This patch fixes this on x86 Linux:
(gdb) watch *buf@2
Hardware watchpoint 8: *buf@2
(gdb) si
0x00000000004005a7 34 for (i = 0; i < 100000; i++); /* stepi line */
(gdb) del
Delete all breakpoints? (y or n) y
(gdb) watch *(buf+1)@1
Hardware watchpoint 9: *(buf+1)@1
(gdb) si
0x00000000004005a7 in main () at ../../../src/gdb/testsuite/gdb.base/watchpoint-reuse-slot.c:34
34 for (i = 0; i < 100000; i++); /* stepi line */
Couldn't write debug register: Invalid argument.
(gdb)
In the example above the debug registers are being switched from this
state:
CONTROL (DR7): 0000000000050101 STATUS (DR6): 0000000000000000
DR0: addr=0x0000000000601040, ref.count=1 DR1: addr=0x0000000000000000, ref.count=0
DR2: addr=0x0000000000000000, ref.count=0 DR3: addr=0x0000000000000000, ref.count=0
to this:
CONTROL (DR7): 0000000000010101 STATUS (DR6): 0000000000000000
DR0: addr=0x0000000000601041, ref.count=1 DR1: addr=0x0000000000000000, ref.count=0
DR2: addr=0x0000000000000000, ref.count=0 DR3: addr=0x0000000000000000, ref.count=0
That is, before, DR7 was setup for watching a 2 byte region starting
at what's in DR0 (0x601040).
And after, DR7 is setup for watching a 1 byte region starting at
what's in DR0 (0x601041).
We always write DR0..DR3 before DR7, because if we enable a slot's
bits in DR7, you need to have already written the corresponding
DR0..DR3 registers -- the kernel rejects the DR7 write with EINVAL
otherwise.
The error shown above is the opposite scenario. When we try to write
0x601041 to DR0, DR7's bits still indicate intent of watching a 2-byte
region. That DR0/DR7 combination is invalid, because 0x601041 is
unaligned. To watch two bytes, we'd have to use two slots. So the
kernel errors out with EINVAL.
Fix this by always first clearing DR7, then writing DR0..DR3, and then
setting DR7's bits.
A little optimization -- if we're disabling the last watchpoint, then
we can clear DR7 just once. The changes to nat/i386-dregs.c make that
easier to detect, and as bonus, they make it a little easier to make
sense of DR7 in the debug logs, as we no longer need to remember we're
seeing stale bits.
Tested on x86_64 Fedora 20, native and GDBserver.
This adds an exhaustive test that switches between many different
combinations of watchpoint types and addresses and widths.
gdb/
2014-06-23 Pedro Alves <palves@redhat.com>
* amd64-linux-nat.c (amd64_linux_prepare_to_resume): Clear
DR_CONTROL before setting DR0..DR3.
* i386-linux-nat.c (i386_linux_prepare_to_resume): Likewise.
* nat/i386-dregs.c (i386_remove_aligned_watchpoint): Clear all
bits of DR_CONTROL related to the debug register slot being
disabled. If all slots are vacant, clear local slowdown as well,
and assert DR_CONTROL is 0.
gdb/gdbserver/
2014-06-23 Pedro Alves <palves@redhat.com>
* linux-x86-low.c (x86_linux_prepare_to_resume): Clear DR_CONTROL
before setting DR0..DR3.
gdb/testsuite/
2014-06-23 Pedro Alves <palves@redhat.com>
* gdb.base/watchpoint-reuse-slot.c: New file.
* gdb.base/watchpoint-reuse-slot.exp: New file.
This commit makes gdbserver access the x86 debug register accessor
functions via the same function vector as GDB proper. This removes
a chunk of conditional code that was previously in i386-{nat,low}.h
and leaves a single macro as the only GDB/gdbserver difference in
nat/i386-dregs.c.
gdb/
2014-06-20 Gary Benson <gbenson@redhat.com>
* i386-nat.h (debug_hw_points): Moved to nat/i386-dregs.c.
(i386_dr_low_type): Moved to nat/i386-dregs.h.
(i386_dr_low): Likewise.
(i386_dr_low_can_set_addr): Moved to nat/i386-dregs.c.
(i386_dr_low_set_addr): Likewise.
(i386_dr_low_get_addr): Likewise.
(i386_dr_low_can_set_control): Likewise.
(i386_dr_low_set_control): Likewise.
(i386_dr_low_get_control): Likewise.
(i386_dr_low_get_status): Likewise.
(i386_get_debug_register_length): Likewise.
