Hello Managers,
I've already posted a summary, but it would be a shame to exclude Dr.
Blinn's wisdom so here is a second answer to my question:
There is code in the kernel that installs breakpoints in user space
processes, for instance, if a debugger is single stepping through a
user program and the program does a syscall, you can't single step
the kernel code, but as you leave the kernel, you put a breakpoint
at the next instruction in user space so that execution will trap
into the debugger. There is special case code for dealing with the
case of signals, as well. I suspect that if a signal is delivered
to a process while it's in a syscall, it MIGHT trigger that message.
Here is the kernel code, and you can see the test that triggers the
message; I *think* it's a kernel debugging message, but there are no
comments in the vicinity of the code to make it clear what anyone
is supposed to do if the message appears:
install_bp()
{
unsigned int inst;
unsigned long target_pc;
#ifdef SHOW
printf("install_bp\n");
#endif
if (current_pcb()->pcb_ssi.ssi_cnt)
printf("install_bp: can't install multiple
breakpoints!!\n");
/*
* If user can't access where his pc points, we give up.
* He'll be getting a SIGSEGV shortly anyway!
*/
if (!useracc(USER_REG(EF_PC), sizeof(int), B_READ))
return;
inst = fuiword(USER_REG(EF_PC));
if (isa_branch(inst)) {
target_pc = branch_target(inst, USER_REG(EF_PC));
if (target_pc != USER_REG(EF_PC))
set_bp(target_pc);
}
set_bp(USER_REG(EF_PC)+4);
/*
* only install breakpoints once!
*/
current_pcb()->pcb_sstep = 0;
}
If you have a support contract, you could report this, if you can
figure out what's triggering it. I *suspect* it's a side effect of
using single stepping while debugging a program that gets signals
while it's in a syscall (that's based on looking at the places in
the kernel where this routine gets called, there might be a race
or some logic error involved).
Otherwise, I suspect you can safely ignore it.
---original question---
> I found the following messages on my console and on /var/adm/messages:
>
> May 10 08:25:26 abel vmunix: install_bp: can't install multiple
> breakpoints!!
> May 10 08:27:06 abel vmunix: install_bp: can't install multiple
> breakpoints!!
>
> I can't find anything on the archives that has an answer. Can someone
> tell me what this means?
>
> The machine is an DS20 running Tru64 4.0F, with no patches (only gigabit
> card driver upgrade).
--
Kevin Dea
UNIX System Administrator
Alpine Electronics Research of America
Received on Sat May 12 2001 - 00:38:39 NZST