[PING 2][PATCH v5 0/4] GDB support for DW_AT_trampoline

[Ijaz, Abdul B]

Ping!

Thanks & Best Regards
Abdul Basit

-----Original Message-----
From: Ijaz, Abdul B 
Sent: Sunday, September 3, 2023 9:14 PM
To: gdb-patches@sourceware.org
Cc: JiniSusan.George@amd.com; tom@tromey.com; eliz@gnu.org; blarsen@redhat.com
Subject: RE: [PING][PATCH v5 0/4] GDB support for DW_AT_trampoline

Ping!

Best Regards
Abdul Basit

-----Original Message-----
From: Ijaz, Abdul B <abdul.b.ijaz@intel.com> 
Sent: Wednesday, August 16, 2023 11:54 PM
To: gdb-patches@sourceware.org
Cc: Ijaz, Abdul B <abdul.b.ijaz@intel.com>; JiniSusan.George@amd.com; tom@tromey.com; eliz@gnu.org; blarsen@redhat.com
Subject: [PATCH v5 0/4] GDB support for DW_AT_trampoline

From: "Ijaz, Abdul B" <abdul.b.ijaz@intel.com>

Hi,

please find attached a series of patches that attempts to enable GDB to handle the DW_AT_trampoline attribute on functions and inlined functions.

DW_AT_trampoline can be emitted by the compiler for functions that are compiler generated trampolines (e.g. wrapping other function calls).
In doing so, the compiler can specify a target as the value of DW_AT_trampoline which the trampoline is wrapping.

This series enables GDB to recognize the DW_AT_trampoline and store the target for a given function.  Patch 3 adapts GDB's stepping behavior when dealing with trampolines and attempts to - by default - hide these trampolines from the user.  When about to step into a trampoline, instead, GDB will try and step through the trampoline and directly towards the target.  Patch 4 in V2 now skip trampoline frames in the stack for printing or finish command.  A new setting has been introduced to turn off this modified stepping behavior or printing of stack for trampolines.

The motivation for these patches comes from ifx which emits the attribute for some of its compiler generated functions.  As I do not know of any other compiler (especially gcc/gfortran) emitting DW_AT_trampoline, I added a gdb.dwarf2 test to this series in order to test the trampoline handling within GDB.

Changes since V4:
  * Fixed reverse finish for trampolines.
  * Elide trampoline frames in backtrace for frame-filters case.
  * Use target subroutine address instead of name in case of ref type
    trampoline target.
  * Fixed loops formatting and now split line where possible at ";".

V4 series of patches can be found here:
https://sourceware.org/pipermail/gdb-patches/2023-August/201263.html

No regression seen on testing x64/native-extended-gdbserver(-m32)/x32/
native-gdbserver test configurations for these changes using Ubuntu 22.

Thanks & Best Regards
Abdul Basit

Abdul Basit Ijaz (1):
  gdb: Skip trampoline frames in the stack for printing or finish
    command.

Nils-Christian Kempke (3):
  gdb, dwarf: add support for DW_AT_trampoline in DWARF reader
  gdb/symtab: add lookup for trampoline functions
  gdb/infrun: handle stepping through functions with DW_AT_trampoline

 gdb/NEWS                                      |  15 ++
 gdb/doc/gdb.texinfo                           |  47 ++++
 gdb/dwarf2/read.c                             |  46 +++-
 gdb/gdbtypes.c                                |  34 ++-
 gdb/gdbtypes.h                                | 113 +++++++-
 gdb/infcmd.c                                  |  13 +
 gdb/infrun.c                                  |  93 ++++++-
 gdb/infrun.h                                  |  10 +
 gdb/python/py-frame.c                         |  15 ++
 gdb/stack.c                                   |   8 +
 gdb/symtab.c                                  |  80 ++++++
 gdb/symtab.h                                  |  19 ++
 .../gdb.dwarf2/dw2-function-trampolines.c     |  80 ++++++
 .../gdb.dwarf2/dw2-function-trampolines.exp   | 245 ++++++++++++++++++
 gdb/testsuite/gdb.fortran/func-trampoline.exp |  69 +++++
 gdb/testsuite/gdb.fortran/func-trampoline.f90 |  39 +++
 .../gdb.fortran/mixed-lang-stack.exp          |  10 +-
 17 files changed, 922 insertions(+), 14 deletions(-)  create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-function-trampolines.c
 create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-function-trampolines.exp
 create mode 100644 gdb/testsuite/gdb.fortran/func-trampoline.exp
 create mode 100644 gdb/testsuite/gdb.fortran/func-trampoline.f90

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