81 lines
3.0 KiB
Diff
81 lines
3.0 KiB
Diff
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From 1d5e3cd80b66a3abd274107e75854476c603617d Mon Sep 17 00:00:00 2001
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From: Josh Stone <jistone@redhat.com>
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Date: Wed, 5 Jul 2017 12:03:17 -0700
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Subject: [PATCH] Skip the main thread's manual stack guard on Linux
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Linux doesn't allocate the whole stack right away, and the kernel has
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its own stack-guard mechanism to fault when growing too close to an
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existing mapping. If we map our own guard, then the kernel starts
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enforcing a rather large gap above that, rendering much of the possible
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stack space useless.
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Instead, we'll just note where we expect rlimit to start faulting, so
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our handler can report "stack overflow", and trust that the kernel's own
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stack guard will work.
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Fixes #43052.
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---
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src/libstd/sys/unix/thread.rs | 44 ++++++++++++++++++++++++++++---------------
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1 file changed, 29 insertions(+), 15 deletions(-)
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diff --git a/src/libstd/sys/unix/thread.rs b/src/libstd/sys/unix/thread.rs
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index 1642baa34d63..15747746611c 100644
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--- a/src/libstd/sys/unix/thread.rs
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+++ b/src/libstd/sys/unix/thread.rs
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@@ -264,23 +264,37 @@ pub mod guard {
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as *mut libc::c_void;
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}
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- // Rellocate the last page of the stack.
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- // This ensures SIGBUS will be raised on
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- // stack overflow.
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- let result = mmap(stackaddr, psize, PROT_NONE,
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- MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
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-
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- if result != stackaddr || result == MAP_FAILED {
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- panic!("failed to allocate a guard page");
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- }
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-
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- let offset = if cfg!(any(target_os = "linux", target_os = "freebsd")) {
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- 2
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+ if cfg!(target_os = "linux") {
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+ // Linux doesn't allocate the whole stack right away, and
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+ // the kernel has its own stack-guard mechanism to fault
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+ // when growing too close to an existing mapping. If we map
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+ // our own guard, then the kernel starts enforcing a rather
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+ // large gap above that, rendering much of the possible
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+ // stack space useless. See #43052.
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+ //
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+ // Instead, we'll just note where we expect rlimit to start
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+ // faulting, so our handler can report "stack overflow", and
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+ // trust that the kernel's own stack guard will work.
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+ Some(stackaddr as usize)
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} else {
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- 1
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- };
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+ // Reallocate the last page of the stack.
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+ // This ensures SIGBUS will be raised on
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+ // stack overflow.
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+ let result = mmap(stackaddr, psize, PROT_NONE,
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+ MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
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+
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+ if result != stackaddr || result == MAP_FAILED {
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+ panic!("failed to allocate a guard page");
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+ }
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- Some(stackaddr as usize + offset * psize)
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+ let offset = if cfg!(target_os = "freebsd") {
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+ 2
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+ } else {
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+ 1
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+ };
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+
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+ Some(stackaddr as usize + offset * psize)
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+ }
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}
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#[cfg(target_os = "solaris")]
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--
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2.13.3
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