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Currently the resource checking is done if REPARSE is true. The hardware watchpoint resource checking in update_watchpoint needs to be redone on each call to function update_watchpoints as the value chain may have changed. The number of hardware registers needed for a watchpoint can change if the variable being watched changes. This situation occurs in this test when watching variable **global_ptr_ptr. Initially when the watch command is issued, only two addresses need to be watched as **global_ptr_ptr has not yet been initialized. Once the value of **global_ptr_ptr is initialized the locations to be tracked increase to three addresses. However, update_watchpoints is not called again with REPARSE set to 1 to force the resource checking to be redone. When the test is run on Power 10, an internal gdb error occurs when the PowerPC routine tries to setup the three hardware watchpoint address since the hw only has two hardware watchpoint registers. The error occurs because the resource checking was not redone in update_watchpoints after **global_ptr_ptr changed. The following descibes the situation in detail that occurs on Power 10 with gdb running on the binary for gdb.base/watchpoint.c. 1 break func4 2 run 3 watch *global_ptr 4 next execute source code: buf[0] = 3; 5 next execute source code: global_ptr = buf; 6 next execute source code: buf[0] = 7; 7 delete 2 (delete watch *global_ptr) 8 watch **global_ptr_ptr 9 next execute source code: buf[1] = 5; 10 next global_ptr_ptr = &global_ptr; 11 next buf[0] = 9; In step 8, the the watch **global_ptr_prt command calls update_watchpoint in breakpoint.c with REPARSE set to 1. The function update_watchpoint calls can_use_hardware_watchpoint to see if there are enough resources available to add the watchpoint since REPARSE is set to 1. At this point, **global_ptr_ptr has not been initialized so only two addresses are watched. The val_chain contains the address for **global_ptr_ptr and 0 since **global_ptr_ptr has not been initialized. The update_watchpoint updates the breakpoint list as follows: breakpoint 0 loc 0: b->address = 0x100009c0 breakpoint 1 loc 1: b->address = 0x7ffff7f838a0 breakpoint 2 loc 2: b->address = 0x7ffff7b7fc54 breakpoint 3 loc 3: b->address = 0x7ffff7a5788c breakpoint 4 loc 4: b->address = 0x0 <-- location pointed to by global_ptr_ptr loc 5: b->address = 0x100200b8 <-- global_ptr_ptr watchpoint breakpoint 5 loc 6: b->address = 0x7ffff7b7fc54 In step 10, the next command executes the source code global_ptr_ptr = &global_ptr. This changes the set of locations to be watched for the watchpoint **global_ptr_prt. The list of addresses for the breakpoint consist of the address for global_ptr_prt, global_ptr and buf. The breakpoint list gets updated by update_watchpoint as follows: breakpoint 0 loc 0: b->address = 0x100009c0 breakpoint 1 loc 1: b->address = 0x7ffff7f838a0 breakpoint 2 loc 2: b->address = 0x7ffff7b7fc54 breakpoint 3 loc 3: b->address = 0x7ffff7a5788c breakpoint 4 loc 4: b->address = 0x10020050 buf loc 5: b->address = 0x100200b0 watch *global_ptr loc 6: b->address = 0x100200b8 watch **global_ptr_ptr breakpoint 5 loc 7: b->address = 0x7ffff7b7fc54 breakpoint 6 However, the hardware resource checking was not redone because update_breakpoint was called with REPARSE equal to 0. Step 11, execute the third next command. The function ppc_linux_nat_target::low_prepare_to_resume() attempts a ptrace call to setup each of the three address for breakpoint 4. The slot value returned for the third ptrace call is -1 indicating an error because there are only two hardware watchpoint registers available on Power 10. This patch removes just the statement "if (reparse)" in function update_watchpoint to force the resources to be rechecked on every call to the function. This ensures that any changes to the val_chain resulting in needing more resources then available will be caught. The patch has been tested on Power 8, Power 10 and X86-64. Note the patch has no effect on Power 9 since hardware watchpoint support is disabled on that processor. |
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| binutils | ||
| config | ||
| contrib | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gdbserver | ||
| gdbsupport | ||
| gnulib | ||
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| include | ||
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| ar-lib | ||
| ChangeLog | ||
| compile | ||
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| configure | ||
| configure.ac | ||
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| depcomp | ||
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| libtool.m4 | ||
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| ltmain.sh | ||
| ltoptions.m4 | ||
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| multilib.am | ||
| README | ||
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README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.