* nat/i386-dregs.h (i386_dr_low_type): Moved from i386-nat.h.
(i386_dr_low): Likewise.
* nat/i386-dregs.c (i386-low.h): Remove include.
(i386-nat.h): Likewise.
(nat/i386-dregs.h): New include.
(i386_dr_low_can_set_addr): Moved from i386-nat.h.
(i386_dr_low_set_addr): Likewise.
(i386_dr_low_get_addr): Likewise.
(i386_dr_low_can_set_control): Likewise.
(i386_dr_low_set_control): Likewise.
(i386_dr_low_get_control): Likewise.
(i386_dr_low_get_status): Likewise.
(i386_get_debug_register_length): Likewise.
(debug_hw_points): Likewise.
gdb/gdbserver/
2014-06-20 Gary Benson <gbenson@redhat.com>
* i386-low.h (i386_dr_low_can_set_addr): Removed.
(i386_dr_low_set_addr): Likewise.
(i386_dr_low_get_addr): Likewise.
(i386_dr_low_can_set_control): Likewise.
(i386_dr_low_set_control): Likewise.
(i386_dr_low_get_control): Likewise.
(i386_dr_low_get_status): Likewise.
(i386_get_debug_register_length): Likewise.
* linux-x86-low.c (i386_dr_low_set_addr):
Changed signature. Made static.
(i386_dr_low_get_addr): Likewise.
(i386_dr_low_set_control): Likewise.
(i386_dr_low_get_control): Likewise.
(i386_dr_low_get_status): Likewise.
(i386_dr_low): New global variable.
* win32-i386-low.c (i386_dr_low_set_addr):
Changed signature. Made static.
(i386_dr_low_get_addr): Likewise.
(i386_dr_low_set_control): Likewise.
(i386_dr_low_get_control): Likewise.
(i386_dr_low_get_status): Likewise.
(i386_dr_low): New global variable.
The above commit did two things:
1) A number of functions were renamed and made nonstatic.
2) A number of other functions were renamed only.
This commit reverts #1 but not #2. In addition, prototypes for
functions now remade static have been removed from i386-dregs.h.
gdb/
2014-06-19 Gary Benson <gbenson@redhat.com>
* i386-nat.c (i386_dr_show): Renamed to
i386_show_dr and made static. All uses updated.
(i386_dr_length_and_rw_bits): Renamed to
i386_length_and_rw_bits and made static.
All uses updated.
(i386_dr_insert_aligned_watchpoint): Renamed to
i386_insert_aligned_watchpoint and made static.
All uses updated.
(i386_dr_remove_aligned_watchpoint): Renamed to
i386_remove_aligned_watchpoint and made static.
All uses updated.
(i386_dr_update_inferior_debug_regs): Renamed to
i386_update_inferior_debug_regs and made static.
All uses updated.
* nat/i386-dregs.h (i386_dr_show): Removed.
(i386_dr_length_and_rw_bits): Likewise.
(i386_dr_insert_aligned_watchpoint): Likewise.
(i386_dr_remove_aligned_watchpoint): Likewise.
(i386_dr_update_inferior_debug_regs): Likewise.
gdb/gdbserver/
2014-06-19 Gary Benson <gbenson@redhat.com>
* i386-low.c (i386_dr_show): Renamed to
i386_show_dr and made static. All uses updated.
(i386_dr_length_and_rw_bits): Renamed to
i386_length_and_rw_bits and made static.
All uses updated.
(i386_dr_insert_aligned_watchpoint): Renamed to
i386_insert_aligned_watchpoint and made static.
All uses updated.
(i386_dr_remove_aligned_watchpoint): Renamed to
i386_remove_aligned_watchpoint and made static.
All uses updated.
(i386_dr_update_inferior_debug_regs): Renamed to
i386_update_inferior_debug_regs and made static.
All uses updated.
Just a small optimization. No need to block/unblock signals if we're
not going to call sigsuspend.
gdb/
2014-02-27 Pedro Alves <palves@redhat.com>
* nat/linux-waitpid.c (my_waitpid): Only block signals if WNOHANG
isn't set.
So that gdbserver's Linux backend can use it too.
gdb/
2014-02-27 Pedro Alves <palves@redhat.com>
PR 12702
* linux-nat.c (status_to_str): Moved to nat/linux-waitpid.c.
* nat/linux-waitpid.c: Include string.h.
(status_to_str): Moved here and made extern.
* nat/linux-waitpid.h (status_to_str): New declaration.
