gdb and binutils branch master updated. b94ade42840d1b0fbf818db49d98da9ba80c1d53

[planglois at sourceware dot org]

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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b94ade42840d1b0fbf818db49d98da9ba80c1d53

commit b94ade42840d1b0fbf818db49d98da9ba80c1d53
Author: Pierre Langlois <pierre.langlois@embecosm.com>
Date:   Tue May 20 15:13:20 2014 +0100

    Invalidate a register in cache when a remote target failed to write it.
    
    As shown by the bug report, GDB crashes when the remote target was unable to
    write to a register (the program counter) with the 'P' packet. This was reported
    for AVR but can be reproduced on any architecture with a gdbserver that fails to
    handle a 'P' packet.
    
    Issue
    =====
    
    This GDB session was done with a custom gdbserver patched to send an error
    packet when trying to set the program counter with a 'P' packet:
    
    ~~~
    (gdb) file Debug/ATMega2560-simple-program.elf
    Reading symbols from Debug/ATMega2560-simple-program.elf...done.
    (gdb) target remote :51000
    Remote debugging using :51000
    0x00000000 in __vectors ()
    (gdb) load
    Loading section .text, size 0x1fc lma 0x0
    Start address 0x0, load size 508
    Transfer rate: 248 KB/sec, 169 bytes/write.
    (gdb) b main
    Breakpoint 1 at 0x164: file .././ATMega2560-simple-program.c, line 39.
    (gdb) c
    Continuing.
    
    Program received signal SIGTRAP, Trace/breakpoint trap.
    main () at .././ATMega2560-simple-program.c:42
    42		DDRD |= LED0_MASK;// | LED1_MASK;
    (gdb) info line 43
    Line 43 of ".././ATMega2560-simple-program.c" is at address 0x178 <main+40> but contains no code.
    (gdb) set $pc=0x178
    Could not write register "PC2"; remote failure reply 'E00'
    (gdb) info registers pc
    pc             0x178	0x178 <main+40>
    (gdb) s
    ../../unisrc-mainline/gdb/infrun.c:1978: internal-error: resume: Assertion `pc_in_thread_step_range (pc, tp)' failed.
    A problem internal to GDB has been detected,
    further debugging may prove unreliable.
    Quit this debugging session? (y or n)
    ../../unisrc-mainline/gdb/infrun.c:1978: internal-error: resume: Assertion `pc_in_thread_step_range (pc, tp)' failed.
    A problem internal to GDB has been detected,
    further debugging may prove unreliable.
    Create a core file of GDB? (y or n)
    ~~~
    
    We can see that even though GDB reports that writing to the register failed, the
    register cache was updated:
    
    ~~~
    (gdb) set $pc=0x178
    Could not write register "PC2"; remote failure reply 'E00'
    (gdb) info registers pc
    pc             0x178	0x178 <main+40>
    ~~~
    
    The root of the problem is of course in the gdbserver but I thought GDB should
    keep a register cache consistent with the hardware even in case of a failure.
    
    Changes
    =======
    
    This patch adds routines to add a regcache_invalidate cleanup to the current
    chain.
    
    We can then register one before calling target_store_registers. This way if the
    target throws an error, the register we wanted to write to will be invalidated
    in cache. If target_store_registers succeeds, we can discard the new cleanup.
    
    2014-06-12  Pierre Langlois  <pierre.langlois@embecosm.com>
    
    	* regcache.c (struct register_to_invalidate): New structure.
    	(do_register_invalidate, make_cleanup_regcache_invalidate): New
    	functions.
    	(regcache_raw_write): Call make_cleanup_regcache_invalidate.

-----------------------------------------------------------------------

Summary of changes:
 gdb/ChangeLog  |    7 +++++++
 gdb/regcache.c |   43 ++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 47 insertions(+), 3 deletions(-)


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