[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[ppluzhnikov at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10645

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yuri at tsoft dot com

--- Comment #8 from Paul Pluzhnikov <ppluzhnikov at google dot com> 2011-07-31 19:08:32 UTC ---
*** Bug 12956 has been marked as a duplicate of this bug. ***

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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=10645

--- Comment #9 from Hannes Domani <ssbssa at sourceware dot org> ---
*** Bug 10557 has been marked as a duplicate of this bug. ***

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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[ppluzhnikov at google dot com]

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           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppluzhnikov at google dot
                   |                            |com
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1


http://sourceware.org/bugzilla/show_bug.cgi?id=10645

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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[dragos dot tatulea at gmail dot com]

------- Additional Comments From dragos dot tatulea at gmail dot com  2010-07-26 21:03 -------
This patch: http://sourceware.org/ml/gdb-patches/2009-11/msg00429.html seems to 
change the behavior of watching an invalid area. Here's what happens now: 

GNU gdb (GDB) 7.0.50.20100131-cvs
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /media/a/gdb/bugzilla/10645/simple...done.
(gdb) start
Temporary breakpoint 1 at 0x400478: file simple.c, line 4.
Starting program: /media/a/gdb/bugzilla/10645/simple 

Temporary breakpoint 1, main () at simple.c:4
4         i = 1;
(gdb) set debug infrun 1
(gdb) watch *p
Hardware watchpoint 2: *p
(gdb) c
Continuing.
infrun: clear_proceed_status_thread (process 13517)
infrun: proceed (addr=0xffffffffffffffff, signal=144, step=0)
infrun: resume (step=0, signal=0), trap_expected=0
infrun: wait_for_inferior (treat_exec_as_sigtrap=0)
infrun: target_wait (-1, status) =
infrun:   13517 [process 13517],
infrun:   status->kind = stopped, signal = SIGTRAP
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x400498
infrun: stopped by watchpoint
infrun: stopped data address = 0x600840
infrun: BPSTAT_WHAT_STOP_NOISY
infrun: stop_stepping
Hardware watchpoint 2: *p

Old value = <unreadable>
New value = -443987883
main () at simple.c:7
7         return 0;

There's no single stepping anymore (at least for this particular case). Need to 
investigate why.

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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2009-11-30 17:29 -------
(a) There should be a GNU ChangeLog.  There should be some description text to
include whensubmitting it.  mmap_watchpoints_triggered() has no comment, also
the IMO-tricky fetch_watchpoint_value() call change and the reasons for
`mem_cnt' and `val' checking.  `if (step == 2)' or `else if (step == 1)' are not
acceptable - currently `int step' was a boolean, if it should be tri-state it
should become `enum' (or a new parameter/flag should be provided); this also
affects step_string().  `struct inferior'->trap_syscalls should be removed and
use the existing `catch syscall' infrastructure (I do not know it much so one
should follow it more closely than these comments of mine).  Is the custom
PT_SYSCALL still needed with the existing `catch syscall' infrastructure?

New parts I expected you could implement: (b) Catch also munmap()s.
(c) mmap_watchpoints_triggered() should trigger only on mmap-related syscalls as
detected by the existing `catch syscall' infrastructure.


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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[dragos dot tatulea at gmail dot com]

------- Additional Comments From dragos dot tatulea at gmail dot com  2009-11-30 16:37 -------
Created an attachment (id=4430)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4430&action=view)
Added more test cases.


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[dragos dot tatulea at gmail dot com]

------- Additional Comments From dragos dot tatulea at gmail dot com  2009-11-30 16:36 -------
Created an attachment (id=4429)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4429&action=view)
Same patch as jank's, only adapted to the latest gdb tree.


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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2009-09-23 14:46 -------
Created an attachment (id=4224)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4224&action=view)
Basic gdb/testsuite/ testcase.


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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2009-09-23 14:45 -------
Created an attachment (id=4223)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4223&action=view)
A (failing now) testcase for possible kernel extensions.

Made for a possible inclusion to:
http://sourceware.org/systemtap/wiki/utrace/tests

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[Bug breakpoints/10645] Watchpoints on unreadable memory need no singlestepping

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2009-09-16 18:00 -------
Created an attachment (id=4199)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4199&action=view)
Work in progress, not even a fix candidate.


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