From cbf276f0b79fdaa08efa7aa8fd1c56ab53acc796 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Tue, 28 Jan 2020 11:01:32 +0100
Subject: [PATCH 1/3] src: use __executable_start for linux hugepages

`__executable_start` is provided by GNU's and LLVM's default linker
scripts, obviating the need to plug in a custom linker script.

The problem with our bespoke linker script is that it works with ld.bfd
but not ld.gold and cannot easily be ported because the latter linker
doesn't understand the `INSERT BEFORE` directive.

The /proc/self/maps scanner is updated to account for the fact that
there are a number of sections between `&__executable_start` and
the start of the .text section.

Fortunately, those sections are all mapped into the same memory segment
so we only need to look at the next line to find the start of our text
segment.

Fixes: https://github.com/nodejs/node/issues/31520
---
 node.gypi                              | 16 ------
 src/large_pages/ld.implicit.script     | 10 ----
 src/large_pages/ld.implicit.script.lld |  3 -
 src/large_pages/node_large_page.cc     | 80 +++++++++++++-------------
 4 files changed, 41 insertions(+), 68 deletions(-)
 delete mode 100644 src/large_pages/ld.implicit.script
 delete mode 100644 src/large_pages/ld.implicit.script.lld

diff --git a/node.gypi b/node.gypi
index e6f5872cc75460..a83c63e23da7f7 100644
--- a/node.gypi
+++ b/node.gypi
@@ -306,22 +306,6 @@
       'ldflags': [ '-Wl,-z,relro',
                    '-Wl,-z,now' ]
     }],
-    [ 'OS=="linux" and '
-      'target_arch=="x64" and '
-      'llvm_version=="0.0"', {
-      'ldflags': [
-        '-Wl,-T',
-        '<!(echo "$(pwd)/src/large_pages/ld.implicit.script")',
-      ]
-    }],
-    [ 'OS=="linux" and '
-      'target_arch=="x64" and '
-      'llvm_version!="0.0"', {
-      'ldflags': [
-        '-Wl,-T',
-        '<!(echo "$(pwd)/src/large_pages/ld.implicit.script.lld")',
-      ]
-    }],
     [ 'node_use_openssl=="true"', {
       'defines': [ 'HAVE_OPENSSL=1' ],
       'conditions': [
diff --git a/src/large_pages/ld.implicit.script b/src/large_pages/ld.implicit.script
deleted file mode 100644
index 7f12e4bd7df9e5..00000000000000
--- a/src/large_pages/ld.implicit.script
+++ /dev/null
@@ -1,10 +0,0 @@
-  SECTIONS {
-    .lpstub            : {
-       *libc.a:*(.text .text.*)
-       *(.lpstub)
-     }
-  }
-  PROVIDE (__nodetext = .);
-  PROVIDE (_nodetext = .);
-  PROVIDE (nodetext = .);
-  INSERT BEFORE .text;
diff --git a/src/large_pages/ld.implicit.script.lld b/src/large_pages/ld.implicit.script.lld
deleted file mode 100644
index b85510bcf07eeb..00000000000000
--- a/src/large_pages/ld.implicit.script.lld
+++ /dev/null
@@ -1,3 +0,0 @@
-  PROVIDE (__nodetext = .);
-  PROVIDE (_nodetext = .);
-  PROVIDE (nodetext = .);
diff --git a/src/large_pages/node_large_page.cc b/src/large_pages/node_large_page.cc
index 252ccba15780d6..9419cb797f241e 100644
--- a/src/large_pages/node_large_page.cc
+++ b/src/large_pages/node_large_page.cc
@@ -65,7 +65,11 @@
 // Use madvise with MADV_HUGEPAGE to use Anonymous 2M Pages
 // If successful copy the code there and unmap the original region.
 
-extern char __nodetext;
+#if defined(__linux__)
+extern "C" {
+extern char __executable_start;
+}  // extern "C"
+#endif  // defined(__linux__)
 
 namespace node {
 
@@ -116,17 +120,6 @@ static struct text_region FindNodeTextRegion() {
     return nregion;
   }
 
-  std::string exename;
-  {
-      char selfexe[PATH_MAX];
-
-      size_t size = sizeof(selfexe);
-      if (uv_exepath(selfexe, &size))
-        return nregion;
-
-      exename = std::string(selfexe, size);
-  }
-
   while (std::getline(ifs, map_line)) {
     std::istringstream iss(map_line);
     iss >> std::hex >> start;
@@ -136,26 +129,42 @@ static struct text_region FindNodeTextRegion() {
     iss >> offset;
     iss >> dev;
     iss >> inode;
-    if (inode != 0) {
-      std::string pathname;
-      iss >> pathname;
-      if (pathname == exename && permission == "r-xp") {
-        uintptr_t ntext = reinterpret_cast<uintptr_t>(&__nodetext);
-        if (ntext >= start && ntext < end) {
-          char* from = reinterpret_cast<char*>(hugepage_align_up(ntext));
-          char* to = reinterpret_cast<char*>(hugepage_align_down(end));
-
-          if (from < to) {
-            size_t size = to - from;
-            nregion.found_text_region = true;
-            nregion.from = from;
-            nregion.to = to;
-            nregion.total_hugepages = size / hps;
-          }
-          break;
-        }
-      }
-    }
+
+    if (inode == 0)
+      continue;
+
+    std::string pathname;
+    iss >> pathname;
+
+    if (start != reinterpret_cast<uintptr_t>(&__executable_start))
+      continue;
+
+    // The next line is our .text section.
+    if (!std::getline(ifs, map_line))
+      break;
+
+    iss = std::istringstream(map_line);
+    iss >> std::hex >> start;
+    iss >> dash;
+    iss >> std::hex >> end;
+    iss >> permission;
+
+    if (permission != "r-xp")
+      break;
+
+    char* from = reinterpret_cast<char*>(hugepage_align_up(start));
+    char* to = reinterpret_cast<char*>(hugepage_align_down(end));
+
+    if (from >= to)
+      break;
+
+    size_t size = to - from;
+    nregion.found_text_region = true;
+    nregion.from = from;
+    nregion.to = to;
+    nregion.total_hugepages = size / hps;
+
+    break;
   }
 
   ifs.close();
@@ -408,14 +417,7 @@ int MapStaticCodeToLargePages() {
     return -1;
   }
 
-#if defined(__linux__) || defined(__FreeBSD__)
-  if (r.from > reinterpret_cast<void*>(&MoveTextRegionToLargePages))
-    return MoveTextRegionToLargePages(r);
-
-  return -1;
-#elif defined(__APPLE__)
   return MoveTextRegionToLargePages(r);
-#endif
 }
 
 bool IsLargePagesEnabled() {

From 569c1e0785e09fbcb8be797be7a8797e10f7bc16 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Tue, 28 Jan 2020 11:38:00 +0100
Subject: [PATCH 2/3] fixup! enable large pages only for executable

---
 node.gyp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/node.gyp b/node.gyp
index 529a36ba83c113..31f95e03a26964 100644
--- a/node.gyp
+++ b/node.gyp
@@ -841,7 +841,8 @@
           ],
         }],
         [ 'OS in "linux freebsd mac" and '
-          'target_arch=="x64"', {
+          'target_arch=="x64" and '
+          'node_target_type=="executable"', {
           'defines': [ 'NODE_ENABLE_LARGE_CODE_PAGES=1' ],
           'sources': [
             'src/large_pages/node_large_page.cc',

From 6d3851904c57e2c3e586a44de1fd535307901252 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Tue, 28 Jan 2020 15:34:17 +0100
Subject: [PATCH 3/3] fixup! reinstate freebsd check

---
 src/large_pages/node_large_page.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/large_pages/node_large_page.cc b/src/large_pages/node_large_page.cc
index 9419cb797f241e..ce58e32e719bc8 100644
--- a/src/large_pages/node_large_page.cc
+++ b/src/large_pages/node_large_page.cc
@@ -417,6 +417,11 @@ int MapStaticCodeToLargePages() {
     return -1;
   }
 
+#if defined(__FreeBSD__)
+  if (r.from < reinterpret_cast<void*>(&MoveTextRegionToLargePages))
+    return -1;
+#endif
+
   return MoveTextRegionToLargePages(r);
 }