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Date: Tue, 9 Jan 2018 12:22:04 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] track pthread stack guard sizes
On Sat, Jan 06, 2018 at 04:44:43AM +0000, William Pitcock wrote:
> some applications (rustc) are dependent on pthread_getattr_np() providing the guard size.
> ---
> src/internal/pthread_impl.h | 1 +
> src/thread/pthread_create.c | 1 +
> src/thread/pthread_getattr_np.c | 1 +
> 3 files changed, 3 insertions(+)
>
> diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
> index 56e19348..c2cafeaa 100644
> --- a/src/internal/pthread_impl.h
> +++ b/src/internal/pthread_impl.h
> @@ -48,6 +48,7 @@ struct pthread {
> void *stdio_locks;
> uintptr_t canary_at_end;
> void **dtv_copy;
> + size_t guard_size;
> };
>
> struct __timer {
> diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
> index 6cbf85b3..0faad765 100644
> --- a/src/thread/pthread_create.c
> +++ b/src/thread/pthread_create.c
> @@ -265,6 +265,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
> new->map_size = size;
> new->stack = stack;
> new->stack_size = stack - stack_limit;
> + new->guard_size = guard;
> new->start = entry;
> new->start_arg = arg;
> new->self = new;
> diff --git a/src/thread/pthread_getattr_np.c b/src/thread/pthread_getattr_np.c
> index ae26a5ab..29a209bd 100644
> --- a/src/thread/pthread_getattr_np.c
> +++ b/src/thread/pthread_getattr_np.c
> @@ -7,6 +7,7 @@ int pthread_getattr_np(pthread_t t, pthread_attr_t *a)
> {
> *a = (pthread_attr_t){0};
> a->_a_detach = !!t->detached;
> + a->_a_guardsize = t->guard_size;
> if (t->stack) {
> a->_a_stackaddr = (uintptr_t)t->stack;
> a->_a_stacksize = t->stack_size;
> --
> 2.15.0
I'm pretty sure there's another bug in this patch: the local variable
guard is uninitialized where you use it if the application provided a
stack and TLS was able to be allocated in the app-provided stack.
The line guard = 0; above should probably just be moved down one line
(and unindented one level).
Does this sound right?
Rich
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