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| .\" Manual page created with latex2man on Thu Aug 5 10:20:31 CEST 2004 |
| .\" NOTE: This file is generated, DO NOT EDIT. |
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| .TH "LIBUNWIND\-PTRACE" "3" "05 August 2004" "Programming Library " "Programming Library " |
| .SH NAME |
| libunwind\-ptrace |
| \-\- ptrace() support in libunwind |
| .PP |
| .SH SYNOPSIS |
| |
| .PP |
| #include <libunwind\-ptrace.h> |
| .br |
| .PP |
| unw_accessors_t |
| _UPT_accessors; |
| .br |
| .PP |
| void *_UPT_create(pid_t); |
| .br |
| void |
| _UPT_destroy(void *); |
| .br |
| .PP |
| int |
| _UPT_find_proc_info(unw_addr_space_t, |
| unw_word_t, |
| unw_proc_info_t *, |
| int, |
| void *); |
| .br |
| void |
| _UPT_put_unwind_info(unw_addr_space_t, |
| unw_proc_info_t *, |
| void *); |
| .br |
| int |
| _UPT_get_dyn_info_list_addr(unw_addr_space_t, |
| unw_word_t *, |
| void *); |
| .br |
| int |
| _UPT_access_mem(unw_addr_space_t, |
| unw_word_t, |
| unw_word_t *, |
| int, |
| void *); |
| .br |
| int |
| _UPT_access_reg(unw_addr_space_t, |
| unw_regnum_t, |
| unw_word_t *, |
| int, |
| void *); |
| .br |
| int |
| _UPT_access_fpreg(unw_addr_space_t, |
| unw_regnum_t, |
| unw_fpreg_t *, |
| int, |
| void *); |
| .br |
| int |
| _UPT_get_proc_name(unw_addr_space_t, |
| unw_word_t, |
| char *, |
| size_t, |
| unw_word_t *, |
| void *); |
| .br |
| int |
| _UPT_resume(unw_addr_space_t, |
| unw_cursor_t *, |
| void *); |
| .br |
| .PP |
| .SH DESCRIPTION |
| |
| .PP |
| The ptrace(2) |
| system\-call makes it possible for a process to |
| gain access to the machine\-state and virtual memory of \fIanother\fP |
| process. With the right set of call\-back routines, it is therefore |
| possible to hook up libunwind |
| to another process via |
| ptrace(2). |
| While it\&'s not very difficult to do so directly, |
| libunwind |
| further facilitates this task by providing |
| ready\-to\-use callbacks for this purpose. The routines and variables |
| implementing this facility use a name\-prefix of _UPT, |
| which is |
| stands for ``unwind\-via\-ptrace\&''\&. |
| .PP |
| An application that wants to use the _UPT\-facility |
| first needs |
| to create a new libunwind |
| address\-space that represents the |
| target process. This is done by calling |
| unw_create_addr_space(). |
| In many cases, the application |
| will simply want to pass the address of _UPT_accessors |
| as the |
| first argument to this routine. Doing so will ensure that |
| libunwind |
| will be able to properly unwind the target process. |
| However, in special circumstances, an application may prefer to use |
| only portions of the _UPT\-facility. |
| For this reason, the |
| individual callback routines (_UPT_find_proc_info(), |
| _UPT_put_unwind_info(), |
| etc.) are also available for direct |
| use. Of course, the addresses of these routines could also be picked |
| up from _UPT_accessors, |
| but doing so would prevent static |
| initialization. Also, when using _UPT_accessors, |
| \fIall\fP |
| the callback routines will be linked into the application, even if |
| they are never actually called. |
| .PP |
| Next, the application can turn on ptrace\-mode on the target process, |
| either by forking a new process, invoking PTRACE_TRACEME, |
| and |
| then starting the target program (via execve(2)), |
| or by |
| directly attaching to an already running process (via |
| PTRACE_ATTACH). |
| Either way, once the process\-ID (pid) of the |
| target process is known, a _UPT\-info\-structure |
| can be created |
| by calling _UPT_create(), |
| passing the pid of the target process |
| as the only argument. The returned void\-pointer then needs to be |
| passed as the ``argument\&'' pointer (third argument) to |
| unw_init_remote(). |
| .PP |
| The _UPT_resume() |
| routine can be used to resume execution of |
| the target process. It simply invokes ptrace(2) |
| with a command |
| value of PTRACE_CONT\&. |
| .PP |
| When the application is done using libunwind |
| on the target |
| process, _UPT_destroy() |
| needs to be called, passing it the |
| void\-pointer that was returned by the corresponding call to |
| _UPT_create(). |
| This ensures that all memory and other |
| resources are freed up. |
| .PP |
| .SH AVAILABILITY |
| |
| .PP |
| Since ptrace(2) |
| works within a single machine only, the |
| _UPT\-facility |
| by definition is not available in |
| libunwind\-versions |
| configured for cross\-unwinding. |
| .PP |
| .SH THREAD SAFETY |
| |
| .PP |
| The _UPT\-facility |
| assumes that a single _UPT\-info |
| structure is never shared between threads. Because of this, no |
| explicit locking is used. As long as only one thread uses |
| a _UPT\-info |
| structure at any given time, this facility |
| is thread\-safe. |
| .PP |
| .SH RETURN VALUE |
| |
| .PP |
| _UPT_create() |
| may return a NULL |
| pointer if it fails |
| to create the _UPT\-info\-structure |
| for any reason. For the |
| current implementation, the only reason this call may fail is when the |
| system is out of memory. |
| .PP |
| .SH FILES |
| |
| .PP |
| .TP |
| libunwind\-ptrace.h |
| Headerfile to include when using the |
| interface defined by this library. |
| .TP |
| \fB\-l\fPunwind\-ptrace \fB\-l\fPunwind\-generic |
| Linker\-switches to add when building a program that uses the |
| functions defined by this library. |
| .PP |
| .SH SEE ALSO |
| |
| .PP |
| execve(2), |
| libunwind(3), |
| ptrace(2) |
| .PP |
| .SH AUTHOR |
| |
| .PP |
| David Mosberger\-Tang |
| .br |
| Hewlett\-Packard Labs |
| .br |
| Palo\-Alto, CA 94304 |
| .br |
| Email: \fBdavidm@hpl.hp.com\fP |
| .br |
| WWW: \fBhttp://www.hpl.hp.com/research/linux/libunwind/\fP\&. |
| .\" NOTE: This file is generated, DO NOT EDIT. |