[PATCH 0/7 V2] Trust readonly sections if target has memory protection

[Yao Qi <yao@codesourcery.com>]

Here is the V2, to address comments to V1,

  - Warn about writes to readonly sections if trust-readonly-sections
is enabled. (patch 1/7)
  - Windows targets have memory protection. (patch 7/7)

Do some refactor in Windows related targets, add a new function
windows_init_abi (done by patch 3/7).  It paves the way for patch
7/7.

Below the description of this series in V1:
https://sourceware.org/ml/gdb-patches/2013-09/msg00193.html

When option "trust-readonly-sections" was introduced in this patch
http://www.sourceware.org/ml/gdb-patches/2002-01/msg00711.html, there
was the discussion to turn it on in default.  However, we didn't do
that because we have a concern that bad or buggy program may modify the
code on the non-memory protected system.  On the other hand, it is
highly recommended to turn this on in remote debugging.

I am wondering if we can teach GDB to trust read-only sections if it
knows the target system has memory protection.  For some targets, such
as linux, we know they do have memory protection.  This is what this
patch series tries to do.

This change improves GDB's out-of-box performance.  I wrote a
micro-benchmark to disassemble GDB in GDB in remote debugging
(native-gdbserver) on x86-linux, and collect the time usage
and the number of 'm' packets,

                    /wo patch     /w patch

time usage    :       0.44s        0.10
number of 'm' :       43157         4

As we can see, the number of RSP 'm' packet is reduced dramatically,
and the time usage is reduced to some extent.  In my experiment,
GDBserver is running natively, so connection speed is quite fast.  In
some slow connections, the improvement will be more.

*** BLURB HERE ***

Yao Qi (7):
  Emit a warning when writing to a readonly section and trust_readonly is true
  set trust-readonly-sections off in test cases
  New function windows_init_abi
  Trust readonly sections if target has memory protection
  DOC and NEWS
  Linux has memory protection.
  Windows has memory protection

 gdb/NEWS                                |    5 ++
 gdb/amd64-windows-tdep.c                |    5 +-
 gdb/arch-utils.c                        |    7 +++
 gdb/arch-utils.h                        |    2 +
 gdb/doc/gdb.texinfo                     |   11 ++++-
 gdb/gdbarch.c                           |   24 ++++++++++++
 gdb/gdbarch.h                           |    6 +++
 gdb/gdbarch.sh                          |    3 +
 gdb/i386-cygwin-tdep.c                  |    9 +---
 gdb/linux-tdep.c                        |   10 +++++
 gdb/target.c                            |   62 ++++++++++++++++++++++--------
 gdb/testsuite/gdb.base/break-always.exp |    4 ++
 gdb/testsuite/gdb.mi/mi-fill-memory.exp |    5 ++
 gdb/windows-tdep.c                      |   31 +++++++++++++++-
 gdb/windows-tdep.h                      |    6 +--
 15 files changed, 156 insertions(+), 34 deletions(-)

-- 
1.7.7.6