From 088912e2fcbfcb67cabe4838a5cb30b40b5955a9 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Fri, 24 Dec 2021 20:15:07 +0900
Subject: [PATCH] [ELF] Create less number of PT_NOTE segments

---
 elf/passes.cc     | 18 ++++++++++--------
 test/elf/note2.sh | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 8 deletions(-)
 create mode 100755 test/elf/note2.sh

diff --git a/elf/passes.cc b/elf/passes.cc
index 334d674e..659cfc4a 100644
--- a/elf/passes.cc
+++ b/elf/passes.cc
@@ -759,23 +759,25 @@ void clear_padding(Context<E> &ctx) {
 //   alloc writable non-RELRO bss
 //   nonalloc
 //   section header
+//
+// .note sections are sorted by their alignments.
 template <typename E>
 i64 get_section_rank(Context<E> &ctx, Chunk<E> *chunk) {
   u64 type = chunk->shdr.sh_type;
   u64 flags = chunk->shdr.sh_flags;
 
   if (chunk == ctx.ehdr.get())
-    return -4;
+    return 0;
   if (chunk == ctx.phdr.get())
-    return -3;
+    return 1;
   if (chunk == ctx.interp.get())
-    return -2;
+    return 2;
   if (type == SHT_NOTE && (flags & SHF_ALLOC))
-    return -1;
+    return (1 << 10) + chunk->shdr.sh_addralign;
   if (chunk == ctx.shdr.get())
-    return 1 << 6;
+    return 1 << 30;
   if (!(flags & SHF_ALLOC))
-    return 1 << 5;
+    return (1 << 30) - 1;
 
   bool writable = (flags & SHF_WRITE);
   bool exec = (flags & SHF_EXECINSTR);
@@ -783,8 +785,8 @@ i64 get_section_rank(Context<E> &ctx, Chunk<E> *chunk) {
   bool relro = is_relro(ctx, chunk);
   bool is_bss = (type == SHT_NOBITS);
 
-  return (writable << 4) | (exec << 3) | (!tls << 2) |
-         (!relro << 1) | is_bss;
+  return (1 << 20) | (writable << 19) | (exec << 18) | (!tls << 17) |
+         (!relro << 16) | (is_bss << 15);
 }
 
 // Returns the smallest number n such that
diff --git a/test/elf/note2.sh b/test/elf/note2.sh
new file mode 100755
index 00000000..bfb15a61
--- /dev/null
+++ b/test/elf/note2.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+export LANG=
+set -e
+cd $(dirname $0)
+mold=`pwd`/../../mold
+echo -n "Testing $(basename -s .sh $0) ... "
+t=$(pwd)/../../out/test/elf/$(basename -s .sh $0)
+mkdir -p $t
+
+cat <<EOF | cc -o $t/a.o -c -x assembler -
+.section .note.a, "a", @note
+.p2align 3
+.quad 42
+EOF
+
+cat <<EOF | cc -o $t/b.o -c -x assembler -
+.section .note.b, "a", @note
+.p2align 2
+.quad 42
+EOF
+
+cat <<EOF | cc -o $t/c.o -c -x assembler -
+.section .note.c, "a", @note
+.p2align 3
+.quad 42
+EOF
+
+cat <<EOF | cc -o $t/d.o -c -xc -
+int main() {}
+EOF
+
+$mold -static -o $t/exe $t/a.o $t/b.o $t/c.o $t/d.o
+
+readelf --segments $t/exe > $t/log
+fgrep -q '01     .note.b' $t/log
+fgrep -q '02     .note.a .note.c' $t/log
+
+echo OK