From 9a010a3ea520bc67b62d7fd1f232c71089038d87 Mon Sep 17 00:00:00 2001 From: Gabriel Schulhof Date: Mon, 30 Mar 2020 01:23:31 -0700 Subject: [PATCH] src: munmap(2) upon class instance destructor Replace `OnScopeLeave` with a class whose instance destructor performs the munmap(2). Signed-off-by: Gabriel Schulhof Fixes: https://github.com/nodejs/node/issues/32532 PR-URL: https://github.com/nodejs/node/pull/32570 Co-Authored-By: Anna Henningsen Co-Authored-By: Ben Noordhuis Reviewed-By: Anna Henningsen Reviewed-By: Ben Noordhuis Reviewed-By: James M Snell Reviewed-By: David Carlier --- src/large_pages/node_large_page.cc | 174 +++++++++++++++++------------ 1 file changed, 102 insertions(+), 72 deletions(-) diff --git a/src/large_pages/node_large_page.cc b/src/large_pages/node_large_page.cc index d0200937b727e6..853a56f5bd5e4c 100644 --- a/src/large_pages/node_large_page.cc +++ b/src/large_pages/node_large_page.cc @@ -20,6 +20,41 @@ // // SPDX-License-Identifier: MIT +// The functions in this file map the .text section of Node.js into 2MB pages. +// They perform the following steps: +// +// 1: Find the Node.js binary's `.text` section in memory. This is done below in +// `FindNodeTextRegion`. It is accomplished in a platform-specific way. On +// Linux and FreeBSD, `dl_iterate_phdr(3)` is used. When the region is found, +// it is "trimmed" as follows: +// * Modify the start to point to the very beginning of the Node.js `.text` +// section (from symbol `__node_text_start` declared in node_text_start.S). +// * Possibly modify the end to account for the `lpstub` section which +// contains `MoveTextRegionToLargePages`, the function we do not wish to +// move (see below). +// * Align the address of the start to its nearest higher large page +// boundary. +// * Align the address of the end to its nearest lower large page boundary. +// +// 2: Move the text region to large pages. This is done below in +// `MoveTextRegionToLargePages`. We need to be very careful: +// a) `MoveTextRegionToLargePages` itself should not be moved. +// We use gcc attributes +// (__section__) to put it outside the `.text` section, +// (__aligned__) to align it at the 2M boundary, and +// (__noline__) to not inline this function. +// b) `MoveTextRegionToLargePages` should not call any function(s) that might +// be moved. +// To move the .text section, perform the following steps: +// * Map a new, temporary area and copy the original code there. +// * Use mmap using the start address with MAP_FIXED so we get exactly the +// same virtual address (except on OSX). On platforms other than Linux, +// use mmap flags to request hugepages. +// * On Linux use madvise with MADV_HUGEPAGE to use anonymous 2MB pages. +// * If successful copy the code to the newly mapped area and protect it to +// be readable and executable. +// * Unmap the temporary area. + #include "node_large_page.h" #include // NOLINT(build/include) @@ -27,15 +62,14 @@ // Besides returning ENOTSUP at runtime we do nothing if this define is missing. #if defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES #include "debug_utils-inl.h" -#include "util.h" -#include "uv.h" #if defined(__linux__) || defined(__FreeBSD__) -#include #if defined(__linux__) #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif // ifndef _GNU_SOURCE +#elif defined(__FreeBSD__) +#include "uv.h" // uv_exepath #endif // defined(__linux__) #include #endif // defined(__linux__) || defined(__FreeBSD__) @@ -44,38 +78,16 @@ #include #if defined(__FreeBSD__) #include -#include #elif defined(__APPLE__) #include #endif -#include // getpid #include // PATH_MAX -#include -#include #include #include #include #include #include -#include -#include - -// The functions in this file map the text segment of node into 2M pages. -// The algorithm is simple -// Find the text region of node binary in memory -// 1: Examine the /proc/self/maps to determine the currently mapped text -// region and obtain the start and end -// Modify the start to point to the very beginning of node text segment -// (from variable nodetext setup in ld.script) -// Align the address of start and end to Large Page Boundaries -// -// 2: Move the text region to large pages -// Map a new area and copy the original code there -// Use mmap using the start address with MAP_FIXED so we get exactly the -// same virtual address -// Use madvise with MADV_HUGEPAGE to use Anonymous 2M Pages -// If successful copy the code there and unmap the original region. #if defined(__linux__) || defined(__FreeBSD__) extern "C" { @@ -282,20 +294,44 @@ bool IsSuperPagesEnabled() { } #endif +// Functions in this class must always be inlined because they must end up in +// the `lpstub` section rather than the `.text` section. +class MemoryMapPointer { + public: + FORCE_INLINE explicit MemoryMapPointer() {} + FORCE_INLINE bool