From 55b54a999bcdb0b1c1f42b6e1ae670beb0717086 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Wed, 31 Jan 2018 11:41:29 -0800 Subject: Use a range to identify SIGSEGV in stack guards MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously, the `guard::init()` and `guard::current()` functions were returning a `usize` address representing the top of the stack guard, respectively for the main thread and for spawned threads. The `SIGSEGV` handler on `unix` targets checked if a fault was within one page below that address, if so reporting it as a stack overflow. Now `unix` targets report a `Range` representing the guard memory, so it can cover arbitrary guard sizes. Non-`unix` targets which always return `None` for guards now do so with `Option`, so they don't pay any overhead. For `linux-gnu` in particular, the previous guard upper-bound was `stackaddr + guardsize`, as the protected memory was *inside* the stack. This was a glibc bug, and starting from 2.27 they are moving the guard *past* the end of the stack. However, there's no simple way for us to know where the guard page actually lies, so now we declare it as the whole range of `stackaddr ± guardsize`, and any fault therein will be called a stack overflow. This fixes #47863. --- src/libstd/sys/windows/thread.rs | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'src/libstd/sys/windows') diff --git a/src/libstd/sys/windows/thread.rs b/src/libstd/sys/windows/thread.rs index 74786d09285..43abfbb1f64 100644 --- a/src/libstd/sys/windows/thread.rs +++ b/src/libstd/sys/windows/thread.rs @@ -93,6 +93,7 @@ impl Thread { #[cfg_attr(test, allow(dead_code))] pub mod guard { - pub unsafe fn current() -> Option { None } - pub unsafe fn init() -> Option { None } + pub type Guard = !; + pub unsafe fn current() -> Option { None } + pub unsafe fn init() -> Option { None } } -- cgit 1.4.1-3-g733a5