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unw_set_caching_policy(3) [debian man page]

UNW_SET_CACHING_POLICY(3)				       Programming Library					 UNW_SET_CACHING_POLICY(3)

unw_set_caching_policy -- set unwind caching policy SYNOPSIS
#include <libunwind.h> int unw_set_caching_policy(unw_addr_space_t as, unw_caching_policy_t policy); DESCRIPTION
The unw_set_caching_policy() routine sets the caching policy of address space as to the policy specified by argument policy. The policy argument can take one of three possible values: UNW_CACHE_NONE Turns off caching completely. This also implicitly flushes the contents of all caches as if unw_flush_cache() had been called. UNW_CACHE_GLOBAL Enables caching using a global cache that is shared by all threads. If global caching is unavailable or unsupported, libunwind may fall back on using a per-thread cache, as if UNW_CACHE_PER_THREAD had been specified. UNW_CACHE_PER_THREAD Enables caching using thread-local caches. If a thread-local caching are unavailable or unsupported, libunwind may fall back on using a global cache, as if UNW_CACHE_GLOBAL had been specified. If caching is enabled, an application must be prepared to make appropriate calls to unw_flush_cache() whenever the target changes in a way that could affect the validity of cached information. For example, after unloading (removing) a shared library, unw_flush_cache() would have to be called (at least) for the address-range that was covered by the shared library. For address spaces created via unw_create_addr_space(3), caching is turned off by default. For the local address space unw_local_addr_space, caching is turned on by default. RETURN VALUE
On successful completion, unw_set_caching_policy() returns 0. Otherwise the negative value of one of the error-codes below is returned. THREAD AND SIGNAL SAFETY
unw_set_caching_policy() is thread-safe but not safe to use from a signal handler. ERRORS
UNW_ENOMEM The desired caching policy could not be established because the application is out of memory. SEE ALSO
libunwind(3), unw_create_addr_space(3), unw_flush_cache(3) AUTHOR
David Mosberger-Tang Email: WWW: Programming Library 16 August 2007 UNW_SET_CACHING_POLICY(3)

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LIBUNWIND-PTRACE(3)					       Programming Library					       LIBUNWIND-PTRACE(3)

libunwind-ptrace -- ptrace() support in libunwind SYNOPSIS
#include <libunwind-ptrace.h> unw_accessors_t _UPT_accessors; void *_UPT_create(pid_t); void _UPT_destroy(void *); int _UPT_find_proc_info(unw_addr_space_t, unw_word_t, unw_proc_info_t *, int, void *); void _UPT_put_unwind_info(unw_addr_space_t, unw_proc_info_t *, void *); int _UPT_get_dyn_info_list_addr(unw_addr_space_t, unw_word_t *, void *); int _UPT_access_mem(unw_addr_space_t, unw_word_t, unw_word_t *, int, void *); int _UPT_access_reg(unw_addr_space_t, unw_regnum_t, unw_word_t *, int, void *); int _UPT_access_fpreg(unw_addr_space_t, unw_regnum_t, unw_fpreg_t *, int, void *); int _UPT_get_proc_name(unw_addr_space_t, unw_word_t, char *, size_t, unw_word_t *, void *); int _UPT_resume(unw_addr_space_t, unw_cursor_t *, void *); DESCRIPTION
The ptrace(2) system-call makes it possible for a process to gain access to the machine-state and virtual memory of another 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''. 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 rou- tines (_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, all the callback routines will be linked into the application, even if they are never actually called. 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(). 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. 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. AVAILABILITY
Since ptrace(2) works within a single machine only, the _UPT-facility by definition is not available in libunwind-versions configured for cross-unwinding. THREAD SAFETY
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. RETURN VALUE
_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. FILES
libunwind-ptrace.h Headerfile to include when using the interface defined by this library. -lunwind-ptrace -lunwind-generic Linker-switches to add when building a program that uses the functions defined by this library. SEE ALSO
execve(2), libunwind(3), ptrace(2) AUTHOR
David Mosberger-Tang Email: WWW: Programming Library 16 August 2007 LIBUNWIND-PTRACE(3)
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