Re: [Lldb-commits] [PATCH] Report stopped by trace if none of the watchpoint was hit
On armv7 architecture systems, there are 4 hardware breakpoint registers (DBGBVR) and 4 hardware watchpoint registers (DBGWVR). The breakpoint registers track values in the pc register. You can also say "stop when the PC is not equal to this value" which is how single instruction stepping is done on armv7. On armv8 architecture systems, AArch32 or AArch64, there is a single instruction step bit (MDSCR_EL1, SS bit) to accomplish this more simply. There are still the dual sets of hardware breakpoint and hardware watchpoint registers -- but the hardware breakpoint registers don't have the "stop when the PC is not equal to this value" capability. The kernel should have no problem distinguishing between an MDSCR_EL1 SS bit stop event and a watchpoint exception (on armv8 systems). On an armv7 system, it's possible to distinguish between a breakpoint and watchpoint event. And exhausting the watchpoint register file won't prevent stepping from working. fwiw, lldb today doesn't use the hardware breakpoints, except for single stepping on armv7 systems. breakpoint set does have the --hardware option to request that the remote gdb stub use a hardware breakpoint if it has that capability. But lldb doesn't do that on its own today. REPOSITORY rL LLVM http://reviews.llvm.org/D8081 EMAIL PREFERENCES http://reviews.llvm.org/settings/panel/emailpreferences/ ___ lldb-commits mailing list lldb-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits
Re: [Lldb-commits] [PATCH] Report stopped by trace if none of the watchpoint was hit
It could be that the kernel reports a watchpoint hit on single stepping because on arm single stepping is actually implemented using hardware breakpoints. This is just a guess, but in any case it might be interesting to create a test case, which what happens with single stepping after we have set the maximum number of watchpoints possible. Does single stepping still work? Do some of our watchpoints get overwritten, etc. REPOSITORY rL LLVM http://reviews.llvm.org/D8081 EMAIL PREFERENCES http://reviews.llvm.org/settings/panel/emailpreferences/ ___ lldb-commits mailing list lldb-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits
Re: [Lldb-commits] [PATCH] Report stopped by trace if none of the watchpoint was hit
The approach looks right. I'll let somebody who works on the NativeThread side weigh in on whether the implementation is correct. http://reviews.llvm.org/D8081 EMAIL PREFERENCES http://reviews.llvm.org/settings/panel/emailpreferences/ ___ lldb-commits mailing list lldb-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits
Re: [Lldb-commits] [PATCH] Report stopped by trace if none of the watchpoint was hit
Thanks for noticing this bug and for all of the suggestions. I created a new fix what address the actual root cause of the problem with reporting the right stop reason from lldb-server. For ARMv8 the watchpoint handling is not implemented yet, but it should be possible to implement the IsWatchpointHit function. http://reviews.llvm.org/D8081 EMAIL PREFERENCES http://reviews.llvm.org/settings/panel/emailpreferences/ ___ lldb-commits mailing list lldb-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits
