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gdb and binutils branch master updated. b94ade42840d1b0fbf818db49d98da9ba80c1d53
- From: planglois at sourceware dot org
- To: gdb-cvs at sourceware dot org
- Date: 13 Jun 2014 09:59:25 -0000
- Subject: gdb and binutils branch master updated. b94ade42840d1b0fbf818db49d98da9ba80c1d53
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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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