Debugger on Solaris
Robert Lunnon
bobNoSpaM at yarrabee.net.au
Sat Jan 5 17:33:55 CST 2002
> On Fri, 4 Jan 2002 10:49, Alexandre Julliard wrote:
> > Robert Lunnon <bobNoSpaM at yarrabee.net.au> writes:
> > > Without calling ptrace (TRACEME,...) Solaris returns ESRCH even though
> > > the process exists which causes the wineserver to assume the process is
> > > defunct and delete the app, apparently causing the deadlock (This
> > > deadlock will have to be fixed too !).
> >
> > Are you sure this is not rather an issue of process id vs. thread id?
> > I would be surprised if Solaris required TRACEME in this case, since
> > this would mean you couldn't attach a debugger to a running process.
>
>it seems something is missing from your mail <grin>
>
>--
>Alexandre Julliard
>julliard at winehq.com
Some strange behaviour of my mail client is removing edits from replies Sorry
all.
Here is what the Sun man page says about Ptrace, with apologies to sun, you
can find this page at docs.sun.com. Not the comment for call 0 (TRACEME) and
ESRCH in the error section
System Calls ptrace(2)
NAME
ptrace - allows a parent process to control the execution of
a child process
SYNOPSIS
#include <unistd.h>
#include <sys/types.h>
int ptrace(int request, pid_t pid, int addr, int data);
DESCRIPTION
The ptrace() function allows a parent process to control the
execution of a child process. Its primary use is for the
implementation of breakpoint debugging. The child process
behaves normally until it encounters a signal (see
signal(3HEAD)), at which time it enters a stopped state and
its parent is notified via the wait(2) function. When the
child is in the stopped state, its parent can examine and
modify its "core image" using ptrace(). Also, the parent can
cause the child either to terminate or continue, with the
possibility of ignoring the signal that caused it to stop.
The request argument determines the action to be taken by
ptrace() and is one of the following:
0 This request must be issued by the child process if it
is to be traced by its parent. It turns on the child's
trace flag that stipulates that the child should be
left in a stopped state on receipt of a signal rather
than the state specified by func (see signal(3C)). The
pid, addr, and data arguments are ignored, and a
return value is not defined for this request. Peculiar
results ensue if the parent does not expect to trace
the child.
The remainder of the requests can only be used by the parent
process. For each, pid is the process ID of the child. The
child must be in a stopped state before these requests are
made.
1, 2 With these requests, the word at location addr in the
address space of the child is returned to the parent
process. If instruction and data space are separated,
request 1 returns a word from instruction space, and
request 2 returns a word from data space. If instruc-
tion and data space are not separated, either request
1 or request 2 may be used with equal results. The
data argument is ignored. These two requests fail if
addr is not the start address of a word, in which case
-1 is returned to the parent process and the parent's
errno is set to EIO.
SunOS 5.8 Last change: 5 Jul 1990 1
System Calls ptrace(2)
3 With this request, the word at location addr in the
child's user area in the system's address space (see
<sys/user.h>) is returned to the parent process. The
data argument is ignored. This request fails if addr
is not the start address of a word or is outside the
user area, in which case -1 is returned to the parent
process and the parent's errno is set to EIO.
4, 5 With these requests, the value given by the data argu-
ment is written into the address space of the child at
location addr. If instruction and data space are
separated, request 4 writes a word into instruction
space, and request 5 writes a word into data space. If
instruction and data space are not separated, either
request 4 or request 5 may be used with equal results.
On success, the value written into the address space
of the child is returned to the parent. These two
requests fail if addr is not the start address of a
word. On failure -1 is returned to the parent process
and the parent's errno is set to EIO.
6 With this request, a few entries in the child's user
area can be written. data gives the value that is to
be written and addr is the location of the entry. The
few entries that can be written are the general regis-
ters and the condition codes of the Processor Status
Word.
7 This request causes the child to resume execution. If
the data argument is 0, all pending signals including
the one that caused the child to stop are canceled
before it resumes execution. If the data argument is a
valid signal number, the child resumes execution as if
it had incurred that signal, and any other pending
signals are canceled. The addr argument must be equal
to 1 for this request. On success, the value of data
is returned to the parent. This request fails if data
is not 0 or a valid signal number, in which case -1 is
returned to the parent process and the parent's errno
is set to EIO.
8 This request causes the child to terminate with the
same consequences as exit(2).
9 This request sets the trace bit in the Processor
Status Word of the child and then executes the same
steps as listed above for request 7. The trace bit
causes an interrupt on completion of one machine
instruction. This effectively allows single stepping
of the child.
SunOS 5.8 Last change: 5 Jul 1990 2
System Calls ptrace(2)
To forestall possible fraud, ptrace() inhibits the set-
user-ID facility on subsequent calls to one of the exec fam-
ily of functions (see exec(2)). If a traced process calls
one of the exec functions, it stops before executing the
first instruction of the new image showing signal SIGTRAP.
ERRORS
The ptrace() function will fail if:
EIO The request argument is an illegal number.
EPERM The effective user of the calling process is not
super-user.
ESRCH The pid argument identifies a child that does not
exist or has not executed a ptrace() call with request
0.
SEE ALSO
exec(2), exit(2), wait(2), signal(3C), signal(3HEAD)
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