operator==(void* rhs) const { return mem_ == rhs; } + FORCE_INLINE void* mem() const { return mem_; } + MemoryMapPointer(const MemoryMapPointer&) = delete; + MemoryMapPointer(MemoryMapPointer&&) = delete; + void operator= (const MemoryMapPointer&) = delete; + void operator= (const MemoryMapPointer&&) = delete; + FORCE_INLINE void Reset(void* start, + size_t size, + int prot, + int flags, + int fd = -1, + size_t offset = 0) { + mem_ = mmap(start, size, prot, flags, fd, offset); + size_ = size; + } + FORCE_INLINE void Reset() { + mem_ = nullptr; + size_ = 0; + } + FORCE_INLINE ~MemoryMapPointer() { + if (mem_ == nullptr) return; + if (mem_ == MAP_FAILED) return; + if (munmap(mem_, size_) == 0) return; + PrintSystemError(errno); + } + + private: + size_t size_ = 0; + void* mem_ = nullptr; +}; + } // End of anonymous namespace -// Moving the text region to large pages. We need to be very careful. -// 1: This function itself should not be moved. -// We use a gcc attributes -// (__section__) to put it outside the ".text" section -// (__aligned__) to align it at 2M boundary -// (__noline__) to not inline this function -// 2: This function should not call any function(s) that might be moved. -// a. map a new area and copy the original code there -// b. mmap using the start address with MAP_FIXED so we get exactly -// the same virtual address (except on macOS). -// c. madvise with MADV_HUGEPAGE -// d. If successful copy the code there and unmap the original region int #if !defined(__APPLE__) __attribute__((__section__("lpstub"))) @@ -305,62 +341,56 @@ __attribute__((__section__("__TEXT,__lpstub"))) __attribute__((__aligned__(hps))) __attribute__((__noinline__)) MoveTextRegionToLargePages(const text_region& r) { - void* nmem = nullptr; - void* tmem = nullptr; + MemoryMapPointer nmem; + MemoryMapPointer tmem; void* start = r.from; size_t size = r.to - r.from; - auto free_mems = OnScopeLeave([&nmem, &tmem, size]() { - if (nmem != nullptr && nmem != MAP_FAILED && munmap(nmem, size) == -1) - PrintSystemError(errno); - if (tmem != nullptr && tmem != MAP_FAILED && munmap(tmem, size) == -1) - PrintSystemError(errno); - }); - - // Allocate temporary region and back up the code we will re-map. - nmem = mmap(nullptr, size, - PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); - if (nmem == MAP_FAILED) goto fail; - memcpy(nmem, r.from, size); + // Allocate a temporary region and back up the code we will re-map. + nmem.Reset(nullptr, size, + PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS); + if (nmem.mem() == MAP_FAILED) goto fail; + memcpy(nmem.mem(), r.from, size); #if defined(__linux__) // We already know the original page is r-xp // (PROT_READ, PROT_EXEC, MAP_PRIVATE) // We want PROT_WRITE because we are writing into it. // We want it at the fixed address and we use MAP_FIXED. - tmem = mmap(start, size, - PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1 , 0); - if (tmem == MAP_FAILED) goto fail; - if (madvise(tmem, size, 14 /* MADV_HUGEPAGE */) == -1) goto fail; - memcpy(start, nmem, size); + tmem.Reset(start, size, + PROT_READ | PROT_WRITE | PROT_EXEC, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED); + if (tmem.mem() == MAP_FAILED) goto fail; + if (madvise(tmem.mem(), size, 14 /* MADV_HUGEPAGE */) == -1) goto fail; + memcpy(start, nmem.mem(), size); #elif defined(__FreeBSD__) - tmem = mmap(start, size, - PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | - MAP_ALIGNED_SUPER, -1 , 0); - if (tmem == MAP_FAILED) goto fail; - memcpy(start, nmem, size); + tmem.Reset(start, size, + PROT_READ | PROT_WRITE | PROT_EXEC, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | + MAP_ALIGNED_SUPER); + if (tmem.mem() == MAP_FAILED) goto fail; + memcpy(start, nmem.mem(), size); #elif defined(__APPLE__) // There is not enough room to reserve the mapping close // to the region address so we content to give a hint // without forcing the new address being closed to. // We explicitally gives all permission since we plan // to write into it. - tmem = mmap(start, size, - PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_PRIVATE | MAP_ANONYMOUS, - VM_FLAGS_SUPERPAGE_SIZE_2MB, 0); - if (tmem == MAP_FAILED) goto fail; - memcpy(tmem, nmem, size); + tmem.Reset(start, size, + PROT_READ | PROT_WRITE | PROT_EXEC, + MAP_PRIVATE | MAP_ANONYMOUS, + VM_FLAGS_SUPERPAGE_SIZE_2MB); + if (tmem.mem() == MAP_FAILED) goto fail; + memcpy(tmem.mem(), nmem.mem(), size); if (mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC) == -1) goto fail; - memcpy(start, tmem, size); + memcpy(start, tmem.mem(), size); #endif if (mprotect(start, size, PROT_READ | PROT_EXEC) == -1) goto fail; - // We need not `munmap(tmem, size)` in the above `OnScopeLeave` on success. - tmem = nullptr; + + // We need not `munmap(tmem, size)` on success. + tmem.Reset(); return 0; fail: PrintSystemError(errno);