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Date: Sat, 24 Oct 2020 11:41:28 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] ldso: notify the debugger when we're doing a
dlopen
On Sat, Oct 24, 2020 at 12:31:56AM -0500, rcombs wrote:
> Otherwise lldb doesn't notice the new library and stack traces containing it
> get cut off unhelpfully.
> ---
> ldso/dynlink.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/ldso/dynlink.c b/ldso/dynlink.c
> index fcc8f6a6..1ab9bf5b 100644
> --- a/ldso/dynlink.c
> +++ b/ldso/dynlink.c
> @@ -1963,7 +1963,7 @@ void __dls3(size_t *sp, size_t *auxv)
> debug.bp = dl_debug_state;
> debug.head = head;
> debug.base = ldso.base;
> - debug.state = 0;
> + debug.state = RT_CONSISTENT;
> _dl_debug_state();
>
> if (replace_argv0) argv[0] = replace_argv0;
> @@ -2012,6 +2012,10 @@ void *dlopen(const char *file, int mode)
> pthread_rwlock_wrlock(&lock);
> __inhibit_ptc();
>
> + int oldstate = debug.state;
> + debug.state = RT_ADD;
> + _dl_debug_state();
> +
> p = 0;
> if (shutting_down) {
> error("Cannot dlopen while program is exiting.");
> @@ -2104,9 +2108,10 @@ void *dlopen(const char *file, int mode)
> update_tls_size();
> if (tls_cnt != orig_tls_cnt)
> install_new_tls();
> - _dl_debug_state();
> orig_tail = tail;
> end:
> + debug.state = oldstate;
> + _dl_debug_state();
> __release_ptc();
> if (p) gencnt++;
> pthread_rwlock_unlock(&lock);
> --
> 2.17.1
This looks good, but saving/restoring oldstate isn't necessary and
doesn't make sense logically. The code here is taking place under an
exclusive lock on the state. The initial state being consistent is a
logical precondition to it, and a requirement for releasing the lock
again when finished.
Rich
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