Commit Graph

4 Commits

Author SHA1 Message Date
Masatake YAMATO
840bb0acb5 unwind-libdw: use the mmap_notify subsystem
The unwind subsystem uses the mmap_cache subsystem even it uses
unwind-libdw as backend. unwind-libdw doesn't need the full set of the
mmap_cache subsystem; libdw has a feature for caching a memory
mapping.

This commit does three things.

(1) Make the unwind subsystem not use the mmap_cache subsystem.
The unwind subsystem never concern the memory mapping of the target.
It becomes a thin layer.

(2) Make unwind-libunwind use the mmap_cache subsystem directly.

(3) Make unwind-libdw use the mmap_notify subsystem to know when it
should call dwfl_linux_proc_report/dwfl_report_end for updating the
cache.

Here is a subsystem structure that this patch
introduces:

	+-------------------------------------+
	|            unwind subsys            |
	+------------------+------------------+
	| unwind-libunwind |   unwind-libdw   |
	+------------------+------------------+
	|    mmap_cache    |                  |
	+------------------+                  |
	|               mmap_notify           |
	+-------------------------------------+
	|                syscall              |
	+-------------------------------------+
               mmap/munmap/mprotect/brk...

* unwind.c: Don't include "mmap_cache.h".
(unwind_init): Don't call mmap_cache_enable.
(unwind_tcb_print, unwind_tcb_capture): Don't call mmap_cache related
functions, just invoke unwinder.tcb_walk.
* unwind.h (struct unwind_unwinder_t): Remove tcb_flush_cache field.

* unwind-libdw.c: Include "mmap_notify.h" instead of "mmap_cache.h".
(struct ctx): Add last_proc_updating field to record the generation
of memory mapping that is cached by dwfl_linux_proc_report
and dwfl_report_end.
(mapping_generation): A variable counting how many times the memory
mapping of targets has been changed.
(updating_mapping_generation): New utility function for updating
mapping_generation.
(init): New function for registering updating_mapping_generation
in the mmap_notify subsystem as a callback function.
(tcb_init): Initialize ctx::last_proc_updating.
(tcb_flush_cache): Rename to flush_cache_maybe.  Rebuild the cache data
only if the data is stale.
(tcb_walk): Call flush_cache_maybe for avoiding referring staled cache data.
(unwinder): Set init function, remove tcb_flush_cache field.
* unwind-libunwind.c (init): Enable the mmap_cache subsystem.
(tcb_walk): Call mmap_cache_rebuild_if_invalid and unw_flush_cache for
updating the cache of the memory mapping before walking the stack.
(tcb_walk): Rename to walk.
(unwinder): Remove tcb_flush_cache field.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
2018-05-03 22:01:30 +00:00
Masatake YAMATO
e09c6c88aa unwind-libdw: introduce indirect data structure for storing unwinding context
unwind-libdw uses Dwfl as the data structure for storing unwinding
context.  It is raw data that come from libdw.

This commit introduces "struct ctx" file local data type for allowing
unwind-libdw to attach strace side data to the unwinding context.

* unwind-libdw.c (struct ctx): New struct definition.
(tcb_init, tcb_fin, tcb_walk, tcb_flush_cache): Use struct ctx instead
of Dwfl directly.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
2018-05-03 22:01:30 +00:00
0635ea34a8 unwind: remove stray newline in error diagnostics
* unwind-libdw.c (tcb_init): Do not pass trailing "\n" to error_msg
as the latter prints newline itself.
2018-04-19 18:03:58 +00:00
Masatake YAMATO
ddb5a4ba73 unwind: add libdw as an unwinder
Implement alternative libdw-based unwinder for stack tracing.
Add --with-libdw configure option to control whether libdw can be used
as an unwinder.

* m4/st_libdw.m4: New file.
* m4/st_stacktrace.m4 (st_STACKTRACE): Invoke st_ARG_LIBDW and st_LIBDW,
check for mutually exclusive configure options,
(AM_CONDITIONAL): Add USE_LIBDW.
* unwind-libdw.c: New file.
* Makefile.am [USE_LIBDW] (strace_SOURCES): Append unwind-libdw.c.
[USE_LIBDW] (strace_CPPFLAGS): Append $(libdw_CPPFLAGS).
[USE_LIBDW] (strace_CFLAGS): Append $(libdw_CFLAGS).
[USE_LIBDW] (strace_LDFLAGS): Append $(libdw_LDFLAGS).
[USE_LIBDW] (strace_LDADD): Append $(libdw_LIBS).
* NEWS: Mention this improvement.

Closes: https://github.com/strace/strace/issues/12
Closes: https://github.com/strace/strace/issues/13
Co-Authored-by: Mark Wielaard <mjw@redhat.com>
Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
2018-04-11 22:01:37 +00:00