On 10/25/2016 11:56 PM, Michael Cree wrote: > On Tue, Oct 25, 2016 at 11:07:38AM -0700, Richard Henderson wrote: >> On 10/25/2016 01:26 AM, Michael Cree wrote: >>> And while I mention gdb, it no longer works on Alpha since version >>> 7.10. Richard, would you be able to take a look at the bug report: >>> https://sourceware.org/bugzilla/show_bug.cgi?id=19061 >> >> In the PR, Pedro has exactly the right pointer to the problem. >> >> >From arch/alpha/kernel/traps.c: >> >> info.si_signo = SIGTRAP; >> info.si_errno = 0; >> info.si_code = TRAP_BRKPT; >> info.si_trapno = 0; >> info.si_addr = (void __user *) regs->pc; >> >> if (ptrace_cancel_bpt(current)) { >> regs->pc -= 4; /* make pc point to former bpt */ >> } >> >> So we report the same si_code for executing a breakpoint insn inserted by gdb, >> and a "hardware" breakpoint managed by the kernel. But for the later, we >> already back up the PC. >> >> So gdb winds up backing up the PC twice. >> >> This ought to be fixed by using TRAP_HWBKPT (4) for the ptrace_cancel_bpt case, >> but telling gdb about the issue in gdb/nat/linux-ptrace.c like so: >> >> #elif defined __alpha__ >> # define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT) >> # define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_BRKPT || (X) == TRAP_HWBKPT) >> >> which looks confusing, but does get checked: >> >> if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code) >> && GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code)) >> { >> /* The si_code is ambiguous on this arch -- check debug >> registers. */ >> if (!check_stopped_by_watchpoint (lp)) >> lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT; >> >> but at the moment the default definition of GDB_ARCH_IS_TRAP_HWBKPT is always >> false for alpha. > > By saying "This ought to be fixed by [...] but at the moment [...]" > are you saying that the fix provided above will not work? What I meant is "this is what I'm going to try". And then forgot about the (annoyingly long) build I'd left running yesterday. > Indeed, > it doesn't work: I tried it and just about every test in the gdb test > suite still fails. For example: > > Running > /home/mjc/toolchain/gdb-build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.base/break.exp > ... > FAIL: gdb.base/break.exp: run until function breakpoint (timeout) > FAIL: gdb.base/break.exp: list marker1 (timeout) > FAIL: gdb.base/break.exp: break lineno (timeout) > FAIL: gdb.base/break.exp: delete $bpnum (timeout) > FAIL: gdb.base/break.exp: run until breakpoint set at a line number > (timeout) > FAIL: gdb.base/break.exp: run until file:function(6) breakpoint > (timeout) Ok. Well, I hope to get back to it soon. r~ -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
