From f2ee6fa6c841ddc37ba665909dafbc7294c34d64 Mon Sep 17 00:00:00 2001
From: Tao Liu <ltao@redhat.com>
Date: Fri, 17 Nov 2023 15:52:19 +0800
Subject: [PATCH 04/14] symbols: expand all kernel module symtable if not all
 expanded previously

There is an issue that, for kernel modules, "dis -rl" fails to display
modules code line number data after execute "bt" command in crash.

Without the patch:
  crsah> mod -S
  crash> bt
  PID: 1500     TASK: ff2bd8b093524000  CPU: 16   COMMAND: "lpfc_worker_0"
   #0 [ff2c9f725c39f9e0] machine_kexec at ffffffff8e0686d3
   ...snip...
   #8 [ff2c9f725c39fcc0] __lpfc_sli_release_iocbq_s4 at ffffffffc0f2f425 [lpfc]
   ...snip...
  crash> dis -rl ffffffffc0f60f82
  0xffffffffc0f60eb0 <lpfc_nlp_get>:      nopl   0x0(%rax,%rax,1) [FTRACE NOP]
  0xffffffffc0f60eb5 <lpfc_nlp_get+5>:    push   %rbp
  0xffffffffc0f60eb6 <lpfc_nlp_get+6>:    push   %rbx
  0xffffffffc0f60eb7 <lpfc_nlp_get+7>:    test   %rdi,%rdi

With the patch:
  crash> mod -S
  crash> bt
  PID: 1500     TASK: ff2bd8b093524000  CPU: 16   COMMAND: "lpfc_worker_0"
   #0 [ff2c9f725c39f9e0] machine_kexec at ffffffff8e0686d3
   ...snip...
   #8 [ff2c9f725c39fcc0] __lpfc_sli_release_iocbq_s4 at ffffffffc0f2f425 [lpfc]
   ...snip...
  crash> dis -rl ffffffffc0f60f82
  /usr/src/debug/kernel-4.18.0-425.13.1.el8_7/linux-4.18.0-425.13.1.el8_7.x86_64/drivers/scsi/lpfc/lpfc_hbadisc.c: 6756
  0xffffffffc0f60eb0 <lpfc_nlp_get>:      nopl   0x0(%rax,%rax,1) [FTRACE NOP]
  /usr/src/debug/kernel-4.18.0-425.13.1.el8_7/linux-4.18.0-425.13.1.el8_7.x86_64/drivers/scsi/lpfc/lpfc_hbadisc.c: 6759
  0xffffffffc0f60eb5 <lpfc_nlp_get+5>:    push   %rbp

The root cause is, after kernel module been loaded by mod command, the symtable
is not expanded in gdb side. crash bt or dis command will trigger such an
expansion. However the symtable expansion is different for the 2 commands:

The stack trace of "dis -rl" for symtable expanding:

  #0  0x00000000008d8d9f in add_compunit_symtab_to_objfile ...
  #1  0x00000000006d3293 in buildsym_compunit::end_symtab_with_blockvector ...
  #2  0x00000000006d336a in buildsym_compunit::end_symtab_from_static_block ...
  #3  0x000000000077e8e9 in process_full_comp_unit ...
  #4  process_queue ...
  #5  dw2_do_instantiate_symtab ...
  #6  0x000000000077ed67 in dw2_instantiate_symtab ...
  #7  0x000000000077f75e in dw2_expand_all_symtabs ...
  #8  0x00000000008f254d in gdb_get_line_number ...
  #9  0x00000000008f22af in gdb_command_funnel_1 ...
  #10 0x00000000008f2003 in gdb_command_funnel ...
  #11 0x00000000005b7f02 in gdb_interface ...
  #12 0x00000000005f5bd8 in get_line_number ...
  #13 0x000000000059e574 in cmd_dis ...

The stack trace of "bt" for symtable expanding:

  #0  0x00000000008d8d9f in add_compunit_symtab_to_objfile ...
  #1  0x00000000006d3293 in buildsym_compunit::end_symtab_with_blockvector ...
  #2  0x00000000006d336a in buildsym_compunit::end_symtab_from_static_block ...
  #3  0x000000000077e8e9 in process_full_comp_unit ...
  #4  process_queue ...
  #5  dw2_do_instantiate_symtab ...
  #6  0x000000000077ed67 in dw2_instantiate_symtab ...
  #7  0x000000000077f8ed in dw2_lookup_symbol ...
  #8  0x00000000008e6d03 in lookup_symbol_via_quick_fns ...
  #9  0x00000000008e7153 in lookup_symbol_in_objfile ...
  #10 0x00000000008e73c6 in lookup_symbol_global_or_static_iterator_cb ...
  #11 0x00000000008b99c4 in svr4_iterate_over_objfiles_in_search_order ...
  #12 0x00000000008e754e in lookup_global_or_static_symbol ...
  #13 0x00000000008e75da in lookup_static_symbol ...
  #14 0x00000000008e632c in lookup_symbol_aux ...
  #15 0x00000000008e5a7a in lookup_symbol_in_language ...
  #16 0x00000000008e5b30 in lookup_symbol ...
  #17 0x00000000008f2a4a in gdb_get_datatype ...
  #18 0x00000000008f22c0 in gdb_command_funnel_1 ...
  #19 0x00000000008f2003 in gdb_command_funnel ...
  #20 0x00000000005b7f02 in gdb_interface ...
  #21 0x00000000005f8a9f in datatype_info ...
  #22 0x0000000000599947 in cpu_map_size ...
  #23 0x00000000005a975d in get_cpus_online ...
  #24 0x0000000000637a8b in diskdump_get_prstatus_percpu ...
  #25 0x000000000062f0e4 in get_netdump_regs_x86_64 ...
  #26 0x000000000059fe68 in back_trace ...
  #27 0x00000000005ab1cb in cmd_bt ...

For the stacktrace of "dis -rl", it calls dw2_expand_all_symtabs() to expand
all symtable of the objfile, or "*.ko.debug" in our case. However for
the stacktrace of "bt", it doesn't expand all, but only a subset of symtable
which is enough to find a symbol by dw2_lookup_symbol(). As a result, the
objfile->compunit_symtabs, which is the head of a single linked list of
struct compunit_symtab, is not NULL but didn't contain all symtables. It
will not be reinitialized in gdb_get_line_number() by "dis -rl" because
!objfile_has_full_symbols(objfile) check will fail, so it cannot display
the proper code line number data.

Since objfile_has_full_symbols(objfile) check cannot ensure all symbols
been expanded, this patch add a new member as a flag for struct objfile
to record if all symbols have been expanded. The flag will be set only ofter
expand_all_symtabs been called.

Signed-off-by: Tao Liu <ltao@redhat.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 gdb-10.2.patch | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/gdb-10.2.patch b/gdb-10.2.patch
index d81030d946e8..2f7d585105aa 100644
--- a/gdb-10.2.patch
+++ b/gdb-10.2.patch
@@ -3187,3 +3187,53 @@ exit 0
        result = stringtab + symbol_entry->_n._n_n._n_offset;
      }
    else
+--- gdb-10.2/gdb/objfiles.h.orig
++++ gdb-10.2/gdb/objfiles.h
+@@ -712,6 +712,8 @@ struct objfile
+      next time.  If an objfile does not have the symbols, it will
+      never have them.  */
+   bool skip_jit_symbol_lookup = false;
++
++  bool all_symtabs_expanded = false;
+ };
+ 
+ /* A deleter for objfile.  */
+--- gdb-10.2/gdb/symfile.c.orig
++++ gdb-10.2/gdb/symfile.c
+@@ -1133,8 +1133,10 @@ symbol_file_add_with_addrs (bfd *abfd, const char *name,
+ 	printf_filtered (_("Expanding full symbols from %ps...\n"),
+ 			 styled_string (file_name_style.style (), name));
+ 
+-      if (objfile->sf)
++      if (objfile->sf) {
+ 	objfile->sf->qf->expand_all_symtabs (objfile);
++	objfile->all_symtabs_expanded = true;
++      }
+     }
+ 
+   /* Note that we only print a message if we have no symbols and have
+--- gdb-10.2/gdb/symtab.c.orig
++++ gdb-10.2/gdb/symtab.c
+@@ -7097,8 +7097,9 @@ gdb_get_line_number(struct gnu_request *req)
+                  */
+                 if (req->lm) {
+                         objfile = req->lm->loaded_objfile;
+-                        if (!objfile_has_full_symbols(objfile) && objfile->sf) {
++                        if (!objfile->all_symtabs_expanded && objfile->sf) {
+                                 objfile->sf->qf->expand_all_symtabs(objfile);
++                                objfile->all_symtabs_expanded = true;
+                                 sal = find_pc_line(pc, 0);
+                         }
+                 }
+@@ -7761,8 +7765,10 @@ iterate_datatypes (struct gnu_request *req)
+ {
+   for (objfile *objfile : current_program_space->objfiles ())
+     {
+-      if (objfile->sf)
++      if (objfile->sf) {
+         objfile->sf->qf->expand_all_symtabs(objfile);
++        objfile->all_symtabs_expanded = true;
++      }
+ 
+       for (compunit_symtab *cust : objfile->compunits ())
+         {
-- 
2.41.0