdb/jit.c                           |  2 ++
 gdb/testsuite/gdb.base/jit-reader.c | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/gdb/jit.c b/gdb/jit.c
index 39c17a5ab98..9736f84cf87 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -665,6 +665,8 @@ jit_object_close_impl (struct gdb_symbol_callbacks *cb,
 
   objfile *objfile = objfile::make (nullptr, current_program_space,
 				    objfile_name.c_str (), OBJF_NOT_FILENAME);
+  objfile->section_offsets.push_back (0);
+  objfile->sect_index_text = 0;
   objfile->per_bfd->gdbarch = priv_data->gdbarch;
 
   for (gdb_symtab &symtab : obj->symtabs)
diff --git a/gdb/testsuite/gdb.base/jit-reader.c b/gdb/testsuite/gdb.base/jit-reader.c
index 414be072a67..78117f04179 100644
--- a/gdb/testsuite/gdb.base/jit-reader.c
+++ b/gdb/testsuite/gdb.base/jit-reader.c
@@ -62,6 +62,18 @@ read_debug_info (struct gdb_reader_funcs *self,
 		   (GDB_CORE_ADDR) symfile->function_stack_mangle.end,
 		   "jit_function_stack_mangle");
 
+  /* Add some line table information.  This ensures that GDB can handle
+     accepting this information, and can scan the table.  However, this
+     information is constructed such that none of the tests actually hit any
+     of these line entries.  */
+  struct gdb_line_mapping mangle_lines[] =
+    {
+      { 1, (GDB_CORE_ADDR) symfile->function_stack_mangle.begin + 0 },
+      { 0, (GDB_CORE_ADDR) symfile->function_stack_mangle.begin + 1 },
+    };
+  int mangle_nlines = sizeof (mangle_lines) / sizeof (mangle_lines[0]);
+  cbs->line_mapping_add (cbs, symtab, mangle_nlines, mangle_lines);
+
   cbs->block_open (cbs, symtab, NULL,
 		   (GDB_CORE_ADDR) symfile->function_add.begin,
 		   (GDB_CORE_ADDR) symfile->function_add.end,