130 lines
3.3 KiB
C++
130 lines
3.3 KiB
C++
/* Stack allocation implementation for coroutine contexts.
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* For POSIX systems only, other implementations are stored elsewhere.
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*
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* This file is part of libostd. See COPYING.md for futher information.
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*/
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#include "ostd/platform.hh"
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#ifndef OSTD_PLATFORM_POSIX
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# error "Incorrect platform"
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#endif
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#include <cstddef>
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#include <cstdlib>
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#include <new>
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#include <mutex>
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#include "ostd/context_stack.hh"
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/resource.h>
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#include <sys/time.h>
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#include <signal.h>
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namespace ostd {
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namespace detail {
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#if defined(MAP_ANON) || defined(MAP_ANONYMOUS)
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constexpr bool CONTEXT_USE_MMAP = true;
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# ifdef MAP_ANON
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constexpr auto CONTEXT_MAP_ANON = MAP_ANON;
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# else
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constexpr auto CONTEXT_MAP_ANON = MAP_ANONYMOUS;
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# endif
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#else
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constexpr bool CONTEXT_USE_MMAP = false;
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#endif
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OSTD_EXPORT void *stack_alloc(std::size_t sz) {
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if constexpr(CONTEXT_USE_MMAP) {
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void *p = mmap(
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nullptr, sz, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | CONTEXT_MAP_ANON, -1, 0
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);
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if (p == MAP_FAILED) {
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throw std::bad_alloc{};
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}
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return p;
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}
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void *p = std::malloc(sz);
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if (!p) {
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throw std::bad_alloc{};
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}
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return p;
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}
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OSTD_EXPORT void stack_free(void *p, std::size_t sz) noexcept {
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if constexpr(CONTEXT_USE_MMAP) {
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munmap(p, sz);
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} else {
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std::free(p);
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}
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}
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OSTD_EXPORT std::size_t stack_main_size() noexcept {
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struct rlimit l;
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getrlimit(RLIMIT_STACK, &l);
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return std::size_t(l.rlim_cur);
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}
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OSTD_EXPORT void stack_protect(void *p, std::size_t sz) noexcept {
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mprotect(p, sz, PROT_NONE);
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}
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/* used by stack traits */
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inline void ctx_pagesize(std::size_t *s) noexcept {
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*s = std::size_t(sysconf(_SC_PAGESIZE));
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}
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inline void ctx_rlimit_get(rlimit *l) noexcept {
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getrlimit(RLIMIT_STACK, l);
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}
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inline rlimit ctx_rlimit() noexcept {
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static rlimit l;
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static std::once_flag fl;
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std::call_once(fl, ctx_rlimit_get, &l);
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return l;
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}
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} /* namespace detail */
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OSTD_EXPORT bool stack_traits::is_unbounded() noexcept {
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return detail::ctx_rlimit().rlim_max == RLIM_INFINITY;
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}
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OSTD_EXPORT std::size_t stack_traits::page_size() noexcept {
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static std::size_t size = 0;
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static std::once_flag fl;
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std::call_once(fl, detail::ctx_pagesize, &size);
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return size;
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}
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OSTD_EXPORT std::size_t stack_traits::minimum_size() noexcept {
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/* always at least 2 pages, typically 8k on x86_64, but for
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* example on ppc64 this will be 128k because 64k page size
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*/
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return std::max(std::size_t(SIGSTKSZ), 2 * page_size());
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}
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OSTD_EXPORT std::size_t stack_traits::maximum_size() noexcept {
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/* can be RLIM_INFINITY, but that's ok, see above */
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return std::size_t(detail::ctx_rlimit().rlim_max);
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}
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OSTD_EXPORT std::size_t stack_traits::default_size() noexcept {
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/* at least 64k unless minimum is bigger (typically 64k page platforms) */
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std::size_t r = std::max(std::size_t(8 * 8 * 1024), minimum_size());
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if (is_unbounded()) {
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return r;
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}
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std::size_t m = maximum_size();
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if (r > m) {
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return m;
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}
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return r;
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}
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} /* namespace ostd */
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