2017-03-08 17:11:39 +00:00
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/* Stack allocation for coroutine contexts.
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* API more or less compatible with the Boost.Context library.
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*
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* This file is part of OctaSTD. See COPYING.md for futher information.
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*/
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#ifndef OSTD_CONTEXT_STACK_HH
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#define OSTD_CONTEXT_STACK_HH
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2017-03-08 23:59:10 +00:00
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#include <new>
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2017-03-08 17:11:39 +00:00
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#include <algorithm>
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#include "ostd/types.hh"
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#include "ostd/platform.hh"
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#if !defined(OSTD_PLATFORM_POSIX) && !defined(OSTD_PLATFORM_WIN32)
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# error "Unsupported platform"
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#endif
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/* we can do this as we only support clang 4+ and gcc 7+
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* which always have support for segmented stacks
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*/
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#ifdef OSTD_USE_SEGMENTED_STACKS
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# if !defined(OSTD_PLATFORM_POSIX) || \
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(!defined(OSTD_TOOLCHAIN_GNU) && !defined(OSTD__TOOLCHAIN_CLANG))
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# error "compiler/toolchain does not support segmented_stack stacks"
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# endif
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# define OSTD_CONTEXT_SEGMENTS 10
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#endif
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#ifdef OSTD_USE_VALGRIND
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# include <valgrind/valgrind.h>
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#endif
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namespace ostd {
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struct stack_context {
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#ifdef OSTD_USE_SEGMENTED_STACKS
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using segments_context = void *[OSTD_CONTEXT_SEGMENTS];
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#endif
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void *ptr = nullptr;
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size_t size = 0;
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#ifdef OSTD_USE_SEGMENTED_STACKS
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segments_context segments_ctx = {};
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#endif
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#ifdef OSTD_USE_VALGRIND
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int valgrind_id = 0;
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#endif
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};
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2017-03-08 23:59:10 +00:00
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struct OSTD_EXPORT stack_traits {
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static bool is_unbounded() noexcept;
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static size_t page_size() noexcept;
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static size_t minimum_size() noexcept;
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static size_t maximum_size() noexcept;
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static size_t default_size() noexcept;
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2017-03-08 17:11:39 +00:00
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};
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2017-03-08 23:25:51 +00:00
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namespace detail {
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2017-03-08 23:59:10 +00:00
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OSTD_EXPORT void *stack_alloc(size_t sz);
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OSTD_EXPORT void stack_free(void *p, size_t sz) noexcept;
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OSTD_EXPORT void stack_protect(void *p, size_t sz) noexcept;
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2017-03-08 23:25:51 +00:00
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}
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2017-03-08 17:11:39 +00:00
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template<typename TR, bool Protected>
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struct basic_fixedsize_stack {
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using traits_type = TR;
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basic_fixedsize_stack(size_t ss = 0) noexcept:
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p_size(ss ? ss : TR::default_size())
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{}
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stack_context allocate() {
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size_t ss = p_size;
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ss = std::clamp(ss, TR::minimum_size(), TR::maximum_size());
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size_t pgs = TR::page_size();
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size_t npg = std::max(ss / pgs, size_t(size_t(Protected) + 1));
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size_t asize = npg * pgs;
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2017-03-08 23:25:51 +00:00
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void *p = detail::stack_alloc(asize);
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2017-03-08 17:11:39 +00:00
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if constexpr(Protected) {
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2017-03-08 23:25:51 +00:00
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/* a single guard page */
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detail::stack_protect(p, pgs);
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2017-03-08 17:11:39 +00:00
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}
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stack_context ret{static_cast<byte *>(p) + ss, ss};
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#ifdef OSTD_USE_VALGRIND
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ret.valgrind_id = VALGRIND_STACK_REGISTER(ret.ptr, p);
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#endif
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return ret;
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}
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void deallocate(stack_context &st) noexcept {
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if (!st.ptr) {
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return;
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}
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#ifdef OSTD_USE_VALGRIND
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VALGRIND_STACK_DEREGISTER(st.valgrind_id);
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#endif
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2017-03-08 23:25:51 +00:00
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detail::stack_free(static_cast<byte *>(st.ptr) - st.size, st.size);
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2017-03-08 17:11:39 +00:00
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st.ptr = nullptr;
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}
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private:
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size_t p_size;
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};
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using fixedsize_stack = basic_fixedsize_stack<stack_traits, false>;
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using protected_fixedsize_stack = basic_fixedsize_stack<stack_traits, true>;
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#ifdef OSTD_USE_SEGMENTED_STACKS
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namespace detail {
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extern "C" {
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/* from libgcc */
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void *__splitstack_makecontext(
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size_t st_size, void *ctx[OSTD_CONTEXT_SEGMENTS], size_t *size
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);
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void __splitstack_releasecontext(void *ctx[OSTD_CONTEXT_SEGMENTS]);
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void __splitstack_resetcontext(void *ctx[OSTD_CONTEXT_SEGMENTS]);
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void __splitstack_block_signals_context(
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void *ctx[OSTD_CONTEXT_SEGMENTS], int *new_val, int *old_val
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);
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}
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}
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template<typename TR>
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struct basic_segmented_stack {
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using traits_type = TR;
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basic_segmented_stack(size_t ss = 0) noexcept:
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p_size(ss ? ss : TR::default_size())
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{}
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stack_context allocate() {
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size_t ss = p_size;
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stack_context ret;
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void *p = detail::__splitstack_makecontext(
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ss, ret.segments_ctx, &ret.size
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);
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if (!p) {
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throw std::bad_alloc{};
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}
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ret.ptr = static_cast<byte *>(p) + ret.size;
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int off = 0;
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detail::__splitstack_block_signals_context(ret.segments_ctx, &off, 0);
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return ret;
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}
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void deallocate(stack_context &st) noexcept {
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detail::__splitstack_releasecontext(st.segments_ctx);
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}
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private:
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size_t p_size;
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};
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using segmented_stack = basic_segmented_stack<stack_traits>;
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#endif /* OSTD_USE_SEGMENTED_STACKS */
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#ifdef OSTD_USE_SEGMENTED_STACKS
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using default_stack = segmented_stack;
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#else
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using default_stack = fixedsize_stack;
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#endif
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} /* namespace ostd */
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#endif
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