[binutils-gdb] gdbserver gnu/linux: stepping over breakpoint

[Yao Qi <qiyao at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c8f4bfdd120601d3841b2617b623412a47b8f35f

commit c8f4bfdd120601d3841b2617b623412a47b8f35f
Author: Yao Qi <yao.qi@linaro.org>
Date:   Thu Apr 9 10:20:48 2015 +0100

    gdbserver gnu/linux: stepping over breakpoint
    
    Hi,
    I see the following error on arm linux gdbserver,
    
    continue^M
    Continuing.^M
    ../../../binutils-gdb/gdb/gdbserver/linux-arm-low.c:458: A problem internal to GDBserver has been detected.^M
    raw_bkpt_type_to_arm_hwbp_type: unhandled raw type^M
    Remote connection closed^M
    (gdb) FAIL: gdb.base/cond-eval-mode.exp: hbreak: continue
    
    After we make GDBserver handling Zx/zx packet idempotent,
    
      [PATCH 3/3] [GDBserver] Make Zx/zx packet handling idempotent.
      https://sourceware.org/ml/gdb-patches/2014-04/msg00480.html
    
    > Now removal/insertion of all kinds of breakpoints/watchpoints, either
    > internal, or from GDB, always go through the target methods.
    
    GDBserver handles all kinds of breakpoints/watchpoints through target
    methods.  However, some target backends, such as arm, don't support Z0
    packet but need software breakpoint to do breakpoint stepping over in
    linux-low.c:start_step_over,
    
      if (can_hardware_single_step ())
        {
          step = 1;
        }
      else
        {
          CORE_ADDR raddr = (*the_low_target.breakpoint_reinsert_addr) ();
          set_reinsert_breakpoint (raddr);
          step = 0;
        }
    
    a software breakpoint is requested to the backend, and the error is
    triggered.  This problem should affect targets having
    breakpoint_reinsert_addr hooked.
    
    Instead of handling memory breakpoint in these affected linux backend,
    this patch handles memory breakpoint in linux_{insert,remove}_point,
    that, if memory breakpoint is requested, call
    {insert,remove}_memory_breakpoint respectively.  Then, it becomes
    unnecessary to handle memory breakpoint for linux x86 backend, so
    this patch removes the code there.
    
    This patch is tested with GDBserver on x86_64-linux and arm-linux
    (-marm, -mthumb).  Note that there are still some fails in
    gdb.base/cond-eval-mode.exp with -mthumb, because GDBserver doesn't
    know how to select the correct breakpoint instruction according to
    the arm-or-thumb-mode of requested address.  This is a separate
    issue, anyway.
    
    gdb/gdbserver:
    
    2015-04-09  Yao Qi  <yao.qi@linaro.org>
    
    	* linux-low.c (linux_insert_point): Call
    	insert_memory_breakpoint if TYPE is raw_bkpt_type_sw.
    	(linux_remove_point): Call remove_memory_breakpoint if type is
    	raw_bkpt_type_sw.
    	* linux-x86-low.c (x86_insert_point): Don't call
    	insert_memory_breakpoint.
    	(x86_remove_point): Don't call remove_memory_breakpoint.

Diff:
---
 gdb/gdbserver/ChangeLog       | 10 ++++++++++
 gdb/gdbserver/linux-low.c     |  8 ++++++--
 gdb/gdbserver/linux-x86-low.c |  6 ------
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 5abdac2..9bdc0de 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,13 @@
+2015-04-09  Yao Qi  <yao.qi@linaro.org>
+
+	* linux-low.c (linux_insert_point): Call
+	insert_memory_breakpoint if TYPE is raw_bkpt_type_sw.
+	(linux_remove_point): Call remove_memory_breakpoint if type is
+	raw_bkpt_type_sw.
+	* linux-x86-low.c (x86_insert_point): Don't call
+	insert_memory_breakpoint.
+	(x86_remove_point): Don't call remove_memory_breakpoint.
+
 2015-04-01  Pedro Alves  <palves@redhat.com>
 	    Cleber Rosa  <crosa@redhat.com>
 
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index e4c5420..6dd9224 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -5115,7 +5115,9 @@ static int
 linux_insert_point (enum raw_bkpt_type type, CORE_ADDR addr,
 		    int size, struct raw_breakpoint *bp)
 {
-  if (the_low_target.insert_point != NULL)
+  if (type == raw_bkpt_type_sw)
+    return insert_memory_breakpoint (bp);
+  else if (the_low_target.insert_point != NULL)
     return the_low_target.insert_point (type, addr, size, bp);
   else
     /* Unsupported (see target.h).  */
@@ -5126,7 +5128,9 @@ static int
 linux_remove_point (enum raw_bkpt_type type, CORE_ADDR addr,
 		    int size, struct raw_breakpoint *bp)
 {
-  if (the_low_target.remove_point != NULL)
+  if (type == raw_bkpt_type_sw)
+    return remove_memory_breakpoint (bp);
+  else if (the_low_target.remove_point != NULL)
     return the_low_target.remove_point (type, addr, size, bp);
   else
     /* Unsupported (see target.h).  */
diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c
index e293ba4..763df08 100644
--- a/gdb/gdbserver/linux-x86-low.c
+++ b/gdb/gdbserver/linux-x86-low.c
@@ -561,9 +561,6 @@ x86_insert_point (enum raw_bkpt_type type, CORE_ADDR addr,
 
   switch (type)
     {
-    case raw_bkpt_type_sw:
-      return insert_memory_breakpoint (bp);
-
     case raw_bkpt_type_hw:
     case raw_bkpt_type_write_wp:
     case raw_bkpt_type_access_wp:
@@ -590,9 +587,6 @@ x86_remove_point (enum raw_bkpt_type type, CORE_ADDR addr,
 
   switch (type)
     {
-    case raw_bkpt_type_sw:
-      return remove_memory_breakpoint (bp);
-
     case raw_bkpt_type_hw:
     case raw_bkpt_type_write_wp:
     case raw_bkpt_type_access_wp: