Adjust breakpoint address by clearing non-significant bits
authorYao Qi <yao.qi@linaro.org>
Fri, 8 Dec 2017 17:27:03 +0000 (17:27 +0000)
committerYao Qi <yao.qi@linaro.org>
Fri, 8 Dec 2017 17:27:03 +0000 (17:27 +0000)
commita0de8c21baf46c40ed8e62faef5f750b1e5453ea
tree137844459043552cc8546120dca8b353e1048f36
parenta738ea1d41daeec0cccb4ab6671f4f6d53bd9e18
Adjust breakpoint address by clearing non-significant bits

Tag in tagged address on AArch64 is treated as a non-significant bits of
address, which can be got by gdbarch method significant_addr_bit, and gdb
can clear these bits.

With this patch, when user sets a breakpoint on tagged address on AArch64,
GDB will drop the top byte of address, and put breakpoint at the new place,
as shown below,

(gdb) hbreak *func_ptr
warning: Breakpoint address adjusted from 0xf000000000400690 to 0x00400690.
Hardware assisted breakpoint 2 at 0x400690

(gdb) break *func_ptr
warning: Breakpoint address adjusted from 0xf000000000400690 to 0x00400690.
Breakpoint 3 at 0x400690

When program hits a breakpoint, the stopped pc reported by Linux kernel is
the address *without* tag, so it is better the address recorded in
breakpoint location is the one without tag too, so we can still match
breakpoint location address and stopped pc reported by Linux kernel, by
simple compare.

gdb:

2017-12-08  Yao Qi  <yao.qi@linaro.org>

* breakpoint.c (adjust_breakpoint_address): Call
address_significant.

gdb/testsuite:

2017-12-08  Yao Qi  <yao.qi@linaro.org>

* gdb.arch/aarch64-tagged-pointer.c (main): Update.
* gdb.arch/aarch64-tagged-pointer.exp: Add test for breakpoint.
gdb/ChangeLog
gdb/breakpoint.c
gdb/testsuite/ChangeLog
gdb/testsuite/gdb.arch/aarch64-tagged-pointer.c
gdb/testsuite/gdb.arch/aarch64-tagged-pointer.exp