From bec83a6f953ab045e85d50b0cab9de176cd00bc0 Mon Sep 17 00:00:00 2001 From: Robert Hensing Date: Mon, 16 Nov 2020 11:03:53 +0100 Subject: [PATCH] BoehmGCStackAllocator: ignore stack protection page This fixes a crash that looks like: ``` Thread 1 "nix-build" received signal SIGSEGV, Segmentation fault. 0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 (gdb) bt 0 0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 1 0x00007ffff7adeefb in GC_push_all_stacks () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 2 0x00007ffff7ad5ac7 in GC_mark_some () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 3 0x00007ffff7ad77bd in GC_stopped_mark () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 4 0x00007ffff7adbe3a in GC_try_to_collect_inner.part.0 () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 5 0x00007ffff7adc2a2 in GC_collect_or_expand () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 6 0x00007ffff7adc4f8 in GC_allocobj () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 7 0x00007ffff7adc88f in GC_generic_malloc_inner () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 8 0x00007ffff7ae1a04 in GC_generic_malloc_many () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 9 0x00007ffff7ae1c72 in GC_malloc_kind () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1 10 0x00007ffff7e003d6 in nix::EvalState::allocValue() () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 11 0x00007ffff7e04b9c in nix::EvalState::callPrimOp(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 12 0x00007ffff7e0a773 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 13 0x00007ffff7e0a91d in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 14 0x00007ffff7e0a8f8 in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 15 0x00007ffff7e0e0e8 in nix::ExprOpNEq::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 16 0x00007ffff7e0d708 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 17 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 18 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 19 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 20 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 21 0x00007ffff7e09e19 in nix::ExprOpNot::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 22 0x00007ffff7e0a792 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 23 0x00007ffff7e8cba0 in nix::addPath(nix::EvalState&, nix::Pos const&, std::__cxx11::basic_string, std::allocator > const&, std::__cxx11::basic_string, std::allocator > const&, nix::Value*, nix::FileIngestionMethod, std::optional, nix::Value&)::{lambda(std::__cxx11::basic_string, std::allocator > const&)#1}::operator()(std::__cxx11::basic_string, std::allocator > const&) const () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so 24 0x00007ffff752e6f9 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 25 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 26 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 27 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 28 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 29 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string, std::allocator > const&, nix::Sink&, std::function, std::allocator > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 30 0x00007ffff757f8c0 in void boost::context::detail::fiber_entry, std::allocator > >::control_block::control_block, std::function)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine, std::allocator > >&)#1}>(boost::context::preallocated, nix::VirtualStackAllocator&&, nix::sinkToSource(std::function, std::function)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine, std::allocator > >&)#1}&&)::{lambda(boost::context::fiber&&)#1}> >(boost::context::detail::transfer_t) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so 31 0x00007ffff6f331ef in make_fcontext () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libboost_context.so.1.69.0 32 0x0000000000000000 in ?? () ``` --- src/libexpr/eval.cc | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index ef9f8efca..c078bf4a1 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -233,22 +233,34 @@ static void * oomHandler(size_t requested) } class BoehmGCStackAllocator : public StackAllocator { - boost::coroutines2::protected_fixedsize_stack stack { - // We allocate 8 MB, the default max stack size on NixOS. - // A smaller stack might be quicker to allocate but reduces the stack - // depth available for source filter expressions etc. - std::max(boost::context::stack_traits::default_size(), static_cast(8 * 1024 * 1024)) + boost::coroutines2::protected_fixedsize_stack stack { + // We allocate 8 MB, the default max stack size on NixOS. + // A smaller stack might be quicker to allocate but reduces the stack + // depth available for source filter expressions etc. + std::max(boost::context::stack_traits::default_size(), static_cast(8 * 1024 * 1024)) }; + // This is specific to boost::coroutines2::protected_fixedsize_stack. + // The stack protection page is included in sctx.size, so we have to + // subtract one page size from the stack size. + std::size_t pfss_usable_stack_size(boost::context::stack_context &sctx) { + return sctx.size - boost::context::stack_traits::page_size(); + } + public: boost::context::stack_context allocate() override { auto sctx = stack.allocate(); - GC_add_roots(static_cast(sctx.sp) - sctx.size, sctx.sp); + + // Stacks generally start at a high address and grow to lower addresses. + // Architectures that do the opposite are rare; in fact so rare that + // boost_routine does not implement it. + // So we subtract the stack size. + GC_add_roots(static_cast(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp); return sctx; } void deallocate(boost::context::stack_context sctx) override { - GC_remove_roots(static_cast(sctx.sp) - sctx.size, sctx.sp); + GC_remove_roots(static_cast(sctx.sp) - pfss_usable_stack_size(sctx), sctx.sp); stack.deallocate(sctx); }