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[binutils-gdb] Fix inferior memory reading in GDBServer for arm/aarch32


https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=694b382c67a4fc656f30acbc74776c5e9cb53622

commit 694b382c67a4fc656f30acbc74776c5e9cb53622
Author: Antoine Tremblay <antoine.tremblay@ericsson.com>
Date:   Mon Jan 9 12:39:07 2017 -0500

    Fix inferior memory reading in GDBServer for arm/aarch32
    
    Before this patch, some functions would read the inferior memory with
    (*the_target)->read_memory, which returns the raw memory, rather than the
    shadowed memory.
    
    This is wrong since these functions do not expect to read a breakpoint
    instruction and can lead to invalid behavior.
    
    Use of raw memory in get_next_pcs_read_memory_unsigned_integer for example
    could lead to get_next_pc returning an invalid pc.
    
    Here's how this would happen:
    
    In non-stop:
    
    the user issues:
    
    thread 1
    step&
    thread 2
    step&
    thread 3
    step&
    
    In a similar way as non-stop-fair-events.exp (threads are looping).
    
    GDBServer:
    
     linux_resume is called
     GDBServer has pending events,
     threads are not resumed and single-step breakpoint for thread 1 not installed.
    
     linux_wait_1 is called with a pending event on thread 2 at pc A
     GDBServer handles the event and calls proceed_all_lwps
     This calls proceed_one_lwp and installs single-step breakpoints on all
     the threads that need one.
    
     Now since thread 1 needs to install a single-step breakpoint and is at pc B
     (different than thread 2), a step-over is not initiated and get_next_pc
     is called to figure out the next instruction from pc B.
    
     However it may just be that thread 3 as a single step breakpoint at pc
     B. And thus get_next_pc fails.
    
    This situation is tested with non-stop-fair-events.exp.
    
    In other words, single-step breakpoints are installed in proceed_one_lwp
    for each thread.  GDBserver proceeds two threads for resume_step, as
    requested by GDB, and the thread proceeded later may see the single-step
    breakpoints installed for the thread proceeded just now.
    
    Tested on gdbserver-native/-m{thumb,arm} no regressions.
    
    gdb/gdbserver/ChangeLog:
    
    	* linux-aarch32-low.c (arm_breakpoint_kind_from_pc): Use
    	target_read_memory.
    	* linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer): Likewise.
    	(get_next_pcs_syscall_next_pc): Likewise.

Diff:
---
 gdb/gdbserver/ChangeLog           | 7 +++++++
 gdb/gdbserver/linux-aarch32-low.c | 4 ++--
 gdb/gdbserver/linux-arm-low.c     | 5 +++--
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index d4d01e7..d3fba9b 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,10 @@
+2017-01-09  Antoine Tremblay  <antoine.tremblay@ericsson.com>
+
+	* linux-aarch32-low.c (arm_breakpoint_kind_from_pc): Use
+	target_read_memory.
+	* linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer): Likewise.
+	(get_next_pcs_syscall_next_pc): Likewise.
+
 2016-12-23  Luis Machado  <lgustavo@codesourcery.com>
 
 	* win32-i386-low.c: Fix incorrect reference to a couple source files.
diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c
index 729b7cf..2b710ba 100644
--- a/gdb/gdbserver/linux-aarch32-low.c
+++ b/gdb/gdbserver/linux-aarch32-low.c
@@ -237,11 +237,11 @@ arm_breakpoint_kind_from_pc (CORE_ADDR *pcptr)
       *pcptr = UNMAKE_THUMB_ADDR (*pcptr);
 
       /* Check whether we are replacing a thumb2 32-bit instruction.  */
-      if ((*the_target->read_memory) (*pcptr, buf, 2) == 0)
+      if (target_read_memory (*pcptr, buf, 2) == 0)
 	{
 	  unsigned short inst1 = 0;
 
-	  (*the_target->read_memory) (*pcptr, (gdb_byte *) &inst1, 2);
+	  target_read_memory (*pcptr, (gdb_byte *) &inst1, 2);
 	  if (thumb_insn_size (inst1) == 4)
 	    return ARM_BP_KIND_THUMB2;
 	}
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index b2b2258..fc2b348 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -263,7 +263,8 @@ get_next_pcs_read_memory_unsigned_integer (CORE_ADDR memaddr,
   ULONGEST res;
 
   res = 0;
-  (*the_target->read_memory) (memaddr, (unsigned char *) &res, len);
+  target_read_memory (memaddr, (unsigned char *) &res, len);
+
   return res;
 }
 
@@ -804,7 +805,7 @@ get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self)
       unsigned long this_instr;
       unsigned long svc_operand;
 
-      (*the_target->read_memory) (pc, (unsigned char *) &this_instr, 4);
+      target_read_memory (pc, (unsigned char *) &this_instr, 4);
       svc_operand = (0x00ffffff & this_instr);
 
       if (svc_operand)  /* OABI.  */


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