unwind: introduce queue_t for capturing stacktrace
This is the second step for splitting capturing from printing.
New `queue' field is added to tcb. Captured stacktrace is stored here.
The field is initialized/finalized at unwind_tcb_init/unwind_tcb_fin.
New API function unwind_capture_stacktrace is added. This function
captures the currest stack using stracktrace_walker and records it in
tcb. It's printing is delayed to the next call of
unwind_print_stacktrace.
unwind_print_stacktrace is extended. Now it checks queue field of
the given tcb at the start of function. If the function finds a
captured stack trace, the latter is printed using stracktrace_walker.
Currently unwind_capture_stacktrace invocations are added directly to
handlers of mmap, munmap, mprotect, and execve.
Here is the difference of output with/without patch:
(without patch)
execve("./test-fork", ["./test-fork"], [/* 56 vars */]) = 0
> /usr/lib64/ld-2.18.so(check_one_fd.part.0+0x82) [0x11f0]
(with patch)
execve("./test-fork", ["./test-fork"], [/* 54 vars */]) = 0
> /usr/lib64/libc-2.18.so(execve+0x7) [0xbcd27]
> /home/yamato/var/strace/strace(exec_or_die+0x10c) [0x26ac]
> /home/yamato/var/strace/strace(startup_child+0x346) [0x134f6]
> /home/yamato/var/strace/strace(init+0x89f) [0x13dff]
> /home/yamato/var/strace/strace(main+0xa) [0x26ca]
> /usr/lib64/libc-2.18.so(__libc_start_main+0xf5) [0x21d65]
> /home/yamato/var/strace/strace(_start+0x29) [0x2799]
In older version output lines of captured elements were built when
printing. In this version they are built when capturing the stack.
As result, unneeded dynamic memory allocations are avoided.
Suggested by Luca Clementi.
In older version the combination of snprintf and realloc were used.
In this version they are replaced with asprintf.
Suggested by Dmitry Levin.
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
4 files changed